Heptix.pptx
- 1. GROUP 4 Post harvest handling Systems for vegetables
- 2. SCOPE INTRODUCTION. FACTORS FOR POST HARVEST LOSSES IN VEGETABLES. POST HARVEST PRACTICES FOR VEGETABLES. a) Preliminary Practices. b) Combined optional treatments. c) Packaging methods. d) Transport, storage, and use of vegetables preserved by combined methods. e) Quality control.
- 3. Factors of quality and postharvest losses in vegetables Water loss Mechanical damage Loss of chlorophyll and other nutrients Respiration rates Microbial growth Sensitivity to ethylene Maturity (immature and overmature) Poor ripening conditioning Chilling injury etc
- 4. Post-harvest Practices For Vegetables 1.Preliminary Practices These are the operations that are carried out after harvesting and before taking the vegetables to the processing industries. As a result of peeling, grating and shredding, vegetable’s shelf life be greatly low, thus, proper postharvest handling practices are required to limit wastage as a result of spoilage. Hence Preliminary Practices include: Washing: Root vegetables are washed first to remove all field dirt and to allow inspection.
- 5. Preliminary Practices…..cont’d Inspection: Vegetables are inspected for quality in line with consumer demands. Selection: Vegetables are selected and graded on a basis of firmness, cleanliness, size, weight, color, shape, maturity, mechanical damage, foreign matter, diseases, and insects. It can be done manually, or by employing a variety of separation machines.
- 6. Waxing: • Waxing is done after washing with an artificial layer of wax that has adequate thickness and consistency to improve appearance and to reduce the loss of water. Classification: • This operation is done to attain a uniform product for the market i.e. vegetables are classified by size, weight, or degree of maturity. • Classification by size can be done manually by trained personnel. • In mechanized packing houses, operations are carried out with perforated belts, divergent belts or cylinders, and sieving. Preliminary Practices…..cont’d
- 7. Preliminary Practices………….cont’d Sorting by mass is usually done electronically or by manually operated machines. Classification by degree of maturity can be done using colour charts or by optical methods Labelling: Commercial vegetables can be labelled individually with automatic adhesive stickers to identify the product brand, farmer, or retailer especially when exporting produce to other countries.
- 8. Premarketing Operations Packaging: Generally, for exporting fresh fruits, corrugated fibreboard boxes of variable capacity are employed. The most common packaging technique for prepared raw vegetables is modified atmosphere packaging (MAP). The basic principle of MAP is that a modified atmosphere can be created eithey by elimination and or introduction of specific gases. Storage: The packaged fresh product can be stored at ambient or refrigeration temperature until it is shipped to the overseas market.
- 9. 2. Combined optional treatments a). Irradiation: • Fruit and vegetable irradiation is a food safety and preservation technology, similar to pasteurization. While pasteurization uses heat to kill microorganisms, irradiation uses ionizing radiation. • The process involves exposing food, either in bulk or packaged, to gamma rays for a specified amount of time. • Note: The moisture content in foods and the surrounding environment during treatment influence the sensitivity of microorganisms to irradiation.
- 10. Combined optional treatments….cont’d b). Refrigeration: • This operation can halt the growth of certain pathogen and spoilage microorganisms however might not eliminate them. • The reduction of temperature increases the lag time and decreases the growth of microorganisms. • It is generally recognized that maintaining foods at 5°C is sufficient to prevent the growth of most common food-borne pathogens
- 11. Combined optional treatments….cont’d Factors that must be controlled during refrigeration Temperature: The system should always be able to meet the demands placed upon it and controlled automatically by the use of thermocouples, pressure valves, etc. Relative humidity: Should be kept high in a refrigerated storage room by controlling the refrigerant temperature. Air movement: In the refrigeration environment must be sufficient to remove respiration heat, gases, and the heat penetrating through the openings.
- 12. Combined optional treatments….cont’d c). Modified atmospheres (MA): MA implies removal or the addition of gases, resulting in an atmospheric composition different from the one normally existing in air. E.g. N2 and CO2 levels may be higher, and the O2 levels lower than those found in a normal atmosphere. Advantages of Using MA: • Reduction in senescence associated with biochemical changes. • Decreased sensitivity of fruit to ethylene.
- 13. Combined optional treatments….cont’d • Can relieve some physiological disorders such as cooling damage in a variety of products. • Can have a direct or indirect effect on post-harvest pathogens and insect control. Disadvantages of MA include: Initiation of physiological damage, such as black spots in potatoes. Irregular maturation of certain fruits, such as bananas and tomatoes.
- 14. Combined optional treatments….cont’d Abnormal development of flavours and odours. Increased susceptibility to diseases. Stimulation of sprouting and delay of epidermis development in roots and tubers (e.g., potatoes). Pickling: Vegetables can be macerated in a brine solution for pickling, which preserves the product for a long time. The high concentration of salts in the brine inhibits the growth of microorganisms that decompose and change the flavour, colour, and texture of vegetables.
- 15. Combined optional treatments….cont’d However; An alternative method is to precook vegetables at 80 to 90°C for 2 to 10 min. Then, packaging is performed using a blend of 3% salt, 6% vinegar, and 5% sucrose. Vegetables can be maintained under maceration with a salt concentration of 6- 10% during the first 10 days of the pickling process and 16% for 6 weeks. Under these conditions, vegetables can be kept in barrels for long periods until final processing.
