Specialty Vegetables Immature Fruit Vegetables squash, cucumber, beans, eggplant, tomatillo, corn Peas in pods Green Onions Marita Cantwell micantwell@ucdavis.edu Postharvest Technology Short Course June 201 Immature Fruit Vegetables Causes of Quality Loss Beans Summer squash Okra Cucumber, chayote, other cucurbits Eggplant Tomatillo Sweet corn Peas Maturity Water loss Physical damage Chilling injury (most) Decay Internal seed development 1
Waxed carton, water absorbent pad, forced air cooled Bulk pack in carton box, forced air cooled. Squash are showing initial symptoms of chilling injury. SEVERE Chilling injury symptoms Water loss from the water soaked areas leads to sunken areas Score 9 7 6 Visual Quality (9 to 1) Decay (1 to ) Browning (1 to ) Pitting (1 to ) Average quality and defects of summer squash varieties after storage for 10 days at temperatures. For Visual quality, 9=excellent 7=good, =fair, =poor, 1=unusable For defects, 1=none, 2=slight, =moderate, =moderately severe, And =severe 2 1 C 1 F 7. C F 10 C 0 F 2
Shelf-life of cucumbers in relation to temperature Chilling Sensitivity Exposure Time Temperature 100 Relative Storage Life Relative Storage Life 90 0 70 60 0 0 0 20 10 0 0 2 1 7. 10 0 1 Temperature 1 9 20 6 2 C 77 F Chilling Symptoms: yellowing discoloration pits and sunken areas increased weight loss increased decay Stored 7 days Stored 7 days + 7 days at 20 C
Interrupting the chilling period before permanent damage has occurred Not practical commercially but could be used on small scale Total storage period = 12 days Pepino almacenado 1 dias a 1 C Deshidratación Cv Luxell (arriba) y Darlington (abajo) Amarillamiento
Pepino almacenado 1 dias a C mas dias a 20 C Cv Luxell (arriba) y Macario (abajo) Mini-pepino more tolerant to low temperature? Handle ~ C Slimy breakdown Mini cucumber packing Alpine Fresh; www.alpinefresh.com
Opo Smooth Luffa Angles luffa Fuzzy melon Bittermelon and other Asian cucurbits Cucumber recommendations are also good guidelines for these and related cucurbits Bittermelon Simple but careful handling Is critical for many specialty vegetables 6
What is wrong with this picture? Chilling Injury Symptoms 7
Table 1. Days to visual chilling symptoms. Chilling symptoms included fruit pitting, discoloration of the fruit and calyx, and internal discoloration. Symptoms were considered to reduce marketability when scores exceeded 2.0 (slight) on a point scale. Days to Visible Chilling Symptoms Temperature Black Bell Japanese Chinese 0 C 2 F 1-2 -- 2-2. C 6 F - -6-6 C 1 F 6-7 -9 10-12 7. C F 12 12-1 1-16 10 C 0 F no chilling no chilling no chilling What Happened To these Eggplants? 9 A. Visual Quality Score 9=excellent, 7=good, =fair, =poor, 1=unuseable 7 6 2 Delays to cool at 7 C 1 Newtons B. Firmness 0 2 26 2 22 20 1 9 C. Gloss Visual quality, firmness, and visual symptoms of water loss were correlated with time to cool. Delays to cool should be < hours at 7 C or <6 hours at 2 C. Gloss values decreased after a delay of 9 hours at both temperatures. 7 6 Units 2 1 0 6 9 12 1 1 Delay to cool: Hours at 7 C
