Weight, g Respiration, µl/g-h Firmness, kg/cm

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1 Postharvest Handling Melons and Winter Squash Ripe Melon Characteristics Cantaloupe Watermelon HoneyDew HoneyLoupe Canary Casaba Days from anthesis Weight, g Respiration, µl/g-h Internal Ethylene, ppm <1 <0.1 Firmness, kg/cm Marita Cantwell, UC Davis micantwell@ucdavis.edu Soluble solids, % Extreme genetic variation among the melons Melon Quality Attributes Flavor Color Texture These quality attributes may vary due to: varieties, growing conditions, season, maturity at harvest, number of harvests, harvest & handling, storage conditions and period... Cantaloupe Maturity/Ripeness Fruit begins to separate from stem abscission zone; slip External color between net Net well developed with wax Subtending leaf dries up Internal color, firmness, soluble solids ½ slip full slip Focus on maturity/ripeness at harvest since this continues to be problematic The slip is a very useful attribute; applicable to old & new cvs. Evaluate melon varieties based on minimal changes Characterization of cantaloupe melons (cv. Laredo) harvested at maturity stages. Data are averages of melons per stage. Attribute ½ slip Full slip, hard ripe LSD.05 Weight (g) 7 19 ns External color score 1.. ns Internal CO (%) ns Internal ethylene (ppm) Internal color (chroma) ns Pulp firmness (N-f, 5mm probe) ns Soluble solids (%).5. ns 1 external color score 1=green, =slight yellow, mostly green, =yellow-green, =greenish yellow 5=yellow or yellow-orange MELON FLAVOR Sugars (>50% sucrose, 0% glucose, % fructose): At harvest, % soluble solids correlates well with extracted sugars For good flavor: Cantaloupe % & Honeydew 11-% S.S. Sugar content determined at harvest Acids <0.1%, important for good flavor? Aroma volatiles specific compounds for characteristic flavors Concentration gradients Sampling problems Sugar Measurement Destructive: % S.S. Nondestructive IR analysis Temperature compensated refractometer Digital readout eliminates errors Cantwell, 00 MCP# 1

2 Sugar loss in fresh-cut cantaloupe may be considerable, but Soluble solids do not change much; Sugar loss typically is not as extreme as in this example. Soluble Solids (%) Soluble Solids (Average varieties) Stage (<1/ slip Stage (1/ slip) Stage (full slip) 0 Days Sugar content (mg/0 g fr.wt.) Sugars Typical loss over days at 5 C (1 F): S.S. 0-% Sugars -0% Days (9 yen/dollar; ~$50 U.S.) Are these melons at optimum maturity/ripeness? Fresh Plaza June0 Italy External and internal appearance of Galia melons (cv. Deneb) harvested at stages of maturity (California, 00). 1 Maturity/Ripeness Stage % Soluble solids Stage 1 = 9. =. =. Aroma score Stage 1 =. =. = 5.0 Pulp firmness Stage 1 =.9 N = 7. =.0 Internal Ethylene Stage 1 = 0. ppm = 0. = 1.1 Melon Maturity & Quality Factors External Color Firmness (blossom end) Surface hairs, smoothness, wax Aroma Internal cavity condition Pulp color and firmness Sugar content (soluble solids) Aroma and flavor Honeydew and Orange Flesh Melons Maturity and Ripeness Classes Class 0: Immature Class 1: Mature, but Unripe Class Int. CH, Pulp firm., ppm kg-f Ground color greenish-white; peel fuzzy; no aroma; % soluble solids; flesh crisp, melon splits when cut; minimum harvest maturity Class : Mature, firmness: 1.1 cm probe Ripening Ground color white; begins to develop surface wax; pulp crisp, melon splits Average cvs Honeydew melons Sol. solids, % 0 = Immature <0.. < 1 = Mature, Unripe 0..1 = Mature, Ripening = Ripe = Overripe

3 Fruit weight, kg Development & Ripening of Honeydew Melons Harvested at Different Stages Soluble solids, % 1 0 Fruit weight Soluble solids Firmness Respiration Ethylene Data from Pratt, 1977; redrawn from Seymour & McGlasson Days from anthesis 0 1 Ripeness Class 1 0 Firmness, kg cm Respiration, mg CO kg-h Internal ethylene, µl L % Soluble solids Honeydew melons: Soluble Solids Fruits of different ripeness classes stored 1 days plus days at 0 C ( F) Soluble Solids Class 1 Class Class Initial.5 C F 5 C 1 F 7.5 C 5 F Cantwell, UC Davis Honeydew melons: Pulp Firmness Fruits of different ripeness classes stored 1 days plus days at 0 C ( F) Determination of watermelon maturity is difficult Immature. pounds-force 11 mm probe Pulp firmness Initial.5 C F 5 C 1³F 7.5 C 5 F Mature. Density Subtle differences external color Subtending dried leaf Ground spot yellowing Overmature or Ethylene exposed 1 0 Class 1 Class Class Cantwell, UC Davis cv. Tri-X 1 Melon Storage Conditions Cantaloupes.5 C ( F), 90-95% RH -5% Oxygen + -15% carbon dioxide - weeks Honeydew, Specialty Melons 5 to 15 C (1 to 59 F), 0-90% RH optimum temperature depends on ripeness - weeks Watermelon -0 C (50- F) Sensitive to ethylene 1- weeks C 50 F 7.5 C 5 F Galia melons (cv Deneb) stored weeks at C (upper) or 7.5 C (lower) and then after transferred to 0 C for days.

