Potato products, ascorbic acid addition

Concern has been shown for the restoration of L-ascorbic acid losses in potato products or its addition for product improvement (317,366, 367,371,372,373,378). Restoration may not be a simple process, depending on the specific product. Mechanical mixing of the potato product, granules, or flakes with crystalline L-ascorbic acid will not yield a uniform product, and mechanical mixing breaks down the potato particle. 

When there is an appreciable aqueous phase in the food product it is advisable to consider ascorbic acid or sodium ascorbate and a- or y-tocopherol in an emulsion form. The removal of traces of peroxide from food has been suggested (645) by the addition of ascorbic acid or sodium ascorbate during the cooking process. There are situations where powdered or fine crystalline ascorbic acid in a salt premix with an antioxidant such as tocopherol or BHA may be applied to oil cooked potato chips (646) as a method of maintaining freshness. 

Still more recent work by the same authors has suggested an alternative possibility. It has been generally assumed that L-ascorbic acid has no effect on the polyphenolase system other than its effect as a reducing agent for the o-quinone formed by the oxidation of the phenols. It has now been shown that ascorbic acid itself has an inhibitory action on the polyphenolase enzyme. When polyphenolase prepared from potato was treated with ascorbic acid under anaerobic conditions, and the ascorbic acid subsequently removed by dialysis, the activity of the enzyme was very considerably reduced. The enzyme after such treatment could not be reactivated by the addition of cupric salts and appeared to bo irreversibly inactivated. It was also shown that neither dehydroascorbic acid nor the further oxidation products of dehydroascorbic acid were responsible for this result. There is at present no explanation of the mechanism of this inhibitory action of ascorbic acid, but it is quite clear that, if these results are confirmed, other explanations are possible of why these enzymes do not exert their full potential effect in vivo. 

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