Drying Atlas: Drying Kinetics and Quality of Agricultural Products [1 ed.] 0128181621, 9780128181621

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Drying Atlas: Drying Kinetics and Quality of Agricultural Products [1 ed.]
 0128181621, 9780128181621

Table of contents :
Cover
DRYING ATLAS
Drying Kinetics and Quality of
Agricultural Products
Copyright
Preface
Biographies
Dr.-Ing. Dr. h.c. Werner Mühlbauer
Dr. Joachim Müller
Acknowledgments
Part 1: Production and processing
1.1
Production
Appropriate cultivars
Optimum stage of maturity [1–3]
Immature crops
Overripe crops
Fully mature crops
Production methods
Pre-treatments
References
1.2
Drying
General aspects
Drying parameters
Morphological characteristics
Diffusion path
Moisture content [6,8–10]
Thermal conductivity [6, 11–16]
Specific heat capacity [6, 11–17]
Density [11, 12, 17]
Thermal diffusivity [11–13, 17]
Drying methods
Sun drying
In-field drying [18, 19]
On-farm sun drying [20]
Solar drying [5, 21–29]
Solar tunnel dryer [26, 27]
Solar greenhouse dryer [5, 28]
Solar processing center [29]
Low-temperature drying [6, 8, 30–32]
High-temperature drying [6, 8, 33]
Batch dryers
Flat-bed dryer [6, 8]
Tray dryer [34, 35]
Recirculating batch dryer [6, 8]
Continuous flow dryer [6, 8]
Cross-flow dryer [6, 8, 36]
Mixed-flow dryer [6, 36, 37]
Multi-belt dryer [33, 38–42]
Tunnel dryer [40, 43]
Drum dryer [7, 9, 40, 44–47]
References
1.3
Storage and packaging
Storage conditions [6–12]
Storage methods
Bag storage [23–26]
Advantages
Disadvantages
Bulk storage [19, 27–30]
Advantages
Disadvantages
Packaging [34–36]
References
1.4
Quality
General aspects
Utilization of dried products
Quality standards
Multilateral standard setting organizations
Supranational standard setting organizations
National standard setting organizations (exemplarily)
Private industry and trade standards
Drying relevant parameters
Chemical composition
Important ingredients
References
Part 2: Drying and quality kinetics
2.1
Drying kinetics
Optimization strategies
Field testing
Simulation
Standardized drying method [1, 8–10]
Thin-layer laboratory dryer
Thin-layer drying curves [1, 9, 10]
Thin layer drying models [1, 8, 11–14]
Lewis/Newton model
Page model
Henderson/Pabis model
Two-term model
Logarithmic model
Midilli model
Thomson model
Wang and Singh model
Diamante et al. model
References
2.2
Quality kinetics
Impact of drying on quality
Optimization strategy [1]
Standardized procedure
Reaction kinetics [12–16]
References
Part 3: Cereals
3.1
Barley ( Hordeum vulgare L.)
Morphological characteristics [1–3] ( Fig. 3.1.1, Table 3.1.1)
Production
Optimum stage of maturity [9]
Production method [10]
Drying
Drying parameters ( Table 3.1.2)
Drying methods [7]
High-temperature drying
Storage
Storage conditions [7] ( Fig. 3.1.2)
Storage facilities [13, 14]
Quality
Utilization of dried products [15] ( Fig. 3.1.3)
Quality standards ( Table 3.1.3)
Drying relevant parameters
Chemical composition ( Table 3.1.4)
Important ingredients
Drying kinetics
Influence of temperature [24, 25] ( Figs. 3.1.4–3.1.6)
Influence of relative humidity [24, 25] ( Figs. 3.1.7 and 3.1.8)
Influence of air velocity [24, 25] ( Figs. 3.1.9 and 3.1.10)
Quality kinetics
Influence of the temperature [24] ( Fig. 3.1.11)
Recommendations
Major quality parameters
Production and processing
References
3.2
Maize ( Zea mays L.)
Morphological characteristics [1–4] ( Figs. 3.2.1 and 3.2.2, Table 3.2.1)
Production
Optimum stage of maturity [8]
Production methods [9]
Seed maize
Feed maize
Drying
Drying parameters ( Table 3.2.2)
Drying methods [6, 7, 10]
Maize cob drying
Maize kernel drying
Storage
Storage conditions [6] ( Figs. 3.2.3 and 3.2.4)
Storage facilities [10, 12]
Quality
Utilization of dried products [5] ( Figs. 3.2.5 and 3.2.6)
Quality standards ( Table 3.2.3)
Drying relevant parameters
Chemical composition ( Table 3.2.4)
Important ingredients
Drying kinetics
Drying of maize kernels
Influence of temperature [6] ( Figs. 3.2.7–3.2.9)
Influence of relative humidity [6] ( Fig. 3.2.10)
Influence of air velocity [6] ( Fig. 3.2.11)
Influence of initial moisture content [6] ( Fig. 3.2.12)
Drying of maize cobs
Influence of temperature [19] ( Fig. 3.2.13)
Quality kinetics
Seed maize
Influence of temperature [20] ( Fig. 3.2.14)
Influence of initial moisture content [20] ( Fig. 3.2.15)
Feed maize
Influence of temperature [6, 21] ( Figs. 3.2.16–3.2.19)
Influence of initial moisture content ( Fig. 3.2.20)
Maize for dry milling
Influence of temperature [22] ( Figs. 3.2.21–3.2.23)
Maize for wet milling
Influence of temperature [23] ( Figs. 3.2.24 and 3.2.25)
Recommendations
Production of maize cobs
Major quality parameter
Production and processing
Production of maize kernels
Major quality parameters
Production and processing
References
3.3
Oat ( Avena sativa L.)
Morphological characteristics [1–4] ( Fig. 3.3.1 and Table 3.3.1)
Production
Optimum stage of maturity
Production method [7, 8]
Drying
Drying parameters ( Table 3.3.2)
Drying methods [5]
Low-temperature in-storage drying
High-temperature drying
Storage [5]
Storage conditions ( Fig. 3.3.2)
Storage facilities
Quality
Utilization of dried products [10] ( Fig. 3.3.3)
Quality standards ( Table 3.3.3)
Drying relevant parameters
Chemical composition ( Table 3.3.4)
Important ingredients
Drying kinetics
Influence of temperature [17] ( Figs. 3.3.4–3.3.6)
Influence of relative humidity [17] ( Figs. 3.3.7 and 3.3.8)
Influence of air velocity [17] ( Figs. 3.3.9 and 3.3.10)
Quality kinetics
Recommendations
Major quality parameters
Production and processing
References
3.4
Rice ( Oryza sativa L.)
Morphological characteristics [1–3] ( Fig. 3.3.1 and Table 3.3.1)
Production
Optimum stage of maturity
General requirements
Traditional cultivars
High-yielding cultivars
Production methods [6–9]
Manual production
Mechanized production
Processing of paddy rice
Milling [10, 11]
Objectives
Method
Parboiling [11, 12]
Objectives
Method
Drying
Drying parameters ( Table 3.3.2)
Drying methods [15–18]
Sun drying
High-temperature drying
Storage
Storage conditions ( Figs. 3.3.2 and 3.3.3)
Storage facilities
Storage in bags [20, 21]
Storage in bulk [11, 22]
Quality
Utilization of dried products [5, 23] ( Figs. 3.3.4–3.3.6)
Quality standards ( Table 3.3.3)
Drying relevant parameters
Chemical composition ( Table 3.3.4)
Important ingredients
Drying kinetics
Influence of temperature [28] ( Figs. 3.3.7–3.3.9)
Influence of initial moisture content [28] ( Fig. 3.3.10)
Quality kinetics
Influence of temperature [28] ( Fig. 3.3.11)
Influence of final moisture content [28] ( Fig. 3.3.12)
Influence of initial and final moisture content [28] ( Fig. 3.3.13)
Recommendations
Major quality parameters
Production and processing
References
3.5
Rye ( Secale cereale L.)
Morphological characteristics [1, 2] ( Fig. 3.5.1 and Table 3.5.1)
Production
Optimum stage of maturity
Production method [5]
Drying
Drying parameters ( Table 3.5.2)
Drying methods [4]
Low-temperature in-storage drying
High-temperature drying
Storage [6]
Storage conditions ( Fig. 3.5.2)
Storage facilities
Quality
Utilization of dried products [8, 9] ( Fig. 3.5.3)
Quality standards ( Table 3.5.3)
Drying relevant parameters [4]
Chemical composition ( Table 3.5.4)
Important ingredients
Drying kinetics
Influence of temperature [4, 17] ( Figs. 3.5.4–3.5.9)
Influence of relative humidity [17] ( Figs. 3.5.10 and 3.5.11)
Influence of air velocity [17] ( Figs. 3.5.12 and 3.5.13)
Influence of initial moisture content [17] ( Fig. 3.5.14)
Quality kinetics
Seed rye
Influence of temperature [17] ( Figs. 3.5.15 and 3.5.16)
Influence of the product temperature [17] ( Figs. 3.5.17 and 3.5.18)
Bread rye
Influence of temperature [17] ( Figs. 3.5.19–3.5.22)
Influence of product temperature [17] ( Figs. 3.5.23 and 3.5.24)
Recommendations
Major quality parameters
Production and processing
References
3.6
Wheat ( Triticum L.)
Morphological characteristics [1–5] ( Fig. 3.6.1 and Table 3.6.1)
Production
Optimum stage of maturity [8]
Production method [9]
Drying
Drying parameters ( Table 3.6.2)
Drying methods [6, 7]
Low-temperature in-storage drying
High-temperature drying
Storage
Storage conditions ( Fig. 3.6.2)
Storage facilities [12, 13]
Quality
Utilization of dried products [14, 15]
Soft wheat ( Fig. 3.6.3)
Hard wheat (durum wheat)
Quality standards ( Table 3.6.3)
Drying relevant parameters
Chemical composition ( Table 3.6.4)
Important ingredients
Drying kinetics
Influence of temperature [6, 23] ( Figs. 3.6.4–3.6.6)
Influence of relative humidity [6, 23] ( Fig. 3.6.7)
