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pom212-tree_nuts_2005_kader_handout - Postharvest Biology...

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Unformatted text preview: Postharvest Biology and Technology of Tree Nuts Nuts are marketed in shell or shelled as whole kernel or prepared in a variety of value-added products in various packages that influence their postharvest-life Adel Kader UC Davis Chemical Composition of Tree Nuts Fatty acids composition of nuts influences their storage potential Maturity Stages Comparison among various cooking oils in their fatty acid composition Almond Walnut 1 Tree Shaker for Almond Harvesting Windrowing Almonds to Facilitate Collection Windrowed Almonds Collecting Almonds from Windrows Sorting Almonds at the Hulling Facility Concealed damage of almonds due to high temperature and relative humidity 2 Tree Shaker for Harvesting Walnuts Windrowed Walnuts Pick-up Machine for Walnuts Kernel Darkening due to Exposure of Harvested Walnuts to the Sun Walnut Kernel Walnut Color Chart Price is inversely related to kernel color 3 Compositional Compositional Changes of Changes Pistachio Nuts during during Maturation of Pistachio Nuts Respiration and Ethylene Production Rates during Development of Pistachio Nuts Pistachio shell split is desirable while early hull split is not desirable because it increases potential for fungal infection Pistachio Nut Maturity Indexes • Ease of hull separation from shell • Shell dehiscence (splitting) • Change in shell color (green to ivory) • Decrease in fruit removal force • Kernel dry weight and crude fat content Early Pistachio Harvesting Causes: • Higher percentage of undeveloped kernels • Lower compositional quality • Loss in yield Delayed Pistachio Harvesting Causes: • Increased shriveled hulls and shell staining • Losses in kernel quality • Increased incidence of insect infestation and fungal attack 4 Tree Shake Catch System for Pistachio Harvesting Cold Storage of Fresh Pistachio Nuts 1. Store nuts before hulling 2. Remove defective nuts, leaves, twigs, and other foreign materials before storage 3. Use forced-air cooling to remove field heat before cold storage 4. Optimum storage conditions: 0ºC (32°F) & 70% or lower RH Pistachio nuts require more careful handling due to their higher water content at harvest than other tree nuts This is why defective nuts, leaves, and twigs should be removed before cold storage of freshly-harvested pistachio nuts Effect of Storage Temperature on Deterioration Rate of Pistachio Nuts Cold Storage of Freshly-harvested Pistachio nuts Pistachio Handling System Pistachio Harvesting (shake-catch), Placed into bins Transport to dehydration plant Sorting to remove foreign materials Sizing into 3 categories Hull removal Drying at 71ºC (160°F) for 10-12 hrs. Placed into bins lined with polyethylene film Transport to processing plant 5 Sorting Pistachio Nuts to Remove Defects Separating Pistachio Nuts by Size Pistachio Nut Hull Removal Pistachio Nut Hull Condition Influences Shell Staining after Hull Removal Pistachio Nut Hull Condition Influences Shell Staining after Hull Removal Pistachio Nut Hull Condition Influences Shell Staining after Hull Removal 6 Pistachio Staining Visual Shell Staining Scores for Pistachio Nuts Drying Methods • Sun drying • Ambient-air drying • Two-stage drying 1. Heated-air drying to about 12% moisture 2. Ambient-air drying to 5-6% moisture Visual Quality of Sun-dried Pistachio Nuts 7 Visual Quality of Ambient Air Dried Pistachio Nuts (numbers refer to bin depth in feet) Drying Methods • Sun drying • Ambient-air drying • Two-stage drying • Heated-air drying Cross-flow Dryers Used for Pistachio Nuts Bulk Storage of Dried Nuts 8 Storage Factors • Moisture content of the nuts • Relative humidity of storage • Storage temperature • Oxygen concentration • Effective insect control 9 Severe Insect Damage in Almond Kernels Insect Control Procedures • Fumigation (methyl bromide or phosphine) • Storage at near-freezing temperatures • Use of heat treatments (104-120°F) • Storage in 0.5% oxygen • Irradiation Stored Products Insects • Navel orangeworm • Indian meal moth • Dried fruit beetles • Saw tooth grain beetle • Merchant grain beetle • Raisin moth • Fruit fly Methyl Bromide On Dried Fruits & Nuts Purpose To control stored products insects in: Raisins Prunes Figs Dates Almonds Filberts Pecans Pistachios Walnuts 10 ...
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