Vegetables Produce Facts English
Recommendations for Maintaining Postharvest Quality
Maturity & Quality
Summer squashes (soft-rind) are consumed at a range of physiological maturities but are defined as immature fruits of the diverse Cucurbitaceae family. Depending on cultivar and temperature, the time from flowering to harvest may be 45 to 60 days for zucchini, yellow straightneck or crookneck, and scallop (Patty Pan-type) squash and 75 days or more for many of the Sponge squash (immature gourds) such as Luffa. Fruit may be harvested at a very immature stage, at the desired fruit size, before seeds begin to enlarge and harden. A thin, soft external rind and external glossiness are also indicators of a pre-maturity condition. The entire fruit is edible, either raw or cooked, without removal of seeds and seed cavity tissue. Small, young fruit are tender and generally have a slightly sweet taste.
Summer squash quality is based on uniform shape, tenderness of rind and internal tissue, overall firmness, a glossy skin color, and an intact well-trimmed stem portion. Uniformity of shape is an important quality factor and is defined to be characteristic of the type or variety, and free of twisting, groves, or other disproportionate growth defects. Size is not part of the United States Standard for grades but may be contractually specified as minimum or maximum diameter or length or both. Additional quality indices are freedom from growth or handling defects (discoloration, cuts bruises, abrasions, pitting) freedom from decay, and an absence of yellowing on dark green varieties.
U.S. Grades are No. 1 and No. 2 (effective Jan. 6, 1984)
Maturity & Quality Photos
Temperature & Controlled Atmosphere
Summer squashes are not stored, ideally, for longer than 10 days. Zucchini squash has been stored at 5°C with acceptable market quality for up to two weeks. Storage at below 5°C for more than 3-4 days will generally result in chilling injury. Visual and sensory quality deteriorate and surface pitting and discoloration or browning progress rapidly following chilling injury . Shriveling, yellowing, and decay are likely to increase following storage beyond two weeks, especially upon removal to typical retail conditions.
Optimum Relative Humidity
To calculate heat production multiply ml CO2/kg·hr by 440 to get Btu/ton/day or by 122 to get kcal/metric ton/day.
0.1-1.0 µl/kg·hr at 20°C (68°F)
Summer squash varieties are low to moderately sensitive to exogenous ethylene. Accelerated yellowing of green types will result from low levels of ethylene during distribution and short-term storage.
Controlled or modified atmosphere storage or shipping offer little benefit to summer squash quality maintenance. Low O2 levels (3-5%) delay yellowing in dark green varieties and delay the onset of decay by a few days. Zucchini tolerates elevated CO2 (less than or equal to 10%) but storage life is not greatly extended. Elevated CO2 (greater than or equal to 5%) has been reported to reduce chilling sensitivity in zucchini.
Physiological and Physical Disorders
Use of Materials
The UC Postharvest Technology Center grants users permission to download textual pages (including PDF files) from this World Wide Web site for personal use or to reproduce them for educational purposes, but credit lines and copyright notices within the pages must not be removed or modified.
Except for these specified uses, no part of the textual materials available on the UC Postharvest Technology Center Web site may be copied, downloaded, stored in a retrieval system, further transmitted or otherwise reproduced, stored, disseminated, transferred or used, in any form or by any means, except as permitted herein or with the University of California's prior written agreement. Request permission from UC Postharvest Technology Center. Distribution for commercial purposes is prohibited.
The information in this fact sheet represents our best understanding of the current state of knowledge at the time of the latest update, and does not represent an exhaustive review of all research results. Links to any of these UC Postharvest Technology Center pages are permitted, but no endorsement of the linking site or products mentioned in the linking page is intended or implied by such a link.
How to Cite
Author(s) names. Initial publication or update date (located at the top). Title. Link to the specific Produce Fact Sheet webpage (Accessed date)
Example: Cantwell, M. and T. Suslow. 2002. Lettuce, Crisphead: Recommendations for Maintaining Postharvest Quality.