Effects of High Hydrostatic Pressure versus Thermal Pretreatment on the Quality of Vacuum Freeze-Dried Reconstituted Fruit and Vegetable Cubes

Mango, melon, pineapple, and carrot were processed into reconstituted fruits and vegetable cubes by conventional thermal pretreatment (TP) or high hydrostatic pressure (HHP) pretreatment at different pressures followed by freeze drying (FD). The effects of different HHP pressures on the physicochemical quality, bioactive substances, antioxidant activity, and sensory quality of FD fruits and vegetable cubes were investigated. The results showed that compared with TP, HHP significantly increased the a* and b* values, titratable acid content and antioxidant activity (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, hydroxyl radical scavenging capacity, and ferric reducing powder), increased the contents of total phenols, flavonoids, and ascorbic acid by 21.11%–30.27%, 59.96%–68.58%, and 13.35%–15.34%, respectively, and increased the contents of volatile alcohols and ketones to 189.65–207.82 and 59.60–81.16 μg/kg, respectively. In addition, the sensory intensities of five aroma attributes and the preferences for color, aroma and taste of HHP-pretreated FD cubes were significantly higher than those of TP-pretreated FD cubes. The sensory quality of FD fruits and vegetable cubes pre-treated at 300 and 500 MPa were closest to that of the non-treatment group. HHP pretreatment improved the antioxidant activity by increasing cell membrane permeability, thereby promoting the release of bioactive and flavor substances. Compared with conventional TP, HHP can effectively improve the quality characteristics of FD fruits and vegetable cubes.