Lab manual for Brown's Understanding Food: Principles and Preparation [2 ed.] 0534506143, 9780534506148

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Lab Manual for Brown's

UNDERSTANDING FOOD Principles and Preparation

J

Suzanne

R. Curtis

2ND EDITION

Lab Manual for

Brown's

UNDERSTANDING FOOD Principles

and Preparation

Second

Edition

Lab Manual for

Brown's

UNDERSTANDING FOOD Principles

and Preparation

Second

Edition

Lab Manual for

Brown's

UNDERSTANDING FOOD Principles

and Preparation

Second

Edition

Suzanne

R.

University of

Curtis

Maryland

THOMSON -*WADSWORTH Australia

•

Canada

•

Mexico

•

Singapore

•

Spain

•

United

Kingdom • United

States

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2004Wadsworth,

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TABLE OF CONTENTS Section

1.

Pages

..

ORIENTATION Objectives

1

To

introduce the student to the purposes, policies, and procedures of the laboratory

sessions.

2.

To

introduce the student to the equipment to be used in the laboratory.

General Laboratory Procedures

1

Food, disposable supplies, dishcloths, dishtowels, and potholders will be available on the supply cart located in the laboratory. Return used dishcloths and towels to the bottom of the supply cart.

your lab unit will be available on the supply cart or from the laboratory instructor. Return all equipment to the supply cart if it was taken from the cart.

2.

Equipment not

3.

Know the

4.

No

in

exact amount of each ingredient that you will need for the lab session. efficient! Make only one trip. Do not take any supplies that you do not need.

Be

coats, books, notebooks, etc. will be allowed in the laboratory except those necessary

for the laboratory period.

5.

Two

or three students will be assigned to each lab unit. At the end of each laboratory

period, the students

6.

Do NOT

MUST check out with the laboratory instructor.

leave the laboratory

instructor.

The

instructor

laboratory period.

room

any reason without checking with the laboratory where every student is at all times during the

for

must know

.. . .

FOOD LABORATORY INSTRUCTIONS Dress

1

A

clean, neat white lab coat

and hair net are to be worn at all times. Students not wearing complete and proper uniforms will NOT be permitted to participate in the laboratory session.

2. 3.

No

sweaters are to be worn over the uniform. Closed-toe shoes must be worn; no sandals.

Personal Sanitation

1

2.

Personal cleanliness and neatness

at all

times are essential.

Hands must be washed with soap before handling equipment

or food and after using a

handkerchief. 3.

Hands should be kept away from or face

4.

is

hair

and face while

in the laboratory.

Wash hands

if hair

touched.

NO smoking is permitted in the laboratory at any time.

5.

Always use a

6.

Do

not

sit

utensil for food testing.

Do

not use your fingers.

on the tables or on the countertops.

Care and Use of Equipment 1

Clean up as you work. Keep working area neat and uncluttered. Use individual trays assembling utensils and getting supplies.

2.

Select the proper size and shape equipment for each preparation.

3.

Do

not borrow equipment from another lab unit unless necessary. Return what borrowed to its proper place immediately after using it.

for

is

Cleaning Duties

1

2. 3.

4.

Scrape dishes with a rubber scraper. Discard all trash in plastic-lined garbage cans. Soak all cooking utensils which have come in contact with starchy foods or egg water to facilitate washing.

Use

a pan and a drainer for dishwashing. Fill the

added about 5.

6. 7. 8.

5

pan with hot water

to

in cold

which has been

ml of detergent.

Wash dishes in the following order: glassware, silverware, chinaware, pots and pans. Rinse dishes thoroughly and place in dish drainer. Dry with a clean towel. Clean burners on stove, burner bins, stove surfaces, and counters. Sinks must be

left clean.

drains are not clogged.

Allow water

to run for a brief period

of time

to

ensure that the

9.

If necessary, clear the

food waste disposer. Always check to be certain that no utensils

are accidentally left in the disposer. 1

0.

Spray counter tops and other surfaces with

sanitizer.

Allow

to air dry.

.

SAFETY 1

Be

when using hot fat. If it catches fire, immediately turn off heat. Cover with a exclude oxygen or pour generous amounts of salt or baking soda on the blaze. Do not attempt to extinguish the fire with water. Deep fry foods in deep fryers provided. careful

lid to

2.

Turn off burners when not

3.

To avoid

4.

Always use

a steam burn,

in use.

tilt lid

Do

not reach over a lighted burner or hot container.

away from you.

thick dry hot pads or oven mitts

use dish towels.

when handling

When removing hot food from

hot pans or dishes.

the oven, slide the

Do

not

oven rack forward and

grasp container with both hands protected by hot pads or oven mitts. 5.

Keep cupboard doors and drawers

6.

Keep handles of pans and skillets from extending over sides of range into the aisle or over the counter. Do not let a handle extend over another hot burner.

7.

Never connect

the current

into outlets in such a

away from 8.

way

the burners

closed.

on an electric appliance when your hands are wet. Plug cords no one will trip over them and also so that they will be

that

on the range.

Use the proper knife for the task. Always use a cutting board when cutting with a knife. Cut downward, never toward you. Wash knives separately and carefully; do not cover a knife with a towel.

9.

If

glassware

is

broken, use a paper towel to pick up the pieces. Dispose of it in the broken

glass container not the regular trash. ,

1

0.

11.

Wipe up Be

grease and water spills immediately.

familiar with instructions for special pieces of equipment such as the

microwave oven

and blenders you are using. Fire Extinguisher

Take note of the location of the trigger.

fire

extinguisher.

To

use,

remove

pin,

lift

horn, aim and pull

First

Aid Kit

with Take note of the location of the first aid kit. Minor cuts and burns may be treated medical a bandages and first-aid cream. More serious wounds should be treated by injury that cannot be professional. An accident/injury form should be filled out for any easily taken care

of with the

first

aid

kit.

.

CARE AND USE OF RANGES Surface Heating.

1

To

set controls,

push

in

and turn the surface unit control

in either direction to obtain the desired

degree of heat. The controls do not need to be set exactly on a particular heat for the range to operate. Start heating operations at a higher than medium heat, then turn control to a lower heat to finish the cooking. A surface unit signal light glows when any surface unit is turned on. Check when heating is finished to be sure all unit controls are turned off.

Using the Ovens.

2.

A typical

oven has two Switch

set the Selector

controls, a Selector Switch to the desired operation

and a Temperature Control dial. To operate, and Temperature Control to the desired

temperature.

The oven

signal light will

temperature for which

glow when

it is

the

oven

is

turned on until the oven reaches the

set.

The is

signal light will go out after preheating and thereafter will glow only being used to maintain the oven temperature.

Be

when

sure to turn the oven Selector Switch and/or the Temperature Control to

electrical current

OFF when

heating

is

completed.

Always arrange oven racks when oven then

3.

lift

slightly

is

cool.

To remove

a rack, pull

it

forward

until

it

stops,

and pull the rack out of the oven.

Minute Timer.

The minute timer simply operates as a buzzer. It does not start or stop heating. To set the minute timer turn the control in a clockwise direction to the desired number of minutes. When the time has elapsed, a buzzer will sound. To stop the buzzer, turn the minute timer control to off. 4.

Be

Cleaning Instructions.

sure all heating elements are turned OFF and are cool. Clean rings after each use to prevent grease build-up and to prevent spills from cooking on.

Outside Metal and Porcelain Surfaces Clean with a cloth using mild liquid dishwashing detergent and water. Dry surface with a soft cloth. Never use abrasives, steel wool ammonia cleaners, acids or commercial oven cleaners on exterior parts of the range .

-

Surface Heating Elements These clean themselves when they are turned on. Food spilled on a hot unit will bum off. Food spilled on a cool unit may be cleaned with a damp cloth. Surface heating elements unplug for complete removal. To remove, lift up edge of unit opposite terminal .

and pull entire unit

out.

Never immerse

a surface heating element in water

-

surface elements are removed, the reflector pans also can be washing. Hard-to-remove soil can be removed by using a nylon scrubber.

Reflector Pans

.

When

removed

Range Top The range top is hinged and may be raised to have access to the panel under the range top for cleaning. The lift-up range top is supported in its raised position by a swing-up

for

.

Raise and lower carefully to protect porcelain

rod.

finish.

Panel The control knobs are removable. With the controls in the OFF position, pull each knob straight off the shaft. Clean control panel with a hot, sudsy cloth and dry. Push knob back on shaft with flat side of shaft against the flat side of the hole in the knob. Control

Knob

.

CARE AND USE OF FOOD WASTE DISPOSERS

ALWAYS LEAVE THE DRAIN COVER IN PLACE TO PREVENT SMALL ITEMS FROM FALLING INTO DISPOSER. Operating Instructions

Remove

1

drain cover from disposer and turn on a

medium flow of COLD

water.

Water

should remain on during complete disposing operation.

ON position to

2.

Flip electric wall switch to

3.

Feed food waste

into disposer

be sure

is

all

waste

start disposer.

and run for about 30 seconds

after grinding

is

completed

to

flushed away.

OFF

4.

Flip wall switch to

5.

Replace drain cover.

position and turn off cold water.

Disposer Care

Most waste can be put through

the disposer. Large items should be cut or broken into smaller

pieces.

DO grind food waste

only with a strong flow of COLD water.

DO

dispose of small amounts of fats and greases in the disposer. Be sure to have disposer operating and use a strong flow of COLD water. The cold water will solidify the fat so it may be flushed away. Never use hot water with grease or fats -- the fat will be melted in the drain, but then will solidify and deposit when it touches cooler drain pipes. If you have a large

amount of

fat

and grease, place

it

in a container,

allow

it

to solidify

DO replace the drain cover when the disposer is

idle to

and then dispose of it

in the trash.

prevent foreign material from

accidentally dropping into disposer.

DON'T sink

use hot water

when

when

the disposer

is

grinding food waste. However, hot water

may

be run through the

not operating.

DON'T

feed large quantities of fibrous food wastes such as corn husks, pea pods, and artichoke leaves into the disposer.