Influence of air velocity [6] ( Fig. 3.6.8)
Influence of initial moisture content [6, 23] ( Fig. 3.6.9)
Quality kinetics
Seed wheat
Influence of temperature [6, 24] ( Fig. 3.6.10)
Influence of initial moisture content [6, 24] ( Figs. 3.6.11 and 3.6.12)
Bread wheat
Influence of temperature [6, 24] ( Figs. 3.6.13–3.6.16)
Influence of initial moisture content [6, 24] ( Fig. 3.6.17)
Recommendations
Major quality parameters
Production and processing
References
Part 4: Root crops
4.1
Cassava ( Manihot esculenta Crantz)
Morphological characteristics ( Figs. 4.1.1 and 4.1.2, Table 4.1.1)
Production
Optimum stage of maturity
Production methods
Food (gari) [4]
Animal feed (tapioca) [5]
Starch production [6]
Pre-treatments
Mechanical pre-treatment [1]
Objectives
Methods
Thermal pre-treatment [6]
Objectives
Methods
Chemical pre-treatment
Drying
Drying parameters ( Table 4.1.2)
Drying methods [8]
Sun drying
High-temperature drying
Storage
Storage conditions ( Fig. 4.1.3)
Storage facilities
Quality
Utilization of dried products [10, 11] ( Figs. 4.1.4–4.1.6)
Quality standards ( Table 4.1.3)
Drying relevant parameters
Chemical composition ( Table 4.1.4)
Important ingredients
Drying kinetics
Influence of temperature [19] ( Figs. 4.1.7 and 4.1.8)
Influence of relative humidity [19] ( Fig. 4.1.9)
Influence of air velocity [19] ( Figs. 4.1.10 and 4.1.11)
Influence of mechanical pre-treatment [19] ( Fig. 4.1.12)
Influence of slice thickness [19] ( Fig. 4.1.13 and 4.1.14)
Influence of thermal pre-treatment [19] ( Fig. 4.1.15)
Comparison of drying modes [19]
Influence of temperature
Through-flow drying ( Fig. 4.1.16)
Over-flow drying ( Figs. 4.1.17 and 4.1.18)
Influence of air velocity [19]
Through-flow drying ( Fig. 4.1.19)
Over-flow drying ( Figs. 4.1.20 and 4.1.21)
Quality kinetics
Influence of temperature [19] ( Figs. 4.1.22–4.1.26)
Influence of air velocity [19] ( Fig. 4.1.27)
Influence of thermal pre-treatment [19] ( Fig. 4.1.28)
Recommendations
Major quality parameters
Production and processing
References
4.2
Potato ( Solanum tuberosum L.)
Morphological characteristics ( Figs. 4.2.1 and 4.2.2, Table 4.2.1)
Production
Appropriate cultivars [7]
Optimum stage of maturity [8]
Production method [4, 9]
Pre-treatments
Mechanical pre-treatment
Objectives
Methods
Thermal pre-treatment [10, 11]
Objectives
Methods
Chemical pre-treatments [12]
Objectives
Methods
Drying
Drying parameters ( Table 4.2.2)
Drying methods [7, 12, 15]
Sun drying
High-temperature drying
Storage [16]
Storage conditions ( Fig. 4.2.3)
Storage facilities
Quality
Utilization of dried products [7, 18] ( Fig. 4.2.4)
Quality standards ( Table 4.2.3)
Drying relevant parameters
Chemical composition ( Table 4.2.4)
Important ingredients
Drying kinetics
Influence of temperature [21] ( Figs. 4.2.5 and 4.2.6)
Influence of air velocity [21] ( Figs. 4.2.7 and 4.2.8)
Influence of slice thickness [21] ( Figs. 4.2.9 and 4.2.10)
Influence of pre-treatment [21] ( Figs. 4.2.11 and 4.2.12)
Influence of cultivar [21] ( Fig. 4.2.13)
Quality kinetics
Influence of temperature [22] ( Figs. 4.2.14 and 4.2.15)
Influence of relative humidity [22] ( Figs. 4.2.16 and 4.2.17)
Influence of slice thickness [21] ( Figs. 4.2.18–4.2.20)
Influence of shape [21] ( Fig. 4.2.21)
Influence of pre-treatment [21] ( Figs. 4.2.22 and 4.2.23)
Influence of cultivar [21] ( Figs. 4.2.24–4.2.26)
Recommendations
Major quality parameters
Production and processing
References
Part 5: Oil crops
5.1
Coconut ( Cocos nucifera L.)
Morphological characteristics ( Figs. 5.1.1 and 5.1.2, Table 5.1.1)
Production
Optimum stage of maturity [3]
Production methods [2, 4]
Production of coconut halves
Production of copra pieces
Pre-treatment
Osmotic dehydration [5]
Drying
Drying parameters ( Table 5.1.2)
Drying methods [6, 7, 9–11]
Sun drying
High-temperature drying
Storage
Storage conditions ( Fig. 5.1.3)
Storage facilities [12]
Quality
Utilization of dried products [2] ( Figs. 5.1.4–5.1.6)
Quality standards ( Table 5.1.3)
Drying relevant parameters
Chemical composition ( Table 5.1.4)
Important ingredients
Drying kinetics
Influence of temperature [6] ( Figs. 5.1.7–5.1.9)
Influence of relative humidity [6] ( Figs. 5.1.10 and 5.1.11)
Influence of air velocity [6] ( Figs. 5.1.12 and 5.1.13)
Influence of nut orientation [6] ( Fig. 5.1.14)
Influence of mechanical pre-treatment and orientation on the drying time [6]
Influence of endosperm size and shape [6] ( Fig. 5.1.15)
Influence of the Shell [6] ( Fig. 5.1.16)
Quality kinetics
Influence of temperature [6] ( Figs. 5.1.17–5.1.21)
Recommendations
Major quality parameters
Production and processing
References
5.2
Peanut ( Arachis hypogaea L.)
Morphological characteristics [1] ( Figs. 5.2.1 and 5.2.2, Table 5.2.1)
Production [4]
Optimum stage of maturity
Production methods
Manual production
Mechanized production
Drying
Drying parameters ( Table 5.2.2)
Drying methods [5]
Sun drying
Low-temperature in-storage drying
High-temperature drying of pods
Storage [9]
Storage conditions ( Figs. 5.2.3 and 5.2.4)
Storage methods
Quality
Utilization of dried products [9] ( Figs. 5.2.5 and 5.2.6)
Quality standards ( Table 5.2.3)
Drying relevant parameter
Chemical composition ( Table 5.2.4)
Important ingredients
Drying kinetics
Drying of kernels
Influence of temperature [13] ( Fig. 5.2.7)
Influence of relative humidity [13] ( Fig. 5.2.8)
Influence of air velocity [13] ( Fig. 5.2.9)
Drying of kernel and hull [14] ( Fig. 5.2.10)
Quality kinetics
Influence of temperature [15] ( Fig. 5.2.11)
Recommendations
Major quality parameters
Production and processing
References
5.3
Rapeseed ( Brassica napus var. napus)
Morphological characteristics [1] ( Figs. 5.3.1 and 5.3.2, Table 5.3.1)
Production [3, 4]
Optimum stage of maturity
Production method
Drying
Drying parameters ( Table 5.3.2)
Drying methods [9, 10]
Low-temperature in-storage drying
High-temperature drying
Storage [10]
Storage conditions ( Fig. 5.3.3)
Storage facilities
Quality
Utilization of dried products [4, 5] ( Fig. 5.3.4)
Quality standards ( Table 5.3.3)
Drying relevant parameters
Chemical composition ( Table 5.3.4)
Important ingredients
Drying kinetics
Influence of temperature ( Figs. 5.3.5–5.3.8)
Influence of relative humidity [19] ( Figs. 5.3.9 and 5.3.10)
Influence of initial moisture content [18] ( Fig. 5.3.11)
Quality kinetics
Influence of temperature [20] ( Fig. 5.3.12)
Recommendations
Major quality parameters
Production and processing
References
5.4
Soybean ( Glycine max (L.) Merr.)
Morphological characteristics [1, 2] ( Figs. 5.4.1 and 5.4.2, Table 5.4.1)
Production [2]
Optimum stage of maturity
Production method
Drying
Drying parameters ( Table 5.4.2)
Drying methods [9]
Sun drying
Low-temperature in-storage drying
High-temperature drying
Storage [10–13] ( Fig. 5.4.3)
Storage conditions
Storage facilities
Quality
Utilization of dried products [15, 16] ( Fig. 5.4.4)
Quality standards ( Table 5.4.3)
Drying relevant parameters
Chemical composition ( Table 5.4.4)
Important ingredients
Drying kinetics
Influence of temperature [20] ( Figs. 5.4.5–5.4.7)
Influence of the relative humidity [20] ( Fig. 5.4.7)
Influence of initial moisture content [20] ( Fig. 5.4.8)
Quality kinetics
Influence of relative humidity [21] ( Fig. 5.4.9)
Influence of initial moisture content [21] ( Figs. 5.4.10 and 5.4.11)
Recommendations
Major quality parameters
Cultivation and processing
References
5.5
Sunflower ( Helianthus annuus L.)
Morphological characteristics ( Figs. 5.5.1 and 5.5.2, Table 5.5.1)
Production [4–7]
Optimum stage of maturity
Production methods
Manual production
Mechanized production
Drying
Drying parameters ( Table 5.5.2)
Drying methods [6, 10]
Sun drying
High-temperature dryings
Storage [6, 7, 11]
Storage conditions ( Figs. 5.5.3 and 5.5.4)
Storage facilities
Quality
Utilization of dried products [4] ( Figs. 5.5.5 and 5.5.6)
Quality standards ( Table 5.5.3)
Drying relevant parameters
Chemical composition ( Table 5.5.4)
Important ingredients
Drying kinetics
Influence of temperature [12] ( Figs. 5.5.7 and 5.5.8)
Influence of relative humidity [12] ( Figs. 5.5.9 and 5.5.10)
Quality kinetics
Influence of temperature ( Figs. 5.5.11 and 5.5.12)
Recommendations
Major quality parameters
Production and processing
References
Part 6: Vegetables
6.1
Carrot ( Daucus carota)
Morphological characteristics ( Figs. 6.1.1 and 6.1.2, Table 6.1.1)
Production
Appropriate properties [2]
Selection criteria
Optimum stage of maturity [3]
Production method [4]
Pre-treatments [5]
Objectives
Mechanical pre-treatment
