The effect of superheated steam drying on physicochemical and microbial characteristics of Korean traditional actinidia (Actinidia arguta) leaves

Abstract

The purpose of this study was to evaluate the effect of superheated steam drying on physicochemical and microbial characteristics of Korean traditional actinidia (Actinidia arguta) leaves. Actinidia leaves were dried at steam temperature of 350℃ and oven temperature of 150℃ for 40-200 sec. Moisture content and water activity decreased with increasing the drying time, while color values including L, a, and b values and total color difference (ΔE) increased as drying time increased. The relationship between moisture content and water activity showed an exponential fit with high correlation vlaue (R2=0.9909). Total phenolics and flavonoids content and antioxidant activity such as DPPH radical scavenging activity, ABTS radical scavenging activity, and FRAP assay of dried actinidia leaves increased with increasing the drying time up to 160 sec, but dramatically decreased at drying of 200 sec. The numbers of total areobic bacteria of leaves was not detected at drying time over 120 sec and coliform of all the samples was not detected. As a results, the superheated steam was an very effective drying method of increase to the nutritional and sanitary quality of dried Korean traditional actinidia leaves.

Inactivation of Potato Polyphenol Oxidase Using Microwave Cold Plasma Treatment

“…The L * values of CP‐treated and non‐CP‐treated potato slices were 57.3 ± 1.6 and 58.9 ± 2.8, respectively, which were higher than the L * value before treatment (52.4 ± 1.8) ( P < 0.05). This increase in the L * value may be explained by a reduction in the water content of the potato samples (Kim et al., ), as the water content of the samples treated without CP was 78.3 ± 4.5%, which was lower than the 84.2 ± 1.4% of potato samples before being placed in the treatment chamber ( P < 0.05). No change was observed between the a * and b * values of potato slices before and after CP treatment ( P > 0.05).…”