Mexican squash: the pale calabacita for sautes, soups and tacos

Mexican squash goes by several names on Los Angeles order sheets: grey squash, calabacita, Mexican zucchini. It is the pale, mottled grey-green summer squash that is shorter and rounder than a zucchini, with tender skin and a delicate flavor. King Quality Produce receives it every day of the year from growers in Mexico and California, packs it in 22 lb boxes, and grades it Fancy, Extra Fancy and #2. Here is what buyers should know.

What Mexican squash is

Botanically it is the same species as zucchini, Cucurbita pepo, harvested immature while the rind is still soft and the seeds undeveloped. Mexican breeding literature calls the type calabacita tipo Grey Zucchini; a 2013 study in Revista Chapingo Serie Horticultura evaluated eight commercial Grey Zucchini hybrids and reported fruit averaging about 11.9 centimeters long and 4.1 centimeters wide at harvest, roughly 4-3/4 by 1-5/8 inches³. The University of California's summer squash guide lists zucchini in dark, medium and light green, with Greyzini as the light green example⁶.

The skin is pale sage green flecked with lighter speckles, the fruit tapers toward the stem and bulges toward the blossom end, and the flesh is whiter, softer and milder, which is why Mexican cooks prefer it for guisados and soups.

KQP carries Mexican squash in three house grades, all in the 22 lb box. Extra Fancy is small, young, glossy fruit with the stem on and no scuffing. Fancy is the standard grade for restaurant and market accounts. #2 is sound, firm fruit that runs larger or shows cosmetic marks, priced for soups, stews and anything diced.

Where it grows and when

Most of this squash comes from Mexico, and most of Mexico's export squash comes here. A University of Florida analysis found that Mexico supplied 96 percent of U.S. fresh squash imports in 2020, that U.S. imports grew from 386 million pounds in 2000 to 1,089 million pounds in 2020, and that about 70 percent of Mexico's 2019 fresh squash production was exported to the United States⁴. More than 90 percent of the Mexican volume arrives between October and June⁴.

California carries the warm months. The UC summer squash guide, published in 1999, names the Imperial Valley, the Central Valley from Kern to Merced counties, and the south-central coast from Santa Barbara north as the major areas, with main production in spring and summer and acreage falling in fall because of virus and whitefly pressure⁶. Between the two countries KQP has Mexican squash on the floor every week of the year: Mexican fruit in winter and spring, California fruit from late spring into fall.

How to buy: grades, packs and what to check on receiving

The USDA standard for summer squash, effective September 2016, has two grades⁵. U.S. No. 1 squash must be fairly young and fairly tender, fairly well formed, firm, with stems attached, and free from decay and from damage by discoloration, cuts, bruises, scars or freezing⁵. U.S. No. 2 must be firm and not old and tough, and free from serious damage⁵. The standard defines fairly young and fairly tender as tender skin for the variety, tender undeveloped seeds and firm, moist seed-cavity tissue, and defines firm as not yielding appreciably to slight pressure and not noticeably wilted⁵. There is no size requirement; size may be specified by diameter or length in inches and quarter inches⁵. KQP Extra Fancy and Fancy sit inside U.S. No. 1; #2 tracks the federal No. 2.

On receiving, look for glossy skin, which the UC Davis Postharvest Technology Center says indicates the immaturity you want, and press gently for firmness². Check the stem end: UC Davis says a poorly trimmed stem promotes decay and that fruit should be cut from the vine rather than snapped². Reject pitting or water-soaked spots, which are chilling injury, and watch for scuffing and compression on the soft rind².

• Pack: 22 lb box
• Grades: Fancy, Extra Fancy, #2
• Availability: year-round, Mexico and California

Storage and shelf life

Summer squash is a short-life item. UC Davis recommends 41 to 50 F (5 to 10 C) at 95 percent relative humidity, with a storage life ideally no more than 10 days; shriveling, yellowing and decay increase beyond two weeks, especially under retail conditions². Chilling injury occurs below 41 F when fruit is held more than a day or two, showing as water-soaked pitting, discoloration and accelerated decay, and the damage is cumulative². Dehydration is the other common failure: fruit shrivels quickly unless it is cooled promptly².

Squash breathes hard. UC Davis measured respiration at 42 to 48 milliliters of CO2 per kilogram per hour at 68 F versus 7 to 10 at 41 F, so a box left on a warm dock ages several times faster than one in the cooler². Ethylene sensitivity is low to moderate, but low levels speed yellowing in green types, so keep squash away from ripening rooms². In practice, hold Mexican squash at 45 F in the box, do not stack heavy cases on it, and turn it inside a week.

Nutrition

USDA's FoodData Central does not list grey squash separately, so the reference is its entry for summer squash, all varieties, raw. Per 100 grams it lists 16 calories, 94.64 grams of water, 3.35 grams of carbohydrate, 1.1 grams of fiber, 2.2 grams of sugars and 1.21 grams of protein¹. Minerals include 262 mg of potassium, 17 mg of magnesium, 38 mg of phosphorus, 15 mg of calcium and 2 mg of sodium; vitamins include 17 mg of vitamin C, 29 micrograms of folate, 0.218 mg of vitamin B6, 120 micrograms of beta-carotene, 2,125 micrograms of lutein plus zeaxanthin and 3 micrograms of vitamin K¹.

Two numbers stand out. The 17 mg of vitamin C is about 19 percent of the 90 mg Daily Value; the National Institutes of Health describes vitamin C as an antioxidant that is required for collagen synthesis, plays a role in immune function and improves absorption of the nonheme iron found in plant foods^{1, 7}. NIH also notes that prolonged storage and cooking reduce vitamin C⁷. The 262 mg of potassium is a step toward an adequate intake that NIH sets at 3,400 mg a day for men and 2,600 mg for women, against a Daily Value of 4,700 mg; NIH says potassium supports nerve transmission, muscle contraction and fluid balance, and that Americans generally consume less than recommended^{1, 8}.

In the kitchen

Mexican squash is a daily vegetable in Los Angeles, not a specialty. Taquerias and fondas dice it with corn, onion, tomato and chile for calabacitas, with queso fresco or crema for calabacitas con queso. It goes into caldo de res and caldo de pollo in large chunks, into picadillo and into sopa de verduras. Because the skin is thin and the seed cavity small, there is no peeling and little waste.

Markets in East LA, South Gate, Huntington Park and the Valley sell it loose by the pound as calabacita. For purchasing, Extra Fancy is the grade when the squash is served whole, halved or stuffed. Fancy covers most sautes and soups. #2 is the right buy for anything diced into a guisado or blended into a crema.

Call the KQP office at (213) 627-7181 or email office@kingqualityproduce.com for this week's Mexican squash counts, grades and pricing.