Thermal pre-treatment [5–8]
Chemical pre-treatments [9, 10]
Osmotic dehydration [11]
Drying
Drying parameters ( Table 6.1.2)
Drying methods [5, 8]
High-temperature drying
Storage
Storage conditions [7, 13] ( Fig. 6.1.3)
Storage/Packaging facilities
Quality
Utilization of dried products [2] ( Figs. 6.1.4 and 6.1.5)
Quality standards ( Table 6.1.3)
Drying relevant parameter
Chemical composition ( Table 6.1.4)
Important ingredients
Drying kinetics
Influence of temperature ( Figs. 6.1.6–6.1.8)
Influence of air velocity [17] ( Fig. 6.1.9)
Influence of shape [17] ( Fig. 6.1.10)
Influence of pre-treatments [17] ( Fig. 6.1.11)
Quality kinetics
Influence of temperature ( Figs. 6.1.12–6.1.16)
Influence of relative humidity [19] ( Figs. 6.1.17 and 6.1.18)
Recommendations
Major quality parameters
Production and processing
References
6.2
Paprika ( Capsicum annuum, C. frutescens)
Morphological characteristics ( Figs. 6.2.1 and 6.2.2, Table 6.2.1)
Production
Optimum stage of maturity [2]
Production method [3]
Pre-treatments [4, 5]
Objectives
Mechanical pre-treatment
Thermal pre-treatment [5, 6]
Chemical pre-treatment [7, 8]
Drying
Drying parameters ( Table 6.2.2)
Drying methods [10, 11]
Sun drying
Solar drying
High-temperature drying
Storage
Storage conditions [12] ( Figs. 6.2.3–6.2.6)
Powder—Flakes
Halved Pods—Stripes—Slices
Storage facilities [10, 11]
Powder—Flakes
Halved Pods—Stripes—Slices
Quality
Utilization of dried products [3] ( Figs. 6.2.7 and 6.2.8)
Quality standards ( Table 6.2.3)
Drying relevant parameters
Chemical composition ( Table 6.2.4)
Pungent components
Carotenoids [17]: 0.1–0.8%
Important ingredients
Drying kinetics
Influence of temperature [18] ( Figs. 6.2.9 and 6.2.10)
Influence of the shape [18] ( Fig. 6.2.11)
Influence of slice width [18] ( Fig. 6.2.12)
Comparison of thermal and chemical pre-treatments [18] ( Fig. 6.2.13)
Influence of the chemical pre-treatment [18] ( Fig. 6.2.14)
Influence of Cultivar [18] ( Fig. 6.2.15)
Quality kinetics
Influence of temperature [18] ( Figs. 6.2.16 and 6.2.17)
Influence of temperature on retention [19] ( Figs. 6.2.18 and 6.2.19)
Influence of thermal and chemical pre-treatments [18] ( Fig. 6.2.20)
Recommendations
Major quality parameters
Production and processing
References
6.3
Tomato ( Solanum lycopersicum L.)
Morphological characteristics [1] ( Figs. 6.3.1 and 6.3.2, Table 6.3.1)
Production
Appropriate properties [4]
Optimum stage of maturity [5, 6]
Production methods [3]
Pre-treatments
Objectives
Ripening [1, 6]
Mechanical pre-treatment
Thermal pre-treatments [7]
Chemical pre-treatments [8, 9]
Drying
Drying parameters ( Table 6.3.2)
Drying methods [4, 12]
Sun drying
High-temperature drying
Storage
Storage conditions [13]  ( Fig. 6.3.3)
Storage facilities
Halved or sliced tomato
Tomato powder [7]
Quality
Utilization of dried products [3] ( Fig. 6.3.4)
Quality standards ( Table 6.3.3)
Drying relevant parameters
Chemical composition ( Table 6.3.4)
Important ingredients
Drying kinetics
Through-flow drying
Influence of temperature [16] ( Figs. 6.3.5–6.3.7)
Influence of air velocity [16] ( Figs. 6.3.8 and 6.3.9)
Influence of mechanical treatment [16] ( Fig. 6.3.10)
Influence of maturity stage [16] ( Fig. 6.3.11)
Over-flow drying
Influence of temperature [4] ( Figs. 6.3.12–6.3.14)
Influence of relative humidity [4] ( Figs. 6.3.15 and 6.3.16)
Influence of air velocity [4] ( Figs. 6.3.17 and 6.3.18)
Influence of mechanical treatment [4] ( Fig. 6.3.19)
Influence of cultivar [4] ( Figs. 6.3.20 and 6.3.21)
Comparison through-flow and over-flow drying [4]
Influence of temperature [4] ( Fig. 6.3.22)
Influence of relative humidity [4] ( Fig. 6.3.23)
Influence of air velocity [4] ( Fig. 6.3.24)
Quality kinetics
Influence of temperature [4] ( Figs. 6.3.25 and 6.3.26)
Influence of relative humidity [4] ( Fig. 6.3.27)
Influence of air velocity [4] ( Fig. 6.3.28)
Recommendations
Major quality parameters
Production and processing
References
Part 7: Spices
7.1
Chili ( Capsicum annuum L.)
Morphological characteristics ( Figs. 7.1.1 and 7.1.2, Table 7.1.1)
Production
Optimum stage of maturity [3, 4]
Production method
Pre-treatments [3, 5, 6]
Objectives
Mechanical pre-treatment
Thermal pre-treatment [7]
Chemical pre-treatments [8]
Osmotic treatments [9]
Drying
Drying properties ( Table 7.1.2)
Drying methods
Sun drying
Solar drying [12]
High-temperature drying [13, 14]
Storage
Storage conditions [14, 15] ( Figs. 7.1.3–7.1.5)
Storage/Packaging facilities
Quality
Utilization of dried products [1] ( Figs. 7.1.6 and 7.1.7)
Quality standards ( Table 7.1.3)
Drying relevant parameters
Chemical composition ( Table 7.1.4)
Important ingredients
Drying kinetics
Influence of temperature [22] ( Figs. 7.1.8–7.1.10)
Influence of the size [22] ( Fig. 7.1.11)
Influence of mechanical pre-treatment [23] ( Fig. 7.1.12)
Influence of chemical pre-treatment [23] ( Fig. 7.1.13)
Influence of cultivar [23] ( Fig. 7.1.14)
Quality kinetics
Influence of drying air temperature ( Figs. 7.1.15–7.1.20)
Green chili pods [23]
Influence of pre-treatment ( Figs. 7.1.21–7.1.23)
Recommendations
Major quality parameters red chilis
Spice
Medicine
Production and processing
References
7.2
Garlic ( Allium sativum L.)
Morphological characteristics ( Figs. 7.2.1 and 7.2.2, Table 7.2.1)
Production [3–6]
Appropriate properties
Optimum stage of maturity [7]
Production method [7]
Pre-treatments
Objectives
Mechanical pre-treatment
Thermal pre-treatment [8]
Chemical pre-treatments [9]
Drying
Drying parameters ( Table 7.2.2)
Drying methods [12]
Sun drying
High-temperature drying
Storage [13]
Storage conditions ( Fig. 7.2.3)
Storage facilities [12]
Quality
Utilization of dried products [1, 2] ( Fig. 7.2.4)
Quality standards ( Table 7.2.3)
Drying relevant parameter ( Table 7.2.4)
Chemical composition
Important ingredients
Drying kinetics
Drying of garlic cloves [19] ( Figs. 7.2.5–7.2.7)
Drying of garlic slices
Influence of temperature [20] ( Fig. 7.2.8)
Influence of relative humidity [20] ( Fig. 7.2.9)
Influence of slice thickness [21] ( Fig. 7.2.10)
Quality kinetics
Garlic cloves [19]
Influence of temperature ( Figs. 7.2.11 and 7.2.12)
Garlic slices
Influence of temperature [22] ( Fig. 7.2.13)
Recommendations
Major quality parameters
Production and processing
References
7.3
Onion ( Allium cepa L.)
Morphological characteristics ( Figs. 7.3.1–7.3.3, Table 7.3.1)
Production
Appropriate properties [1–3]
Optimum stage of maturity [3]
Production method [3]
Post-ripening process
Pre-treatment
Objectives
Mechanical pre-treatments
Thermal pre-treatments [4]
Chemical pre-treatment [5, 6]
Osmotic pre-treatment [7]
Drying
Drying parameters ( Table 7.3.2)
Drying methods [2, 9]
Sun drying
High-temperature drying
Storage [10]
Storage conditions ( Fig. 7.3.4)
Storage facilities
Quality
Utilization of dried products ( Fig. 7.3.5)
Quality standards ( Table 7.3.3)
Drying relevant parameters
Chemical composition ( Table 7.3.4)
Important ingredients
Drying kinetics
Influence of temperature [14] ( Figs. 7.3.6–7.3.8)
Influence of relative humidity [14] ( Figs. 7.3.9 and 7.3.10)
Influence of air velocity [14] ( Figs. 7.3.11 and 7.3.12)
Influence of slice thickness [14] ( Figs. 7.3.13 and 7.3.14)
Influence of cultivar [14] ( Fig. 7.3.15)
Influence of drying mode [14] ( Figs. 7.3.16–7.3.18)
Quality kinetics [14, 15]
Influence of temperature ( Figs. 7.3.19–7.3.23)
Influence of relative humidity [14, 15] ( Fig. 7.3.24)
Influence of air velocity [14] ( Fig. 7.3.25)
Influence of slice thickness [14] ( Figs. 7.3.26–7.3.28)
Recommendations
Major quality parameters
Production and processing
References
Part 8: Stimulants
8.1
Cocoa ( Theobroma cacao L.)
Morphological characteristics [1] ( Figs. 8.1.1–8.1.3 and Table 8.1.1)
Production
Optimum stage of maturity
Production method [4]
Fermentation [5–7]
Objectives
Anaerobe fermentation
Aerobe fermentation
Fermentation methods
Drying
Drying parameters ( Table 8.1.2)
Drying methods
Sun drying [4, 7, 8]
Solar drying [7–9]
High-temperature drying [6, 8]
Storage [10]
Storage conditions ( Fig. 8.1.4)
Storage facilities [12]
Quality
Utilization of dried products [4] ( Fig. 8.1.5)
Quality standards ( Table 8.1.3)
Drying relevant parameters
Sun drying
High-temperature drying
Chemical composition ( Table 8.1.4)
Important ingredients
Drying kinetics
Influence of temperature [8] ( Figs. 8.1.6 and 8.1.7)
Influence of relative humidity [8] ( Fig. 8.1.8)
Influence of air velocity [8] ( Figs. 8.1.9 and 8.1.10)
Influence of pH-value [8] ( Fig. 8.1.11)
Quality kinetics
Influence of the temperature [16] ( Figs. 8.1.12 and 8.1.13)
