干燥方式对苜蓿超微粉物化特性及抗氧化活性的影响

为研究不同干燥方式对苜蓿超微粉物化特性及抗氧化活性的影响,以苜蓿超微粉总色差为指标,采用正交实验法,确定苜蓿超微粉的最佳护色方法,优化热风干燥工艺参数;通过测定苜蓿超微粉粒度、溶解度、持水力、持油力、DPPH自由基清除率等理化指标,比较热风干燥和真空冷冻干燥得到的苜蓿超微粉之间的物化特性和抗氧化活性差异。结果表明,采用热风干燥法干燥苜蓿的最佳工艺参数为:干燥温度70℃、干燥时间8 h,护色剂为0.15% L-半胱氨酸时,此条件制备的苜蓿粉具有较好的物化性质。并且苜蓿超微粉粒度的减小能明显提高苜蓿粉的抗氧化活性。真空冷冻干燥苜蓿超微粉具有很好的物理化学特性,经过干燥粉碎后能够很好的保留其中的营养价值和抗氧化活性,但其时间和能源消耗较大;而热风干燥苜蓿粉的物化特性及抗氧化活性相对较差,但其干燥时间短,能源消耗较少。

Effects of Drying Methods on Physical and Chemical Properties and Antioxidant Activity of Alfalfa Superfine Powders

In order to study the effect of different drying methods on the physical and chemical properties and antioxidant activity of alfalfa superfine powder,through orthogoral experiment,the optimal color protection method was determined and the parameters of hot air drying were optimized by using the total color difference of alfalfa as an index. Alfalfa superfine powder obtained by hot-air drying and vacuum freeze-drying were compared with the difference of physicochemical properties and antioxidant activity by determining the physical and chemical indexes of alfalfa including particle size,solubility,water holding capacity,oil holding capacity and DPPH free radical scavenging rate. The results showed that the optimum technological parameters of hot air drying were as follows:when the drying temperature was 70℃,the drying time was 8 h and the coloring agent was 0.15% L-cysteine,the prepared alfalfa powder had good physical and chemical properties. Moreover,the decreasing of the fine particle size of alfalfa could significantly improve the antioxidant activity of alfalfa meal. Alfalfa powder made by vacuum freeze drying had a good physical and chemical properties,and its nutritional value and antioxidant activity could be retentive well,while it had more time and energy consumption. In contrast,the physicochemical properties and antioxidant activity of alfalfa powder made by hot air drying was relatively poor and had a less time and energy consumption.