Effect of thermal treatment and storage on the quality of apple juice

Abstract

Thermal processing of liquid foods is a widely utilized procedure in the food industry. Usually, the time and temperature required for a safe process depend upon the destruction of microbial spores and inactivation of enzymes. With regard to this fact, the influence of pasteurization temperature on quality of apple (Malus domestica V. Red Delicious) juice during 2 month refrigerated storage was studied. After extracting the juice from screw type juice extracting machine, it was divided into three lots. One lot was heat processed separately at 65 °C with 15, 25 and 35 min holding time. Other two lots were heat processed separately at 75 °C with 10, 20 and 30 min and 85 °C with 5, 10 and 15 min holding times in glass bottles. The experiment was laid out in FCRD with three replications. The results showed that the ascorbic acid and titratable acidity in thermally treated samples decreased with increase in storage period. Increase of TSS was due to hydrolysis of starch into sugar, due to dehydration and degradation of pectic substances of juice into soluble solids. From these results, the juice extracted with screw type juice extractor, processed at 65 °C for 15 minutes maintained better quality characteristics in terms of TSS, acidity, ascorbic acid and reducing sugars during 2 month refrigerated storage.