Recommendations
Major quality parameters
Production and processing
References
8.2
Coffee (Coffea L., Rubiaceae)
Morphological characteristics (Figs. 8.2.1–8.2.3 and Table 8.2.1)
Production
Optimum stage of maturity [7]
Production methods
Harvesting methods [1]
Dry processing [1, 8, 9]
Wet processing [1, 8, 9]
Drying
Drying parameters (Table 8.2.2)
Drying methods [1, 8]
Sun drying cherries
High-temperature drying beans
Storage [1, 12, 13]
Storage conditions (Figs. 8.2.4 and 8.2.5)
Storage facilities
Quality
Utilization of dried products [1] (Figs. 8.2.6–8.2.8)
Quality standards (Table 8.2.3)
Organoleptic characteristics
Drying relevant parameters
Chemical composition (Table 8.2.4)
Important ingredients
Drying kinetics
Drying of coffee cherries
Influence of temperature [20] (Figs. 8.2.9 and 8.2.10)
Influence of air velocity [20] (Fig. 8.2.11)
Drying of coffee beans
Influence of temperature [20] (Figs. 8.2.12 and 8.2.13)
Influence of relative humidity [20] (Figs. 8.2.14 and 8.2.15)
Influence of air velocity [20] (Figs. 8.2.16 and 8.2.17)
Comparison dry and wet processing [20] (Fig. 8.2.18)
Quality kinetics
Dry processing
Influence of temperature [20] (Figs. 8.2.19 and 8.2.20)
Wet processing
Influence of temperature (Figs. 8.2.21–8.2.23)
Comparison dry and wet processing [20] (Figs. 8.2.24–8.2.27)
Recommendations
Major quality parameters
Production and processing
References
Part 9: Fruits
9.1
Apple (Malus domestica Borkh.)
Morphological characteristics (Figs. 9.1.1 and 9.1.2, Table 9.1.1)
Production
Appropriate cultivars
Selection criteria
Sweet varieties
Sour varieties
Optimum stage of maturity [3, 4]
Production methods
Pre-storage [5]
Objectives
Cold storage
Controlled atmosphere storage
Pre-treatments [6]
Objectives
Mechanical pre-treatment
Thermal pre-treatments
Chemical pre-treatments
Osmotic dehydration [7]
Drying
Drying parameters (Table 9.1.2)
Drying methods [8]
High-temperature drying
Storage
Storage conditions [10, 11] (Fig. 9.1.3)
Storage facilities
Quality
Utilization of dried products [1] (Figs. 9.1.4–9.1.7)
Quality standard (Table 9.1.3)
Drying relevant parameters
Chemical composition (Table 9.1.4)
Important ingredients
Drying kinetics
Influence of temperature [15] (Figs. 9.1.8 and 9.1.9)
Influence of relative humidity [16] (Figs. 9.1.10 and 9.1.11)
Influence of air velocity [15] (Figs. 9.1.12 and 9.1.13)
Influence of slice thickness [15] (Figs. 9.1.14 and 9.1.15)
Influence of cultivar [15] (Fig. 9.1.16)
Influence of chemical pre-treatment [15] (Fig. 9.1.17)
Quality kinetics (Fig. 9.1.18)
Influence of temperature (Figs. 9.1.19–9.1.22)
Influence of relative humidity (Figs. 9.1.23 and 9.1.24)
Influence of air velocity [15] (Fig. 9.1.25)
Influence of slice thickness [15] (Fig. 9.1.26)
Influence of chemical pre-treatment [15] (Fig. 9.1.27)
Recommendations
Major quality parameters
Production and processing
References
9.2
Apricot ( Prunus armeniaca L.)
Morphological characteristics ( Figs. 9.2.1 and 9.2.2, Table 9.2.1)
Production
Appropriate cultivars
Selection criteria
Cultivars [5]
Optimum stage of maturity [1, 5, 6]
Production methods [7]
Whole fruits
Halved fruits
Pre-treatments [1, 2, 7–9]
Objectives
Mechanical pre-treatments
Chemical pre-treatments
Gaseous sulfuring [7]
Liquid sulfuring [9, 10]
Drying
Drying parameters ( Table 9.2.2)
Drying methods [2]
Sun drying
Solar drying
High-temperature drying
Storage
Storage conditions [13] ( Fig. 9.2.3)
Storage facilities
Quality
Utilization of dried products [2] ( Figs. 9.2.4–9.2.6)
Quality standards ( Table 9.2.3)
Drying relevant parameters
Chemical composition ( Table 9.2.4)
Important ingredients
Drying kinetics
Influence of temperature [2] ( Figs. 9.2.7 and 9.2.8)
Influence of relative humidity [2] ( Figs. 9.2.9 and 9.2.10)
Influence of air velocity [2] ( Figs. 9.2.11 and 9.2.12)
Influence of fruit size [2] ( Figs. 9.2.13 and 9.2.14)
Influence of cultivar [2] ( Fig. 9.2.15)
Influence of chemical pre-treatment [2] ( Fig. 9.2.16)
Quality kinetics
Influence of temperature [2] ( Figs. 9.2.17 and 9.2.18)
Influence of relative humidity [2] ( Figs. 9.2.19 and 9.2.20)
Influence of sulfuring method [19] ( Fig. 9.2.21)
Influence of cultivar on reconstitution kinetics [2] ( Fig. 9.2.22)
Recommendations
Major quality parameters
Production and processing
References
9.3
Banana ( Musa × paradisiaca)
Morphological characteristics [1] ( Figs. 9.3.1 and 9.3.2, Table 9.3.1)
Production
Appropriate cultivars
General selection criteria
Production of whole fruits
Production of slices
Cultivars for banana drying
Production of whole fruits
Production of slices
Production methods
Dried whole fruits [3]
Dried slices [4]
Ripening [5, 6]
Optimum ripening stage [7]
Natural ripening
Ripening with accelerators
Pre-treatments
Drying of whole fruits
Objectives
Mechanical pre-treatment
Fermentation [3]
Objectives
Method
Drying of slices
Objectives
Mechanical pre-treatments
Chemical pre-treatments [8, 9]
Osmotic treatment [10]
Drying
Drying parameters ( Table 9.3.2)
Drying methods [12]
Drying of whole fruits
Sun drying
Solar drying [3, 13]
High-temperature drying [14]
Drying of slices [4]
High-temperature drying
Storage
Storage conditions ( Fig. 9.3.3)
Storage—Packaging methods
Quality
Utilization of dried products [16, 17] ( Figs. 9.3.4–9.3.6)
Quality standards ( Table 9.3.3)
Drying dependent parameters
Chemical composition ( Table 9.3.4)
Important ingredients
Drying kinetics
Drying of slices
Influence of temperature [20] ( Figs. 9.3.7 and 9.3.8)
Influence of air velocity [20] ( Figs. 9.3.9 and 9.3.10)
Influence of the shape [20] ( Fig. 9.3.11)
Drying of whole fruits
Influence of temperature [14] ( Figs. 9.3.12 and 9.3.13)
Influence of relative humidity [14] ( Fig. 9.3.14)
Quality kinetics
Drying of slices
Influence of temperature [21] ( Figs. 9.3.15 and 9.3.16)
Influence of relative humidity [21] ( Figs. 9.3.17 and 9.3.18)
Drying of whole fruit
Influence of temperature [22] ( Figs. 9.3.19 and 9.3.20)
Influence of moisture content [22] ( Fig. 9.3.21)
Recommendations
Production of dried banana slices
Major quality parameters
Production and processing
Production of dried whole fruits
Major quality parameters
Production and processing
References
9.4
Fig ( Ficus carica L.)
Morphological characteristics [1] ( Figs. 9.4.1 and 9.4.2, Table 9.4.1)
Production
Appropriate cultivars
Objectives
Cultivars [5]
Optimum stage of maturity [6]
Production method [7]
Ripening [8]
Pre-treatments
Objectives
Thermal pre-treatment [9, 10]
Chemical pre-treatments [9, 10]
Osmotic pre-treatment [11, 12]
Drying
Drying parameters ( Table 9.4.2)
Drying methods [15]
Sun drying
High-temperature drying
Storage
Storage conditions [16] ( Fig. 9.4.3)
Storage methods
Quality
Utilization of dried products ( Fig. 9.4.4)
Quality standards ( Table 9.4.3)
Drying relevant parameters
Chemical composition ( Table 9.4.4)
Important ingredients
Drying kinetics
Drying of whole fruits
Influence of temperature [22] ( Figs. 9.4.5 and 9.4.6)
Influence of air velocity [22] ( Fig. 9.4.7)
Influence of relative humidity [22] ( Fig. 9.4.8)
Drying of halved fruits
Influence of temperature [23] ( Figs. 9.4.9 and 9.4.10)
Influence of air velocity [23] ( Fig. 9.4.11)
Influence of pre-treatment [10] ( Fig. 9.4.12)
Quality kinetics
Influence of pre-treatment [10] ( Figs. 9.4.13–9.4.16)
Recommendations
Major quality parameters
Production and processing
References
9.5
Grape ( Vitis vinifera L.)
Morphological characteristics [1] ( Figs. 9.5.1 and 9.5.2, Table 9.5.1)
Production [5]
Appropriate cultivars
Selection criteria
Thompson sultana seedless (sultanas)
Zante black currant (currants)
Malaga Muscat grapes
Optimum stage of maturity [5]
Production method [5]
Pre-treatments
Objectives
Thermal pre-treatments [6]
Chemical pre-treatments [5, 7]
Drying
Drying parameters ( Table 9.5.2)
Drying methods [5]
Sun drying
High-temperature drying
Storage
Storage conditions ( Fig. 9.5.3)
Storage facilities
Quality
Utilization of dried products [5] ( Figs. 9.5.4–9.5.7)
Quality standards ( Table 9.5.3)
Drying relevant parameters
Chemical composition ( Table 9.5.4)
Important ingredients
Drying kinetics
Influence of temperature [5] ( Figs. 9.5.8–9.5.10)
Influence of relative humidity [5] ( Fig. 9.5.11)
Influence of air velocity [5] ( Figs. 9.5.12 and 9.5.13)
Influence of size [5] ( Fig. 9.5.14)
Influence of chemical pre-treatment [5] ( Fig. 9.5.15)
Quality kinetics
Influence of temperature ( Figs. 9.5.16–9.5.18)
Recommendations
Major quality parameter of sultana raisins
Cultivation and processing
References
