Solar dehydration of blueberries (Vaccinium corymbosum L.)

To determine the effect of blanching pre-treatment on the quality of the dehydrated blueberry fruit of 'Biloxi' (Vaccinium corymbosum L.), grown in San Andrés Yucuita, Nochixtlán, Oaxaca, Mexico, fruit were collected at commercial maturity and subjected to solar dehydration. Prior to dehydration, blueberries were washed with 25 ppm chlorine and selected by size (9.0±1.0 mm diameter) and colour (H° 295±5). The fruit were separated in four batches: the first was dehydrated directly and the others were blanched at 98°C for 10, 20 or 30 s and then dehydrated. Each lot was placed in room trays of 0.0625 m² with an equivalent of 2.0 kg of fruit m^-2 in a natural convection solar drier with air velocities between 0.6-0.8 m s^-1 and a temperature of 68.0±3.0°C. The quality parameters evaluated were: total solids, soluble solids, titratable acidity, total reducing sugars, total phenols, total anthocyanins and antioxidant capacity. The results indicated that the fruit given a blanching treatment required 11.5 h to reach 12.5% moisture level, while the fruit without blanching reached the same moisture level after 13.0 h. Fruit with blanching had a greater response to rehydration compared with those that did not receive this treatment; both lots had light browning by dehydration, and moderate losses of phenolic compounds and antioxidant capacity.