QUALITY OF MINIMALLY PROCESSED YAM (Dioscorea sp.) STORED AT TWO DIFFERENT TEMPERATURES

Abstract

This work studied the physical, chemical and biochemical alterations in minimally processed yam stored at two different temperatures, as well as the incidence of bacteria of the genus Pseudomonas. The experimental design was completely randomised in a 2x8 factorial design, with two storage temperatures (5 and 10°C) and eight storage times (0, 2, 4, 6, 8, 10, 12 and 14 days). Experiments were in triplicate. Yam was selected, peeled and cut into slices of approximately 3 cm thickness. The slices were rinsed with water, sanitised and then drained in kitchen strainers. Approximately 300 g of the processed product were packed in nylon multilayers 15 µm thick, 15 cm wide and 20 cm long. The packs were sealed, weighed and kept at 5 and 10 ± 2°C for 14 days. Fresh weight loss, baking time, enzymatic activity of polyphenol oxidases, peroxidases and catalases, total soluble phenol content, and antioxidant capacity were evaluated, as well as visual analysis and incidence of Pseudomonas sp. Means of temperatures were compared by Tukey´s test at 5% significance. Yam storage at 5°C reduced weight loss and kept visual quality for longer; it also reduced cooking time and the activity of the enzymes polyphenol oxidase and peroxidase. In contrast, it promoted higher content of total soluble phenols, as well as a higher catalase activity and antioxidant capacity. During the storage time, there was no incidence of Pseudomonas sp. Minimally processed yam stored at 10°C may be sold for up to six days, and yam stored at 5ºC for up to 14 days.