DON'T is

turn off the

heard.

motor or water

until

grinding

is

completed and only a motor and water sound

DON'T

grind nonfood items, food wrappings, paper, tea bags, bones or strings. Dispose of these

items in the trash can.

DO turn off the

switch immediately

if

you hear a sound of loose metal

in the disposer.

COOKING TERMS BAKE

To cook in an oven. Covered or uncovered containers may be used. applied to meats in uncovered containers, it is called Roasting.

BASTE

To moisten foods while cooking, fat,

BEAT

meat drippings,

To make

When

especially while roasting meat. Melted

stock, water, or fruit juices

may be

used.

a mixture smooth or to introduce air by whipping, using rapid

regular motion.

BLANCH

To preheat briefly in boiling water so as to inactivate enzymes, or remove skins from fruits, nuts, and vegetables.

BLEND

To mix two

BOIL

To cook in a liquid which bubbles actively during the time of cooking. The boiling temperature of water at sea level is 212° F (100° C).

BRAISE

To brown meat

or

to

more ingredients thoroughly.

or vegetables in a small amount of fat, then to simmer slowly in a small amount of liquid in a covered container. The liquid may be juices from meat, or additional water, milk, meat stock, or vegetable juices.

BREAD

To

coat foods by dipping into fine dry crumbs, into an egg-milk mixture, and then into crumbs again.

BREW

See STEEP.

BROIL

To cook by

CANDY

To cook

CARAMELIZE

To

CHILL

To

place in a refrigerator or cool place until cold.

CHOP

To

cut into small pieces with a knife or chopper.

COAT

To cover

in

direct heat; to grill.

heavy syrup.

heat sugar, or foods containing sugar, until the sugar melts and a color and characteristic flavor develop.

entire surface

of food with a given mixture.

10

brown

CREAM

To

creamy by beating with a spoon sugar, shortening, and other ingredients are creamed

more foods

soften or blend one or

or electric mixer, e.g.

until

together to incorporate air so that the resultant mixture increases appreciably in volume and is thoroughly blended.

CUBE

To

cut into approximately A- to 54-inch squares.

CUT

To

divide food materials with a knife or scissors.

CUT IN

To

distribute solid fat in dry ingredients with knives, pastry blender, or in

l

mixer with proper attachments. cut into '/4-inch or smaller cubes.

DICE

To

DISSOLVE

To mix

a solid dry substance with a liquid until the solid substance

is

in

solution.

DREDGE

To

FRICASSEE

To cook by

FRIZZLE

To cook

sprinkle or coat with flour, sugar, or meal. braising; usually applied to poultry or veal cut into pieces.

in a small

ham, bacon, dried

FRY

amount of fat

until crisp

and curled

at the

edges,

e.g..

beef.

To cook in hot fat. When a small amount of fat is used, the process is known as pan-frying or sauteing or shallow-fat frying. When sufficient is used to keep food afloat, the process is known as deep fat frying.

GRILL

See BROIL.

GRIND

To reduce

LARD

To cover uncooked

MARINATE

To cover with

dressing or sauce and

from

an hour to overnight.

to particles

less than

by

To

MIX

To combine two

cut or

chop

cutting, crushing, or grinding.

lean meat or fish with strips of fat.

sauce in which the food

MINCE

fat

is

let

stand for a length of time varying

NOTE: MARINADE

is

the liquid or

MARINATED.

fine using knife or chopper.

or

more

ingredients so that they are evenly distributed.

11

PAN-FRY

See FRY.

PARBOIL

To

PARE/PEEL

To remove

POACH

To cook

RENDER

To

boil in water until food

is

partially cooked.

skin or outside covering using knife or mechanical peeler.

in hot liquid using precautions to retain shape.

extract fat

from connective

tissue

by heating slowly

at

low

temperature.

ROAST

See

SAUTE

See FRY.

SCALD

To

BAKE.

heat liquid, usually milk, until hot but not boiling. Alternatively, to dip

certain foods into boiling water. See

SCALLOP

To bake

SCORE

To make shallow lengthwise

BLANCH.

food, usually cut in pieces, with a sauce or other liquid.

or crosswise

slits

across surface of food with

knife, fork, or other implement.

SEAR

To brown the surface of meat by a short application of intense heat develop flavor and improve appearance.

SHRED

To

SIFT

To put dry

SIMMER

to

cut or tear into strips or pieces using a knife or a shredder attachment.

To cook 210°

ingredients through a sieve.

in liquid at a

temperature just below the boiling point

(1

85° F

F).

STEAM

To cook

STEEP

To

let

in

steam with or without pressure.

stand in hot liquid below boiling temperature to extract flavor,

color, or other qualities

STEW

To simmer

TOAST

To brown

TOSS

To mix

in a small

from a specific food.

amount of liquid.

surface of food by application of direct or dry heat.

lightly; usually for salad ingredients. 12

-

TRUSS

To bind

WHIP

To

or fasten together.

beat rapidly to increase volume by incorporating

13

air.

.

MEASURING TECHNIQUES A.

Commonly Used Measurements

Objectives

1

2.

To To

learn

learn

commonly used household measurements. metric equivalents of the commonly used measurements.

Procedure

1.

Learn the following

3

teaspoons

lists

of measurements.

..

Measuring Techniques

B.

for Flour

Objectives

To learn correct techniques for measuring flour. To compare experimental results with standard results. To become familiar with the top loading balance.

1

2. 3.

Procedure

1

Weigh an empty 1-cup measure.

2.

Fill the

3.

Level flour with the edge of a spatula. Weigh the flour and the cup on the top loading balance and record the combined weight. Subtract the weight of the empty cup from the combined weight. Record the weight of the

4. 5.

1-cup measure following the directions below.

flour.

Spooned, unsifted:

Spoon

Spooned,

Sift

sifted:

unsifted flour directly into a

approximately

1

Vi

1

-cup measure.

cups of flour onto a

flat surface.

Then spoon

the

flour into a 1-cup measure.

Sifted:

Method

Place a 1-cup measure on a

Weight of Cup and

flat surface. Sift flour directly into

the cup.

Weight of

Weight of

Class Avg.

Standard

Cup

Flour

Weight of

Weight

Flour

Flour

125 g

Spooned, Unsifted

120 g

Spooned. Sifted

115 g

Sifted

15

...

Measuring Techniques

C.

for

Sugar

Objectives

To learn correct techniques for measuring various sugar To compare experimental results with standard results. To become familiar with the top loading balance.

1

2. 3.

products.

Procedure

Weigh an empty 1-cup measure.

1

3

-cup measure with the sugars below, following the directions indicated. Level the sugar with the edge of a spatula (except for brown sugar).

4.

Weigh

Fill the

2.

1

the sugar and the cup on the top loading balance and record the combined weight. Subtract the weight of the empty cup from the combined weight. Record the weight of the

5

sugar.

Granulated sugar:

Dip the cup

Brown

Pack the sugar

sugar:

into the container

into a

of sugar.

measuring cup with a spoon

until

it is

level

with the top of the cup. Free-flowing brown sugar:

Pour sugar

Confectioners' sugar:

Place a 1-cup measure on a

into 1-cup

measure

until

it

overflows.

flat surface. Sift the

sugar directly into

the cup.

Type of

Weight of

Weight of

Weight of

Class Avg.

Standard

Sugar

Cup and

Cup

Sugar

Weight of Sugar

Weight

Sugar Granulated

200 g

Brown

200 g

Free-Flowing

95 g

Brown Confectioners'

95 g

16

..

D.

Measuring Techniques

for Liquids

Objectives

1

2. 3.

To learn correct techniques for measuring liquids. To compare experimental results with standard results. To become familiar with metric measurements for liquids.

Procedure

1

2.

Place a 1-cup glass measuring cup on a level surface. Fill the cup with water to the 1 -cup mark. Read the volume

3.

Transfer the water from the cup to a graduated cylinder.

4.

of the meniscus. Record the volume in milliliters. Repeat the above procedure for Va cup, V 3 cup, Y2 cup,

Volume in Glass Cup

at the

Read

2 /3

the

cup and

bottom of the meniscus. volume at the bottom Va cup.

..

E.

Using a Thermometer

Objectives

1

2. 3.

To demonstrate the correct method of setting up a ring stand and thermometer. To correctly read and calibrate a thermometer. To learn the conversion factors between degrees Celsius and degrees Fahrenheit.

Procedure

1

2.

Choose a thermometer from the laboratory supply. If the thermometer selected does not have a string tied through

the loop, attach such a

string. 3.

4.

5.

Suspend the thermometer with a ring stand as demonstrated by the instructor. some water in a saucepan on top the stove. Calibrate the thermometer by immersing it in the boiling water. Allow the temperature to stabilize before taking a reading. The top of the mercury column should be at eye level when a reading is taken. The bulb should not touch the bottom or the sides of the saucepan. Boil

Also, calibrate the thermometer by using an ice-water mixture in a beaker. Again, allow the temperature to stabilize.

The bulb should not touch

the

bottom or the sides of the

beaker. 6.

Record readings on your thermometer.

Boiling Point

7.

Learn

Freezing Point

how

temperatures on the Celsius scale (°C) to temperatures on the Fahrenheit scale (°F) and vice versa by using the following equations. to convert

°C = (°F-32)/1.8 °F= 1.8(°C) + 32

Study Questions

The most accurate cup a.

1

b.

1

to use for

cup liquid measure cup solid measure filled

measuring

Vi

cup of tomato juice

Vi

cup flour

is:

filled to Vi cup.

to Vi cup.

cup fractional measure.

c.

Vi

d.

8 tablespoons.

The most accurate cup

to use for

measuring

is:

(same choices as #1).

Which measuring utensils are best for measuring 7 8 cup sucrose? Which method of measuring flour gives results closest to the standard weight of allpurpose flour?

Give some reasons why the experimental weight of a cup of flour might

differ

from the

standard weight?

The standard weight of sifted

flour

is

Weighing and measuring sifted of 125 g, 127 g, and 123 g. Are these

1 1

flour three

5 g.

times (three replications) gives results measurements accurate or precise or both?