4 Decay Control: Cantaloupe Minimize physical injury Storage temperature: - C (- F) Chlorinated water wash (0 ppm) Fungicide in wax Hot water dip (15 F for min) High CO concentrations (-15%) MA-stored cantaloupe; Bag in Box Open bag to de-gas Allow time (- days, ambient) to change color, improve aroma Conditioning or Ripening Melons Honeydew Melon Example Conclusions from a study on cv Emerald hours 0-50 ppm ethylene Hold - days at 0 C ( F) Maturity stage (minimum ~11% SS) Honeydew melon harvest and packing in field or shed Improve external color Improve aroma BUT Loss of texture No improvement in sugars Control Ethylene 0 ppm Field packing watermelon and cantaloupes Galia melon harvest Pakistan 0 Cantaloupe harvest, Honduras 0 Greenhouse Galia harvest

5 Forced air cooled - hours required Gravity flow racking 1-MCP & Melons Field packed melons waiting to be cooled Western shipping cantaloupes-not much benefit on firmness at storage temperature. Eastern shipping cantaloupes-maintain texture loss at warm temperatures. Galia; extend shelf-life, reduce firmness loss Watermelon-clear benefit; reduce firmness loss Night harvest of cantaloupes Watermelon photo D. Huber Delays to Cool and 1-MCP treatment of Honeydew Melons Quality attributes of honeydew melon (cv Summerdew) stored days at 7.5 C (5 F) plus days at 0 C ( F). Data average of 15 melons per treatment. T1=fruit cooled to 7.5C (5F) within hr after harvest. T=fruit cooled and treated with 1 MCP at 7.5C within hr after harvest. T=fruit held at C (7F) for hr and then cooled to 7.5 C. T=fruit held at C for hr and then cooled and treated with 1 MCP at 7.5C. Treatment Visual quality Surface Decay Discoloration Stem end Decay surface External color (Hue) Pulp Firmness, N Soluble solids, % T T T T Average LSD.05 ns ns ns ns ns Common Postharvest Defects: Cantaloupes Harvested immature Overripe Sunken areas on surface - scuffing, water loss Discolored surface areas - sunburn, scuffing Soft ground spot Decay, especially on stem end Shaker melons Cantwell, 011 Melon visual quality after delays to cool at 7 C storage at d 5 C + d 0 C Suture Browning associated with increased water loss due to delays to cool Sunburn Good Quality Melon Defects (severe) and Internal Quality Ground Spot 0 h.% h.% Parameter Firmness (N)* (LSD=0.) Good Quality.7 Ground Spot 9. Sunburn. Total Weight loss Soluble Solids (%) (0.) Color (chroma) (0.7) h.0% h.% * 5 mm diameter probe 5

6 Internal breakdown Overmature Internal damage to Honeydew due to drops Shaker cantaloupes due to excessive rolling or dropping Common Postharvest Defects: Honeydews Harvested immature Overripe Chilling injury Brown blotch Decay Internal breakdown -dropping -impact injuries A B Golden Honeydew Stored 1 month C Fusarium sp. DK1 Botryodiplodia sp C External appearance of stored honeydew melons: DK Epicoccum sp DK Excellent appearance (A) Severe surface discoloration (B) Speckles (C). DK Sclerotinia sp. DK5 Penicillium sp Mature or Winter Squash Green acorn squash Kabocha squash Spaghetti squash Sweet Dumpling squash Ukranian Winter squash Buttercup squash Chinese winter squash Green Hubbard squash Red Kuri squash Turban squash Blue Hubbard squash Delicata squash Kabocha Butternut squash Maturity at harvest is key Careful Handling is essential Curing important for storage life Squash are chilling sensitive

7 1 External Appearance fruit previous slide 1 Hue Dry Weight (%) Total Sugar (sucrose) (mg/g DW) (mg/g FW) October 00 Stem integrity is Important to reduce decay October 00 Stored 7 months (air) C (50 F) % decay.5 C (55 F) 5% decay 15 C (59 F) % decay Respiration, µl CO/g-h Respiration rates of Butternut Squash Changes in physiology precede postharvest decay problems 0 Respiration rate Butternut Squash Stored 1 month, then transferred to 0 C 0 C ( F) 15 C (59 F).5 C (55 F) C (50 F) Days storage Respiration, µl CO/g-h 0 Respiration rate Butternut Squash Stored months, then transferred to 0 C 0 C ( F) 15 C (59 F).5 C (55 F) C (50 F) Days storage 0 C ( F) % decay Cantwell and Zacchari, 00 Winter Squash and Pumpkin Storage Conditions Well cured Temperature:.5-15 C (55-59 F) RH: 50-70% with 0% usually considered optimum - months Avoid ethylene Modified atmosphere not beneficial 7