Developmental changes and postharvest physiology of tomatillo fruits ( Physalis ixocarpa Brot.)

Abstract

The tomatillo or husk tomato ( Physalis ixocarpa Brot.) is a solanaceous fruit vegetable used to prepare the green sauces of Mexican cooking. Developmental changes were studied from anthesis to yellowing in fruits of cultivar ‘Rendidora’. During an 8 week growth period both chlorophyll and carotene contents decreased. Sugar content increased to 7.0% due to accumulation of non-reducing sugars. Titratable acidity also increased with fruit development, reaching 1.3% at 8 weeks. Total pectin content reached a maximum (1.1%) at 6 weeks of development. The ascorbic acid content of tomatillos was low (3–4 mg 100 g −1) and did not change during fruit development. Tomatillos may be harvested commercially from about 5 to 8 weeks of development, or when the fruits have filled the calyx (husk). The respiration rate of tomatillos was low (18–25 l CO 2 g −1 h −1 at 20 °C) and decreased with time in storage. Respiration rates were higher for immature than for mature and ripening fruits. Rates of ethylene production were also low (0.2–2.0 nl g −1 h −1 at 20°C) for immature and mature fruits. Ripening and ripe fruits (horticulturally over-mature) showed much higher rates of ethylene production (20–40 nl g −1 h −1) than developing fruits. Storage of fruits at 10°C and 20°C resulted in greater weight loss and color change than storage at lower temperatures. The freshness of the husks was also maintained at lower temperatures. Storage at 2.5°C for 3 weeks resulted in higher decay levels and surface pitting than storage at 5°C. Decay incidence was decreased by a chlorinated water wash before storage.