Why is granulated sugar easier to measure more precisely than flour? Why is granulated sugar easier to measure more precisely than brown sugar? How does free-flowing brown sugar differ from ordinary brown sugar? If you

were using

light

use more or less or the

brown sugar in same volume?

would you

a recipe instead of granulated sugar,

Your thermometer, when calibrated, reads 102° C in boiling water and -1° C in an ice bath. Explain how you would correct for your thermometer's inaccuracy in each of the following cases. a.

b. c.

You wish to You wish to You wish to

concentrate a sucrose solution so that

it

boils at

1

10° C.

record the correct boiling point of a liquid that boils at 96° C. record the correct freezing point of a solution that freezes at -5° C.

19

.. .

ENERGY TRANSFER Effect of Pan Surface Characteristics on Energy Transfer

A.

Objectives

To demonstrate

1

the influence of baking pan material

on heating of a

rich

dough such

as

cookies.

To observe

2.

the effects of shiny and dull

aluminum cookie

sheets on the

crumb color of

cookies.

Recipe

1

V2

cups sugar

cup shortening cup margarine 2 eggs !/2

Vi

2

3

/4

cups flour

2 teaspoons cream of tartar 1

V*

1

teaspoon baking soda teaspoon

salt

Preheat oven to 204°

2.

Cream

C

(400° F).

sugar, shortening and margarine. Beat in the eggs.

3.

Blend

4.

Shape dough

5.

Place 2" apart on ungreased cookie sheets.

6.

Cookies will puff up and then

in a

mixture of the

flour,

cream of tartar, soda, and

salt.

into small balls.

flatten out

while baking.

Procedure

1

Prepare cookie dough using the recipe above.

2.

Divide the balls of dough into three groups.

3.

6.

Bake one-third of the cookies Bake one-third of the cookies Bake one-third of the cookies Bake all cookies for exactly 9

7.

Cool

4. 5.

8.

all

on an ungreased very dark cookie sheet. on an ungreased medium dark cookie sheet. on an ungreased shiny cookie sheet. minutes at 204° C (400° F). Be sure

to preheat

your oven.

cookies on cooling racks.

Display the cookies on a plate labeled with the type of cookie sheet on which they were baked.

20

.

B.

Effect of Container Material on Energy Transfer

Objectives

1

To compare the transfer of energy of various To gain experience in plotting data.

materials.

Procedure

Measure 200 ml of water Bring the water to a

As

into a small saucepan.

full boil

top of the stove. Set the burner on high.

soon as the water comes to a

boil, transfer the

water to a Pyrex 1-cup liquid measuring

cup.

Read

the water temperature immediately after the transfer

thermometer

is

suspended properly from a ring stand. at 30 sec

Continue to read and record the temperature

is

made. Be sure your

intervals. If the

temperature drops

very rapidly, use a time interval smaller than 30 sec. If the temperature drops very slowly, use a time interval larger than 30 seconds.

Read and record

the temperature until

Plot your data. Let the

Y

room temperature

axis represent temperature and

reached.

is

let

Repeat the above procedure, but transfer the boiling water

the

X axis represent time.

to a metal 1-cup fractional

measure.

Repeat the above procedure, but transfer the boiling water Pyrex

Metal

to a

Styrofoam cup.

Stvrofoam

.

C.

Effect of Shape of Container on Energy Transfer

Objectives

1

To compare

the transfer of energy in containers of the

same material but with

different

shapes. 2.

To

gain experience in plotting data.

Procedure Preheat the oven to 204° C (400° F). The oven rack should be in the center position. Measure 500 ml of room temperature water into both a small aluminum loaf pan and a square aluminum cake pan (8" x 8"). Place both pans on the oven rack. Be sure the pans are positioned so that air flow around all

sides of the pans

Read and record Read and record

is

possible.

the initial water temperature.

the water temperature at 4 min. intervals. Record the highest temperature observed. If the temperature rises very rapidly, use a time interval smaller than 4 minutes. If the temperature rises very slowly, use a time interval larger than 4

minutes. However, use the same interval for both pans.

any longer than

is

Do

not keep the oven door open

necessary.

Plot your data. Let the

Y axis represent temperature and let the X axis represent time.

Aluminum Loaf Pan

.

Studv Questions

1

2. 3.

4. 5.

Which cookies had Account

the brownest bottom surface?

for the color differences observed in the

The

palest

bottom surface?

baked cookies.

the cookie sheets according to their ability to transmit heat energy.

Rank Which cookie sheet would you choose when baking cookies? Why? How would the varying shapes of the Pyrex, metal and Styrofoam cups influence time-temperature data? Which other variables might influence the data in this

the

experiment? 6. 7.

During which time interval did the greatest drop in temperature occur? How is energy being transferred to the Pyrex, metal and Styrofoam cups

filled

with hot

water? 8.

How

is

energy being transferred

to the

water in the aluminum pans

when heated

in the

oven? 9.

aluminum pans containing water had been covered, would you expect heat more or less slowly? Why? If the

23

the water to

.

SENSORY EVALUATION OF FOODS AND SEASONINGS Study of the chemical and physical properties of food components and the interactions of these components during preparation and storage provides a basis for understanding factors which influence food quality. Measuring quality differences in foods

A number of objective tests have been devised

is

an essential part of such a study.

for this purpose, but there are

still

many

aspects

of food quality for which no appropriate objective tests are available. Instead, subjective tests must be used to assess differences in the quality of foods. The ultimate criterion used to evaluate food quality characteristics such as appearance, texture, taste and aroma is the degree of appeal to

human

sensory organs.

Sensory evaluation of foods has been applied to many situations in research and development, quality control, and food product marketing.

Such applications include: new product development, product matching and improvement, process change, selection of a new source of supply, quality control, storage stability, product selection and training, and correlation of sensory with chemical and physical measurements. Four types of sensory

tests often

used are difference

tests,

descriptive tests, affective tests

(acceptance/preference), and sensitivity tests (detection and recognition). Specific points to keep in

1

2. 3.

4.

5.

6.

mind during sensory evaluation

studies include:

Each individual must work independently. There must not be any discussion while foods are being evaluated. Class discussion will be led by the lab instructor following individual evaluations. The success of the scoring procedure depends on the degree to which the student can put himself/herself into the position of an impartial judge. To avoid bias, samples are generally coded with 3-digit random code numbers. Samples should be representative of the product being tested.

By

being careless, the scorer

being hypercritical the scorer

may miss differences that should have been may record deviations that in reality do not

24

detected and by exist.

A GUIDE FOR FOOD PRODUCT EVALUATION Quality

is

commonly thought of as degree of excellence. Food

quality

is

a

complex concept

that

includes appearance, flavor, texture, and nutrient content. In the food laboratory, food quality refers to the sensory quality of the food, which is often evaluated subjectively by means of the

sensory organs. The specific sensory characteristics which are evaluated include appearance, flavor, and texture. Taste and odor are components of flavor.

human

Appearance includes shape, example, also

is it

size, color,

transparent, opaque, dull,

and the condition of the outside surface of the food. For glossy, free of defects? In baked products, appearance

include the color of the interior crumb.

may

Flavor has been defined as the sensation caused by those properties of any substance taken into the mouth which stimulates one or both of the senses of taste and smell. Included in this definition are the sensations from the pain and temperature receptors in the mouth. In other

words, flavor is a combination of taste and aroma as well as some mouthfeel sensations. Examples of mouthfeel sensations include pain (pepper and horseradish), temperature (hot and cold), astringency (green bananas and strong tea), and metallic sensation (tinny).

buds of the tongue are stimulated by substances in solution and are believed to respond to four primary tastes -- bitter, salty, sour, and sweet. It is unclear whether umami is a fifth basic of taste or a flavor enhancer. All other tastes are believed to be a combination of these. The sense

The

taste

taste is

weak compared

are of fluid consistency

to the sense of smell. Taste

and

is

often

more

easily perceived in foods that

in liquids.

component of flavor that strongly influences acceptance or rejection of a food. The sense of smell is very keen. Only a few molecules of a volatile compound are necessary to produce an olfactory sensation. Aroma is modified by food temperature. Higher temperatures result in greater volatility of flavor compounds and therefore in greater flavor perception.

Aroma is

Texture

the

is

the response of the tactile senses to the physical characteristics of a food.

movement) is what we generally influenced by both the structure of the

Interpretation of these tactile sensations (touch, pressure, and refer to as texture.

food and by

its

Our evaluation of a

food's texture

resistance to forces applied

by

is

the teeth, tongue, roof of the mouth, knife, and

fork.

25

..

Descriptive

Terms

The following adjectives are terms which may be used in sensory evaluation. This by no means exhaustive. The terms merely serve as examples. Appearance

:

list

of terms

is

symmetrical, asymmetrical, level, sunken, rounded, pebbled, sticky, greasy, shiny, dry, pale, golden brown, light brown, black, smooth, rough, puffy, any color or shape.

Flavor

sweet, bitter, sour, salty, soapy, floury,

:

fruity, sharp, burnt,

flat,

eggy, rancid, pasty, bland, flowery,

minty, pungent, putrid, musky, puckery, hot, cold, metallic,

burning (peppery), cool (minty). Texture

:

crisp, velvety,

gummy,

smooth, rough, hard, firm, thick,

thin, viscous, springy, gritty,

adhesive, moist, tender, fibrous, chewy, curdled, lumpy, pasty, rubbery,

tough, greasy, fibrous.

Evaluation of Food Products

When

evaluating a food product, a natural reaction might be to say simply

really good." Statements such as these represent a

"I

don't like

it"

or

"it's

summation of instantaneous evaluation of the

product's appearance, flavor and texture. In addition, an evaluation

is

undoubtedly influenced by

the cultural, emotional and psychological biases that play a role in determining individual food

preferences. Because sensory evaluation of food products

influenced by the evaluator's personal biases.

food laboratory are

is

subjective,

it

can subconsciously be

The desired objectives of sensory evaluation

to set individual preferences aside; to

consciously

make an

evaluation based

on only the relevant sensory characteristics of appearance, flavor, and texture; and communicate your evaluation to others by using appropriate descriptive terms. A.

to

Evaluation of Food Products Using Descriptive Terms

Objectives

1

2.