Quality of Japanese Eggplant after cooling delays at 2 temperatures and after storage at 7. C for 7 days. Data averages 10 fruits per rep x 2 reps. Temperature & Hrs Delay to Cool 7 C Visual Quality Dehydration Decay Texture Firmness, Newtons Gloss score Gloss Meter Value 0 7. 1. 1.0.2 29.0.2 7.6 7.2 1. 1.0. 26.7. 7.6 6. 2. 1.6. 2.. 6.9 9.6 2.6 2.1.2 2.9.2.79 12.2..1 2. 2. 2..7 1 2.2.2. 1. 21.6 1..0 2 C 0 7. 1. 1.0. 29.0.2 7.6 7. 1. 1.0.2 0.0.9 7.7 6 6. 2.0 1.2.7 27..6 6.2 9. 2.2 1..0 2.0 2.6.0 12. 2. 2.0 2.6 2.1.2.6 1.7.6 2.6 1. 21.1 1..07 LSD.0 0.6 0. 0. 0.6.2 0. 1.76 Cantwell and Thangiah, Acta Hort, in press. Green Beans Storage Conditions -7. C (1- F) and 9-100% (RH) Very good quality can be maintained for a few days at temperatures below C but chilling injury will be induced. Some chilling may occur even at the recommended storage temperature of C after 7- days. At -7. C (1- F) a shelf-life of -12 days is expected. Water loss is a common postharvest problem. About % weight loss is needed before shrivel and limpness are observed. Botrytis develops as nests on damaged beans. 9
Visual Quality (9=excellent, 1=unuseable) Green Bean Quality and Weight Loss 9 7 6 2 1 M. Cantwell, UC Davis, 1997 y = -0.22x + 9.6 r 2 = 0.6 0 10 1 20 2 0 % Weight Loss Visual Quality (9=excellent, 1=unuseable) Limpness (1=none, =severe) 9 7 6 2 1 2 1 2 6 10 12 Days cv. Xera % Weight Loss Shrivel (1=none, =severe) 0 0 2 20 1 10 0 2 1 2 6 10 12 Days 2 C 77 F 20 C 6 F 1 C 9 F 10 C 0 F C 1 F Green Bean 0 C 2 F Quality and Storage Temperature No transfer to warmer temperature to simulate retail handling and therefore few symptoms of chilling injury 10
Symptoms of chilling injury Surface pitting Water soaking Browning Necrosis Rots days C (1 F) 7. C ( F) Green Beans: Chilling symptoms are different at different temperatures Stored 7-10days 0 C 2 F C 1 F 11
Edamame Seed Development IM M OM Stage of Maturity Pod Wt. (g) Seed Wt. (g) Seed % Immature 1.7 + 0. 0.6 + 0.2.7 +. Mature 2. + 0. 1.0 + 0.1. + 2. Overmature 2. + 0. 1. + 0.2. + 6.2 cv. Emperor, data average of 0 pods per stage maturity Visual Quality of Edamame Decreases Quite Rapidly in Storage 9= excellent, = poor, unsalable 9 7 Limit of Salability 6 Edamame Visual Quality Average 7 cultivars 0 2 6 10 12 1 Days Discoloration damaged, dried areas 0 C (2 F) C (1 F) 10 C (0 F) CA at C can Be beneficial to maintain visual quality Shelf-life is ~7 days at 0- C Pods at 10 C lose color but otherwise look okay 9=excellent, 1=unuseable 9 7 6 2 1 Limit of Salability Air 1% O 2 Air + 10% CO 2 1% O 2 + 10% CO 2 Visual Quality of Edamame 0 10 1 20 Days at C 12
Tomatillo Often sold without husk Maturity important for composition and quality 10 C (0 F) Husk dries at warmer temperature Husk decay at lower temperatures Fruit is chilling sensitive weeks VISUAL SYMPTOMS OF CHILLING INJURY ON SELECTED FRUIT VEGETABLES Vegetable Beans Cucumbers Eggplant Peppers, bell and chili Okra Symptoms Surface pitting, diagonal brown streaks, dullness of normal surface color, discoloration of seeds, increased susceptibility to decay Shallow surfaces pits of various sizes, water-soaked spots, and increased decay Pitting: brown surface areas that become sunken with time; calyx discoloration, and flesh browning Numerous minute to fairly large, shallow, roundish surface depressions (sheet pitting), seed browning, and calyx discoloration Discoloration, water-soaked areas, pitting, and increased calyx discoloration Squash, summer Surface pitting and rapid decay From Jeff Brecht 1
