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Application of thermal inactivation of enzymes during vitamin C analysis to study the influence of acidification, crushing and blanching on vitamin C stability in Broccoli (Brassica oleracea L var. italica)

Author:
Munyaka, Ann Wambui, Oey, Indrawati, Van Loey, Ann, Hendrickx, Marc
Source:
Food chemistry 2010 v.120 no.2 pp. 591-598
ISSN:
0308-8146
Subject:
ascorbic acid, enzyme inactivation, food analysis, food composition, heat inactivation, broccoli, acidification, crushing, blanching, ascorbate oxidase, extraction, pH, florets, stems, dehydroascorbic acid, temperature, food nutrient losses, food matrix
Abstract:
The effectiveness of heat inactivation of oxidative enzymes e.g., ascorbic acid oxidase (AAO) to stabilise vitamin C during extraction and analysis was evaluated. The influence of different sequences of performing treatments including acidification (pH 4.3 vs. pH 6.5), crushing, high temperature short time (90°C/4min-HTST) and low temperature long time (60°C/40min-LTLT)) blanching on vitamin C stability in broccoli florets and stalks was also investigated. Heat inactivation of enzymes prior to matrix disruption resulted in higher vitamin C values mainly in L-ascorbic acid (L-AA) form, while lack of enzyme inactivation resulted in high vitamin C losses resulting from conversion of L-AA to dehydroascorbic acid. Various treatments and their sequence of application influenced vitamin C stability as follows: (i) crushing prior to blanching reduced vitamin C stability and (ii) in the absence of heating, acidification increased vitamin C stability (iii) blanching prior to crushing resulted in higher vitamin C retention, with HTST blanching retaining more vitamin C than LTLT blanching.
Agid:
774463