Impacts of hot air and vacuum drying on the quality attributes of kiwifruit slices

• The physical and chemical properties of the dried kiwifruit slices were evaluated.
• These properties were analyzed by reaction rate theory.
• The results would be useful in an engineering application concerning kiwifruits.

Hot air and vacuum drying were performed to investigate changes in the moisture content, hardness, l-ascorbic acid content, antioxidant activity, and surface color of kiwifruit samples over the course of the drying process at temperatures of 50, 60, and 70 °C and a vacuum drying pressure of 3.00 kPa. The residual ratio of AsA and the antioxidant activity in the dried kiwifruit samples was 0.75–0.99 and 4.3–5.5, respectively. The l-ascorbic acid changes in the kiwifruit samples during the hot air drying process followed first order reaction kinetics. Changes in the sample hardness and antioxidant activity were represented by zero-order reaction kinetics. The sample surface color changes after drying were also measured, and the total color change (ΔE) of the samples at all temperatures and for each drying process was greater than 12. The sample color changes (Δa*) after vacuum drying at each temperature level were significantly (P < 0.01) lower than those associated with hot air drying.