To become familiar with descriptive terms used in sensory To evaluate food products by using the human senses.

evaluation of foods.

Procedure

1

Evaluate a baked muffin for appearance and volume by using the descriptive terms

provided above, or other appropriate terms. 2.

Smell the muffin and evaluate

3.

Taste the same muffin and describe

4.

its

aroma.

its flavor and Record sensory responses on the forms provided.

26

texture.

in the

..

Repeat above procedures by using a raw apple, strongly brewed black

5.

tea,

and cottage

cheese.

Muffin

Characteristic

Apple

Tea

Cottage Cheese

Appearance

Aroma

Flavor

Texture

Paired Comparison Test

B.

A paired comparison test is a difference test. Two

coded samples are presented simultaneously and evaluated for intensity of a specific characteristic. The chance of selecting the correct sample is

1

out of 2.

Objectives

1

2.

To conduct a paired comparison test and participate as a sensory panelist. To determine which sample possesses a greater intensity of the characteristic being evaluated.

Procedure

1

Taste both samples.

2.

Determine which sample has the greater intensity

for the specific characteristic.

Sample code

Sample code

Characteristic being evaluated

Which sample has C.

the greater intensity?

Triangle Test a difference test performed on three coded samples. Two samples are identical different. All samples are presented simultaneously. The panelist is to determine

A triangle test is

and the third is which sample is different from the other two samples. The chance of guessing the odd sample 1

out of

3.

27

is

. ..

.

Objectives.

1

2.

To conduct a triangle test and participate as a sensory panelist. To identify the odd sample of a series of three coded samples.

Procedure

1

Taste each of the three coded samples and identify the sample which differs from the other two.

2.

Determine the total number of correct responses in the class and evaluate likelihood of selecting the odd sample by chance.

Sample code

Sample code

Which sample D.

is

different

results as to the

Sample code

from the other two?

Ranking Test

In a ranking

test,

a sensory panelist simultaneously compares coded samples on the basis of a

single characteristic. characteristic.

Samples are ranked according

The sample with

to the intensity

of the designated

the greatest intensity of the characteristic

is

ranked as #1

.

No

are permitted in the ranking.

Objectives

1

2. 3.

To conduct a ranking test and participate as a member of the sensory panel. To rank a series of samples in order of intensity of a specific characteristic. To rank a series of samples in order of preference.

Procedure

2.

coded samples. Rank the coded samples

3.

You may

1.

Taste

all

re-taste

in

descending order of intensity.

any of the samples while ranking for intensity of the specific

characteristics. 4.

No

5.

Record

ties are

allowed

in the ranking.

results in the table below.

Remember

that the

most intense sample should be

ranked # 1 6.

Rank

the samples again according to preference.

The order may be

the

different than the ranking for intensity.

Intensity

Sample code #1

#2

#4

#3

28

#5

same

as or

ties

...

Preference

Sample code #1

E.

#4

#3

#2

#5

Identification of the Primary Tastes

Objectives

1

To

identify the four primary tastes.

Procedure

1

Five coded solutions are available. Each contains either tonic water (or

phenylthiocarbamide),

citric acid,

NaCl, or sucrose. One solution

is

a duplicate.

2.

Pour a small amount of each coded solution

into a cup.

3

Taste each of the four coded samples one

a time and identify the primary taste of each

at

coded sample. 4.

Water should be used

5.

Record

to rinse the

results in the table below.

mouth between samples.

Spiced

rice: color,

form, palatability, and suggested uses of the spice

T

Spice

Color'

7ZT

Form'

Palatability

Suggested Uses

Curry Powder

Paprika

Saffron

Turmeric

1.

Color: color of the dry spice used

3.

Describe

2.

Form: finely ground, coarsely ground, shredded

Tomato Bouillon Prepare

recipe of tomato bouillon according to the recipe listed. Heat the mixture to boiling and divide into small teapots or liquid measuring cups. Stir V teaspoon of one of 8 the herbs listed into each portion, cover, and steep for 3 minutes. Use just enough herb to 1

distinguish the characteristic flavor. Serve hot.

Recipe cups tomato juice

1

Vi

3

cups beef bouillon (use cubes, liquid concentrate, or granules)

Display some of each herb used, in a labeled custard cup or on waxed paper, next cup of seasoned hot bouillon.

30

to the

Herbed tomato

Herb

bouillon: color, form, palatability,

and suggested use of the herb

Spiced applesauce: color, palatability, and suggested uses of the spice Spice

Seasoned cheese spread:

BEVERAGES There are two objectives in the preparation of a good cup of coffee or tea. One is to optimize the extraction of desirable, water soluble, flavor constituents from the coffee bean or tea leaf and retain them in the beverage. The other is to minimize the extraction of undesirable favor constituents

.

To achieve

these objectives, grind of coffee, size of tea leaves, contact time, water

temperature and brewing methods must be controlled.

The coffee grind determines the proper proportions of coffee and water. When a fine grind of coffee is used, more surface area is available for contact with water. The greater surface area can result in more efficient extraction of flavor compounds such as tannins, volatile oils and organic acids. Therefore a smaller proportion

strength than if a large grind

of coffee

to

water

is

required to yield brews of acceptable

used.

is

Because the flavor compounds are extracted by water, the contact time between the coffee or tea and water will influence the final beverage characteristics. Too long a contact time results in a bitter

beverage due

in a flat, flavorless

to the extraction

of large amounts of tannins. Too brief a contact time results oils and organic acids are incompletely extracted.

beverage since desirable

The optimum brewing temperature

F). A brewing because more tannins are extracted at higher temperatures and volatile flavor compounds are lost. A lower brewing temperature produces a flat, flavorless beverage since organic acids and oils are not maximally extracted.

temperature greatly above 95°

Coffee

is

steeping.

C

for both coffee

and tea

is

85-95°

C

(185-203°

results in bitter coffee

commonly brewed by percolation or filtering and is Tea is commonly prepared by steeping tea leaves in

only occasionally prepared by hot water for 3-5 minutes.

Black, green, and oolong teas are available. Black tea refers to leaves that have been fermented resulting in a decrease in tannins

and an increase in desirable flavor compounds. Brewed black amber color and a full flavor. Green tea refers to leaves that have not been fermented. Such tea contains more tannins than black tea and fewer flavor compounds. Brewed green tea has a pale yellow-green color, is somewhat bitter and has little flavor. Oolong tea is a partly fermented tea which has quality characteristics between those of green and black teas. tea has an

Black tea leaves are classified by their size. Orange pekoe refers to the smallest leaves, pekoe to the middle size leaves and souchong to the largest leaves. "Broken" simply means the leaves are not intact. Broken orange pekoe

is

generally considered the best grade of black tea and consists

The buds and the first two leaves of the harvested tea shoot have a high polyphenol and enzyme content which contribute to the color and flavor of the fermented chiefly of buds.

34

tea.

.

grinding the seeds of Chocolate and cocoa are produced by fermenting, roasting, cracking and chocolate liquor and solidifies on cooling the pods of the cacao tree. The resulting paste is called are added to produce milk chocolate. to form bitter chocolate. Milk, sugar and flavorings of cocoa, the cocoa Chocolate contains approximately 50% fat (cocoa butter). In the production remaining is dried and ground to a butter is pressed from the chocolate liquor. The solid material natural-processed or Dutchfine cocoa powder. Cocoa and chocolate are classified as either with alkali to improve color processed. Dutch-processed means that the seeds have been treated flavor and darker and solubility. Dutch-processed products have a slightly milder, less bitter color than natural-processed products.

Quality Characteristics of Coffee, Tea, Chocolate and Cocoa Beverages

Appearance

clear, bright

deep amber

to rich

3rown

Chocolate and Cocoa

Tea

Coffee -

clear, bright

-

black

-

green

tea:

tea:

surface free from

amber

milk "skin" or

yellow-

iglobules

fat

green - depth of color is dependent on time of

steeping

Aroma

highly fragrant

distinct but subtle

definite chocolate

aroma

pleasing aroma i

Flavor

Mouthfeel

typical coffee flavor

characteristic of type

with no bitterness or

-

staleness

mellow

taste

black tea

smooth

feel

on

may

green tea

more

bitter

astringent

be

clean, characteristic

chocolate flavor

than

-

tongue

dependent on type

slightly astringent

and length of

smooth consistency, body similar to thin cream

brewing

A.

Coffee Brewing Methods

Objectives

1

2. 3.

To observe different methods of brewing coffee. To compare the quality of coffee beverages prepared by different brewing methods. To compare the amounts of tannins present in coffee brewed by different methods.

35

..

Procedure

1

.

Prepare drip, percolated and steeped coffees following the directions below. a.

Drip

(Filter)

Put a

1.

2. 3.

the filter holder and add coffee.

Record the temperature of the brewed

4.

b.

filter into

Use two tablespoons of

drip-grind coffee and one cup of water per serving. Pour boiling water into the filter section of the coffee assembly. Record the temperature of the water in the filter holder. Remove the filter and the coffee grounds when the coffee has finished dripping into the pot. coffee.

Percolated

Put cold water into coffee pot. Use one cup of water per serving. coffee to basket. Use two tablespoons of regular-grind coffee per cup

1

2.

Add

of water. 3.

4. 5.

c.

Cover pot and heat until percolation begins. Percolate gently 8-12 minutes. Record the temperature of the coffee as soon as percolation stops.

Remove

coffee grounds.

Steeped

1

Measure water

into utensil

and bring

to a boil.

Use one cup of water per

serving.

d.

Remove

2.

water from heating unit, add coffee and stir well. Use two tablespoons of regular-grind coffee per cup of water.

3.

Steep 3-5 minutes. Record the temperature of the steeped coffee as steeping proceeds. If the temperature drops below 85° C, heat gently but do not exceed 95° C.

4.

Carefully strain coffee through cheesecloth.

Using either the percolator or the drip method, brew a decaffeinated coffee beverage.

36

Complete the following chart

Method

after evaluating

each coffee beverage.

..

C.

Teas

Objectives

1

2.

To gain experience in brewing tea. To compare black, oolong and green

teas for quality characteristics.

Procedure

1

Preheat a teapot by filling it with boiling water, allowing then pouring out the water.

