碳酸氢钠对组织化小麦蛋白体外消化特性的影响

Effect of Sodium Bicarbonate on in Vitro Digestion of Textured Wheat Protein

摘要:

近年来，基于组织化植物蛋白的植物肉受到越来越多的关注。有关植物肉的蛋白质消化特性还不明确。碳酸氢钠是组织化蛋白质制备中常用的添加剂。为了探究碳酸氢钠对组织化蛋白质的纤维结构和蛋白质消化特性的影响，制备了含0、0.05%和0.10%（质量分数，以干粉质量计）碳酸氢钠的组织化小麦蛋白。通过测定样品的堆积密度、质构特性、组织化度、微观结构和蛋白质分子间相互作用力分析样品的纤维结构特性。结果表明，随着碳酸氢钠质量分数由0增加到0.1%，组织化小麦蛋白的堆积密度、硬度和组织化度逐渐减小，其纤维结构更加纤细，纤维之间的间隙更多。经过体外口腔和胃消化阶段后，3种组织化小麦蛋白的食糜粒径均随碳酸氢钠质量分数的增大而增大（P >0.05）；在模拟小肠消化结束后，3种样品的消化产物粒径接近（P>0.05）。胃消化30 min时，蛋白质电泳图谱中，3组样品中相对分子质量小于14 300的蛋白质条带颜色随着碳酸氢钠质量分数的增加而变浅。在体外消化结束后，消化食糜中可溶性氮质量分数随碳酸氢钠质量分数的增大而增大（P ＜0.05）。这些结果表明，随着碳酸氢钠质量分数的增大，组织化小麦蛋白中蛋白质的消化速度和程度逐渐增大，消化结束后3种组织化小麦蛋白释放的游离氨基酸总质量分数分别为（39.53±0.56）、（41.56±0.59）、（44.85±0.39） mg/g（以消化液质量计），这可能主要是由其较细的纤维和更多的纤维间隙促进蛋白酶与作用位点的接触导致的。

Abstract:

In recent years, textured-vegetable-protein-based meat analogs have received more and more attention. The protein digestibility of plant-based meat analogs is still unclear. Sodium bicarbonate is a commonly used additive in the preparation of textured proteins. In order to explore the effect of sodium bicarbonate on the fibrous structure and protein digestibility of textured protein, textured wheat proteins containing 0, 0.05%, and 0.1% (mass fraction of dry powder) sodium bicarbonate were prepared. The fibrous structure was analyzed by measuring the bulk density, texture properties, degree of texturization, microstructure, and protein-protein intermolecular interactions of the samples. The results showed that with the increase of sodium bicarbonate mass fraction from 0 to 0.1%, the bulk density, hardness, and degree of texturization of the textured wheat protein decreased gradually, and the gaps between fibers became larger when the fibers became thinner. After in vitro oral and gastric digestion, the digesta particle size of three textured wheat proteins increased with the increase of sodium bicarbonate concentration (P>0.05). After the simulated small intestinal digestion, the particle sizes of the digestion products of three textured wheat proteins were similar (P>0.05). After 30 min of gastric digestion, the band intensity of protein with relative molecular weight less than 14 300 in three samples declined with the increase of sodium bicarbonate mass fraction. After the in vitro digestion, the content of soluble nitrogen in digesta increased with the increase of sodium bicarbonate mass fraction (P<0.05). These results suggested that the protein digestion rate and degree of textured wheat proteins gradually increased with the increase of sodium bicarbonate mass fraction. After digestion, the total free amino acids obtained released from three textured wheat proteins were （39.53±0.56）, （41.56±0.59）, and （44.85±0.39） mg/g of digesta, respectively. The greater extent of proteolysis in the textured wheat proteins containing the higher mass fractions of sodium bicarbonate might be due to the thinner fibers and more fiber gaps, which promoted the proteases to interact with the cleavage sites.