Vegetable Crops PLSC 451/551 Lesson 7, Harvest, Handling, Packing Instructor: Stephen L. Love Aberdeen R & E Center 1693 S 2700 W Aberdeen, ID 83210 Phone: 397-4181 Fax: 397-4311 Email: slove@uidaho.edu Vegetable Handling Maximum quality exists at the moment of harvest Quality Maintenance Limit mechanical injury Limit losses to disease Meet biochemical and culinary quality specifications Vegetable Handling - Principles Factors that determine post-harvest quality Stage of crop maturity Harvest and handling injury Water loss Temperature during harvest, transport and storage Rate of respiration, ripening, and breakdown Infection with pathogenic organisms 1
Crop Maturity Harvest Timing Factors that modify harvest decisions: Crop Market availability Commodity price Intended use Crop Maturity Basis for harvest timing decisions Harvest index based on: Size Color Ability to withstand handling, storage, and transport Tendency for post-harvest ripening Crop Maturity Examples of maturity index characteristics: Cantaloupe: fruit color and stem slip Cantaloupe: fruit color and stem slip Tomato: fruit color Broccoli: head size and floral development Lettuce: head and/or leaf size Sweet corn: kernel color, kernel starchiness 2
Crop Maturity Examples of maturity index characteristics: Onion: drying and falling of tops Potato: top death and skin-set Carrot: length and diameter of root Radish: size, time from planting Cucumbers: size, color, firmness Crop Maturity Some crops can be harvested at multiple stages of growth, but handling practices will be modified at each stage. Tomato - green pick, pink stage, vine ripened Squash immature, mature Potato new potatoes, mature Harvest and Handling Injury Most vegetable losses result from harvest and handling damage Blemishes resulting from bruising Increased respiration Moisture loss from damaged tissue Entrance wounds for pathogens 3
Handling Injury Effect of drop height and picking stage: Percent bruised fruit 0 in drop, green stage 0% 12 in drop, green stage 1.8% 0 in drop, breaker stage 0% 12 in drop, breaker stage 24.3% Harvest Practices Mechanical harvest: Root crops, tuber crops, bulb crops, many processing vegetables Manual Harvest Most vegetables including leafy greens, salad crops, fruit vegetables, crucifers, and herbs Harvest Practices Preventing mechanical harvest damage Harvest only well-matured crops Harvest only well-matured crops Proper machine calibration and maintenance Padding on all surfaces Minimize drop heights Operate all equipment at full capacity 4
Harvest Practices Preventing manual harvest damage Train labor to handle produce gently Harvest at the proper stage of maturity Field pack where feasible, minimize handling Have labor trim fingernails or wear gloves Use padding on all conveyor surfaces and packing containers Water Loss Effects of water loss: Quality reduction shriveling and desiccation Excessive trim losses Loss of salable weight Water Loss Methods for reducing water loss: Harvest and handle in cool conditions Harvest and handle in cool conditions Harvest well-watered crops Rapidly cool produce to proper storage temperatures Employ humidification procedures 5
Water Loss Optimum humidity level: Asparagus 95-100% Beet 98-100% Sweet corn 95-98% 98% Garlic 60-70% Lettuce 98-100% Watermelon 90% Pepper (dry) 60% Pepper (bell) 90-95% Temperature Impact of improper temperatures Above optimum High rate of respiration i and ripening i High rate of water loss Rapid growth of decay organisms Below optimum Frost injury Cold injury Temperature Vegetables that require cooling Leafy greens and salad crops Leafy greens and salad crops Vegetable fruits with high respiration rates Any crop with a short shelf-life All crops when temperatures are very high 6
Temperature Cooling techniques and equipment Room cooling Forced-air cooling Hydro-cooling Top-icing Vacuum cooling Evaporative cooling Temperature Optimum storage temps, cooling method, and shelf life Broccoli 32 HC,ICE 10-14 d Cabbage 32 RM 5-6 m Cucumber 50 HC 10-14 d Okra 45 FA 7-10 d Squash 50 RM 2-8 m Sweet corn 32 HC,VAC 5-8 d Ginger 60 RM 6 m Packing, Storing, Marketing The shelf life and period of effective storage of vegetables is determined by respiration and ripening. Respiration: the process by which cells produce energy through oxidation of sugars and other energy-rich compounds Ripening: irreversible softening and sweetening process by which vegetables become more edible 7
