Effects of osmo-air dehydration treatments on chemical, antioxidant and morphological characteristics of blueberries

- Osmodehydration causes losses in the antioxidant activity of blueberries.
- Air-drying rates of osmodehydrated blueberries are higher than those of untreated ones.
- Drying rates are related to the size of berries.
- Osmo-air dehydrated blueberries have better morphological characteristics than air-dried ones.

Osmo-air dehydration treatments are widely applied to fruits in order to prolong shelf-life, reduce packaging and logistic costs, and to improve both sensory and nutritional quality of the end products. In this work, osmo-air dehydration was applied to blueberries (Vaccinium corymbosum); blanched blueberries were dipped in sucrose (60 °Bx) and fructose/glucose (48.6 °Bx) osmotic solutions (aw = 0.90) for 24 h, and the osmotic exchanges were determined by mass balances (water loss, solid gain, sugar intake, changes in total phenolics and anthocyanins). Untreated and infused berries were subsequently air dried at 70 °C to final moisture content of 10-14%, and drying kinetics as well as compositional and morphological changes of berries were followed in the course of drying. Data show that the osmotic treatment causes significant losses in the antioxidant components (total phenolics, total and individual anthocyanins) and in the antioxidant activity. Losses in the antioxidant components also occur in the course of air drying, with similar kinetics in untreated and infused blueberries. Glucose/fructose infusion gives better results in terms of morphological changes, with lower shrinkage and wrinkling of the berries.