CAJ | 학술논문

在糙米碾米过程中普遍存在碎米较多及碾米能耗高的问题，为改善糙米碾米品质，提出以纤维素酶和木聚糖酶的复合酶溶液处理替代常规水加湿方法的酶法预处理工艺。以贮藏期糙米（含水率15%以下）为原料，采用二次正交旋转中心组合设计试验，研究复合酶溶液处理工艺中复合酶配比、酶质量浓度、加液量及酶处理时间对碾米后整精米率和碾米能耗的影响规律，建立了各因素对整精米率和碾米能耗影响的数学模型。结果表明：构建的整精米率、碾米能耗与复合酶配比、酶质量浓度、加液量及酶处理时间之间的回归方程极显著（P<0.01），得到优化参数组合为纤维素酶和木聚糖酶质量比1.3∶1 g/g、复合酶溶液质量浓度65 mg/mL、加液量1.25%，酶处理时间102 min，该条件下整精米率为80.07%、碾米能耗为90.72 kJ/kg。复合酶溶液处理后整精米率较加湿调质处理提高约3.98%，节约能耗约13.06%；较纤维素单一酶溶液加湿处理后整精米率提高约0.98%，节约能耗约5.48%。并通过微观结构分析证实了糙米皮层粗纤维的局部破损是其碾米性能改善的主要原因。研究结果可为实际生产条件下的酶法糙米预处理工艺提供参考。
재조미년미과정중보편존재쇄미교다급년미능모고적문제，위개선조미년미품질，제출이섬유소매화목취당매적복합매용액처리체대상규수가습방법적매법예처리공예。이저장기조미（함수솔15%이하）위원료，채용이차정교선전중심조합설계시험，연구복합매용액처리공예중복합매배비、매질량농도、가액량급매처리시간대년미후정정미솔화년미능모적영향규률，건립료각인소대정정미솔화년미능모영향적수학모형。결과표명：구건적정정미솔、년미능모여복합매배비、매질량농도、가액량급매처리시간지간적회귀방정겁현저（P<0.01），득도우화삼수조합위섬유소매화목취당매질량비1.3∶1 g/g、복합매용액질량농도65 mg/mL、가액량1.25%，매처리시간102 min，해조건하정정미솔위80.07%、년미능모위90.72 kJ/kg。복합매용액처리후정정미솔교가습조질처리제고약3.98%，절약능모약13.06%；교섬유소단일매용액가습처리후정정미솔제고약0.98%，절약능모약5.48%。병통과미관결구분석증실료조미피층조섬유적국부파손시기년미성능개선적주요원인。연구결과가위실제생산조건하적매법조미예처리공예제공삼고。
Generally, lots of broken rice is generated and high energy consumption occurs during the rice milling processing, which bring adverse effect to the economic benefits of rice milling enterprises. Therefore, milling quality improvement is of important significance in practice for rice processing industry. Moisture conditioning treatment for the brown rice, which is an advanced technology, can increase head rice yield and reduce the milling energy consumption to some extent. It reduces the maximum compressive strength and maximum tensile strength with the increase of moisture content and generated moisture gradient within the rice by gradual penetration from the exterior into the interior of kernels. However, it does not fundamentally solve the problem caused by the resistant cortex of brown rice. The brown rice’s tough cortex is mainly caused by the coarse fiber structure, whose major components are cellulose and araboxylan. This study proposes a new process with composite enzyme of cellulase and xylanase instead of the conventional humidifying method. This method substantially decreases broken rice in the milling process and reduces the milling energy consumption to improve milling quality. The humidification of compound enzyme solution selectively degrades the cortex of brown rice, which can not only reduce the hardness of brown rice kernel and decrease the whitening pressure, but also facilitate the moisture penetration, which would boost cortex softening and increase the grain’s toughness. Moreover, the synergy of compound enzyme can improve the efficiency of the enzymatic hydrolysis. A central composite rotatable orthogonal experimental design of response surface methodology with 4 factors and 5 levels was employed. Taking brown rice in storage with moisture content below 15%as raw material, the influences of the 4 parameters including cellulose-to-xylanase mass ratio, concentration of compound enzyme solution, adding liquid proportion and enzyme treating time on the head rice yield and the milling energy consumption in the humidification process of compound enzyme solution were investigated, as well as the optimal parameters of this process. Mathematical models for the influences of various parameters on the head rice yield and the milling energy consumption were established. The test data were processed with Excel, Matlab and Design Expert. Experiment results showed that the parameters of compound enzyme solution humidification had significant impact on the head rice yield and the milling energy consumption. The optimized pretreatment parameters were as follows:the cellulose-to-xylanase mass ratio was 1.3:1 g/g, the concentration of composite enzyme solution was 65 mg/mL, the adding liquid proportion was 1.25%and the enzyme treating time was 102 min. Under the optimized parameters, the head rice yield was 80.07%and the milling energy consumption was 90.72 kJ/kg. To verify the optimization results, 3 groups of rice milling tests were made under the optimal combination of parameters, and the experiment results showed that there was no significant difference between predicted values and observed values. Contrast validation experiments indicated that the head rice yield and the milling energy consumption were respectively 3.98%higher and 13.06%lower than the values from the moisture conditioning treatment, and 0.98%higher and 5.48% lower than the values from the cellulase solution humidification. The cortex crude fiber degradation of brown rice proved to be the main reason for the improvement of rice milling quality through the optics electronic microscope analysis. This research can provide a theoretical basis for the new technology of rice milling pretreatment.