Fruit development, harvest index and ripening changes of guavas produced in central Mexico

The variabilities in guava (Psidium guajava cv. 'Media China') development period, and physical and chemical properties were determined for the spring-summer and autumn-winter harvest seasons in Mexico. At 20 day intervals, fruit diameter, weight, specific gravity (SG), total soluble solids content (SSC), ascorbic acid, titratable acidity, color and firmness were determined. Fruit growth showed a double sigmoidal pattern, with spring-summer fruit needing 130 days while autumn-winter fruit required 190 days to reach the ripe stage. Acidity decreased during development while ascorbic acid and SSC increased during the last stage of growth. Autumn-winter fruit had higher SCC, titratable acidity, and ascorbic acid concentrations than spring-summer fruit. The climacteric peaks in carbon dioxide and ethylene production were reached after 7-8 days in autumn-winter fruit as compared with 4-5 days in spring-summer fruit. The best maturity index was color: the mature green fruit could be harvested with L*, a* and Hue values of 65 +/- 3, -15 +/- 2 and 110 +/- 2, respectively. These values corresponded to fruit with yellowish green external color. (C) 1998 Elsevier Science B.V. All rights reserved.