Osmotic dehydrofreezing of strawberries: polyphenolic content, volatile profile and consumer acceptance

We evaluated dehydrofreezing in strawberries in terms of retention of healthy compounds (i.e. polyphenolics) and sensory qualities for direct consumption in substitution of fresh fruit. Different osmodehydration (OD at 30°C and 5°C), vacuum osmodehydration (VOD at 30°C) and immersion chilling freezing (ICF) processes were applied in sucrose syrup. Samples were analyzed for dry matter, soluble solids, pH, titratable acidity, mass transfers, polyphenolic content by HPLC-DAD/MSD, volatile profile by SPME-GC/MSD and consumer acceptance. The results of sensory evaluation, in particular, confirmed the cryoprotective effects of osmotic processes of fruits with respect to untreated frozen control samples. The OD samples at 5°C presented a water loss to solid gain ratio comparable to OD at 30°C and VOD samples. Moreover, while osmo-dehydrofreezing at relatively high temperatures caused a slight depletion of phenolic compounds, the samples osmodehydrated at 5°C showed higher polyphenolic retention. Data on aromatic compounds showed that some compounds increased (e.g. ethanol and acetaldehyde), while others did not appear to be affected by the pre-treatments.