Effect of blanching, dehydration method and temperature on the ascorbic acid, colour, sliminess and other constituents of okra fruit

Abstract

Freshly harvested okra fruits were blanched in boiling water (with or without 0.2% sodium metablsulphite salt) and the effect of this treatment, dehydration methods and temperature on certain characteristics of okra investigated. Blanching resulted in the slight decrease in carbohydrate, fat, ash, colour components, ascorbic acid and viscosity. Besides this initial loss, blanching in sulphite solution led to the retention of more of the colour components and ascorbic acid during dehydration. All dehydrated okra samples had higher contents of carbohydrate, fat and ash but lesser contents of protein and ascorbic acid than fresh okra. Fresh okra fruits, on the other hand, had higher content of the colour pigments and were more viscous than all dehydrated products. Samples blanched prior to dehydration retained more of the colour components but were less viscous than unblanched samples. Vacuum dehydrated samples retained more ascorbic acid, colour pigment and mucilage at each of the dehydration temperatures than those from a hot air oven. High dehydration temperatures had negative effect on the colour, ascorbic acid and viscosity of okra.

Evolution of ascorbic acid and peroxidase during industrial processing of broccoli

“…A combination of leaching, oxidation to biologically inactive forms, 33 enzymatic degradation and destruction of the ascorbic acid by heat during hot water blanching would explain such losses, 38 which vary in broccoli from 40 to 55%. 2,27,39 The comparatively large surface area of broccoli compared with its volume facilitates the migration of water towards the vegetable's exterior.…”

Effect of air drying temperature on the quality of rehydrated dried red bell pepper (var. Lamuyo)

“…The fresh red pepper contained 1.60 ± 0.26 g ascorbic acid/100 g sample. All rehydrated samples contained less ascorbic acid than the fresh pepper due to a combination of leaching, oxidation and thermal destruction of ascorbic acid during hot-air drying and subsequent rehydration (Inyang & Ike, 1998). The air drying temperature had a detrimental effect on the retention of ascorbic acid, as heated air inherently exposes the products to oxidation, reducing their ascorbic acid content.…”

Efeito de diferentes processamentos sobre o teor de ácido ascórbico em suco de laranja utilizado na elaboração de bolo, pudim e geléia

“…Alguns trabalhos publicados avaliaram a perda de nutrientes durante o processo de cocção de hortaliças verdes [11,13,14,23,26] e de batatas [5,12,18]. BENASSI & ANTUNES [3] avaliaram, também, a influência de diferentes métodos de cocção de hortaliças na degradação de AA.…”