Packing, Storing, Marketing Vegetable crops differ widely with respect to rates of respiration and ripening Root Crops: low rates of respiration and small ripening changes Packing, Storing, Marketing Vegetable crops differ widely with respect to rates of respiration and ripening Leafy Crops: high rates of respiration and no or minor ripening changes Packing, Storing, Marketing Vegetable crops differ widely with respect to rates of respiration and ripening Mature fruits: intermediate rate of respiration and significant ripening changes. 8
Packing, Storing, Marketing Vegetable crops differ widely with respect to rates of respiration and ripening Immature Fruit Crops: high rates of respiration and incomplete ripening processes Rate of Respiration, Ripening Sample of respiration rates Very Low: Low: Moderate: High: Very High: peanut potato, onion, sweet potato tomato, lettuce, pepper green onions, snap beans broccoli, peas, sweet corn Rate of Respiration, Ripening Importance of respiration rate High respiration g p = rapid changes (decline) in quality = need for rapid handling and transport = short storage capabilities = short shelf life 9
Rate of Respiration, Ripening Impact of temperature Respiration can be controlled by lowering temperature For every 18 degree F above optimum, the rate of deterioration doubles or triples (i.e. sweet corn at 50 (32) has shelf life of 2-4 days (4-8) Ripening, Production of Ethylene Vegetable that produce or are sensitive Produce: cantaloupe, tomato, pepper many tree fruits often shipped with vegetables Sensitive: tomato, lettuce, cabbage, cauliflower, eggplant, okra, pepper, squash, watermelon Ethylene Injury Symptoms on Vegetables Carrots bitterness Cole Crops turn yellow and limp Cucumbers turn yellow and develop soft spots Asparagus become fibrous and woody Lettuce develop rust-spots Squash turn yellow and develop soft spots 10
Rot and Breakdown Rot in storage requires three things: Susceptible host (vegetable) All vegetable crop are prone to some disease Pathogenic organism Mostly fungal or bacterial Proper conditions or environment Temperature and humidity are critical Rot and Breakdown Conditions that increase incidence of rot Entry wounds and tissue damage High humidity High temperature Lack of adequate ventilation Packing Vegetables Importance of proper packaging Provides conditions for quality maintenance Provides conditions for quality maintenance Improves shelf life Identifies the produce Simplifies shipping Creates sales appeal 11
Packing Vegetables Common steps in packaging produce 1. Washing 2. Presizing 3. Grading and Sizing 4. Trimming, waxing, cosmetic improvement 5. Packaging 6. Inspection 7. Palletizing Grade Standards for Vegetables Purpose of grade standards Ensure quality for the seller and buyer Provide a common language for quality Provide legal protection for all parties Provide third party confirmation Grade Standards for Vegetables Origin of published grade standards USDA/AMS State departments of agriculture Local marketing order organizations Local grower groups Individual sellers and buyers 12
Grade Standards for Vegetables USDA Standards 158 published standards 85 vegetable crops Include specifications for size, shape, defects, damage Web site: http://www.ams.usda.gov/gac/index.htm Grade Standards for Vegetables Enforcement of grade standards Inspections conducted by Federal/State inspectors Packing-site inspections Shipping point inspections Receiving point inspections Grade Standards for Vegetables Application of standards Commercial U.S. Production USDA-AMS grading standards applied USDA-AMS grading standards applied Organic/Market Production Variable: grade and/or organic standards often applied in developed countries Worldwide subsistence production No application of standards 13