9.6
Litchi ( Litchi chinensis Sonn.)
Morphological characteristics [1] ( Figs. 9.6.1 and 9.6.2, Table 9.6.1)
Production
Appropriate cultivars
Selection criteria [5]
Optimum stage of maturity [2, 6–8]
Production methods
Dried whole fruits [1, 9]
Dried flesh [1, 5, 9]
Pre-treatments
Objectives
Mechanical pre-treatments
Thermal pre-treatment [10]
Chemical pre-treatments [10]
Osmotic dehydration of flesh [11]
Objectives
Method
Drying
Drying parameters ( Table 9.6.2)
Drying methods [5, 12]
Whole fruit
Flesh
Storage [13]
Storage conditions ( Fig. 9.6.3)
Whole fruit
Flesh
Storage facilities
Whole fruit
Flesh
Quality
Utilization of dried products ( Figs. 9.6.4 and 9.6.5)
Quality standards ( Table 9.6.3)
Drying relevant parameters
Chemical composition ( Table 9.6.4)
Important ingredients
Drying kinetics
Drying of whole stoned fruit
Influence of temperature [10] ( Figs. 9.6.6 and 9.6.7)
Influence of fruit size [10] ( Fig. 9.6.8)
Influence of chemical pre-treatments [10] ( Figs. 9.6.9–9.6.12)
Influence of thermal pre-treatment [10] ( Fig. 9.6.13)
Drying of flesh
Influence of temperature [17] ( Figs. 9.6.14 and 9.6.15)
Quality kinetics
Drying of whole stoned fruit
Influence of temperature [10] ( Figs. 9.6.16–9.6.18)
Influence of pre-treatment ( Fig. 9.6.19)
Drying of flesh
Influence of temperature [17] ( Figs. 9.6.20 and 9.6.21)
Recommendations
Production of dried whole fruits
Major quality parameters
Production and processing
Production of fruit flesh
Major quality parameters
Production and processing
References
9.7
Longan ( Dimocarpus longan Lour.)
Morphological characteristics ( Figs. 9.7.1 and 9.7.2, Table 9.7.1)
Production
Appropriate cultivars [2]
Selection criteria
Optimum cultivar
Optimum stage of maturity [3, 4]
Production method [5, 6]
Production dried whole fruits
Production dried flesh
Pre-treatments of Longan flesh
Objectives
Mechanical pre-treatment
Chemical pre-treatment
Drying
Drying parameters ( Table 9.7.2)
Drying methods [2, 7]
Drying whole fruit
High-temperature drying
Drying flesh
High-temperature drying
Storage [8]
Storage conditions ( Figs. 9.7.3–9.7.7)
Whole fruits
Flesh
Storage/packaging facilities
Whole fruits
Flesh
Quality
Utilization of dried products [10] ( Figs. 9.7.8 and 9.7.9)
Quality standards ( Tables 9.7.3 and 9.7.4)
Drying relevant parameters
Chemical composition ( Table 9.7.5)
Important ingredients
Drying kinetics
Drying of whole fruits [1]
Influence of temperature ( Figs. 9.7.10 and 9.7.11)
Influence of relative humidity [1] ( Fig. 9.7.12)
Influence of the air velocity [1] ( Fig. 9.7.13)
Influence of fruit size [1] ( Figs. 9.7.14 and 9.7.15)
Drying of the flesh
Influence of temperature [15] ( Fig. 9.7.16)
Comparison of components [1] ( Fig. 9.7.17)
Quality kinetics
Drying of whole fruit
Influence of temperature [16] ( Figs. 9.7.18 and 9.7.19)
Drying of flesh [17]
Influence of temperature ( Figs. 9.7.20–9.7.23)
Recommendations
Production of whole dried fruits
Major quality parameters
Production and processing
Production of dried fruit flesh
Major quality parameters
Production and processing
References
9.8
Mango ( Mangifera indica L.)
Morphological characteristics [1] ( Figs. 9.8.1 and 9.8.2, Table 9.8.1)
Production
Appropriate cultivars
Selection criteria
Cultivars
Production methods
Mango slices [3, 4]
Mango leather [5]
Ripening [6–9]
Traditional ripening method
Artificial ripening
Optimum stage of maturity
Production of sliced mango [8, 9]
Production of mango leather [5]
Pre-treatments [6]
Objectives
Mechanical pre-treatments
Mango slices
Mango leather
Thermal pre-treatment
Chemical pre-treatments
Osmotic dehydration [10–12]
Objectives
Osmotic treatment
Drying
Drying parameters ( Table 9.8.2)
Drying methods
Drying mango slices
Sun drying
Solar drying [15]
High-temperature drying [16]
Drying mango leather [5]
High-temperature drying
Storage
Storage conditions ( Fig. 9.8.3)
Storage facilities
Mango slices
Mango leather [18]
Quality
Utilization of dried products ( Figs. 9.8.4–9.8.6)
Quality standards ( Table 9.8.3)
Drying relevant parameters
Chemical composition ( Table 9.8.4)
Important ingredients
Drying kinetics
Drying of mango slices
Influence of temperature [21] ( Figs. 9.8.7 and 9.8.8)
Influence of relative humidity [21] ( Figs. 9.8.9 and 9.8.10)
Influence of air velocity [21] ( Figs. 9.8.11 and 9.8.12)
Influence of slice thickness [21] ( Figs. 9.8.13 and 9.8.14)
Influence of shape and size [21] ( Fig. 9.8.15)
Influence of pre-treatment [21] ( Figs. 9.8.16–9.8.20)
Drying of mango leather
Influence of temperature [5, 22] ( Figs. 9.8.21 and 9.8.22)
Influence of thermal pre-treatment [5, 22] ( Figs. 9.8.23 and 9.8.24)
Drying of slices and drying of mango leather [5, 22] ( Fig. 9.8.25)
Quality kinetics
Drying of slices
Influence of temperature [22] ( Fig. 9.8.26)
Influence of pre-treatment [22] ( Fig. 9.8.27)
Drying of mango leather
Influence of temperature [5, 22] ( Figs. 9.8.28–9.8.31)
Recommendations
Production of mango slices
Major quality parameters
Production and processing
Production of mango leather
Major quality parameters
Production and processing
References
9.9
Papaya ( Carica papaya L.)
Morphological characteristics [1] ( Figs. 9.9.1 and 9.9.2, Table 9.9.1)
Production
Appropriate cultivars
Selection criteria
Cultivars
Optimum stage of maturity [3–5]
Production methods [6]
Ripening
Natural ripening [5]
Ripening with accelerators [7]
Pre-treatments
Objectives
Mechanical pre-treatments
Thermal pre-treatment [8]
Chemical pre-treatments [8]
Osmotic pre-treatment [9–11]
Objectives
Methods
Drying
Drying parameters ( Table 9.9.2)
Drying methods [10]
Sun drying
Solar drying
High-temperature drying
Storage
Storage conditions ( Figs. 9.9.3 and 9.9.4)
Storage/packaging facilities [15]
Quality
Utilization of dried products ( Figs. 9.9.5–9.9.7)
Quality standards ( Table 9.9.3)
Drying relevant parameters
Chemical composition ( Table 9.9.4)
Important ingredients
Drying kinetics
Through-flow drying
Influence of temperature [18] ( Fig. 9.9.8)
Influence of relative humidity [18] ( Fig. 9.9.9)
Influence of air velocity [18] ( Fig. 9.9.10)
Over-flow drying
Influence of temperature [18] ( Fig. 9.9.11)
Influence of humidity [18] ( Fig. 9.9.12)
Influence of air velocity [18] ( Fig. 9.9.13)
Comparison through-flow and over-flow drying [18] ( Figs. 9.9.14 and 9.9.15)
Quality kinetics
Influence of temperature [19] ( Figs. 9.9.16–9.9.19)
Influence of velocity [19] ( Figs. 9.9.20–9.9.22)
Influence of chemical pre-treatment [20] ( Figs. 9.9.23–9.9.25)
Recommendations
Major quality parameters
Production and processing
References
9.10
Pineapple ( Ananas comosus (L.) Merr.)
Morphological characteristics [1] ( Figs. 9.10.1 and 9.10.2, Table 9.10.1)
Production
Appropriate cultivars
Selection criteria
Cultivar
Optimum stage of maturity [4]
Production method [5]
Pre-treatments
Objectives
Mechanical pre-treatments
Thermal pre-treatment [6–8]
Chemical pre-treatments [6–10]
Osmotic pre-treatment [11, 12]
Drying
Drying parameters ( Table 9.10.2)
Drying methods
High-temperature drying [15]
Solar drying [16]
Storage
Storage conditions ( Fig. 9.10.3)
Storage methods
Quality
Utilization of dried products [18] ( Figs. 9.10.4 and 9.10.5)
Quality standards ( Table 9.10.3)
Drying relevant parameters
Chemical composition ( Table 9.10.4)
Important ingredients
Drying kinetics
Influence of temperature [22] ( Figs. 9.10.6 and 9.10.7)
Influence of air velocity [22] ( Figs. 9.10.8 and 9.10.9)
Influence of chemical pre-treatment [23] ( Fig. 9.10.10)
Quality kinetics
Influence of temperature [22] ( Figs. 9.10.11 and 9.10.12)
Influence of air velocity [22] ( Figs. 9.10.13 and 9.10.14)
Influence of chemical pre-treatment ( Figs. 9.10.15–9.10.17)
Recommendations
Major quality parameters
Production and processing
References
9.11
Plum ( Prunus domestica subsp. domestica)
Morphological characteristics [1] ( Figs. 9.11.1 and 9.11.2, Table 9.11.1)
Production
Appropriate cultivars [2–4]
Selection criteria
Cultivars
Optimum stage of maturity [5]
Production methods [5]
Pre-treatments [6]
Objectives
Mechanical pre-treatments
Halved fruits
Whole fruits [7]
Thermal pre-treatment [8]
Chemical pre-treatments [9, 10]
Drying
Drying parameters ( Table 9.11.2)
Drying methods [6]
Sun drying
High-temperature drying
Storage
Storage conditions [13] ( Fig. 9.11.3)
Storage/packaging facilities [13]
Quality
Utilization of dried products ( Fig. 9.11.4)
Quality standards ( Table 9.11.3)
Drying relevant parameters
Chemical composition ( Table 9.11.4)
Important ingredients
Drying kinetics
Drying of halved fruits