Using

3.

it

to stand for 3

minutes and

teaspoon of tea leaves per cup of water, place leaves in the preheated teapot, and pour boiling water over them. Steep 3 minutes. Record the temperature at the end of steeping. Then 1

strain the tea into a

cup. 4. 5.

Carry out steps 1-3 for green, oolong, black, decaffeinated and herbal Compare the characteristics of the various teas.

Tea

teas.

..

.

Procedure Steep 2 black tea bags in 2 cups of boiling water for 4 minutes. divide the tea equally among 4 custard cups.

1

2.

Add

3.

Stir

4. 5.

Vi

Remove

tea bags and

tablespoon lemon juice to 2 of custard cups.

each cup well. Compare the teas with and without lemon juice for clarity and color. lemon juice. Compare Refrigerate 1 cup of tea without lemon juice and 1 cup of tea with the chilled teas for clarity and color.

E.

Chocolate and Cocoa Beverages

Objectives

3

To compare homemade chocolate and cocoa beverages. To compare commercial and homemade cocoa beverages. To observe the effects of heat on cocoa and chocolate.

a.

Homemade Cocoa Beverage

1

2.

2 tablespoons cocoa 2 tablespoons granulated sugar Vt.

1

Va

cup water cups milk teaspoon vanilla

Vi

dash of salt Procedure

2.

Mix together cocoa, sugar and Add water and blend well.

3.

Heat

1

a small saucepan.

to boiling, stirring constantly.

5.

Continue heating and stirring allow the mixture to scorch. Add milk and heat to 94° C.

6.

Add

7.

Evaluate product and record

b.

Commercial Cocoa Beverage

4.

salt in

vanilla and

stir

until

mixture thickens and

well. results.

2 packages commercial instant cocoa beverage

39

is

smooth. Be careful not to

.

Procedure Prepare instant cocoa beverage as directed on the package. Evaluate product and record results.

Homemade

c.

Chocolate Beverage

square unsweetened chocolate 2 tablespoons granulated sugar Vi

Vi 1

('/2

ounce)

cup water cups milk

Vz

A

l

teaspoon vanilla

dash of salt

Procedure

Combine Heat

water, chocolate and sugar in a small saucepan.

to boiling, stirring constantly.

Continue heating and stirring allow the mixture to scorch. Add milk and heat to 94° C.

Add

vanilla

and

until

mixture thickens and

is

smooth. Be careful not

to

stir well.

Evaluate product and record results.

Beverage

Color

Aroma

Homemade Cocoa Commercial Cocoa

Homemade Chocolate

F.

Selected Beverage Recipes

Objectives

1

2.

To gain experience in beverage preparation. To become familiar with a variety of beverages.

40

Flavor

Consistency

.

a.

Viennese Coffee Mix Va

Va

cup hot cocoa mix cup nondairy creamer mix

3 tablespoons instant coffee

powder

2 tablespoons powdered sugar Vg tsp. cinnamon Vg tsp.

nutmeg

Procedure

1.

Combine

2.

Add

b.

Cafe Aruba

1

/4

all

ingredients.

3 tablespoons to a cup. Fill

with boiling water,

stir,

and serve.

orange

cup coffee

1

tablespoon sugar (divided)

1

quart water

Vi

cup heavy cream

Procedure

1

Peel orange with a vegetable peeler into thin strips. Make the strips very thin, avoiding the bitter white underneath. Set aside / 3 of the peelings for garnish. l

2.

Cut the remaining

3.

Combine

4. 5.

7.

/3

of the peelings into large pieces.

the large pieces of orange peelings, the coffee, and

Prepare coffee using the indicated amount of water. Meanwhile, whip cream until it is almost thickened.

Add

in

1

Vi tsp. sugar.

remaining

has the appearance of whipped cream. Finish peeling orange and cut half of the orange into thin crosswise

Continue beating 6.

2

until

tsp. sugar.

it

of the orange

is

not needed.)

When

is

brewed, remove coffee basket and add orange

coffee

A

X

1

slices.

slices.

Let

it

(The other half

mellow 10

minutes before serving. 8.

and pour coffee into serving cup. Cover with approximately the whipped cream and garnish with an orange peel.

Remove orange

slices

41

Va

of

.

.

Hot Spiced Tea quart boiling water

1

cup sugar 10 whole cloves 2 cinnamon sticks 4 tea bags Va cup orange juice Va

tablespoon orange rind, grated Vi lemon, sliced thin and seeded 1

Procedure

1

Combine

the water, sugar, cloves, and

cinnamon

sticks in a saucepan.

2.

Boil the mixture for

3.

Remove from heat, add the tea bags, and steep for 4 minutes, covered. Remove tea bags, add last 3 ingredients, and place over low heat to keep warm. Hold

4.

below

1

minute.

the boiling point for about 5 minutes.

5.

Strain and serve in beverage cups.

d.

French Chocolate square bitter chocolate

1

Va

3

tablespoons water

A cup +

X

cup heavy cream, whipped

Vi 1

2 tablespoons sugar

quart milk, scalded

Procedure

1

Cook

the chocolate with water until thick, stirring as necessary to prevent sticking or

burning. 2. 3.

4.

e.

Add

the sugar and let the mixture boil up once. Remove from heat and cool. Fold whipped cream into cooled chocolate mixture. Place a heaping tablespoon of the chocolate-whipped-cream mixture in the bottom of a beverage cup. Fill the cup with hot milk. Serve at once.

Mexican Chocolate 2 cups milk 1

cinnamon

1

Vi

stick

square semisweet chocolate

42

.. ..

....

Procedure

Heat the milk and cinnamon slowly over low

1

heat, stirring occasionally to prevent

sticking.

When the When the

2.

3

milk

is

scalding hot, add the chocolate.

chocolate has melted, remove the mixture from the heat and beat vigorously

with a rotary beater. Serve in beverage cups, making sure that each cup

4.

is

topped with foam.

Study Questions

What is 95° C?

1

the effect

on brewed coffee

Why should the water used to make

2.

if

the temperature of the water

is

above or below 85-

drip coffee be boiling?

7.

Compare the contact time between water and grounds for the brewing methods What causes percolation to occur in a percolator? Name some factors which may influence the strength of brewed coffee. Why are coffee makers of glass or porcelain usually recommended? What contribution does caffeine make to the flavor of coffee?

8.

Why

3 4.

5 6.

would you expect

flavor differences

used.

between brewed and instant or freeze-dried

beverages?

What

9. 1

0.

1 1

is

the

1

3

14. 1

5

16. 1

7.

18.

tea.

on a package of tea? Which components of black tea contribute to the flavor of the beverage? Which components of black tea contribute to the color of the beverage? How did lemon juice affect the tea at room temperature? At refrigerator temperature? Why does tea become less cloudy when lemon juice is added?

How is the

size of the tea leaves designated

does tea change color when lemon juice is added? What is the difference between "chocolate" and "cocoa"?

Why

chocolate beverage looked the richest or darkest in color? chocolate beverage tasted the richest or darkest in color?

20.

Which Which

2

Why did the

19.

for steeping tea?

Was the temperature of the water in the preheated pots within the range recommended for brewing tea after 3 minutes of steeping? Compare the beverages made from green tea, black tea, and oolong tea, decaffeinated tea, and herbal

12.

optimum temperature

23.

commercial cocoa beverage have a reddish tint? What caused the differences in mouthfeel between the chocolate and cocoa beverages? What caused the homemade beverages to thicken? The commercial beverage?

24.

Why

1

22.

is

chocolate normally melted in a double boiler?

43

.

FATS AND OILS

A

wide variety of fats and oils are available in the marketplace. They are used in numerous food products, such as spreads for breads and bread products, as shortening or tenderizing ingredients in baked products, as ingredients in emulsions, as flavoring agents, as a source of energy and as a cooking medium

in deep-fat frying.

Fats do not boil.

At high temperature, fats decompose and may form a blue smoke. When this occurs, fats have reached their "smoke point." Smoke points of fats or oils used for high heat cooking, such as deep-fat frying, must be high enough to prevent decomposition of the fats during use. The smoke point is lowered by the presence of low molecular weight fatty acids in triglycerides, and by the presence of emulsifiers, free fatty acids, and food particles in the fat.

When

amount of fat absorbed by the food product should be minimized. Fat absorption is increased: by increasing the contact time of the food and the fat; by lack of a coating or breading on the food to form a physical barrier against the fat; by increasing the surface area of food exposed to the fat; and by increasing the proportion of fat, sugar or egg yolk in a batter. Increased fat absorption results in a less desirable fried product. Cooking methods such as sauteing and stir frying generally minimize the amount of fat absorbed by the deep-fat frying foods, the

foods.

In

many

products, substitutions can be

made

for part or all

of the

fats

and

oils.

Common

such as

by consumers include fruit purees such as applesauce. The use of flavored olive and sesame oils, is desirable in some products.

A.

Comparison of Selected Commercial Fat Products Used

substitutes used

as Spreads

Objectives

1

2. 3.

4.

To To To To

emphasize differences in composition of selected spreads. compare the spreadability of selected spreads. compare the flavor of selected spreads. compare the price of selected spreads.

44

oils,

Procedure

Obtain samples of each commercial spread available. Chill half of each spread for one-half hour in the refrigerator. Keep the spread

5.

6.

room

of each

temperature.

tablespoon of each chilled spread and each room temperature spread on fresh bread. Note the "spreadability" of each product. Taste each product, chilled and at room temperature. Compare flavor and mouthfeel.

Spread

4.

at

rest

V2

Using the labeling on the packages as a guide, compare the ingredients and value of the commercial products. Compare the price per pound of the commercial products. Product

nutritional

.

Recipe 2 medium-sized raw zucchini 54

Vi

cup all-purpose flour teaspoon salt

'

A teaspoon pepper

l

2 cups

oil

Procedure

1

2.

Wash

the zucchini.

Do

not peel.

Slice the zucchini into !/2-inch-thick circles.

3.

Combine

4.

Beat the egg and

5.

Heat the

6.

