Effect of calcium addition and acidification on the quality characteristics of canned okra (Hibiscus esculentus L).

A study was conducted on calcium chloride treatments of canned okra acidified by adding either acetic, citric, lactic, malic or tartaric acids or by lactic fermentation. The quality of the processed okra was determined by physical, chemical, microbiological and sensory analyses after a two month storage period at room temperature. The results indicated the possibility of processing high quality canned okra by small canneries, with low cost equipment and low energy requirements. The acidification procedures ensure minimal risk of botulism.

The control of polyphenol oxidase activity in fruits and vegetables. A study of the interactions between the chemical compounds used and heat treatment.

Objective of this research was to find alternative methods for the control of polyphenol oxidase (PPO) activity in fruits and vegetables with the purpose of reducing or eliminating the use of SO2 for this purpose. Interactions between the use of ascorbic acid, citric acid, EDTA, sodium metabisulphite and heat treatment (70 degrees C for 2 min) in the control of PPO activity were studied in avocado (var. Fortuna), banana (var. Nanica), apple (var. Ana, Fuji, Gala & Golden), pear (var. D'Agua), peach (var. Réal), potato (var. Bintje), eggplant (var. Super F100), mushroom (Agaricus bisporus) and hearts-of-palm (Euterpe edulis Mart). The results demonstrated that PPO of avocado and eggplant was most resistant to inhibition by the methods used. The least efficient method tested for the control of PPO was the addition of ascorbic acid and EDTA, while the most efficient methods investigated included the use of ascorbic acid, citric acid, sodium metabisulphite and heat treatment. The results indicated that, with the exception of PPO from avocado, the most adequate alternative method to substitute for the use of SO2 in the control of PPO was a combination of ascorbic acid, citric acid and heat treatment.

[Effect of storage on the levels of ascorbic acid and beta-carotene in freeze dried red guava (Psidium guayava L.)]. / Efeito do armazenamento nos teores de ácido ascórbico e beta-caroteno em goiaba (Psidium guayava L.) liofilizada.

The retention of ascorbic acid, beta-carotene and sensory properties of freeze-dried red guava pulp stored during 18 months in hermetically sealed brown glass flasks, at room temperature (ca. 25 degrees C) was studied. The results showed that the losses during freeze-drying were of 8.13% for ascorbic acid and 0.63% for beta-carotene. During storage more pronounced losses of these elements occurred during the first six months, becoming progressively smaller and almost irrelevant at the end of the period. The sensory evaluation of the reconstituted pulp showed that the retention of flavor was good. A Gompertz curve was fitted to observe data and showed to be efficient in explaining the trend of reduction for both elements under study. The excellent retention of ascorbic acid, the relatively fair retention of beta-carotene during processing and storage of freeze-dried red guava pulp, and the good conservation of flavor of the reconstituted pulp are evidences of the importance of this process for preserving and storing fruit pulps.