Osmotic Dehydration as a Pretreatment Modulating the Physicochemical and Biological Properties of the Japanese Quince Fruit Dried by the Convective and Vacuum-Microwave Method

Abstract

The aim of this study was to determine the effect of osmotic dehydration (OD) using fruit concentrates (apple, pear, pineapple, sour cherry, blackcurrant, and chokeberry), before combined drying involving convective drying and vacuum-microwave finish drying, on the drying kinetics and physiochemical parameters (dry weight, water activity, content of l-ascorbic acid, sugars, organic acids, and phenolic compounds). Moreover, biological activities, including antioxidant, antidiabetic, and anticholinergic activities, of the dried Japanese quince fruit and osmotic fluids before and after osmotic dehydration have been assessed. The chokeberry concentrate reduced the final moisture ratio by half compared with the non-OD Japanese quince fruit, and the pineapple and sour cherry concentrates hindered the dehydration process during vacuum-microwave drying. OD significantly shortened the combined drying time compared with non-OD samples. The OD Japanese quince fruit was characterized by an increased content of sugars (up to 20 times more) and a significant reduction in the content of organic acids (even 77% reduction compared with non-OD fruit). Total phenolic content and antioxidant capacity of OD fruits decreased, but increased inhibition potential of α-amylase, acetylcholinesterase, and butyrylcholinesterase was observed. Osmotic fluids were also analyzed before and after the OD, and the following changes were found: reduction of sugars and increase of organic acid content, increase in phenolic content, antioxidant and antidiabetic potential, regardless of the concentrate used. To sum up, the osmotic dehydration process has the potential to modulate the chemical composition and biological properties of the Japanese quince fruit.