Abstract: Mango, melon, pineapple, and carrot were used as raw materials, and the blended fruit and vegetable pulp was pre-treated by conventional thermal processing (TP) and different high hydrostatic pressure (HHP) conditions, then the blended fruit and vegetable cubes were produced using freeze drying (FD). The effects of different pressures on the physicochemical quality, bioactive substances, antioxidant activity, and sensory evaluation of FD fruit and vegetable cubes were investigated. The results showed that HHP pre-treatment significantly increased the a* and b* values, the content of titratable acid, and antioxidant activity (DPPH radical scavenging rate, hydroxyl radical scavenging rate, and iron ion reduction capacity). The contents of total phenols, flavonoids, and ascorbic acid of HHP-pretreated FD cubes were significantly increased by 21.11%-30.27%, 59.96%-68.58%, and 13.35%-15.34%, respectively, compared with those of TP-pretreated FD cubes. The contents of volatile alcohols and ketones compounds in HHP-pretreated FD cubes were 189.65-207.82 μg/kg and 59.60-81.16 μg/kg, respectively, which were 5-8 times higher than those in TP-pretreated FD cubes. In addition, the sensory intensities of the 5 aroma attributes and the preferences of color, aroma, and taste of HHP-pretreated FD cubes were significantly higher than those of TP-pretreated FD cubes. The aroma sensory evaluation of FD fruit and vegetable cubes pre-treated under 300 MPa and 500 MPa were closest to that of the untreated group. The HHP pre-treatment improved the antioxidant activity by increasing the cell membrane permeability, thereby promoting the release of bioactive and flavor substances. Compared with the conventional TP pre-treatment, HHP pre-treatment effectively improved the quality characteristics of FD fruit and vegetable cubes.

Key words: reconstituted fruit and vegetable cubes, snack foods, high hydrostatic pressure, vacuum freeze drying, volatile compounds, antioxidant activity