发芽糙米焙炒过程中品质变化研究

Quality Changes of Germinated Brown Rice during Roasting

为研究焙炒过程中发芽糙米品质的变化,将发芽糙米分别进行轻度、中度和强度焙炒,测定其主要成分、色泽和挥发性风味物质的变化。结果表明:3种焙炒程度的发芽糙米中的还原糖、可溶性蛋白含量均显著低于未焙炒(P<0.05)但三者之间差异不显著(P>0.05),γ-氨基丁酸(γ-aminobutyric acid,GABA)含量随焙炒程度增加而显著降低(P<0.05),强度焙炒的发芽糙米总酚显著高于其他两种焙炒(P<0.05)。焙炒后直链淀粉和抗性淀粉含量均增加但3种焙炒程度差异不显著(P>0.05)。焙炒对总淀粉含量的变化影响不明显。a*、b*和△E值随焙炒程度增强逐渐增加,而L*值逐渐降低。采用顶空固相微萃取和气相色谱-质谱联用对未焙炒及不同焙炒程度发芽糙米风味物质进行提取、鉴定与分析,发现吡嗪和呋喃类物质种类和合量均显著增加(P<0.05)。发芽糙米轻度焙炒GABA含量损失最少,且对焙烤香气起主要贡献的吡嗪类物质含量最高,达到焙炒增香目的,因此轻度焙炒较为适宜发芽糙米焙炒加工。

The effect of different roasting degrees on the quality of germinated brown rice was examined by investigating the changes in major components,color and flavor volatile compounds in germinated brown rice with mild,moderate and intensive roasting.Results showed that the contents of reducing sugar and soluble protein in germinated brown rice roasted to three different degrees were significantly lower than in those without roasting(P < 0.05),but there was no significant difference among the roasting degrees(P > 0.05).Meanwhile,γ-aminobutyric acid(GABA) content significantly reduced with an increase in roasting degree(P < 0.05).Total phenolic content in highly roasted germinated brown rice was significantly higher than that observed at lower roasting levels(P < 0.05).After roasting,the contents of amylose and resistant starch increased,but no significant difference was found among the three degrees(P > 0.05).Roasting had little effect on the total starch content.With increasing roasting degree,a*,b*and △ Evalues increased,whereasL*value decreased.By using headspace solid-phase micro-extraction(HS-SPME) coupled with gas chromatography and mass spectrometry(GC-MS),the flavor volatile compounds of germinated brown rice without roasting and with different roasting degrees were analyzed.It was found that the kinds and contents of pyrazines and furans significantly increased.The loss of GABA content in germinated brown rice with mild roasting was the least,and it had the highest relative content of pyrazines that could be a majorfactor contributing to baked fragrance.Therefore,mild roasting is more appropriate for germinated brown rice.