DEVELOPMENTAL-CHANGES AND POSTHARVEST PHYSIOLOGY OF TOMATILLO FRUITS (PHYSALIS-IXOCARPA BROT)

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-mu-l CO2 g-1 h-1 at 20-degrees-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-degrees-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-degrees-C and 20-degrees-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-degrees-C for 3 weeks resulted in higher decay levels and surface pitting than storage at 5-degrees-C. Decay incidence was decreased by a chlorinated water wash before storage.