Improvement of Physicochemical and Nutritional Quality of Red Jujube Chips by Instant Controlled Pressure Drop
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Abstract:
In order to obtain the better drying technology of red jujube chips, jujube slices were dried by heat pump drying (HPD), vacuum freeze drying (FD) and instant controlled pressure drop (DIC) with hot air drying (HAD). The physicochemical and nutritional quality of red jujube slices and dried red jujube chips (RJC) were evaluated and performed a comparative study. Results showed that moisture contents of RJC after four drying methods were all around 4.5%. In terms of texture, HPD, FD and DIC significantly reduced the hardness of RJC and significantly increased the brittleness (p<0.05). As for appearance, compared with HAD, the volume shrinkages of RJC dried by FD and DIC were small, especially for DIC treatment, in which the volume of RJC increased by 3.57%. The least color difference (ΔE) value (1.24) of RJC with brighter surface color was obtained by HPD. However, RJC dried by DIC presented attractive redder surface color even though had a larger ΔE value of 7.19. In terms of nutritional properties, the polysaccharide and flavonoid contents of RJC with four drying treatments all decreased. The highest polysaccharide retention rate was obtained by DIC, which was significantly different from other drying methods. The retention rate of flavonoids in HPD and DIC was significantly higher than that of HAD and FD. In conclusion, DIC can significantly improve the appearance and nutritional quality of RJC, and have a broad industrial application prospects.