Dip half of the zucchini

the flour,

oil in a

salt,

and pepper.

set aside.

deep-fat fryer to

1

85°

C

(365°

F).

circles into the flour mixture, then into the beaten

egg and then

again into the flour mixture. 7. 8.

Fry the coated zucchini until lightly browned. Note the frying time. Fry the other half of the zucchini circles without the coating. Fry at 185° the

same amount of time

9.

Drain each batch of fried zucchini on paper towels.

10.

Note any differences

Type of Zucchini

in

C

(365° F) for

that the coated zucchini circles are fried.

appearance, texture, flavor and mouthfeel of the two batches.

Appearance

Recipe

V 3 cups

1

2

sifted all-purpose flour

teaspoons baking powder

1

/3

V*

teaspoon

Va

cup sugar

salt

4 teaspoons shortening

egg

1

milk

3 14 tablespoons

Procedure dry ingredients together.

1.

Sift

2.

Cream

3.

Blend

4.

Add the

the sugar and shortening. in the egg.

milk and dry ingredients alternately

to the

creamed mixture, blending well

after

each addition. 5.

Lightly flour a surface appropriate for rolling out the dough.

6.

Roll dough

Vi

inch thick with a lightly floured rolling pin.

Using a biscuit cutter, cut uniform circles out of the rolled dough. Cut each circle in half and then roll the halves into balls with lightly floured hands. Divide the doughnut holes into four groups of three. Weigh each group and record the group weight. Be sure to label each group so that no mix-ups occur.

7. 8.

9.

10. 11. 12. 13.

14. 15.

Heat the

oil in a

deep-fat fryer to 190°

C

(375°

F).

group of doughnut holes for 2 minutes (1 minute per side). Fry the Fry the second group for 4 minutes (2 minutes per side). Fry the third group for 6 minutes (3 minutes per side). Fry the fourth group for 10 minutes (5 minutes per side). Drain doughnut holes on paper towels after removing from the hot oil. Be sure to label them to avoid mix-ups. Allow them to cool and then reweigh each group of doughnut first

holes. 16.

Calculate both the weight gained in grams and the percentage of weight gained for each group.

Cooking Time (Minutes)

..

D.

Fritters

Objectives

To prepare and evaluate food products that are To become familiar with factors that influence

1

2.

deep-fat fried. fat

absorption by deep-fried products.

Recipe

1

cup all-purpose flour

1

Vi

Vi

teaspoons baking powder

teaspoon

salt

1

tablespoon granulated sugar (use only in

1

egg

Vi 1

Vi

fruit fritters)

cup milk tablespoon melted butter

cup drained, canned

(peaches, pears, fruit cocktail, crushed pineapple) or fresh, chopped

fruit

bananas, peaches, blueberries)

fruit (apples, pears,

OR Vi

cup drained, canned or cooked vegetables (corn,

oil for

carrots, onions)

deep-fat frying

Procedure

1

Put

oil into

a deep-fat fryer to the

line (or

fill

about three inches).

dry ingredients. Set aside.

2.

Sift together all the

3.

Place the egg in a small bowl.

4.

Add

5.

Using a

Add

the milk and melted butter and blend thoroughly.

the liquid ingredients to the dry ingredients

all at

once. Stir just enough to blend.

sieve, drain fruit or vegetables thoroughly. Press out

any excess liquid with a

spoon. 6.

Add

7.

Heat the

8.

Carefully spoon the

9.

Do

the fruit or vegetable. Blend with only four or five strokes. oil to

not fry

until the

190°

C

F).

fritter batter into

more than

second side

(375°

the hot

oil.

three fritters at one time. Fry until golden brown. is

golden brown.

Two

or three minutes

Turn and cook

on each side should be

adequate. 10.

Remove

the

cooked

fritters.

Drain well on paper towels. Keep

baking sheet in an oven preheated to 93.5°

48

C

(200°

F).

warm by

placing on a

.

E.

Stir

Fry and Saute Cooking Methods

Objectives

To compare methods of cooking with fats and To gain practice in stir frying and sauteeing.

1

2.

oils.

Recipe

Vi lb. 1

fresh green beans

small onion

A teaspoon A teaspoon

l

l

garlic

powder

salt

2 tablespoons

oil

Procedure

Chop washed green beans Heat

oil in a

to

A

l

1

lengths.

frying pan.

Add beans and cook with occasional Add remaining ingredients. Stir fry for

stirring.

about 4 min. until crisp and tender.

Transfer into serving dish.

Observe the appearance, flavor, and texture. Repeat, except use 1 ounce of margarine. Steam the washed and chopped beans for 5-6 minutes. Melt the margarine in a saucepan, add seasonings and toss with steamed beans.

Method of Cooking

.

Recipe

Vi

pound cucumbers pound tomatoes

V2

red onion

V2

teaspoon

Vi

salt

pinch black pepper Va

cup vinegar

Vi

cup corn

oil

OR olive oil

Procedure

1

Wash and

slice

2.

Slice tomatoes

cucumbers

A" thickness. and onions on cutting board.

3.

Place in large bowl.

4.

Combine

salt oil

to

l

mixing bowl. and vinegar alternately, mixing and pepper

in a

5.

Add

6.

Pour over salad

7.

Repeat, using olive

8.

Evaluate the salads for appearance, flavor, and texture.

corn

Salad Dressing

until

thoroughly combined.

oil.

Recipe

cup butter or margarine OR 2 squares baking chocolate !/2

V*

cup applesauce

cup sugar

1

2 eggs

A

teaspoon

Vi

cup flour

X

1

Vi

salt

teaspoons vanilla

Procedure Preheat oven to 350° F. Lightly grease an 8" or 9" pan.

Melt butter and chocolate. Add to sugar. Add the remaining ingredients, including applesauce as appropriate. Pour into pan. Bake for approximately 25-30 minutes, checking periodically for doneness.

Evaluate the brownies for appearance, flavor, and texture.

Fat or Fat Substitute

.

Recipe 3 1 3

/4

/4

cup

sifted flour

teaspoon

salt

V3 cup sugar

2 teaspoons baking

powder

2 eggs

A cup

l

shortening

OR A l

cup vegetable

oil

A cup milk 1

cup chopped cranberries or whole blueberries

Procedure

1

Preheat oven to 400°

2.

Sift together the flour, salt, sugar,

3.

Beat eggs

4.

Add

5.

Combine

F.

in a separate

Grease muffin

tins.

and baking powder.

bowl.

the milk and the shortening/oil to the eggs.

7.

the liquid and dry ingredients with a few strokes. Do not over-mix. Fold berries into batter before the dry ingredients are completely moist. 2 Fill muffin pans / 3 full. Bake 20-25 minutes.

8.

Evaluate muffins for appearance, flavor, and texture.

6.

Fat

...

..

Study Questions

1

What

2.

If

are the standard techniques for measuring plastic fats such as shortening?

you measured melted

3

before

it

had

solidified rather than after,

would you have more

Why?

fat or less?

Compare

fat

the calorie content of

1

00 grams of shortening,

1

00 grams butter and

1

00 grams

of regular margarine. spreadability of a commercial spread related to the composition of the fat?

How is the

4.

To

the temperature of the fat?

Compare

5.

the spreadability of regular butter and margarine with their

whipped

counterparts.

What advantages does

a margarine-butter blend offer?

How is energy transferred to foods fried in deep-fat? Why are foods cooked in deep-fat instead of water? What was

the effect of the coating on the appearance, flavor and mouthfeel of the fried

zucchini? 10. 1 1

12. 13.

Why were the zucchini sliced in circles rather than in small cubes? Why are both beaten egg and flour used to coat the zucchini rather than just flour alone? Why does increasing the amount of sugar in the batter affect the amount of browning? Why did the fruit or vegetables need to be well-drained before being mixed into the fritter batter?

14.

What

is

the difference between

compare with deep 1

5

1

6.

1

7.

1

8.

19.

stir

frying and sauteing?

How does the

fat

content

fat frying?

Which oil imparted the most pleasing flavor to the cucumber-tomato salad? What is the difference between monounsaturated and polyunsaturated oils?

When would you choose to use a flavored oil instead of vegetable Name other oils which impart a distinctive flavor to foods.

oil?

the differences in appearance, flavor, and texture between the brownies with fat and the brownies made with applesauce? What are the reasons for the

What were

made

differences?

21

What are other fat substitutes available to the consumer? What were the differences in appearance, flavor, and texture between the muffins made with shortening and the muffins made with oil? What are the reasons for the differences?

22.

Why does the muffin recipe

20.

state that the batter

53

should not be over-mixed?

.

EMULSIONS An

formed when one liquid is dispersed in another liquid with which it is ordinarily immiscible. Emulsions may be temporary, semi-permanent, or permanent depending on their stability. The stability of an emulsion is dependent on the particle size of the dispersed liquid and on the type of emulsifier present. An effective emulsifier must be a molecule which has both polar and non-polar ends. The non-polar end dissolves in the lipid phase and the polar end dissolves in the water phase of the emulsion. Emulsifiers aid in forming an emulsion both by decreasing the surface tension of the liquids, and by preventing the coalescence of dispersed droplets through the formation of a monomolecular layer of emulsifier around the droplets. emulsion

is

Emulsion

instability

emulsion.

Many

temperatures.

time during

emulsion beating.

A

its

may

is

evidenced by the separation of the two liquid phases,

emulsions are unstable

to repeated freezing

mayonnaise emulsion may break due

i.e.,

breaking of the

and thawing, and heating adding too

to over-beating,

formation, drying of the surface, freezing or heating.

A

to elevated

much

oil at

one

broken mayonnaise

be re-emulsified by adding the broken emulsion slowly to an egg yolk while

The broken emulsion

Egg yolk and milk

acts as the fat in the original preparation

of the mayonnaise.

are naturally occurring emulsions. Emulsions are also

formed during the

processing and preparation of many food products. These include peanut butter, margarine,

whipped topping, icings, puddings, sauces, gravies, mayonnaise, salad dressings, frozen desserts and beverages. Emulsions also are formed in sausages and baked products. A.

Commercial Products

Objectives

1

2.

To become familiar with selected commercial emulsion products. To compare flavor, appearance and ingredients of selected commercial emulsion products.