Peas Snow peas Sugar Snap Peas 1
Storage temperature affects sugar content relatively more than Visual appearance. Cantwell UC Davis A. Soluble solids 11 Temperature impacts flavor (sweetness) More than visual appearance in sugar Snap peas. The best quality and longest shelf-life achieved at 0 C (2 F). Soluble solids, % Sugars, mg/g FW 10 9 7 70 6 0 C (2 F) C (1 F) 10 C (0 F) B. Total Sugars (spectrophotometry) 60 C. Total Sugars (HPLC) 7 Sugars, mg/g FW 70 6 60 0 C (2 F) C (1 F) 10 C (0 F) Cantwell and Paulenas, 200 0 6 12 1 Days 1
Sugar Snap and Snow Peas 2012 Frutesa FRUTAS TROPICALES DE GUATEMALA S.A. 1 days at C; sugar snap peas in modified atmospheres A B C D E +7 +12 +1 10+12 Air (O2+CO2) HIGH CO2 INJURY 16
Apariencia de sugar snap peas (cv Sugar Snap) después de 1 días a ºC en atmósferas controladas + días en aire a ºC. Air +6 +12 +1 1+12 10+12 Problema de arveja China durante la distribución Snow peas from Young (Y) and old (O) Plantings in California Peas were stored in air At temperatures for 20 days. Note the differences in Appearance of the calyxes As well as the pod. Cantwell, UC Davis 17
Sweet corn quality Fresh green husks No decay on silks Tender kernels (differences among cvs) Typical flavor-sweet, not starchy Mechanically harvested Hydrocooled or liquid iced Temperature and Visual Quality Silks and Ears Score, 9=excellent, 1=unuseable 9 7 6 A. Visual quality silks cv Diamonds 7A 0 C (2 F) C (1 F) 10 C (0 F) LSD.0 B. Visual quality ears cv Diamonds 7A LSD.0 0 C (2 F) C (1 F) 10 C (0 F) 0 2 6 10 Days 0 2 6 10 Days Cantwell, 200 1
Temperature and Loss of Soluble Solids in Corn kernels from 2 cultivars 16 1 0 C (2 F) C (1 F) 10 C (0 F) % Soluble solids 1 1 12 11 LSD.0 LSD.0 10 9 A. Soluble solids cv Diamonds 7A 0 2 6 10 Cantwell, 200 Days B. Soluble solids cv Snow White 0 2 6 10 Days Green or Spring Onions 19
Curvature and telescoping of cut stem end Telescoping or growth of cut stem end Trimmed Green Onions Relationship between water temperature and exposure time on extension growth Temperature, C 60 6 2 0 Effective, Non-injurious 0 2 6 10 12 1 Time, min y = 9.7 + (11.1/x) R 2 = 0.92 60 6 2 0 Low temperature (0 C) best Low O 2 retards growth (curvature, extension) High CO 2 retards senescence Hot water dips effective to control telescoping Combination of low O 2 and high CO 2 beneficial for storage of heat-treated onions Shelf-life > 1 days C 20
Postharvest Handling Nopalitos (Opuntia sp.) Traditional vegetable in Mexico Green vegetable, little water needed Nutritional quality between that of lettuce and spinach Challenges Spines and glochids Fresh-cut product Manage acidity (CAM plant) Storage Conditions for Nopalitos Temperature Short periods: ambient temperatures (1- days) Longer periods: - C (2- weeks) Susceptible to chilling injury; reports are variable Clean (remove spines) after storage High relative humidity, 90-9% RH Reduce dehydration, especially in damaged areas Manage with cold room and packaging Modified atmospheres 10 a 20% CO2 can be beneficial at C ( days) Decay control Hot water and fungicides Minimize harvest damage Cantwell. 200. Nopalitos. http://www.ba.ars.usda.gov/hb66/ Guervara et al., 200, Postharvest Biol. Tech. 29: 167 21