为解决传统工艺生产发芽糙米浸泡时间长、生产效率低等问题，提出以纤维素酶和木聚糖酶的复合溶液代替蒸馏水浸泡发芽前糙米的新工艺。以糙米为原料，探究复合酶预处理工艺中酶解时间、酶解温度、复合酶浓度及配比对发芽糙米得率的影响规律，采用二次正交旋转中心组合设计试验，建立了各因素对发芽糙米得率影响的数学模型。结果表明：酶解时间、酶解温度、复合酶浓度及酶配比对发芽糙米得率影响显著（P<0.05），得到优化参数组合为：酶解时间135 min，酶解温度35℃，复合酶浓度0.57 g/L、纤维素酶和木聚糖酶质量比1.86：1，在此条件下，与传统工艺相比浸泡时间缩短62.5%、发芽糙米得率及γ-氨基丁酸含量分别提高约3.90%和3.86 mg/(100 g)。通过对酶解后糙米皮层微观结构的观察分析，糙米皮层在复合酶作用下部分降解，胚乳中淀粉更易与水分子相结合，从而吸水速率提升。研究结果可为发芽糙米生产提供参考。%The purpose is to solve the problems about long soak time of germinated brown rice as well as low production efficiency in traditional production process. A novel processing technology is developed using compound enzyme solution pretreatment with cellulase and xylanase rather than distilled water soak brown rice during the process of producing germinated brown rice. The brown rice’s tough cortex is mainly caused by the coarse fiber structure, whose major components are cellulose and araboxylan. The xylan layer with its covalent linkage to lignin and its noncovalent interaction with cellulose may play a significant role in maintaining the integrity of the cellulose in situ and protecting the fibers against degradation by cellulases. Using compound enzyme pretreatment to degrade some cortex resulted in a significant increase in water absorption rate over brown rice. What’s more, the brown rice obtained a suitable water content to sprout in a much shorter time. By shortening the soak time, it could improve the efficiency of germinated brown rice production. Brown rice degraded some cortex during soaking, which thereby reduced the block of cortex to water. Compared with soaking methods, the new method not only reduced the soak time but also improved the germinated rate. Beyond that, a central composite rotatable orthogonal experimental design of response surface methodology with 4 factors and 5 levels was employed. Taking raw material of brown rice, the influences of the 4 parameters including enzyme treatment time, enzyme treatment temperature, concentration of compound enzyme solution, percentage of cellulase quality on the germinated brown rice yield as well as the optimal parameters of this process were investigated. Additionally, mathematical models for the influences of various parameters on the germinated brown rice yield were set up. As shown, the mathematical models for the germinated brown rice yield were extremely significant (P<0.01). Meanwhile, the optimum process parameters for maximizing the germinated brown rice yield were 0.57 g/L of enzyme concentration, 35℃ of enzyme treatment temperature, 135 min of enzyme treatment time and 1.86:1 of cellulose-to-xylanase mass ratio, respectively. Moreover, the germinated brown rice yield and the content ofγ-aminobutyric acid (GABA) under the optimum parameters were 3.90% and 3.86 mg/(100 g), which was higher than that of germinated brown rice produced by soaking method. Compared with conventional soaking method, compound enzyme pretreatment method significantly shortened the time of water absorption (135 min), in which soak time was reduced by 62.5%. As a result, it greatly improved the efficiency of germinated brown rice production. Through enzymatic soaking pretreatment, seed germination can be promoted. Brown rice has the characteristic of seed. Compound enzymatic soaking pretreatment will not only wake up the dormancy of brown rice but also improve the activity of endogenous enzyme to bud. GABA in germinated brown rice is produced by glutamic acid, and it removes carboxyl under the effect of glutamate decarboxylase (GAD). Moreover, the activity of GAD is closely related to the accumulation of GABA. The optimum pH of GAD is acidity. The brown rice soaked in acidic environment of compound enzyme solution increases the activity of GAD, which will be conducive to generation of GABA. Surface structure of the germinated brown rice degraded by enzyme was studied by Scanning Electron Microscopy. Microstructure of brown rice cortex confirmed that part of the cortex degraded because the brown rice soaked in compound enzymes solution. Furthermore, hydration characteristics of brown rice under different soaking conditions showed that the water absorption rate of brown rice soaked in compound enzyme solution was significantly faster than that soaked in distilled water. Starch in the endosperm was easier to combine with water molecules, and brown rice with a suitable water content to sprout in a much shorter time was obtained. By utilizing the technology described in this paper, the research results can provide a reference to improve industrial production of germinated brown rice.
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