Influence of temperature [18] ( Figs. 9.11.5–9.11.7)
Influence of relative humidity [18] ( Fig. 9.11.8)
Influence of air velocity [18] ( Figs. 9.11.9 and 9.11.10)
Drying of whole fruits
Influence of temperature [19] ( Fig. 9.11.11)
Influence of thermal pre-treatment [19] ( Figs. 9.11.12 and 9.11.13)
Influence of chemical pre-treatment [20] ( Fig. 9.11.14)
Influence of size [21] ( Fig. 9.11.15)
Quality kinetics
Influence of temperature [22] ( Figs. 9.11.16–9.11.18)
Influence of relative humidity [18] ( Figs. 9.11.19 and 9.11.20)
Influence of chemical pre-treatment [18] ( Figs. 9.11.21 and 9.11.22)
Recommendations
Major quality parameters
Production and processing
References
Part 10: Medicinal plants
10.1
Basil (Ocimum basilicum L.)
Morphological characteristics (Fig. 10.1.1 and Table 10.1.1)
Production
Optimum stage of maturity
Production method [2–5]
Drying
Drying parameter (Table 10.1.2)
Drying methods [6, 7]
In-field drying
Natural drying
High-temperature drying
Storage [8, 9]
Storage conditions (Figs. 10.1.2–10.1.4)
Storage facilities [11]
Quality
Utilization of dried products [12] (Fig. 10.1.5)
Quality standards (Table 10.1.3)
Drying dependent parameters
Chemical composition (Tables 10.1.4 and 10.1.5)
Drying kinetics
Influence of temperature [10] (Figs. 10.1.6 and 10.1.7)
Influence of relative humidity [10] (Figs. 10.1.8 and 10.1.9)
Influence of the cultivar [10] (Figs. 10.1.10–10.1.12)
Quality kinetics
Influence of temperature [10] (Figs. 10.1.13–10.1.20)
Influence of relative humidity [10] (Figs. 10.1.21–10.1.23)
Recommendations
Major quality parameters
Production and processing
References
10.2
Chamomile ( Matricaria recutita L.)
Morphological characteristics ( Fig. 10.2.1 and Table 10.2.1)
Production [3–8]
Optimum stage of maturity
Production method
Drying
Drying parameters ( Table 10.2.2)
Drying methods [9–12]
Natural drying
Solar drying
High-temperature drying
Storage [13]
Storage conditions ( Fig. 10.2.2)
Storage facilities [15]
Quality
Utilization of dried products [2] ( Figs. 10.2.3 and 10.2.4)
Quality standards ( Table 10.2.3)
Drying dependent parameters
Chemical composition ( Table 10.2.4)
Drying kinetics
Influence of temperature [11] ( Figs. 10.2.5–10.2.7)
Influence of relative humidity [11] ( Figs. 10.2.8 and 10.2.9)
Influence of air velocity [11] ( Fig. 10.2.10)
Quality kinetics
Influence of temperature [11] ( Figs. 10.2.11–10.2.13)
Influence of relative humidity [11] ( Figs. 10.2.14 and 10.2.15)
Influence of moisture content [11] ( Fig. 10.2.16)
Recommendations
Major quality parameters
Production and processing
References
10.3
Lemon Balm (Melissa officinalis L.)
Morphological characteristics (Fig. 10.3.1 and Table 10.3.1)
Production [2–5]
Optimum stage of maturity
Production method
Drying
Drying parameters (Table 10.3.2)
Drying methods [6, 7]
Sun drying
High-temperature drying
Storage [9]
Storage conditions (Figs. 10.3.2–10.3.4)
Storage facilities
Quality
Utilization of dried products [1] (Fig. 10.3.5)
Quality standards (Table 10.3.3)
Drying dependent parameters
Chemical composition (Table 10.3.4)
Drying kinetics
Influence of temperature [15] (Figs. 10.3.6 and 10.3.7)
Influence of relative humidity [15] (Figs. 10.3.8 and 10.3.9)
Comparison of leaves and stalks [15] (Fig. 10.3.10)
Quality kinetics
Influence of temperature (Figs. 10.3.11–10.3.16)
Influence of relative humidity (Figs. 10.3.17–10.3.19)
Recommendations
Major quality parameters
Production and processing
References
10.4
Marjoram ( Origanum majorana L.)
Morphological characteristics ( Fig. 10.4.1 and Table 10.4.1)
Production [2–5]
Optimum stage of maturity
Production method
Drying
Drying parameters ( Table 10.4.2)
Drying methods [6–8]
In-field drying
High-temperature drying
Storage [10]
Storage conditions ( Fig. 10.4.2)
Storage facilities
Quality
Utilization of dried products [1] ( Fig. 10.4.3)
Quality standards ( Table 10.4.3)
Drying dependent parameters
Chemical composition ( Table 10.4.4)
Drying kinetics ( Figs. 10.4.4 and 10.4.5)
Influence of temperature [17]
Influence of relative humidity [17] ( Figs. 10.4.6 and 10.4.7)
Quality kinetics [17]
Influence of temperature ( Figs. 10.4.8 and 10.4.9)
Influence of the relative humidity ( Figs. 10.4.10 and 10.4.11)
Recommendations
Major quality parameters
Production and processing
References
10.5
Peppermint ( Mentha x piperita L.)
Morphological characteristics ( Fig. 10.5.1 and Table 10.5.1)
Production
Optimum stage of maturity
Production method [2–4]
Drying
Drying parameters ( Table 10.5.2)
Drying methods [5, 6]
Sun drying
Shade drying
High-temperature drying
Storage [8]
Storage conditions ( Fig. 10.5.2)
Storage facilities
Quality
Utilization of dried products [1, 10] ( Fig. 10.5.3)
Quality standards ( Table 10.5.3)
Drying dependent parameters
Chemical composition ( Table 10.5.4)
Drying kinetics
Drying of leaves
Influence of temperature [14] ( Figs. 10.5.4 and 10.5.5)
Influence of relative humidity [14] ( Figs. 10.5.6 and 10.5.7)
Drying of the whole plant
Influence of temperature [14] ( Figs. 10.5.8 and 10.5.9)
Influence of relative humidity [14] ( Figs. 10.5.10–10.5.12)
Quality kinetics
Influence of temperature [14] ( Fig. 10.5.13)
Recommendations
Major quality parameters
Production and processing
References
10.6
Sage ( Salvia officinalis L.)
Morphological characteristics ( Fig. 10.6.1 and Table 10.6.1)
Production [3–7]
Optimum stage of maturity
Production method
Drying
Drying parameters ( Table 10.6.2)
Drying methods [8, 9]
Natural drying
Solar drying
High-temperature drying
Storage [11]
Storage conditions ( Fig. 10.6.2)
Storage facilities [11]
Quality
Utilization of dried products [2] ( Fig. 10.6.3)
Quality standards ( Table 10.6.3)
Drying dependent parameters
Chemical composition ( Tables 10.6.4 and 10.6.5)
Drying kinetics
Influence of temperature [16] ( Figs. 10.6.4–10.6.6)
Influence of relative humidity [16] ( Figs. 10.6.7 and 10.6.8)
Influence of air velocity [16] ( Fig. 10.6.9)
Quality kinetics
Influence of temperature [16] ( Figs. 10.6.10–10.6.12)
Influence of relative humidity [16] ( Figs. 10.6.13 and 10.6.14)
Influence of drying progress [16] ( Fig. 10.6.15)
Recommendations
Major quality parameters
Production and processing
References
10.7
St. John’s Wort ( Hypericum perforatum L.)
Morphological characteristics ( Fig. 10.7.1 and Table 10.7.1)
Production [3–6]
Optimum stage of maturity
Production method
Drying
Drying parameters ( Table 10.7.2)
Drying methods [7, 9]
High-temperature drying
Storage
Storage conditions ( Fig. 10.7.2)
Storage facilities
Quality
Utilization of dried products [2, 11] ( Fig. 10.7.3)
Quality standards ( Table 10.7.3)
Drying dependent parameters
Chemical composition ( Table 10.7.4)
Drying kinetics
Influence of temperature [16] ( Figs. 10.7.4 and 10.7.5)
Quality kinetics
Influence of temperature [16] ( Figs. 10.7.6 and 10.7.7)
Recommendations
Major quality parameters
Production and processing
References
10.8
Tarragon ( Artemisia dracunculus L.)
Morphological characteristics ( Fig. 10.8.1 and Table 10.8.1)
Production [3, 4]
Optimum stage of maturity
Production method
Drying
Drying parameters ( Table 10.8.2)
Drying methods [5, 6]
High-temperature drying
Storage [7]
Storage conditions ( Figs. 10.8.2–10.8.4)
Storage facilities
Quality
Utilization of dried products [2, 10, 11] ( Fig. 10.8.5)
Quality standards ( Table 10.8.3)
Drying dependent parameters
Chemical composition ( Table 10.8.4)
Drying kinetics
Influence of temperature [14] ( Figs. 10.8.6–10.8.9)
Quality kinetics
Influence of temperature [15] ( Fig. 10.8.10)
Influence of dew point temperature [15] ( Figs. 10.8.11–10.8.13)
Influence of moisture content [15] ( Fig. 10.8.14)
Recommendations
Major quality parameters
Production and processing
References
10.9
Valerian ( Valeriana officinalis L.)
Morphological characteristics ( Fig. 10.9.1 and Table 10.9.1)
Production [4–9]
Optimum stage of maturity [10]
Production method
Drying
Drying parameters ( Table 10.9.2)
Drying methods [11, 12]
High-temperature drying
Storage [14]
Storage conditions ( Fig. 10.9.2)
Storage facilities
Quality
Utilization of dried products [1–4] ( Fig. 10.9.3)
Quality standard ( Table 10.9.3)
Drying dependent parameters
Chemical composition ( Table 10.9.4)
Drying kinetics
Influence of temperature [17] ( Figs. 10.9.4 and 10.9.5)
Influence of components [18] ( Fig. 10.9.6)
Quality kinetics
Influence of temperature [18] ( Figs. 10.9.7–10.9.9)
Recommendations
Major quality parameters
Production and processing
References
Nomenclature
Index
A
B
C
D
F
G
H
I
L
M
N
O
P
Q
R
S
T
V
W
Z
Back Cover

