ASABE Technical Library - Abstract

Abstract.

Guava fruit (Psidium guajava) is a climacteric tropical fruit highly appreciated by its flavor, aroma and nutritional value. Guava is the fruit with the highest vitamin C content (even 228 mg of ascorbic acid per 100 g of fresh fruits, according to USDA food database composition). However, high losses in harvested guava are due to mold attacks, being the main problem the anthracnose, caused by the mold Colletotrichum gloeosporioides. In this study, microwave-assisted hydrothermal treatments in guava were developed in order to control anthracnose. Guava fruits (250 g of fruits in 250 g of water) were treated in a microwave oven at 350 W or 500 W. Additionally, a batch of guavas was treated with convective hydrothermal treatment (water bath with stirring) and another batch was left untreated as a control. Immature guavas were heated till an internal temperature of 50°C, this target temperature has been reported as the appropriate to control C. gloeosporioides. After heating, guavas were cooled in water at 4°C. Treatments times using microwaves were shorter than the convective treatment, even 1/8 of the time in water bath. Titratable acidity (0.48-0.58% citric acid), pH (3.7-4.1), total soluble solids (11-13ºBx), color, firmness (12.14 N in immature stage to 0.26 N for commercial maturity) and ascorbic acid content (244.7-278.8 mg ascorbic acid/100 g fruit) were determined before and after the thermal treatments and during the storage of the fruits at room temperature. Hydrothermal treatments were able to control anthracnose in guava fruits. Microwave-assisted treatment performed at 350 W preserving fruit quality for over 9 days at room temperature.