POSTHARVEST HANDLING OF CUCUMBERS

WHAT IS CUCUMBER? Cucumis sativus L. of Cucurbitaceae family. Plant of tropical origin (India?) Relative of melons, pumpkins, squashes, watermelons In contrast to most of them – harvested immature (young) Greenhouse cucumbers: parthenocarpic, develop without pollination. Smooth tender skin, eaten without peeling Types of greenhouse cucumbers: European (or Dutch, English) type – long and Beit-Alpha type (Israeli origin) – short. Beit Alpha type gives 2-3 times higher yield than the Dutch type, and better fruit quality (but the Dutch tends to be more resistant to powdery mildew). Dutch type Beit-Alpha type

Senescence-related changes in cucumbers Postharvest biology of cucumber = Postharvest problems of cucumber Immature fruit: tends to continue the development → yellowing, change of texture and taste Senescence-related changes in cucumbers SENSITIVE TO ETHYLENE! NOT TO BE KEPT WITH ETHYLENE-PRODUCING COMMODITIES: TOMATOES, AVOCADO, BANANA, APPLE, PEAR, FIG, MELON, etc.

AIR HUMIDITY IS IMPORTANT: 90-95% Tender skin: tends to easily lose water → SENSITIVE TO DESICCATION Shriveling AIR HUMIDITY IS IMPORTANT: 90-95% WHY NOT HIGHER? Water condensation favors disease development. SENSITIVE TO POSTHARVEST DISEASES

Major postharvest pathogens of cucumber (in Israel): fungi Botrytis, Sclerotinia, bacterium Pseudomonas lachrymans Sclerotinia Botrytis cinerea P. lachrymans The Botrytis attacks damaged (e.g., by low temperature) or senescent tissues (=“dieing”). Stimulated by ethylene. The Botrytis decay often starts the blossom end (from the flower residue). If possible, the flower residue should be removed. The Botrytis at the stem end usually results from inaccurate picking (smashed peduncle). Combination of Botrytis and P. lachrymans.

Develops chilling injury at temperatures below 9°C Tropical/subtropical origin → VERY SENSITIVE TO LOW STORAGE TEMPERATURE Develops chilling injury at temperatures below 9°C Pitting: a chilling injury symptom OPTIMAL STORAGE TEMPERATURE 10-11°C The chilling injury often transforms into fungal rots Another postharvest disorder: development of warts during storage of initially smooth cucumbers

Postharvest technology : Trying to solve the problems Harvest criteria: size (for Beit Alpha type): diameter 25-35 mm, length 150-200 mm); smooth, glossy dark-green skin. Sanitation at harvest: clean tools; avoiding contact of fruit with soil / substrate. Reducing mechanical damage: accurate hand-picking. Avoid dropping fruit, minimum transfers. Selective picking.

Postharvest procedures Local market (currently – most of the cucumbers) Transfer into 12-kg plastic boxes lined with perforated polyethylene bag (to reduce moisture loss) Transportation to “logistic centers” of marketing companies or wholesale market (up to 2-3 hours) Harvesting Marketing on open shelves (up to 2 days) at ≥ 20C and 50-70% RH Storage at “logistic centers” up to 3 days at 15-17C and 85-90% RH MAJOR STAGE OF DETERIORATION

Retail packaging: protection for the produce on the shelf PVC-wrapped tray Long “European” (= “Dutch”, “English”) greenhouse cucumbers: individually shrink-wrapped (no photo shown) US: waxing (usually peeled before eating) Bags (Japan)

Fresh-cut cucumbers (supermarket, China)

Transfer to packing facility Sorting by size and shape Local market (advanced scheme, currently in progress) Hot water wash (55-58C, 15-20”, no brushes!), drying Transfer to packing facility Harvesting Transportation to “logistic centers” of marketing companies or wholesale market (up to 2-3 hours) Packaging into polyethylene-lined plastic boxes Sorting by size and shape Retail packaging Storage at “logistic centers” up to 3 days at 15-17C and 85-90% RH Marketing on open shelves at ≥ 20C and 50-70% RH

SORTING AND PACKAGING Automated packing-house for cucumbers, Japan Cooperative of ~10 growers Optical sorting facility

Export (mostly cucumbers from “organic” growing) Transfer to packing facility Sorting by diameter Harvesting Packaging in 4-kg boxes (2 layers of fruit) with Xtend bags (liners) Gentle wiping with soft and clean tissue, removal of flower residue Quality control and transportation to export outlet Shipment to Europe by sea: up to 12 days at 10-11C Marketing in Europe MAJOR POTENTIAL FOR DETERIORATION

Xtend liners have higher water vapor permeability than polyethylene. “Xtend” effects: combination of modified atmosphere (MA) and modified humidity (MH) packaging Xtend liners allow accumulation of increased CO2 concentration due to the produce respiration (modified atmosphere). CO2 inhibits ethylene. Xtend liners have higher water vapor permeability than polyethylene. They allow optimal RH level of 92-97%, reduce weight loss and prevent the accumulation of condensed water.

Effects of Xtend packaging on cucumbers 12 days at 10C +3 days at 20C 3 days at 10C+ 3 days at 20C Inhibition of yellowing Inhibition of decay Comparison with perforated polyethylene liner (as for local market) and non-packaged fruit

Effects of Xtend packaging on chilling injury of cucumbers Xtend packaging prevents external signs of chilling injury, but not the internal signs Recommended to ship cucumbers in Xtend at optimal temperature of 10C

Potential problems with applying the Xtend packaging with cucumbers 1. Potential to CO2 damage (>10% CO2) NOT TO OVERLOAD THE PACKAGES! OBSERVE THE TEMPERATURE RECOMMENDATIONS! OPEN THE PACKAGES AFTER TRANSFER TO SHELF-LIFE (NON-COOLED) CONDITIONS! CO2>12% CO2<9% CO2 damage to cucumbers 6 kg cucumbers in the liner for 4-kg load 2. High cost

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