Postharvest Biology. of Horticultural Crops. Profitable Horticulture Depends on Good Postharvest Handling

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1 Elizabeth Mitcham Faculty Director Fruits, MA & IPM Research POSTHARVEST SPECIALISTS Carlos Crisosto Associate Director Fruits, Stone Fruit Postharvest Biology Overview of Horticultural Crops Mary Lu Arpaia Diane Barrett Subtropical Processing & Fruits Quality Christine Bruhn Marita Cantwell Consumer Vegetables & Issues Fresh-Cut Roberta Cook Marketing & Economics Marita Cantwell, UC Davis Linda Harris Food Safety Adel Kader Fruit & Nut Quality Michael Reid Cut Flowers & Potted Plants Trevor Suslow Vegetables & Microbial Safety Jim Thompson Cooling, Transport, Fumigation Postharvest Losses are costly Represent loss of inputs and profits Reduce postharvest losses and increase sustainability --reduce land, chemical, energy other inputs --conserve land, water, energy From Adel Kader, Nov 9, BMG project Profitable Horticulture Depends on Good Postharvest Handling Reduce losses! Increase sales and consumption Improve quality Taste Nutritional New products Niche markets Lightly processed Food safety Causes of Quality & postharvest Losses Leafy Vegetables Causes of Quality & Postharvest Losses Fruits Lettuces Spinach Cabbage Chard Broccoli Celery Herbs Endives Asparagus Water loss Mechanical damage Loss of chlorophyll h ll and other nutrients Respiration rates Microbial growth Sensitivity to ethylene Banana Apple Avocado Melons Citrus Mango Tomato Chiles Berries Mechanical damage Maturity, immature, overmature Poor ripening, conditioning Softening, texture loss Changes in composition Water loss Chilling injury Microbial growth

2 Fresh Produce Deterioration Metabolic changes: respiration, ethylene, texture, aroma, etc. Growth and development Transpiration Mechanical injury Decay; microbial growth Temperature Affects All Causes of Deterioration From Gordon Mitchell, UC Davis Temperature why is it important? Rate of deterioration rate of respiration Respiration: Sugar + O CO + H + Energy (Heat) Respiration increases exponentially with T Respiration (µ µl CO /g-h) Cauliflower heads and florets have very similar respiration rates & quality changes during storage A. Heads C ( F) B. Florets C ( F) C ( F) C (9 F) C (68 F) O CO Hevajulige & Cantwell, Relative Perishability Asparagus Peas Artichoke Sweet Corn Broccoli Strawberry Banana Apple Tomato Carrot Peach Citrus Onion Garlic Potato Nuts Dates Da ays (to initiate yellowing) Storage temperature cv. Legacy C 68 F Broccoli Shelf-lifelife & Temperature Relative Respiration Rate

3 7 days Broccoli Compositional Quality and Storage Temperature Chlorophyll Carotenoids C F C 9F C F C 68F C F mg/ g FW mg/ g FW Limit of Salability Ascorbic Acid mg/g FW mg/ gfw C ( F) C ( F) C (68 F) Sugars Cantwell, UC Davis Importance of Temperature to Maintain Quality Commercial Cooling Methods 7 days Room Cooling Forced Air Cooling Vacuum Cooling Hydrocooling Icing Cooling in refrigerated transport A B C C C C F F F Product requirements Scale appropriate technology Conventional, Organic products Microbial food safety issues Maintaining temperature is a major challenge during distribution Cold Chain Monitoring Effect of Temperature on Deterioration Temp. F Temp. Relative Velocity C Q of Deterioration Relative Shelf-life Daily Loss (%) Q = rate of deterioration at T+ rate of deterioration at T

