Storage stability of dried raspberry foam as a snack product: Effect of foam structure and microwave-assisted freeze drying on the stability of plant bioactives and ascorbic acid

We compared the effects of the use of microwaves during freeze drying with conventional freeze drying on the structure and storage behavior of dried raspberry puree foam. The effects of hydrocolloids, such as potato protein (as a foaming agent), maltodextrin, pectin (as foam stabilizers), and the impact of foam structure on the stability of plant bioactives (namely anthocyanins and ascorbic acid) and color during storage was investigated. Dried samples were vacuum-packed and stored at 37 °C for 12 weeks. Water sorption and glass transition temperatures were also measured. The results suggest that the raspberry puree is not as stable as the foamed structure. Storage stability of microwave-assisted freeze-dried samples revealed equivalent or even slightly better characteristics when compared with those produced via the conventional freeze-drying method. It can be concluded that microwave freeze drying does not induce specific detrimental changes during storage as compared to the freeze-drying technology used as control.