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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. [ABSTRACT FROM AUTHOR]

Maillard reaction browning is one of the quality deterioration in dried fruit products, but how pectin affects Maillard reaction in the fruit drying and storage process is not clear. This study aimed at investigating the mechanism of pectin variation impact on the browning of Maillard reaction by using simulated system (l -lysine, d -fructose and pectin) in thermal (60 °C and 90 °C for 8 h) and storage (37 °C for 14 days) process. Results showed that apple pectin (AP) and sugar beet pectin (SP) significantly enhanced the browning index (BI) of the Maillard reaction system by 0.01 to 134.51 in the thermal and storage processes, respectively, which were methylation degree of pectin-dependent. The pectin depolymerization product participated Maillard reaction by reacting with l -lysine, and increasing the 5-hydroxymethyl furfural (5-HMF) content (1.25–11.41-fold) and Abs 420nm (0.01–0.09). It also produced a new product (m / z 225.1245), which finally increased browning level of the system. [Display omitted] • Pectin improved Maillard reaction system browning in the processing. • The effect of pectin on Maillard reaction browning was pectin structure-dependent. • Pectin promoted the accumulation of Maillard reaction products. • Maillard reaction system with pectin produced a new product (m / z 225.1245). • The degradation of pectin with different molecular properties was different. [ABSTRACT FROM AUTHOR]