Influence of Novel Infrared Freeze Drying of Rose Flavored Yogurt Melts on Their Physicochemical Properties, Bioactive Compounds and Energy Consumption

Abstract

Attempt was made to produce a novel snack viz. dried rose flavored yogurt melts via the use of infrared freeze drying (IRFD). Selected physicochemical properties; color; hardness; rehydration time; total phenolics, flavonoids, and anthocyanins contents; microstructure; as well as sensory characteristics of samples prepared at different drying temperatures (45, 55, and 65 °C) were determined. Energy consumption of the drying process was also evaluated. The results were compared with those of conventional freeze drying (FD). IRFD samples exhibited smaller total color changes than those prepared by FD at the same drying temperatures. Hardness of FD samples was lower than that of IRFD samples at the same drying temperatures; IRFD sample prepared at 55 °C nevertheless received the highest total score among all the samples. FD samples exhibited shorter rehydration time compared with IRFD samples at the same drying temperatures. The analysis of microstructure of IRFD samples showed more compact layer structure compared to FD samples at the same drying temperature. Drying at 55 °C resulted in higher contents of phenolics and flavonoids, while drying at 45 °C resulted in the highest retention of anthocyanins. IRFD could save 5–14% of the drying time and 9–19% of the energy compared to FD at different drying temperatures.