On the effects of freeze-drying processes on the nutritional properties of foodstuff: A review

The aim of this paper is to review the effects of several different types of freeze-drying processes on some nutritional properties of foodstuff. Both the vacuum freeze-drying (VFD) process and the atmospheric freeze-drying (AFD) process have been considered, as well as the possibility of accelerating both using ultrasound (US), microwave (MWD), infrared (IR) heating, and other techniques. The effects of these processes on ascorbic acid, phenolic compounds, and total antioxidant capacity have been extensively reviewed in this paper, as these molecules were widely investigated in the literature. Finally, a summary of effects on other less recurrent studied compounds is also presented. It appears that for vitamin C, VFD most of the time gives the best results; MWD and IR combined processes with VFD seem to be able to decrease processing time, while having a mild effect on product quality. With respect to phenolic compounds and total antioxidant capacity, VFD and AFD seem to have fairly similar effects, with a mild effect of IR and US.