4 No fresh product freezes at C ( F) Lettuce freezes at -. C (.7ºF) Non-chilling sensitive products Chilling sensitive products Chilling sensitivity occurs at temperatures above the freezing point Eggplants are Chilling Sensitive Cantwell, UC Davis Symptoms of chilling injury Surface pitting Water soaking Browning Necrosis Rots Poor flavor Poor ripening Commonly chilling symptoms do not appear until product is transferred from the cold room to a warmer temperature C vs 7.C, wk Galia melon Temperature and other Postharvest Recommendations Produce Facts USDA Agriculture Handbook Number 66 The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks Modified or Controlled Atmospheres Reducing oxygen Increasing carbon dioxide Removing carbon dioxide Removing ethylene and other volatiles Degree of precision differentiates MA and CA Composition of Normal Air 78.8% Nitrogen (N ).9% Oxygen (O ).9% Argon (Ar).% Carbon dioxide (CO ).% Ethylene (CH) ( ppm)

5 Some uses of MA for fruits and vegetables MAP Salad Products MA for strawberry pallets to control Botrytis Bag in box MA for melons Factors contributing to postharvest losses Water loss Damage Diseases Continued growth Transpiration (water loss) Loss of Salable Weight Loss Fresh Appearance Loss of Texture <% no visual effect, texture -% visual quality affected >% shrivel, lose salability Water loss is Cumulative Wt loss (%/day) = product K x VPD Water loss Products are covered with holes - needed for gas exchange Loss of water depends on the vapor pressure deficit (VPD) VPD increases exponentially with rising temperature Increases linearly with falling humidity Stomates in leaves; lenticels in fruits Water loss and temperature Wt loss (%/day) = product K x VPD Psychrometric Chart Thermodynamic properties of air Temperature and Water Content oss, % per day Weight lo Weight loss in relation to VPD in products Strawberry y =.6x +. R =.9 Broccoli y =.x +. R =.97 Romaine y =.6x +. R =.9 Mushroom y =.8x +., R = Vapor pressure deficit, mm Hg Strawberry Romaine lettuce Broccoli Mushroom Cantwell, UC Davis

6 Preventing water loss - reduce VPD Harvest when cool Reduce temperature Increase external VP polyethylene bags increase humidity Beware of condensation disease! Packaging to reduce water loss. Contain, Protect, Inform RPCs, Paper, Carton, Plastic Hammock Pack for Ripe Fruit Thompson & Slaughter, UC Davis % Water Loss From G. Mitchell, UC Davis 7 6 Table Grapes Ideal vs Poor Postharvest Handling 6 hrs 8 F % RH hr Delay Before Cooling Cooled at F, 7% RH F, 9% RH 6 hours Cooling Stored at F, 7% RH air at mph F 9% RH, air at. mph 7 day Storage Load at F, Transport at F Load at F, Transport at F 7 day Transit Factors contributing to postharvest losses Water loss Damage Diseases Continued growth Overcoming damage What s wrong with this picture? CARE! Careful harvesting Into lined baskets/bins Don t throw, dump, or drop Avoid rough surfaces Minimize touch points Pack gently but securely 6

7 Ranch Pack Peach Handling: Simple, Clean and Careful Handling for High Quality Product Diseases Reduce Physical damage Major cause of loss Relatively few important genera Most are weak pathogens and need injury Many products are not infected Now packers wear hairnets, sometimes gloves Hairnets; gloves rd party Inspectors Forced Air Cooling Temperature and Postharvest Decay SPINACH: DAMAGE, DECAY, TEMPERATURE 9=excellent, =unuseable 9=excellent, =unuseable 9 Visual Quality Decay =green, =yellow 9=excellent, =unuseable Color. C 6 F C F 7. C F C F Off-odors Changes in Spinach quality: washed and bagged product stored at Temperatures DAMAGE AND DECAY Cantwell, 999 Raw foods contain microorganisms Some are pathogenic to humans Microbes present an "invisible challenge They don't usually change the appearance, taste or odor of food. Fresh produce with no kill step Prevention of Contamination is key Food Safety Issues Sources of Contamination; Prevention Good Production & Handling Practices plants FECES sewage insects harvesting, handling, processing environments ANIMALS, BIRDS WATER PRODUCE HUMANS silage, feed soil meat, milk, eggs (cross contamination) From Trevor Suslow, UC Davis 7

