热风和热风-脉动压差闪蒸联合干燥对草莓色泽及品质的影响

Effect of Hot Air Drying and Hot Air-pulsed Sudden Decompression Flash Drying on the Color and Quality of Strawberries

摘要:

为探究草莓热风单一干燥和热风-脉动压差闪蒸联合干燥后产品品质变化，对草莓实施均匀试验，研究不同干燥温度、真空干燥温度和预干燥含水量对草莓干燥特性、色泽和理化品质的影响，并采用层次分析法优化干燥工艺条件。实验结果得到：草莓热风-脉动压差闪蒸联合干燥最佳工艺条件为预干燥含水率60%，闪蒸温度90 ℃、停滞时间15 min、闪蒸压力差0.10 MPa，真空干燥温度70 ℃(60 min)~60 ℃(40 min)，总干燥时间255 min；温度对草莓热风干燥影响较为显著，其最优工艺条件为干燥温度70 ℃，干燥时间360 min。两种最优工艺条件相比，草莓热风-脉动压差闪蒸联合干燥品质佳，硬度低(为2323.65N)，Vc含量较高，达到339.38?10-2 mg/g DW，Pg-3-Glu和Cy-3-Glu的保留率也远远大于单一热风干燥，分别是热风干燥含量的2.5倍和2.2倍；且干燥产品色相值为24.66，色泽好，干燥时间短。

Abstract:

To study changes in strawberry quality after drying by hot air drying (HAD) or hot air-pulsed sudden decompression flash drying (HA-PSDFD), the effects of drying temperature, vacuum drying temperature, and pre-drying water content on drying characteristics, color, and physical and chemical qualities of dry strawberry products were studied. Uniform design tests and drying technologies were analyzed and evaluated using analytic hierarchy processes. The results showed that the optimum HA-PSDFD drying conditions were a pre-drying water content of 60%, flashing temperature of 90 ℃, dead time of 15 min, pressure difference of 0.10 MPa, vacuum drying temperature of 70 ℃ (60 min) -60 ℃ (40 min), and a total drying time of 255 min. Drying temperature had a more significant impact on strawberry drying rate during HAD. The optimum HAD drying process was a drying temperature of 70 ℃ for 360 min. Comparing these two optimal process conditions, the quality of strawberry products dried by HA-PSDFD was superior to the quality of products dried by HAD, resulting in a lower hardness value (2323.65 N) and a higher Vc content (339.38?10-2 mg/g DW). In addition, pelargonidin-3-glucoside and cyanidin-3-glucoside contents after HA-PSDFD were 2.5 and 2.2 higher than those by HAD, respectively. Moreover, drying time was reduced and the color of the product was superior, upon HA-PSDFD treatment, with a hue value of 24.66.