Procedure

1

2.

Using carrots and

stalk

of celery, prepare small sticks

to

be used for tasting.

Display a small dish of the following commercial products: mayonnaise; low-fat

mayonnaise; imitation mayonnaise; Miracle Whip; regular French dressing; low-calorie

French dressing. Display the containers next 3.

4.

Compare Compare

the

mayonnaise products

to the products.

for flavor, texture,

calories per serving for each product.

mayonnaise product. Compare each French dressing

appearance and ingredients.

Compare

the emulsifiers listed for each

for flavor, texture, appearance

calories per serving for each product.

Compare

dressing product.

54

and ingredients. Compare

the emulsifiers listed for each French

.

Compare Product

the price per ounce for

Appearance

all

Flavor

products.

Texture

Calories

Ingredients

Price ;

Per

Serving

Mayonnaise

Imitation

Mayonnaise

Low-Fat Mayonnaise

liracle

Whip

F rench Dressim

Low-Calorie

French Dressing

B.

Mavonnaise Variations

Objectives

1

2.

3.

To demonstrate the preparation of mayonnaise. To emphasize some factors that affect the stability and formation of emulsions. NOTE: Do not eat any of the mayonnaise variations which contain raw eggs.

55

Per

Ounce

...

.

Recipe

1

egg yolk

1

tablespoon vinegar or lemon juice

54

cup vegetable

V*

teaspoon

oil

salt

teaspoon dry mustard

1%

Vg teaspoon paprika Va

teaspoon sugar

Procedure

1

Put egg yolk into a small bowl.

2.

Add

3.

Beat with a rotary beater or hand mixer

4.

Add

seasonings and vinegar.

the oil

emulsion

is

until well blended.

by teaspoonfuls at the beginning of beating and then by tablespoonfuls as the formed. Each quantity of oil added should be thoroughly emulsified before

the next quantity of oil

is

added.

5.

Label and display the remaining mayonnaise for class discussion.

6.

Repeat Steps

1-6,

except use melted butter instead of vegetable

7.

Repeat Steps

1-6,

except use an egg white instead of the egg yolk. Leave out the spices.

8.

Repeat Steps

1-6,

except use

9.

Repeat Steps

1-4.

oil.

A cup oil. Cover and freeze some of the mayonnaise. Thaw and observe during 1

cup

oil

instead of

l

the next laboratory period. 10.

Prepare blender mayonnaise: a.

Substitute

b.

Put

c.

Pour

all

egg for the egg yolk;

1

ingredients except oil into a blender;

in oil in a

slow stream and continue blending

at

low speed

until all

of the

has been incorporated. 1 1

Label and display

C.

Repairing a "Broken" Emulsion

all

emulsions.

Objectives

1

2.

To observe a "broken" emulsion and become familiar with its characteristics. To demonstrate the technique of reforming an emulsion from a "broken" emulsion.

Procedure

1

Use

2.

Break an egg yolk

the

mayonnaise from Part

B

that

was prepared using egg

"broken" emulsion. into a

bowl and beat

it

slightly.

56

white. This should be a

oil

.

3.

..

Add

the broken emulsion slowly, a small

each addition

4.

Beat thoroughly after

5.

Label and display the emulsion.

D.

Salad Dressings

amount

at

a time, to the beaten egg yolk.

until emulsification is complete.

Objectives

1

familiar with the composition of various types of dressings used in salad

To become preparation.

2.

To prepare

various salad dressing emulsions.

Procedure

1

Prepare the salad dressing assigned.

3.

Determine the functions of each ingredient. Determine whether the emulsion is temporary, semi-permanent or permanent.

a.

French Dressing

2.

2

cup vegetable oil 73 cup wine or cider vinegar Va teaspoon salt /3

Va

teaspoon paprika

Va

teaspoon dry mustard

few grains cayenne pepper

1

Blend together

2.

Add

3.

Compare with commercial French dressing. Serve over tossed green salad.

4.

b.

all

dry ingredients.

the vinegar and the vegetable

oil.

Shake vigorously.

Easy Thousand Island Dressing

1

Yi Va

cup low

fat

mayonnaise

cup catsup - V3 cup sweet pickle

relish

mix

1

Combine

2.

Serve over tossed green salad or Chefs salad.

all

ingredients and

well.

57

..

Curried Sour Cream- Yogurt Dressing

cup low-fat cultured sour cream cup plain yogurt - 1 teaspoon curry powder

Vi

Vi Vi

2 tablespoons pineapple juice

1

Combine

2.

Serve over

all

ingredients and

fruit salad or

mix

well.

chicken salad.

Cooked Dressing 2 egg yolks 2 /3

cup milk

3

tablespoons fresh lemon juice or vinegar

1

tablespoon butter

1

Vi

Va,

tablespoons sugar

teaspoon

salt

2 tablespoons all-purpose flour Vi

teaspoon dry mustard

1

Mix

2.

Blend

together dry ingredients.

egg yolks and milk. Put the mixture into the top of a double boiler over boiling water and cook

3.

in slightly beaten

thick, stirring continuously.

5.

Remove from heat. Add the butter and lemon juice.

6.

Chill

4.

and use with Waldorf salad.

Waldorf Salad 3 apples, cored

A cup

l

1

Vi

and cubed, but not peeled

raisins

cup celery, diced cup chopped nuts of your choice

mix

1.

Lightly

2.

Add cooked

ingredients together.

dressing and

mix

well.

58

until

..

Studv Questions Define an emulsion.

What is the difference between an oil-in-water emulsion and What type of an emulsion is mayonnaise? What are the roles of the dry ingredients in mayonnaise? What is the role of the egg yolk in mayonnaise? What causes the mayonnaise to thicken? 8.

9. 1

0.

a water-in-oil emulsion?

Why must the oil be added slowly? How do mayonnaise, imitation mayonnaise,

low-fat mayonnaise, and Miracle

differ in composition? In calories? In price?

Which do you

How do

think

is

the best

Whip

buy

commercial mayonnaise products differ? preparation when melted butter was used mayonnaise on the

the emulsifiers in the various

What was

the effect

in place

of the oil? 1 1

12.

Compare Compare

mayonnaise prepared with egg yolk and egg white. the blender mayonnaise to the conventional method mayonnaise prepared with the

whole eggs. 13.

Why is

14.

Name some

it

not

recommended

to eat

any of the mayonnaise variations which contain raw

eggs?

1

5

16. 1

7.

How can

factors that can cause an

to "break."

a broken oil-in-water emulsion be re-established?

Does freezing influence the

How

emulsion

stability

of mayonnaise?

does the homemade French dressing compare

Why?

to the

commercial product? Account

for the differences. 18.

Which

ingredients in the cooked dressing function as emulsifying agents?

As thickening

agents?

W hy does the cooked dressing need to be heated? Why r

okay to eat? Why is there little danger of breaking the cooked dressing emulsion as it What ingredient(s) contribute fat to the cooked dressing?

59

is it

is

heated?

FRUITS AND VEGETABLES The

fruit

of a plant consists of one or more ripened ovaries together with flower parts that

may

be associated with the ovaries. The ripened ovary contains the seeds of the plant. Almost any other part of the plant

maybe

roots, tubers, flowers, sprouts

classified as a vegetable. Vegetables include leaves, stems, bulbs,

and seeds.

A wide variety of fruits and vegetables are available

in

the marketplace in fresh, canned, frozen and dried forms. Fresh fruits and vegetables are often

picked before optimum ripeness and are then stored under controlled atmosphere conditions.

The cut or bruised surfaces of many

fruits and vegetables are susceptible to enzymatic oxidative browning process, the oxidation of colorless polyphenols compounds present in fruits and vegetables is catalyzed by enzymes called polyphenolases (polyphenol oxidases). The resulting quinone is rearranged, undergoes oxidation and is polymerized to produce colored melanins. Enzymatic oxidative browning may be inhibited by lowering the pH, by addition of an antioxidant, by immersion in a dilute sodium chloride or a sugar syrup, or by blanching the fruit

browning. In

this

or vegetable.

Objectives of fruit and vegetable cooking include minimizing vitamin and mineral losses, maximizing the development of desirable textures, and maximizing the retention of characteristic desirable flavor compounds. Cooking results in both texture and flavor changes. The texture becomes less firm as structural tissues soften and pectic substances are hydrolyzed. Starch gelatinization also contributes to softening in starchy vegetables. The texture of cooked fruit is affected by the

medium

in

which the

fruit is

cooked. If the

fruit is

heated in water alone, water

diffuses into the fruit to equalize the differing solute concentrations. burst,

producing a

soft,

mushy

texture.

However, when

fruit is

The

fruit tissues

swell and

heated in a sugar syrup that

is

more concentrated than the cell sap, water diffuses out of the tissues. The loss of water results in shrinking of the fruit and produces a firm texture. Flavor changes in cooked fruits and vegetables depend on the time of cooking and on the specific cooking technique used. In general, a short cooking time will result in a more flavorful fruit or vegetable and also minimize the loss of nutrients.

60

..

.

A.

Enzymatic Oxidative Browning

Objectives

1

To observe

the effects of various treatments

on development of browning on the cut

surface of apples, potatoes and lettuce. 2. 3.

To explain the mechanism by which various treatments To compare browning tendencies of the selected foods.

inhibit oxidative

browning.

Procedure

(Granny Smith), a sweet apple (Red Delicious), a potato and some

1

Use

2.

iceberg lettuce leaves. Do not peel the apples or the potato. Prepare the solutions that you will need in Steps 8-10. Do not cut samples until after you

a tart apple

prepare solutions.

5.

Cut ten uniformly sized samples from the apples, potato and lettuce, leaving the peel on: The samples should fit into a custard cup. Put all fruit and vegetable samples into separate custard cups. Leave one set of samples (tart apple, sweet apple, potato, lettuce) exposed to air.

6.

Blanch one

7.

Cover one

3.

4.

of samples in boiling water for 2 minutes. of samples with orange juice and one with lemon juice. Determine the

set

set

of the juices with 8.

