China-Canada Joint Lab of Food Nutrition and Health (Beijing), School of Food and Health, Beijing Technology and Business University (BTBU), 11 Fucheng Road, Beijing 100048, China.
College of Chemistry and Materials Engineering, Beijing Technology and Business University (BTBU), 11 Fucheng Road, Beijing 100048, China.
Ultrason Sonochem. 2022 Feb;83:105920. doi: 10.1016/j.ultsonch.2022.105920. Epub 2022 Jan 19.
Brown rice is nutritionally superior to polished white rice, as it maintains a large content of external bran that involves a series of bioactive compounds. However, the presence of bran also restricts water diffusion and results in adverse quality of brown rice. In this work, ultrasound conditions were optimized for cellulase to improve its hydrolysis effect on rice bran, and combinations of enzymatic and ultrasound treatment in different manners were conducted on brown rice, to improve the textural attributes. The results showed significant improvements in the catalytic activity and efficiency of cellulase after ultrasonication at the optimal intensity of 1.67 W cm and duration of 30 min, with the conformational variation of cellulase observed from the fluorescence spectra and circular dichroism (CD). Despite the enhanced activity of ultrasonicated cellulase, it leaded to a similar rice surface morphology and a comparable amount of released glucose, and equivalent textural parameters of brown rice treated by native cellulase. However, for the pre-sonicated brown rice, the ultrasonicated cellulase showed a significantly higher hydrolysis capacity than the untreated enzyme, suggesting the important influence of ruptured bran surface on amplifying the hydrolysis effect of cellulase. Compared to the successive ultrasound stimulation on both cellulase and brown rice, ultrasound-assisted cellulase treatment on brown rice produced less glucose from rice bran, but induced similar textural properties of brown rice, possibly resulting from the simultaneously promoting effect of ultrasonication on cellulase and water diffusion. Ultimately, this study highlighted that the mild rice surface rupture is a crucial factor to display the promoted hydrolysis effect of ultrasonicated cellulase on brown rice. Ultrasound-assisted cellulase treatment potentially provides an effective strategy to improve the edible quality of brown rice.
糙米在营养上优于精白米，因为它保留了大量的外部糠层，其中涉及一系列生物活性化合物。然而，糠层的存在也限制了水分的扩散，导致糙米的品质下降。在这项工作中，优化了超声条件以用于纤维素酶，以提高其对米糠的水解效果，并以不同方式组合酶法和超声处理对糙米进行处理，以改善其质构特性。结果表明，在最佳超声强度 1.67 W cm 和 30 min 处理时间下，超声处理显著提高了纤维素酶的催化活性和效率，从荧光光谱和圆二色性（CD）观察到纤维素酶的构象变化。尽管超声处理后的纤维素酶活性增强，但它导致了类似的米粒表面形态和释放的葡萄糖量相当，以及用天然纤维素酶处理的糙米的等效质构参数。然而，对于预超声处理的糙米，超声处理后的纤维素酶显示出比未处理酶更高的水解能力，表明破裂的糠层表面对放大纤维素酶的水解效果具有重要影响。与在纤维素酶和糙米上连续进行超声刺激相比，在糙米上进行超声辅助纤维素酶处理从米糠中产生的葡萄糖较少，但诱导了糙米相似的质构特性，这可能是由于超声处理对纤维素酶和水分扩散的同时促进作用。最终，本研究强调了轻度的米粒表面破裂是展示超声处理后的纤维素酶对糙米促进水解效果的关键因素。超声辅助纤维素酶处理为改善糙米的食用品质提供了一种有效的策略。
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