POST-HARVEST TECHNOLOGY OF AGRICULTURAL PRODUCT
- 1. 4/10/2017 1 FET 418 POST-HARVEST TECHNOLOGY OF AGRICULTURAL PRODUCT What is Post-Harvest Technology? • Post‐harvest technologies constitute an inter‐disciplinary science and techniques applied to agricultural commodities after harvest for the purpose of preservation, conservation, quality control/enhancement, processing, packaging, storage, distribution, marketing, and utilization to meet the food and nutritional requirements of consumers in relation to their needs.
- 2. 4/10/2017 2 Post‐harvest technology stimulates agricultural production by • prevents post‐harvest losses; • improves nutrition ; • adds value to agricultural products; • opens new marketing opportunities; and • generates new jobs The three main objectives of applying postharvest technology 1. to maintain quality (appearance, texture, flavor and nutritive value) 2. to protect food safety, and 3. to reduce losses between harvest and consumption.
- 3. 4/10/2017 3 Major field crops in Bangladesh Cereals Pulses Oilseeds Sugar- cane Fruits & Vegetables 1. Rice 2. Wheat 3. Maize 4. Barley 5. Oat 6. Rye 7. Millets 8. Triticale (cross variety of wheat and rye) 1. Bengal gram (chick pea) 2. Lentil (Masoor) 3. Black gram (Maskalai) 4. Green gram (Moog) 5. Lathyrus pea (Khesari) 6. Peas (Motor) 7. Red gram (Arohor) 1. Mustard 2. Indian mustard (rai) 3. Indian rapel (Tori) 4. Gingelly (Seasame) 5. Linseed (Tisi) 6. Soyben 7. Sunflower Storage of Cereal Grains • Cereal grains are harvested, threshed, dried, and stored to prevent deterioration of quality of grain. Purposes of storage:- 1. Retain the supply of the food grain throughout the year, 2. Retain viability of the seed for planting in the following season 3. Take advantages of higher prices by the traders, and 4. Serve as a reserve during the times of scarcity.
- 4. 4/10/2017 4 Factors influencing deteriorative changes during storage 1. Physical: Temperature, humidity 2. Chemical: Moisture, oxygen, oxidation 3. Physiological: Respiration, heating 4. Biological: Insects, microorganisms, mites, rodents, birds. Changes occurring during storage: CHO, Proteins, Fats, Vit., Minerals, Discoloration, Viability, Flavor. Nature of loss during storage 1. Weight loss 2. Nutritional loss 3. Quality loss presence of dust, contaminants e.g. insects fragments, rodent hairs, pesticide residue, damaged grains) 4. Loss in viability 5. Damage physical damage during harvesting, threshing or milling)
- 5. 4/10/2017 5 Principles of grain storage • The deterioration of grain is done indirectly by controlling moisture, air movement, and preventing attack of microorganism, insects and rodents. • Here the main objective is to reducing the metabolic activity to such stable level that that grain mass is sufficiently stable with minimal deterioration. • Two alternative methods are: a) Reduction of moisture content to safe level and cooling of the grain, b) Modification of atmospheric condition of storage system. • Deterioration of cereal grains can be retarded by controlling temperature and moisture, although oxygen free environment are also useful in this regard. • Moisture: high moisture content favors biochemical and chemical changes in the grain as well as the growth of microorganisms, insects and mites during storage. • Temperature: critical factor for storage up to certain limits.
- 6. 4/10/2017 6 • Moisture • Moisture content important for Economic value: 1% moisture = 1% value • Safe storage! • More correct: importance of water activity (aw= p/p0) as a measure for water availability • Differences in relation between moisture content and water activity can exist • Mostly: analysis of moisture content
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- 8. 4/10/2017 8 • Moisture content analysis is difficult: • Not average is important, but highest concentration at a particular spot • Variation in moisture content in a storage facility due to ‐ Harvest time ‐ position in the field ‐Different suppliers ‐ Variation in a single year... • Given sufficient time (often matter of weeks): equilibrium • Techniques: NIR, Karl‐Fisher, weight loss,... Drying of cereal grains • Often moisture content at harvest: too high • Low temperature air drying • Forced convection • No damage to the grain • Cheap • Slow • Need for low humidity air • Only possible if moisture content is low enough to begin with to assure safe storage during drying
- 9. 4/10/2017 9 • High temperature drying • Forced convection with heated air • More expensive • Could damage kernels • Physical damage • Loss of germination capacity • Loss of bread making capacity in case of wheat • Poor gluten starch separation behaviour Aeration • During storage, aeration prevents • Formation of hot spots • Accumulation of moisture at specific places due to ‐ Increased metabolic activity, coupled to moisture ‐ Seasonal temperature changes
- 10. 4/10/2017 10 Assessment of deterioration • Changes in grain colour • Sour or musty smell • Loss of viability ‐ Germination test ‐ Tetrazolium test • Fat acidity increase • Glutamic acid decarboxylase activity decrease • For wheat: “Sick wheat”