Influence of Postharvest Hot Water Treatment on Nutritional and Functional Properties of Kumquat (Fortunella japonica Lour. Swingle Cv. Ovale) Fruit

Abstract

The present study investigated the influence of a hot water dip (HWD) for 2 min at 50 °C, a standard and effective treatment for postharvest decay control of citrus fruit, on the nutritional and health-related properties of kumquats. The results show that most of the parameters examined, including titratable acidity, soluble solids content, maturity index, glucose, fructose, sucrose, ascorbic acid, dehydroascorbic acid, α- and γ-tocopherols, β-carotene, zeaxantin, rhoifolin, and antioxidant activity, were not significantly affected by treatment. The levels of β-cryptoxanthin, narirutin, and total flavonoids increased after HWD, whereas lutein and total phenols decreased. The concentration of the essential oil and the relative percentage of the individual components of the essential oil were not affected by HWD except for the minor compound p-menta-1,5-dien-1-ol, which increased after HWD. After storage, lower levels of glucose, total sugars, β-carotene, β-cryptoxanthin and lutein were recorded in HWD fruit. A decrease in antioxidant activity and increases in α-tocopherol and total vitamin E were found both in control and HWD fruit. The influence of HWD at 50 °C for 2 min on individual nutraceuticals and health-related properties was thus generally low and may depend on storage conditions.