Effect of Removal of Amino Acids and Phenolic Compounds on Non-enzymic Browning in Stored Kiwifruit Juice Concentrates

Abstract

The effect of the removal of phenolics and amino acids, and initial oxidation of ascorbic acid on non-enzymic browning in kiwifruit juice concentrate during storage at 20°C was investigated. Kiwifruit juice was passed through cation exchange resin Dowex 50W and/or adsorbent resins Amberlite XAD-4 and XAD-2, to remove amino acids and phenolic compounds. The extent of the initial oxidation of ascorbic acid which occurred during treatments was determined before concentration. After the initial storage period, during which products from ascorbic acid oxidation were most reactive, the browning rates in concentrates which had approximately 90% of the amino acids removed were half that of the control. Initial oxidation of ascorbic acid led to an initially accelerated browning rate, which affected the overall browning occurring during storage. Removal of amino acids with minimal oxidation of the juice produces a kiwifruit juice concentrate with the least overall browning during storage, while removal of phenolic compounds does not appear to be a beneficial procedure for the control of browning in kiwifruit juice concentrate.