Effect of Osmotic Pre-treatment and Temperature Storage Conditions on Water Activity and Colour of Dried Apple

Abstract

Abstract The cylinders of apples cv. Braeburn were subjected to osmotic dehydration in a sucrose solution with the addition of chokeberry juice concentrate. After osmotic pre-treatment the pieces of apples were dried by two methods: freeze-drying and air-drying. The storage results of dried apples at temperature 25–45 °C for 7 and 12 months were satisfactory. Mass changes were very minor. During storage dried apples obtained by both methods exhibited microbiological stability even after 7 and 12 months of storage, due to the fact that the water activity did not exceed the value of 0.4. Under the influence of the technological processes application, as well as storage conditions, appearance changes in the samples occurred. Higher temperature of storage had an increase impact in colour changes of control samples (without osmotic pre-treatment) and also osmotically dehydrated into sucrose solution, mainly in the case of samples which had dried using freeze-drying. Previously immersed in chokeberry juice concentrate, dried apples had colour changes comes from colour of solution.