超声波辅助酶预处理对糙米发芽及发芽糙米理化特性的影响

Effect of Ultrasound-Assisted Enzymatic Pretreatment on Germination of Brown Rice and Its Physicochemical Properties

结合超声波和外源酶对糙米进行预处理,利用中心组合试验模型,以超声温度、超声时间、酶质量浓度3个因素为自变量,糙米预处理后处理液中总糖含量、糙米发芽率、发芽糙米γ-氨基丁酸(γ-amiobutyric acid,GABA)含量为响应值,设计了三因素三水平的响应面分析试验,并对数据进行拟合和相关性分析。同时研究超声波辅助酶预处理对发芽糙米中GABA含量、总酚含量、内源淀粉酶活力以及发芽糙米糊化黏度、蒸煮后质构特性的影响。结果表明:超声辅助酶预处理的超声温度和超声时间对糙米发芽率和GABA含量均有显著的影响。通过响应面分析,超声波辅助酶预处理超声温度31.21℃、超声时间0.71 h、酶质量浓度0.28 g/L时,发芽率最高预测值为91.98%;超声波辅助酶预处理超声温度35.65℃、超声时间0.5 h、酶质量浓度0.22 g/L时,GABA含量最高预测值为38.25 mg/100 g。从发芽糙米的理化特性来看,超声波辅助酶预处理有利于GABA的富集,但不利于总酚的积累。超声波辅助酶预处理可以有效地提高内源淀粉酶的活力,相应地降低发芽糙米粉的糊化黏度以及发芽糙米蒸煮后的硬度。

Ultrasound-assisted enzymatic hydrolysis was utilized for the pretreatment of brown rice. The 3-factor 3-level response surface analysis was designed using temperature, ultrasound processing time and enzyme concentration as the independent variables, and using total sugar content after brown rice pretreatment, brown rice germination percentage, and γ-amiobutyric acid(GABA) content of germinated brown rice as the response values through central composite design model. At the same time, the effect of pretreatment on the physicochemical properties of germinated brown rice such as GABA content, total content of phenols, amylase activity, gelatinization viscosity and texture characteristics of cooked rice was investigated. Results indicated that both processing temperature and time had significant effects on rice germination percentage and GABA content. Treatment time of 0.71 h, temperature of 31.21 ℃, and enzyme concentration of 0.28 g/L could result in the optimal germination percentage with the predicted maximal germination rate of 91.98%. The predicted maximal GABA content could be up to 38.25 mg/100 g after pretreatment for 0.5 h at 35.65 ℃ with an enzyme concentration of 0.22 g/L. Based on physical and chemical properties of germinated brown rice, the ultrasound-assisted enzymatic pretreatment is beneficial to the enrichment of GABA, but unfavorable to the accumulation of total phenols. This pretreatment could effectively enhance the activity of endogenous amylase, accordingly reducing the pasting viscosity of germinated brown rice and its hardness after cooking.