水分调节协同微波处理米糠储藏期品质变化规律的研究

Study on Quality Change of Rice Bran Treated by Microwave Collaborating with Water Regulating During Storage

研究采用微波协同调节水分探讨了对米糠中酶活变化、储藏期米糠品质以及生理活性物质变化规律。结果表明:调节初始含水量对微波稳定化米糠具有明显的协同增效作用,初始水质量分数为24%时,过氧化物酶酶活为0,脂肪酶约为7%,多酚氧化酶约为3%;初始水质量分数为24%,微波功率1 000 W,微波时间180 s和料层厚度1.5 cm,米糠在12周储藏期时的酸价和过氧化值分别为21.45 mg KOH/g和4.22 mmol/kg,相比较原料(初始水质量分数11%),酸价降低约35%,过氧化值降低约26%;影响因素大小依次为:米糠初始水质量分数>微波功率>微波时间>料层厚度;生育酚和生育三烯酚总含量12周储藏期内线性下降趋近于0,只有在较高初始含水量下第8周时出现阶段上升后再下降,微波处理对γ-生育酚和γ-生育三烯酚含量影响较大,平均降低50%和33%,较高初始含水量处理的米糠α-生育三烯酚含量(200 mg/kg)较低;米糠油脂肪酸组成在储藏期内棕榈酸含量增加,油酸和亚油酸含量降低;谷维素含量出现先增加后下降的趋势,在8周时达到最大1.35%。水分调节对储藏期米糠脂肪酸组成和谷维素含量无显著性影响。综合考虑,为了得到较好品质的米糠原料,储藏的时间不宜超过2周。

In this study,the change of enzyme activity in rice bran,the quality of rice bran and the changes of physiological active substances were investigated by microwave collaborating with water regulating during the storage.The results indicated that adjustment of initial moisture content had obvious synergistic effects on microwave stabilization of rice bran,when the initial moisture mass fraction was of 24%,the peroxidase activity was of 0,lipase was about 7%,and polyphenol oxidase was about 3%.With microwave power of 1000 W,microwave time of 180 s,layer thickness of 1.5 cm and initial moisture mass fraction of 24%,the acid value and peroxide value of rice bran in 12-week storage were 21.45 mg KOH/g and 4.22 mmol/kg,respectively,the acid value was reduced by about 35%,and the peroxide value was reduced by about 26%compared with the raw material(initial moisture mass fraction of 11%.The influencing factors were as follows:initial moisture content of rice bran>microwave power>microwave time>layer thickness;the total contents of tocopherol and tocopherol decreased linearly,and the contents tended to be 0 at 12 weeks,the phenomenon which the total contents of tocopherol and tocopherol increased and decreased only occurred at week 8 at higher initial moisture content.Microwave treatment had a significant effect on the contents ofγ-tocopherol andγ-tocopherol,decreased by 50%and 33%on average.Theα-tocopherol content(200 mg/kg)was lower in rice bran treated with higher initial water content.During the storage,the contents of palmitic acid in rice bran oil increased,while the contents of oleic acid and linoleic acid decreased.Theγ-oryzanol content increased first and then decreased,reaching a maximum of about 1.35%at 8 weeks.Water regulation had no significant effect on the fatty acid composition and the oryzanol content of rice bran during storage.In order to get better quality rice bran raw materials,storage time shall not exceed 2 weeks.