Browning of ascorbic acid-containing ethanolic solutions
Date Issued
2011
Date
2011
Author(s)
Chuang, Pei-Ting
Abstract
Color is a major quality attribute of alcoholic beverages (wine and related products). Nonenzymatic browning occurs in alcoholic beverages readily and downgrades their value. Ascorbic acid degradation can be a major browning pathway in alcoholic beverages that contain fruit juice as an ingredient. The present study took ascorbic acid as the major object in the experiments. The composition of various juice-containing alcoholic beverages on the market was analyzed for composition first. Model systems that contain the similar composition in proper buffer solutions at various ethanol concentrations were then constructed to simulate the real products. The degradation rate, the degradation products, and the relation between ascorbic acid and browning index were investigated.
In the result, the aerobic degradation pathway was found to dominate over the anaerobic pathway in all model solutions. The compounds 2-furoic and 3-hydroxy-2-pyrone were among the major degradation products. Higher ethanol concentrations corresponded with higher 3-hydroxy-2-pyrone plus 2-furoic acid contents among solutions. Bad correlation was found between browning index and the amount of degradation products. Tannins, as represented by catechin, were found to be more influential than other components, including sugars, amino acids, metal ions and organic acids. Different ethanol concentrations resulted in the formation of different profiles of ascorbic acid degradation products. It can be attributed to the difference in water activity (Aw) as the major cause. High ethanol concentrations, or low Aw, favor the dehydration and further degradation of L-xylosone, an intermediate compound in ascorbic acid degradation. L-xylosone has been recognized as the only substance that may react with catechin to cause browning. The accelerated degradation of L-xylosone reduces its own availability to react with catechin in ascorbic acid-catechin browning.
The above-described results suggest that the tannin contents in ascorbic acid-containing alcoholic beverages would better be decreased for avoiding over-browning in long-term storage. A high ethanol concentration corresponds to a low Aw that although promotes the degradation of ascorbic acid may actually reduce browning as a consequence of the decreased rate in ascorbic acid-tannin reaction.
Subjects
Ethanol
Browning
Ascorbic acid
Catechin
Water Activity
Alcoholic Beverage.
Type
thesis
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