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Effects of vacuum microwave drying on the flavor, textural and color characteristics of banana chips Mui, Winnie Wing Yan

Abstract

Bananas were peeled, sliced, and dipped in a solution of 2000 ppm potassium metabisulfite. These slices were next air dried (AD) to remove 60%, 70%, 80% and 90% of the initial moisture respectively and then vacuum microwave dried (VMD) to a final moisture content of about 3% db. The effects of different drying techniques (air drying, air drying / vacuum microwave drying, and freeze drying) on volatile retention in the banana chips were determined using headspace solid-phase microextraction. The effects of these drying techniques on the textural and color characteristics of banana chips were also investigated. Both gas chromatographic and sensory analysis showed that banana chips which underwent more vacuum microwave drying had significantly lower levels of volatile compounds and significantly lower ratings for both the aroma and flavor attributes. 90% AD & 10% VMD chips had significantly higher volatile levels and significantly higher sensory ratings than 100% AD samples. Textural analysis of the banana chips showed that the AD / VMD samples were significantly crisper than the AD and FD samples. Microscopic analysis also showed that vacuum microwave drying exerted a puffing effect on the VMD samples. Color analysis showed that less browning occurred in the VMD and the AD/VMD chips than in the AD samples. The inhibiting effect of five chemicals on banana polyphenoloxidase was studied. 2000 ppm potassium metabisulfite with or without 2% citric acid was the most effective inhibitor. Nevertheless, gas chromatographic analysis showed that bananas dipped in sulfite had significantly lower volatile levels compared to fresh bananas.

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