The effects of drying temperature on the kinetics, color, structure, and pectin composition of Zizyphus jujuba Mill. cv. Junzao

Abstract

Drying kinetics, color, and texture changes in different drying temperatures of jujubes were investigated in this study. With the increase of temperature, the drying time reached a minimum (140 min) at 80℃. At the temperature of 40℃, the retention of the original color was the greatest (ΔE = 1.66); similar results were also reflected by the measured pulp browning (4.186 ± 0.350 Abs/g) and 5‐HMF (0.517 ± 0.044 mg/g). After drying, the fruit hardness decreased to 55.91%–86.59% of the initial (2,543.2 ± 181.4 g). SEM showed that the HAD temperature exceeded 60℃ and the pulp tissue sharp dramatically, causing the fruit to harden. Affected by drying temperature and polygalacturonase, WSP increased in drying, whereas CSP and NSP showed the opposite trend, and they were significantly correlated with the texture of fruits. The results expanded our understanding of the jujube drying process and provided guidance for controlling the quality of jujube during HAD processing. Practical applications The drying method of jujube fruit in China is special, which is a combination of air drying and hot air drying. However, discoloration, shrinkage, and other quality deterioration occurred during the drying process, significantly affecting the quality of jujube fruit. In this study, semi‐air‐dried jujubes were used to investigate the color and texture during hot air drying. These results will provide valuable information to the pilot or industrial scale processors and also served as an operational guide for the jujube fruit drying process.

Effects of variable-temperature drying on the qualities and sweet-substance profile of Zizyphus jujuba Mill. cv. Junzao

“…It can be seen from the drying-rate curve ( Fig. 1 B) that the dehydration of jujube occurs mainly in the deceleration period ( Liu, Zhang, et al, 2021 ). With the extension of drying time, the drying rate decreases due to most surface water being lost and it being more difficult to remove internal water.…”

“…The texture characteristics of the jujube were evaluated according to Liu et al (2021) . A texture analyzer (Surface Measurement Systems, Ltd., UK) was used to determine the texture characteristics of the samples before and after being subjected to different drying methods.…”

“…The microstructures of the jujube fruits were evaluated according to Liu, Zhang, et al (2021) . The internal microstructures of the dried samples were observed using scanning electron microscopy (SEM; S-3400 N, Hitachi Ltd., Japan).…”

Comparative Analysis of Physicochemical and Functional Properties of Pectin from Extracted Dragon Fruit Waste by Different Techniques

“…Conversely, the CW method, without heat treatment, had the highest a* value, and US and HW resulted in progressively lower a* values (CW > US > HW), indicating a decrease in red color intensity, attributed to betacyanin breakdown or separation. Enzyme-assisted extraction showed a diminished red hue compared with the non-enzymatic treatment, suggesting enzymatic treatment may have degraded or altered the betacyanin during the extraction process [ 53 ]. Moreover, the b* value reflecting yellowness was higher in EZX compared with other pectins.…”

Postharvest treatment with 1‐methylcyclopropene and chitosan enhances the antioxidant capacity and maintains the quality of Hui jujube ( Ziziphus jujuba Mill. cv. Huizao) during cold storage

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Chinese jujube (Ziziphus Jujuba Mill. Rhamnaceae) has been cultivated for over 4,000 years, accounting for 90% of the world's production with more than 700 varieties (Liu et al, 2021;Xie et al, 2017). Hui jujube (Ziziphus jujuba Mill.

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