Broken rice has become more popular to be sustainably used due its low-cost and potential utilization for preparing purified/modified starches and fermented products. The use of broken rice as substrate of an enzymatic extrusion process modified by divalent metal salts was investigated. Six metal salts with concentrations 0.6, 1.2, and 1.8 mmol/100g (db of starch) were premixed with a thermostable α-amylase and with broken rice before being extruded. Extrudates were characterized using RVA, X-ray, FT–IR, and SEM techniques. RVA results showed that Mg(II), Ca(II), Mn(II), and Zn(II) decreased extrudate viscosity whereas Fe(II) and Cu(II) increased it compared to extrusion performed in absence of salts. DNS test demonstrated that nontransition metals Mg(II) and Ca(II) activated the enzyme and improved the extrusion performance, while transition metals Mn(II), Fe(II), Cu(II), and Zn(II) inhibited the activity of the enzyme. X-ray Diffraction (XRD) showed that all ions contributed to slightly increase the extrudate crystallinity. Holes of various sizes were observed on the surface of the extruded material when salts were used, indicating changes in enzymatic action. The residual content of phenolics increased when the ions Mg(II), Ca(II), and Mn(II) were used while the hydrogen (rather than electron) donating capacity of phenolics was slightly influenced.

中文翻译：

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二价金属盐存在下大米的生物膨化：对淀粉微结构和酚类化合物的影响

碎米因其低成本和潜在用途来制备纯化/改性的淀粉和发酵产品而变得越来越受欢迎，可以持续使用。研究了将碎米饭用作经二价金属盐改性的酶促挤出工艺的底物。将六种浓度分别为0.6、1.2和1.8 mmol / 100g（每分贝淀粉）的金属盐与热稳定的α-淀粉酶和破碎的大米预先混合，然后挤出。使用RVA，X射线，FT-IR和SEM技术对挤出物进行表征。RVA结果表明，与无盐挤压相比，Mg（II），Ca（II），Mn（II）和Zn（II）降低挤出物粘度，而Fe（II）和Cu（II）则增加挤出物粘度。DNS测试表明，非过渡金属Mg（II）和Ca（II）激活了酶并改善了挤出性能，而过渡金属Mn（II），Fe（II），Cu（II）和Zn（II）抑制了酶的活性。X射线衍射（XRD）显示所有离子都有助于稍微增加挤出物的结晶度。当使用盐时，在挤出材料的表面上观察到各种大小的孔，表明酶作用的变化。当使用离子Mg（II），Ca（II）和Mn（II）时，酚醛的残留含量增加，而酚的氢（而不是电子）的供电能力受到轻微影响。