Instant controlled pressure drop (DIC) assisted dehydrofreezing for improving freezing/thawing efficiency and apple fruit texture

Abstract

Partial air-drying, instant controlled pressure drop, freezing, and thawing operations were combined to minimize the texture loss of frozen/thawed apple fruits. Fresh apple samples (700% db) and samples previously dehydrated until different water contents [200, 100, and 30% dry basis (db)] and DIC treated at constant conditions (0.2 MPa, 25 s) were completely frozen at − 30 °C and at two different freezing velocities and then thawed at 4 °C. The effects of sample water content and freezing velocity on freezing/thawing durations and apple texture were assessed. Lower sample water content implied higher freezing and thawing rates, and lower freezing and thawing times. Indeed, freezing times are 108 min and 30 min for samples with water contents of 700% and 100% db, respectively. Thawing time was also reduced from 588 to 42 min for conventionally frozen and DIC-dehydrofrozen samples (100% db). During thawing, the amount of water exudate was approximately 12% (g/100 g residual water) for conventionally frozen apples at the lower freezing velocity. Whereas, it is lowered to 1.6% for 100% db DIC-dehydrofrozen samples. Moreover, the impact of freezing velocity on water exudate was significant and very important only for conventionally frozen apples (with high water content) and remains insignificant for DIC-dehydrofrozen samples with different water content levels. Thawed apple firmness was as higher as the water content was lower, without any significant impact of freezing velocity. Dehydrofreezing assisted by instant controlled pressure drop exhibited significant effects on reducing thawing duration and enhancing frozen apple fruit texture.