Changes in quality attributes of intermediate-moisture raisins during storage

Abstract

The aim of this research was to determine the changes in chemical and microbiological qualities of ready-to-eat intermediate-moisture raisins during storage. Raisins were immersed into hot (98±1°C) glucose solutions (10% w/v and 20% w/v) containing 1% (w/v) potassium sorbate to inhibit mould and yeast growth. Raisins were kept in glucose solutions until the moisture content became 20%, 25% and 30%, respectively. The reconstituted raisins were then stored at ambient temperature (23±3°C) and 50–60% relative humidity for 8 months in polyethylene/polyamide (PE/PA) packaging material. The changes of moisture content, water activity, pH values, total titratable acidity, total sugar contents, Hunter L, a and b color values, total mesophylic aerobic bacteria counts, and mould and yeast counts were determined during storage at 2-month intervals. The results of chemical analysis showed that changes in the total titratable acidity, total mesophylic aerobic bacteria, and mould and yeast counts of the products were increased significantly (P<0.05). However, the pH values, total sugar contents, and Hunter L, a, and b color values were decreased during the storage period (P<0.05).