- 16. 3. Packaging methods a). Plastic containers and bags: The plastic containers used to handle fresh and processed vegetables are tough, easy to handle due to light weight, can be reused, and facilitate the stacking of produce into piles without damaging the product. NB. Plastic bags are suitable for handling small amounts of vegetable products, and used at supermarkets and retail stores.
- 17. Packaging methods…………..cont’d b). Vacuum packaging: This extends the shelf life of vegetables for long periods. This technique relies on withdrawing air from the package with a suctioning machine. Thus creating a MA kind of environment. Removal of air retards the development of enzymatic reactions and bacterial spoilage.
- 18. 4. Transport, storage, and use of vegetables preserved by combined methods a). Open Vs Refrigerated Vehicles • Open vehicles (trucks, boats, ships, etc.) are used to transport the product to the packing houses and retail markets. These vehicles are not equipped with refrigeration units and thus the produce decays faster, unless if pretreated with chemicals. • Refrigerated vehicles (trucks, trains, ships, airplanes, etc.) contain installed refrigeration units with sufficiently low temperatures to maintain vegetables in a fresh-like state.
- 19. Transport, storage, and use of vegetables preserved by combined methods • Vegetables must be classified in order to separate those susceptible to cold temperatures and those that are not. • This eliminates the possibility of product damage when cooling at low temperatures during transport. b).Offloading: This is a very delicate operation and can be done by hand with a box tipper or with the aid of a forklift. Generally, vegetables and fruits are stacked on pallets to ease the unloading process and to prevent damage to the product.
- 20. Optimum storage conditions Expected Vegetable Temperature Relative Shelf life storage (°C) Humidity (%) Onions 1 to 2 70 to 75 4-5 mo Garlic 0 70 to 75 6-8 mo Beets 0 90-95 1-3 mo Carrots 0 90-95 4-5 mo Cabbage 0 98 3-6 mo Lettuce 0 90-95 2-3 mo Broccoli 0 90-95 7-10 weeks Cauliflower 0 85-90 2-3 weeks Celery 0 90-95 3-2 mo Sweet corn 0 85-90 4-8 days Tomato 12.5-13 85-90 2 weeks Green pepper 10 95 2 weeks Chili pepper 10 95 2 weeks Egg plant 10 to 12 95 3 weeks Cucumber 10 to 13 95 10-14 days Optimum Storage Conditions Table for some Vegetables
- 21. Transport, storage, and use of vegetables preserved by combined methods c). Storage temperature vs. shelf life: As recommended from the table above storage temperatures for vegetables can range from (0-13)°C with RH between (70-95)%; under these conditions shelf life can range from days to months. Controlled or modified atmosphere packaging techniques assist in maintaining adequate temperature and RH for refrigerated products.
- 22. Transport, storage, and use of vegetables preserved by combined methods These systems can be used during transportation of fresh produce for short or prolonged storage periods. Injection of 𝐶𝑂2 gas into controlled or modified atmosphere systems to control pathogens was carried out. d). Repackaging considerations: This is done commonly when the vegetables have been packaged in large containers, such as sacks, boxes, plastics containers, etc. The repackaging process is often carried out using small trays covered with transparent plastic film, which gives the product an attractive appearance.
- 23. Transport, storage, and use of vegetables preserved by combined methods e). Optimal utilization of the final product This can vary according to consumer demand. In most cases, the demand is high for fresher products. Thus, the optimal utilization of fresh vegetables should be for direct consumption, with very small quantities for processing. The produce must meet official regulations concerning product safety and quality i.e must be free of foreign matters, chemicals, and microbes that constitute a risk to human health.
- 24. 5. Quality control a). Recommended microbial tests Control tests for microbial invasion in fresh vegetables must be assayed to analyze the growth of spoilage and pathogenic microorganisms. Total aerobic, psychrophile, and coliform bacteria counts are performed in standard plate count agar (SPC) and red violet bilis agar (VRBA). b). Nutritional changes Minimally processed vegetables retain nutritional and fresh-like properties because heat is not a major detrimental factor during processing. When using CAP or MAP in combination with refrigerated storage, prolonged shelf life of vegetable products and retention of vitamins is favoured compared to thermally treated vegetables (e.g., canned vegetables), in which high amounts of nutrients are lost due to severe temperature treatment.
- 25. Quality control………….cont’d c). Changes in sensory attributes and acceptability Since minimally processed vegetables resemble fresh produce, changes in sensory attributes and acceptability are minimized during processing. Thus, flavour, texture, and appearance are retained. Traditional food preservation processes involving high temperature treatments, freezing or dehydration however produce an adverse effect, on the texture, flavour and aroma of processed food products.
- 26. Quality control………….cont’d In Summary these Factors are critical in maintaining the quality and shelf life of minimally processed products: Using the highest quality raw product; Reducing mechanical damage before processing; Reducing piece size by tearing or by slicing with sharp knives; Rinsing cut surfaces to remove released cellular nutrients and to kill microorganisms; Centrifugation to the point of complete water removal or even slight desiccation; Packaging under a slight vacuum with some addition of CO2 to retard discoloration; Maintaining product temperature from 1° to 2°C (34° to 36°F) during storage and handling.
- 28. GROUP MEMBERS 1. Asiimwe Gerald Masereka 2. Nkuutu Semei Edgar 3. Kirabo Pamela 4. Wasswa Shonia Mutebi 5. Batenga Martha 6. Iraguha Frederick 20/U/12107/PS 20/U/12095/PS 20/U/12092/PS 20/U/12097/PS 20/U/14998/PS 20/U/15005/PS
- 29. END OF PRESENTATION THANK YOU FOR ,,,,,LISTENING,,,,,