压差闪蒸干燥改善红枣脆片理化和营养品质的研究

Improvement of Physicochemical and Nutritional Quality of Red Jujube Chips by Instant Controlled Pressure Drop

为了探究更好的红枣脆片干燥技术,本研究以传统热风干燥(HAD)作为对照,对红枣片进行热泵干燥(HPD)、真空冷冻干燥(FD)和压差闪蒸干燥(DIC),测定了红枣片及干燥后红枣脆片的理化品质和营养品质。结果表明:四种方式干燥后的红枣脆片水分含量均在4.5%左右。在质构方面DIC和FD相对HAD显著降低红枣脆片的硬度同时显著提高了脆度(p<0.05);外观方面:FD和DIC相对HAD红枣脆片体积皱缩较小,DIC尤为显著(p<0.05),红枣脆片体积增加了3.57%,色泽方面HPD的红枣脆片表面亮白(ΔE=1.24),DIC的红枣脆片表面呈诱人的枣红色(ΔE=7.19);在营养品质方面:四种干燥方式的多糖含量和黄酮含量均降低(以干质量计,下同)DIC的多糖保留率最高且与其他干燥方式差异显著,HPD和DIC的红枣脆片黄酮保留率显著高于HAD和FD。综上,DIC对红枣脆片外观及营养品质均有显著提升,产业加工具有明显优势,应用前景广阔。

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.