米糠储存条件对米糠毛油品质及脱色效果的影响

Influence of storage conditions of rice bran on quality and bleaching effect of crude rice bran oil

通过对室温通风(18±2)℃及高温高湿(温度50℃,70%湿度)储存的米糠粗脂肪、粗蛋白含量及制备的米糠浸出毛油酸值、过氧化值、色泽等指标的测定,分析研究储存条件对米糠及米糠毛油品质的影响,并通过吸附脱色试验,研究储存条件对其浸出毛油脱色难易程度的影响。结果表明:两种储存条件均会使米糠的粗脂肪含量降低、粗蛋白含量升高;随储存时间的延长,室温通风储存下米糠浸出毛油色泽变化不大,过氧化值呈波动小幅增长,储存10 d的米糠制备的米糠毛油经脱色后色泽接近米糠油国标二级标准;然而米糠经高温高湿储存6 d后,因发热霉变和严重酸败,其浸出毛油酸值大幅度升高,过氧化值降低,毛油色泽呈黑棕色,并有难闻的霉变味,对其进行吸附脱色时活性白土用量达到油质量的13%仍难将其色泽脱除,达不到米糠油国标四级色泽的指标要求。

Rice bran was separately stored in ventilated environment at room temperature（18 ± 2） ℃ and high temperature with high humidity environment（temperature 50 ℃,humidity 70%）,and the contents of crude fat,crude protein of the two kinds of rice bran and the acid values,peroxide values and color of the solvent extracted crude rice bran oils were detected to study the effect of storage conditions on the qualities of rice bran and crude rice bran oil. In addition,the impact of storage conditions on the bleaching effect of crude rice bran oil was studied through adsorption bleaching experiment. The results showed that the content of crude fat in rice bran decreased while the content of crude protein increased under the two types of storage conditions; with storage time prolonging,the color of solvent extracted crude rice bran oil changed a bit in the ventilated environment at room temperature,the peroxide value increased slightly,and the color of bleached rice bran oil was close to the second grade rice bran oil of the national standard after ten days＇ storage of rice bran. After six days＇ storage at high temperature with high humidity,the acid value of the solvent extracted crude rice bran oil increased greatly for the moldy and rancidity of rice bran,in the same time,its peroxide value reduced,its color became dark brown with unpleasant mildew,the pigments were hard to be removed from the oil and its color could not reach the requirement of the fourth grade rice bran oil of national standard even if the dosage of activated clay was 13% in the process of adsorption bleaching.