Different air velocity drying impacts on browning reaction and antioxidant activity of apple cube and its storage counterparts

Abstract

The colour quality and functional activity of dried fruits are important quality indexes. The purpose of this study was to evaluate the effects of heat pump drying with different air velocity on browning-related reactions and antioxidant activities of products and their storage counterparts. The results showed that apple cubes possessed different Maillard reaction levels, polyphenol and pectin variation, and antioxidant capacity, which could be controlled by different drying air velocity when the temperature is constant. In present work, high air velocity (2.0-2.5 m/s) drying (HHD) apple cubes possessed 22.58% more browning comparing to low air velocity (0.02-0.50 m/s) drying (LHD), which correlated with its 8.13 μg/g, 132.35 μg/g and 6.21% more of 5-HMF, chlorogenic acid and DE level of pectin, respectively. Interestingly, the b value of HHD and LHD samples decreased after storage, which was related to the DE, GalA, structural properties (Ratio1, Ratio2 and Ratio3) and conformational properties (PDI, RG and RC) of pectin in samples. Besides, HHD treatment promoted higher DPPH and FRAP capacity than LHD, which significantly involved Mw of pectin. The research would provide a new insight from the perspective of pectin for regulating the browning and antioxidant activity in apple thermal process.