射频是一种新型热处理技术。通过监测全麦粉常温贮藏过程中脂肪氧化、淀粉和蛋白质结构变化等相关指标,探究射频处理对全麦粉理化性质的影响。将射频处理前后的全麦制粉,分为射频组、射频脱氧组和未处理组进行贮藏实验。贮藏6个月后,脂肪酸值为射频组(50.89 mg/100 g)<射频脱氧组(52.18 mg/100 g)<未处理组(95.93 mg/100 g),过氧化值和自由基强度均为射频脱氧组<射频组<未处理组;与贮藏0 d的样品相比,未处理组、射频组和射频脱氧组淀粉结晶度分别下降了4.59%、2.94%、2.82%,巯基含量分别下降了18.29%、8.33%、11.11%。结合淀粉短程有序度及热力学性质变化结果和蛋白质二级结构及分子质量分布变化结果,发现贮藏后全麦粉淀粉有序结构下降,蛋白质分子聚集,但射频组变化更为缓慢,添加脱氧剂作用不明显。上述结果表明,射频加脱氧处理能有效抑制全麦粉贮藏过程中脂肪水解氧化,且对淀粉与蛋白质结构的影响较小,可以有效改善全麦粉贮藏稳定性及品质,延长其保质期。
Radio frequency (RF) is a new heat treatment technology.By monitoring fat oxidation and structural changes of starch and protein during the storage of whole wheat flour at room temperature, this study investigated the effect of RF treatment on the physicochemical properties of whole wheat flour.The whole wheat flours were divided into three groups, including RF group, RF and deoxygenated group, and the untreated group, and were stored at room temperature for 6 months.After storage, the fatty acid value of RF group (50.89 mg/100 g) was a little lower than that of RF and deoxygenation group (52.18 mg/100 g) and much lower than that of untreated group (95.93 mg/100 g), while both the peroxide value and free radical intensity of RF and deoxygenation group were lowest, followed by RF group and untreated group.The starch crystallinity of the untreated group, RF group, and RF and deoxygenation group decreased by 4.59%, 2.94%, and 2.82%, respectively, and their free sulfhydryl content decreased by 18.29%, 8.33%, and 11.11%, respectively compared with the samples before storage.According to the results of changes in starch short-range ordering degree and thermodynamic properties, as well as changes in protein secondary structure and molecular weight distribution, it was found that the ordered structure of starch decreased and protein molecules aggregated after storage of whole wheat flour, while these changes in RF group were slower and were not different with that in RF and deoxygenation group.These results indicated that RF and deoxidization treatment could effectively inhibit the hydrolysis and oxidation of fat during the storage of whole wheat flour, and had little effect on the structure of starch and protein, thereby effectively improving the storage stability and quality of whole wheat flour and prolong its shelf life.
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