8 Factors contributing to postharvest losses Water loss Damage Diseases Continued growth Ethylene - an important factor Plant hormone with positive and negative effects on fresh produce Useful: Accelerates ripening Causes abscission Chlorophyll destruction Problematic: Accelerates ripening Causes abscission Chlorophyll destruction Accelerates senescence Control Ethylene 7 d C (68 F) Respiration rates of Ripening Fruits Ethylene Production Rates by Fruits at C (68 F) ml O or CO per kg-h Climacteric Fruits 8 Breadfruit 6 Cherimoya Mango 8 6 Fig Tomato Apple ml O or CO per kg-h Nonclimacteric Fruits Strawberry Grape Pineapple Cherry Lemon 6 8 Range (µl/kg-h) Product.-. Citrus, grape, cherry strawberry MOST VEGETABLES.-. Pineapple, blueberry, cucumber.-. Banana, mango, tomato, honeydew melon, fig - Apple, avocado, cantaloupe, nectarine, papaya, pear > Cherimoya, passion fruit, sapotes Manipulating Ethylene Effects. Avoidance Products, combustion engines, smoke. Removal Ventilation, oxidation, absorption. Inhibition of production Lettuce Apples Low temperature, chemical inhibitors enzymes, antisense technology. Inhibition of action Low temperature, high CO, low O, STS, -MCP (Smartfresh). Germplasm selection/engineering Compatibility Relative Humidity Odor 7 day storage compatibility chart Transportation and Loading Distribution warehouses and Storage rooms Retail & Food Service outlets 8

9 Factors contributing to postharvest losses Water loss Damage Diseases Continued growth TIME Continued growth--temperature Sprouting (potato, onion, garlic) Rooting (onion, potato) Growth away from gravity (asparagus, flowers) Internal seed growth (cucumber, beans) Opening of immature buds (broccoli) PHYSIOLOGICAL DISORDERS Disorders resulting from abnormal conditions during production and marketing Abnormal temperatures Et Extended ddstorage Abnormal gases Nutritional imbalance Factors that influence U.S. Consumers Produce Purchases Brand name Prepackaged Organic Growing region/country Calorie content Bulk (loose) display In-season Size Convenient, prepared Certified safe, testing Storage life Price Nutritional value 6 8 % of Consumers Fresh Trends, 99. Vance Research Services. Appearance Freshness, ripeness Taste/Flavor Postharvest Problem Quality is maximized when the product is harvested more mature or ripe, whereas shelfand storage life are extended if the product is harvested less mature or unripe. Taste and the Sugar:Acid Ratio ACIDS Low Moderate to High Low Insipid, tasteless Sour, tart SUGARS High Sweet Best flavor combination Toivonen, P. 7. Fruit maturation and ripening and their relationship to quality. Stewart Postharvest Review :7. Soluble solids measured by a refractometer = sugars, but also organic acids, soluble pectins, anthocyanins, phenolic compounds, ascorbic acid 9

10 Based on Flavor & Nutritional Quality Based on Firmness & Texture Based on Appearance (Visual Quality) 6 8 % Postharvest Life Under Optimum Conditions From Adel Kader, UC Davis Characteristics of horticultural crops High water content Easily damaged Diverse genome tissue type physiological state Alive a biological system Factors contributing to postharvest losses TIME Water loss Damage Diseases Continued growth Light Basic Postharvest Principles ) Harvest at correct maturity ) Reduce physical handling ) Protect product from sun ) Keep packingline simple and clean; ensure good worker hygiene ) Select, classify, and pack carefully 6) Align cartons, strap pallet 7) Cool as soon as possible 8) Know market and product requirements 9) Coordinate efficient & rapid handling )Train and compensate workers adequately