Citation preview

DRYING ATLAS

DRYING ATLAS Drying Kinetics and Quality of Agricultural Products Werner Mühlbauer Joachim Müller

An imprint of Elsevier

Woodhead Publishing is an imprint of Elsevier The Officers’ Mess Business Centre, Royston Road, Duxford, CB22 4QH, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, OX5 1GB, United Kingdom © 2020 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-12-818162-1 (print) ISBN: 978-0-12-818163-8 (online) For information on all Woodhead publications visit our website at https://www.elsevier.com/books-and-journals

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Preface

Drying is the most common process for the preservation of all kinds of agricultural products. However, optimization of the drying process is rather complex, since heat and mass transfer phenomena occur simultaneously during the drying process. In addition, chemical and biochemical reactions occur during the drying process, which can significantly influence the quality of the dried product. In order to provide a unified procedure to determine the drying characteristics of agricultural commodities, highly accurate test benches and standardized procedures have been developed at the Institute of Agricultural Engineering of the University of Hohenheim, Stuttgart (Germany) and refined throughout more than 40  years of experimental work. The test benches allow the variation of temperature, humidity and air velocity in a range, which is relevant for all kinds of high-temperature dryers. Furthermore, drying processes can be investigated both in through-flow as well as in over-flow mode. Aside of the moisture content, the product temperature also is measured continuously providing valuable information about the impact of the drying process on the quality of the product. In addition, the influences of the physical properties of the product and the impact of the mechanical, thermal and chemical pre-treatments on the drying curves are determined. The thin layer drying curves of the various commodities can be used as a database for scientists to validate thin layer drying models. Special care was given, to investigate the impact of the drying parameters on the quality according to the official quality standards and the demands of food industry and consumers using standardized analytical methods. Quasi-continuous measurement of the quality parameters during the drying process allows to establish quality curves that can be used together with the drying curves to determine the reaction rate. The reaction rate describes the time gradient of biochemical processes and is the basis to develop reaction kinetic equations, allowing the mathematical description of the influence of the drying process on the different quality parameters. Thin layer drying models together with reaction kinetic equations are required to simulate and optimize the different types of high-temperature dryers in terms of capacity, energy consumption and quality as well as for process control.

The Drying Atlas is a compilation of drying and quality curves gathered from our own research complemented by data from journal articles, books and reports. The Drying Atlas consists of two major parts: a general section and a specific section. The general section presents brief information on the morphology of the products. Physical and chemical properties of the products are listed in tables. Official quality standards for the different applications, most important ingredients and quality parameters mainly influenced by the drying process, are compiled. Appropriate cultivars for drying, optimum stage of maturity and impact of harvesting methods on product quality are described for the different products. Furthermore, the impact of mechanical, thermal and chemical pre-treatments for the different products, which can be used to accelerate the drying process, improve the quality and extend the shelf life of the product, are described. Detailed information is provided for the most common drying methods. The characteristic drying curves of the different drying methods are illustrated and the advantages and disadvantages of the drying methods are listed. Storage conditions, sorption isotherms and storage facilities give information about the optimal storage of the different products. The special section forms a database containing thin layer drying curves and related quality curves of 40 agricultural commodities compiled systematically and presented in a condensed way. Engineers and food scientists can use this information to develop and validate simulation models for heat- and mass transfer and biochemical processes, which are an important tool to optimize and control drying processes. Students and faculty members in agricultural engineering, food science and related subjects can use the Drying Atlas for teaching purposes as well as for research. Dryer manufacturers, and food scientists in the drying industry need to know the optimal temperatures, drying times, energy requirements and quality aspects concerning the drying systems and the product to be dried. The Drying Atlas provides a valuable source to answer those questions, which are decisive for economic and successful drying.

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Biographies

Dr.-Ing. Dr. h.c. Werner Mühlbauer Werner Mühlbauer received his master degree (Dipl.Ing.) in 1969 and his doctoral degree (Dr.-Ing.) in 1974 in mechanical engineering from the University of Stuttgart, Germany. His dissertation on grain drying was honored as the most outstanding dissertation in mechanical engineering in 1974. In 1986 he completed his habilitation at the Faculty of Agricultural Sciences of the University of Hohenheim, Stuttgart (Germany). From 1969 until 1989, he held the positions of senior researcher, lecturer and managing director at the Institute of Agricultural Engineering of the University of Hohenheim. In 1986, the Faculty of Agriculture at the University of Hohenheim awarded him the qualification of professor in agricultural engineering. In 1989, he was appointed as full professor for the newly founded department “Agricultural Engineering in the Tropics and Subtropics” at the University of Hohenheim. He established the new department and served as its director until his retirement in 2004. From 1996 to 2000, he was head of the Scientific Centre for Tropical Agriculture. In 1996, the Agricultural University of Bucharest (Romania) appointed him as doctor honoris causa for his “outstanding contribution to secure the food supply in developing countries”. Dr. Mühlbauer has been working in the field of drying agricultural commodities since 1970. His research covers almost all aspects of drying technologies (physical properties, drying theory, drying simulation, drying kinetics, impact of drying on quality, energy saving, development of drying methods, dryer testing and evaluation, etc.). Dr. Mühlbauer developed high accuracy test benches and standardized procedures to measure drying curves to predict drying behavior and impact on quality of most important drying products (cereals, root and oil crops, vegetables and spices, stimulants, fruits and medicinal plants). Based on his investigations, a low-temperature in-storage drying system for small grains was introduced in Germany. He also developed small scale low-temperature in-storage paddy dryers and initiated the dissemination of more than 100,000 units in South Korea between 1982 and 1985, which is considered as success story of the German development aid program. Since 1980, his research focuses on the development of solar dryers for various agricultural commodities.

