INHIBITION OF ENZYMATIC BROWNING OF FRESH-CUTrnPOTATO BY IMMERSION IN CITRIC ACID IS NOT SOLELYrnDUE TO PH REDUCTION OF THE SOLUTION

摘要

In order to elucidate the mechanisms of citric acid in fresh-cut potato browningrninhibition, various concentrations of immersion solutions were prepared usingrneither citric or sulfuric acid for pHu00024 and sodium hydroxide for pH>7. Dippingrnpotato slices in water (control, pH=5.84) allowed severe browning torndevelop during 6 days of storage at 5C. Citric acid at concentrations >0.5% inhibitedrnbrowning on the cut surfaces of fresh-cut potato without affecting the antioxidantrncontent or PPO activity, and induced the highest increase of tissue pHrnduring storage. Dipping in 1 or 2% citric acid (pH 2.42 and 2.24) reduced allrncolor changes equally, resulting in the lowest discoloration scores. Acidification ofrnthe immersion solution using H_2SO_4 also reduced discoloration, as NaOH solutionsrnwith pH>7, but neither was as effective as citric acid. Further reducing thernpH of 0.5% citric acid from 2.59 to 2.24 with H_2SO_4 also did not improve browningrninhibition.