Effects of apple de-hydration by innovative technologies on the microstructure and olfactory quality

The effects of innovative technologies of apple de-hydration based on the application of biopolymer films on the flavour content and on microstructure have been investigated. The microstructure is analysed by means of Environmental Scanning Electronic Microscopy (ESEM), while the olfactory quality of differently preserved apple were analysed using an electronic nose equipped with Metal Oxide Semiconductors (MOS) sensors. Our approach were based on the use of films made of blends of biodegradable and biocompatible polymers belonging to well know families of natural polysaccharides, already approved for use in agro-food industry. Different compositions of the two components of blends are been utilized in order to verify the differences in the final morphologies and olfactory quality. The results have demonstrated that the utilized films made of polysaccharides are able to selectively control the loss of water from fruits by adsorbing it at slow rate, without losing volatiles and flavours. Moreover some compositions of the polymeric blends preserve the olfactory quality better than other. Infact the analysis of electronic nose data shows that the apple slices packed in blends composed by Agar as major component, better preserve olfactory properties. The texture of dried apple slices, packed in polysaccharides films, has been investigated by ESEM analysis and compared to freeze dried slices. We found that whereas freeze drying leads to cell structure breakage, the slices dried by packaging in our films preserve a packed structure, with few regular cavities, with no evidence of cell wall collapse. Re-hydration tests showed that the re-hydration rate of slices dried in polysaccharides films is very low respect to the freeze dried slices; moreover, after re-hydration, the texture closely resembles that of the fresh fruit.