Cover one the

pH

set

pH

pH

paper.

of samples with a

of the solution with

pH

1% (W/V)

vitamin

paper. Sprinkle

C

(ascorbic acid) solution. Determine

powdered ascorbic acid on one

set

of

samples. 9.

10. 1 1

12.

Cover one set of samples with a 4% (W/V) sodium chloride solution. Cover one set of samples with a 50% (W/V) sucrose solution. Wrap one set of samples in plastic wrap. Then cover the samples, store in the refrigerator and observe again at the end of class. Record all observations. Note any changes in the peel of the apples and potato.

61

Observations

.

Procedure

1

Peel and core eight apples. Cut the apples into quarters.

2.

Heat 500 ml of water to boiling in a saucepan.

Add

eight of the apple quarters.

Simmer

until tender. 3.

Repeat Step

50 grams of sucrose in the boiling water before adding

2,

except dissolve

2,

except dissolve 500 grams of sucrose in the boiling water before adding

2,

except dissolve an amount of sugar substitute equivalent to 500 grams

1

the apples. 4.

Repeat Step the apples.

5.

Repeat Step (about 2

V2

cups) sucrose in the boiling water before adding the apples.

Cooking Medium

Appearance

..

.

V*

1

cup vanilla wafer crumbs

cup flour

1%

Va

teaspoon cinnamon

Va

cup melted butter

Mix

1

the sugar,

tablespoon flour,

salt

and lemon rind with the

fruit.

Put the mixture into a casserole dish. Bake at 232° C (450° F) for 10 minutes. Reduce the heat to 1 77° C (350° F) and top with a mixture of the crumbs,

2. 3.

4.

flour,

cinnamon and

3

/g

cup

butter.

Bake at 177° C (350° F) brown and crusty.

5.

b.

1

for

30 minutes or

until fruit is tender

and topping

is

Guacamole 2 ripe avocados, mashed

and finely chopped

1

ripe tomato, peeled

1

tablespoon fresh lime or lemon juice

Vz

teaspoon

salt

Tabasco sauce

to taste

2 tablespoons chopped onion

4 tablespoons canned green tortilla

1

2. 3.

chopped

chilies, finely

chips

Mash avocado

pulp well after peeling the avocados and removing the

Blend the avocado until smooth. Add the remaining ingredients. Mix

well. If a

smooth texture

is

pits.

desired, use a

blender to mix ingredients. 4.

c.

Serve with

tortilla chips.

Fruit Display

Display various unusual fresh

Suggested

fruits

and evaluate for appearance, texture, and

fruits include: pineapple, kiwi,

coconut, pomegranate, mango, papaya, star

fruit.

D.

Fresh Vegetables as Ingredients in Food Preparations

Objectives

1

2.

flavor.

To prepare and taste different types of fresh To demonstrate various cooking techniques

64

vegetables. for preparing fresh vegetables.

. .

Procedure

a.

Artichoke with Lemon-Butter Sauce

1

artichoke

Vi

lemon, sliced thinly

V*

cup butter

2 teaspoons

teaspoon

V2

lemon juice salt

water for cooking artichoke

Wash

1

the artichoke.

Trim

the stem and leaf tips. Place the artichoke in a saucepan

and water. Enough water should be used to keep the artichoke afloat. Toss lemon slices into the water. Cover the saucepan. Cook 30-45 minutes, until the underside of the artichoke is tender. Test with the with

2. 3.

tip

salt

of a sharp knife. cooking, prepare sauce by combining melted butter and

4.

While the artichoke lemon juice.

5.

Drain the artichoke and serve accompanied by the lemon-butter sauce. Dip the stem end of each leaf in sauce and scrape the tender part of the leaf with

6.

is

the teeth.

When

7.

all

the leaves have been eaten,

remove the choke

to

uncover the artichoke

bottom. Cut into pieces and dip in sauce.

b.

Braised Carrots and Leeks with Yogurt-Dill Sauce

8

medium

1

bunch leeks

carrots, peeled

and cut

into

%-inch slices

2 tablespoons butter salt 1

and pepper

to taste

cup plain yogurt

2 tablespoons chopped fresh Va

1

dill (or

dried

dill to taste)

cup chicken bouillon Peel and slice the carrots. Carefully clean the sand from the leeks. Cut the white portions of the leeks into bite-sized pieces. Discard the remainder of the leeks.

2. 3.

Saute carrot slices and leeks in butter for a minute or two over medium heat. Reduce heat to low. Add the bouillon and braise until the vegetables are tender.

and pepper,

4.

Season with

5.

Combine yogurt and

salt

dill.

if desired.

Just before serving, stir yogurt-dill mixture into

vegetable mixture.

65

c.

Spaghetti Squash with

1

spaghetti squash

1

onion, chopped

clove garlic, crushed

1 1

Tomato Sauce

5

ounces canned stewed tomatoes

12 ounces tomato sauce 1

teaspoon basil

1

teaspoon oregano

2 tablespoons olive 1

teaspoon

1

Vi

oil

salt

teaspoons sugar

pepper

to taste

1.

Cut squash

2.

Place over medium-high heat, cover and steam until tender.

in half length-wise. Place

each half into a large, deep saucepan

in 2-3

inches of water.

3.

While squash

is

cooking, saute onions and garlic in

oil in

a saucepan for 5

minutes. 4. 5.

Add the remaining ingredients and simmer until serving time. To serve, scoop out insides of the squash and place in a serving sauce over the squash,

d.

stir

and serve warm.

Steamed Parsnips 6 fresh parsnips, peeled and thinly sliced 3 tablespoons butter salt

and pepper

1.

Slice and peel parsnips.

2.

Cook

the sliced parsnips in water for

3.

Drain and add melted

4.

Add

salt

and pepper

1

5

butter, if desired.

to taste.

66

minutes or

until tender.

dish.

Pour tomato

.

Study Questions

1

Discuss the techniques used to prevent browning and explain the underlying mechanisms.

Which technique was most 2.

Explain

3.

Assuming would be more

4. 5.

browning? Why? Did both varieties of apples brown to the same extent? Explain. Compare the textural differences observed between apples cooked

7. 8.

effective in preventing

in

water and apples

How did the

apples cooked Account for these differences. with sugar substitute compare? Compare the appearance of cooked and raw apples. Why is there a difference? Why were lime juice and tomato added to the guacamole? Describe the texture and flavor of the various types of fresh vegetables and fruits tasted

cooked

6.

effective?

a grapefruit would not be used to illustrate enzymatic oxidative browning. that a solution of ascorbic acid and vinegar both have the same pH, which

why

in a sugar solution.

the laboratory.

67

in

.

FRUIT AND VEGETABLE PIGMENTS The pigments

in fruits and vegetables are divided into three classes on the basis of chemical and properties. These classes include chlorophyll, the carotenoids and the flavonoids. Chlorophyll and the carotenoid pigments are fat soluble, while the flavonoid pigments are water

structure

soluble.

The pH of the cooking medium and

determining the color of

fruits

the length of cooking time are and vegetables containing these pigments.

critical factors in

of heat and acid, the magnesium atom in the green chlorophyll molecule is replaced by two hydrogen atoms to form a molecule of olive-green pheophytin. The enzyme In the presence

chlorophyllase can hydrolyze the phytol side chain of chlorophyll and produce the bright-green compound called chlorophyllide. Chlorophyllin, an intense green compound, results when the phytol and the methyl ester side chains on the porphyrin ring of the chlorophyll molecule are hydrolyzed. This will occur if sodium bicarbonate is added during cooking of a green vegetable.

Carotenoid pigments range in color from pale yellow to orange-red and are relatively stable at acid or alkaline pH values. Carotenoid pigments include the carotenes and the xanthophylls.

Carotene pigments can range from pale yellow to red hues, depending on the arrangement of double bonds in the molecule. Examples of carotene pigments include beta-carotene in carrots and lycopene in tomatoes. Xanthophyll pigments are yellow in color.

Flavonoid pigments constitute a heterogeneous group of compounds which include anthocyanins and anthoxanthins. Flavonoids are sensitive to changes in pH and to the presence of some metals.

Anthocyanins change from red

in

an acid

medium

to blue in a

anthoxanthins change from white or cream-colored in an acid

more

alkaline environment, while

medium

to

yellow in a more

Examples of foods containing predominantly anthocyanin pigments are plums and grapes. Some foods which contain predominantly anthoxanthin pigments are potatoes, onions, cauliflower and turnips. alkaline environment.

cherries, blueberries, red cabbage, strawberries,

A.

Effects of Cooking Treatments

on Vegetable Pigments

Objectives

1

2.

To observe To observe

the effect of cooking time

on plant pigments.

the effects of acid and alkali on plant pigments.

Procedure

1.

2.

Clean fresh vegetables and cut into pieces of uniform size. Suggested vegetables include broccoli, carrots, red cabbage, and cauliflower. Divide each vegetable into 5 portions. Use one portion for each cooking method.

68

Use only

3.

Cook uncovered. Add

2 cups water. not

let

cooking vegetables. For each cooking method, use more water during cooking as water evaporates. Do

stainless steel saucepans for

vegetables boil dry.

Cooking methods:

4.

vegetable to 2 cups boiling water and boil for 1 minutes. vegetable to 2 cups boiling water and boil for 25 minutes.

b.

Add Add

c.

Microwave vegetables on

a.

with

1

for 3 minutes in a small covered casserole dish

tablespoon water added.

vegetables to 2 cups boiling water containing 2 teaspoons cream of tartar and

Add

d.

HIGH

boil for about 10 minutes.

vegetables to 2 cups boiling water containing

Add

e.

Vi

teaspoon baking soda and

boil for about 10 minutes.

After cooking, drain the liquid into a custard cup and determine the pH with pH paper. Display the cooking liquid. Place vegetables on a white plate for display. Label all

5.

samples. Evaluate appearance, texture, and flavor of vegetables. Note the color of the cooking

6.

liquid

Be

7.

Vegetable

and of the vegetable.

able to identify the predominant pigment in each sample.

-

Cooking Method

Broccoli

Appearance Veggie Liquid

10 min.

pHof

Texture

Explanation of

Flavor

Observations

Liquid

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25 min.

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Microwave

3 Soda

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