Dr. Mühlbauer initiated and coordinated bilateral research projects in 26 countries. Within his research activities, he developed several solar drying systems and supported his former students to establish their own companies. The multi-purpose solar tunnel dryer was commercialized and was distributed throughout more than 100 countries. The solar sewage sludge dryer is produced by a spin-out company of the University of Hohenheim. The World´s Number One in solar sewage sludge drying so far sold about 800,000 m2 of solar dryers in 28 countries all over the world. Dr. Mühlbauer has published 353 papers in national and international scientific journals; he holds six patents and gave more than 250 presentations at scientific conferences in 25 countries, mainly on drying of agricultural products. He supervised 31 doctoral theses, 168-MSc theses and 95-BSc theses. He is author of the Handbook on Grain Drying (in German), the only book on this topic worldwide containing all aspects of drying from drying theory to practical applications. Since his retirement in 2004, Dr. Mühlbauer is working as scientific adviser to a leading German drying company.

Dr. Joachim Müller Joachim Müller received his master degree (Dipl.-Ing. agr.) in 1985 and his doctoral degree (Dr. sc. agr.) in 1992 at the University of Hohenheim, Stuttgart (Germany). Subsequently he held the position as postdoctoral research fellow from 1992 to 1997 in the Department of Postharvest Technology and from 1997 to 2001 in the Department of Mechanization and Irrigation at the Institute for Agricultural Engineering in the Tropics and Subtropics at the University of Hohenheim. In 1999 he completed his habilitation at the Faculty of Agricultural Sciences of the University of Hohenheim. In 2001, Dr. Müller was appointed as full professor to the Department Agrotechnology and Food Sciences, Farm Technology at the Wageningen University (NL) and held this position until 2004. In 2004 he was appointed as full professor at the University of Hohenheim, Institute of Agricultural Engineering, where he has since been head of the Tropics and Subtropics Department. He has functioned as Director General of the Institute of Agricultural Engineering from 2012 to 2016. In 2018

xiii

xiv Biographies he has been additionally appointed Academic Director of the State Institute of Agricultural Engineering and Bioenergy at the University of Hohenheim. Dr. Müller is Editor-in-Chief for the Journal of Applied Research of Medicinal and Aromatic Plants and is a member of the editorial board for several other journals as well as a member of the scientific advisory council of the Fiat-Panis-Foundation, Ulm. He also acts as reviewer for the German Science Foundation (DFG), the Alexandervon-Humboldt Foundation and the German Ministry of Education and Research (BMBF). He is also a member of the Committee of Experts in Food Technology of the German Agricultural Society (DLG). Since his doctoral thesis on solar drying of medicinal plants, his research interests are focusing on drying of

agricultural commodities using various drying technologies such as convective-, osmotic-, microwave- and freeze drying. Applied research of Dr. Müller is always accompanied by fundamental research such as establishing sorption isotherms and drying curves on precision laboratory test benches. For process monitoring, he is developing non-invasive sensor systems for in situ measurements of product quality. Dr. Müller contributed chapters to three books in German and five books in English. He is author or co-author of 190 international, peer-reviewed publi­ cations. 20 doctoral theses, 149 MSc-theses and 67 BSctheses have been completed under his supervision. Under his guidance, five patents were issued between 2003 and 2015 and another four patent applications are pending.

Acknowledgments

The authors gratefully acknowledge the valuable contribution to the editorial assistance of Ingrid Amberg, Ann-Christine Schmalenberg, Dr. Parika Rungpichaya­ pichet, and Sabine Nugent; Dorothea Hirschbach-Müller for the excellent pictures of the products and for the

preparation of the diagrams. The authors appreciate the contribution of the graphic designers of unger + kreativ Strategen GmbH, Stuttgart (Germany), for producing the graphs of the structure of the products.

xv

C H A P T E R

1.1 Production 1.1.1  General aspects

Stone easy to separate from fruit flesh

Apricot, plum, litchi, longan, mango

The production methods of agricultural commodities have a significant impact on the quality of the dried product. The production chain starts with the selection of cultivars, which are appropriate for drying. The beginning of the harvest is determined by the producer when the optimum stage of maturity of the product is reached. After harvesting the product is transported to the farm or to the commercial drying enterprise where the product undergoes various pre-treatments depending on the species before the drying process can start.

Well sliceable

Apple, mango, papaya

Thin skin

Fig, grape, plum, tomato

Small size

Grape, banana

Large size

Apricot, fig, plum

Low fiber content

Mango, pineapple

Seedless

Grape

High dry matter content

Carrot

1.1.2  Appropriate cultivars

Well sliceable

Tomato

Low fiber content

Carrot

With the exception of rice and maize, the cultivar of cereals, roots and tubers, oil crops and stimulants has little influence on the drying behavior and the quality of the dried product. However, fruits, vegetables, spices and medicinal plants require specific properties to produce dried products with optimum quality. Therefore, appropriate cultivars with specific properties have to be selected, which can be dried easily and also guarantee the desired quality characteristics of the dried product (Table 1.1.1).

Uniform shape and size

Carrot, paprika

Intensive color

Carrot, tomato, paprika

High carotene content

Carrot

Low pungency content

Paprika

Low fruit juice and seed content

Tomato

Vegetables

Spices Light color

Onion, garlic

Papery skin easy to remove

Onion, garlic

TABLE 1.1.1  Required properties of products to achieve good drying quality.

Intensive pungency flavor

Onion

High capsaicin content

Chili

Required property

High coloring agents content

Chili

Product

Cereals

Stimulants

Uniform ripening

Rice

High caffeine and theobromine content Coffee, cocoa

Early maturing

Rice, maize

Low acid content

Cocoa

Pulp easy to remove

Coffee, cocoa

Fruits High sugar content

Fig, banana, apricot, grape, mango, pineapple, papaya

High carotene content

Mango

Drying Atlas. https://doi.org/10.1016/B978-0-12-818162-1.00001-8

Medicinal Plants and Herbs

3

High essential oil content

Medicinal plants, herbs

High content of active ingredients

Medicinal plants

© 2020 Elsevier Inc. All rights reserved.

4

1.1.  Production

1.1.3  Optimum stage of maturity [1–3] The stage of maturity of the product at the beginning of the drying process is extremely important for the quality of the dried product.

1.1.3.1  Immature crops Premature harvest is causing problems during drying and also lowers the quality of the dried product such as: – Low germination rate (cereals, oil seeds) – Low milling yield (rice) – Low nutrient content (cereals, root crops, oil seeds, fruits) – Discolouration during drying (maize, rice, fruits) – Tough or rubbery texture (coconut, fruits) – Off-flavor (fruits, coffee, cocoa) – Low content of active ingredients (medicinal plants)

1.1.3.2  Overripe crops Delayed harvest leads to significant losses prior to harvest and also causes low quality of the dried product: – Infestation with microorganisms (cereals, oil seeds, medicinal plants) – Contamination with mycotoxins (cereals, figs) – High in-field losses caused by shattering, rodents and birds (cereals, oil seeds) – Off flavor (fruits, coffee, cocoa) – Discolouration (fruits) – Increased fiber content (cassava)

1.1.3.3  Fully mature crops The optimum stage of maturity is greatly influenced by the commodity. Depending on the crop, the stage of maturity can be described by the following essential requirements: Cereals – Accumulation of the nutrients is completed – Kernel transition from soft to hard dough stage is finalized – Color of the seed coat/husk changes from green to brown Root crops – Accumulation of the nutrients is completed – Low fiber content Oil seeds – Color of the pods changes from green to brown – Color of the seed changes from green to yellow, brown or black according to the cultivar

Vegetables – High dry matter content – High sugar content – High carotene content – Intensive color Spices – High content of coloring agents – Intensive pungency flavor – Skin can be easily removed Stimulants – Color of the skin/pod changes from green to yellow/ red – Consistency of the pulp – Easy separation of the pulp from the seeds Fruits Non-climacteric fruits (grape, longan, litchi, pineapple etc.) have to be harvested in the full mature stage; climacteric fruits (apple, apricot, banana, fig, mango, papaya, plum etc.) are harvested before full maturity and ripened naturally or artificially after harvesting until the fruit reaches the required properties: – Starch is completely converted into sugar – Low acid content – High sugar and acid ratio – Color of peel and flesh is fully developed – Flesh firmness is decreasing – Easy separation of the stone from the flesh Medicinal plants – Accumulation of the active ingredients is completed – Plant is in the beginning of the flowering stage

1.1.4  Production methods The production method also greatly affects losses and product quality. Especially the harvesting method greatly influences the drying process. Cereals and oil seeds [4–9] In industrialized countries and increasingly in developing countries, cereals and oil seeds are harvested at high capacity with fully automated combine harvesters, which have the following advantages: – – – –

Reduction of field losses Enable harvest at optimum maturity of the grains Harvest losses