Bayrak Meltem, Mata Jitendra, Raynes Jared K, Greaves Mark, White Jacinta, Conn Charlotte E, Floury Juliane, Logan Amy
CSIRO Agriculture and Food, 671 Sneydes Road, Werribee, Victoria 3030, Australia; School of Science, STEM College, RMIT University, 124 La Trobe Street, Melbourne, VIC 3000, Australia.
Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia.
J Colloid Interface Sci. 2021 Jul 15;594:561-574. doi: 10.1016/j.jcis.2021.03.087. Epub 2021 Mar 19.
This study aimed to understand the structural devolution of 10% w/w rennet-induced (RG) and transglutaminase-induced acid (TG) gels in HO and DO under in vitro gastric conditions with and without pepsin. The real-time devolution of structure at a nano- (e.g. colloidal calcium phosphate (CCP) and micelle) and micro- (gel network) level was determined using ultra-small (USANS) and small-angle neutron scattering (SANS) with electron microscopy. Results demonstrate that gel firmness or elasticity determines disintegration behaviour during simulated mastication and consequently the particle size entering the stomach. Shear of mixing in the stomach, pH, and enzyme activity will also affect the digestion process. Our results suggest that shear of mixing primarily results in erosion at the particle surface and governs gel disintegration behaviour during the early stages of digestion. Pepsin diffusivity, and hence action, occur more readily in the latter stages of gastric digestion via access to the particle interior. This occurs via the progressively larger pores of the looser gel network and channels created within the larger, less dense casein micelles of the RG gels. Gel firmness and brittleness were greater in the DO samples compared to HO, facilitating gel disintegration. Despite the higher strength and elasticity of RG compared to TG, the protein network strands of the RG gels become more compact when exposed to the acidic gastric environment with comparatively larger pores observed through SEM imaging. This led to a higher degree of digestibility in RG gels compared to TG gels. This is the first study to examine casein gel structure during simulated gastric digestion using scattering and highlights the benefits of neutron scattering to monitor structural changes during digestion at multiple length scales.
本研究旨在了解在有或没有胃蛋白酶的体外胃条件下，10% w/w凝乳酶诱导（RG）和转谷氨酰胺酶诱导酸性（TG）凝胶在高水分（HO）和低水分（DO）条件下的结构降解情况。使用超小角（USANS）和小角中子散射（SANS）结合电子显微镜，测定了纳米级（如胶体磷酸钙（CCP）和胶束）和微米级（凝胶网络）结构的实时降解情况。结果表明，凝胶的硬度或弹性决定了模拟咀嚼过程中的崩解行为，进而决定了进入胃中的颗粒大小。胃中的混合剪切力、pH值和酶活性也会影响消化过程。我们的结果表明，混合剪切力主要导致颗粒表面的侵蚀，并在消化早期控制凝胶的崩解行为。胃蛋白酶的扩散率以及由此产生的作用，在胃消化后期通过进入颗粒内部更容易发生。这是通过RG凝胶中较大、密度较小的酪蛋白胶束内形成的较松散凝胶网络的逐渐增大的孔隙和通道实现的。与HO样品相比，DO样品中的凝胶硬度和脆性更大，有利于凝胶崩解。尽管RG凝胶比TG凝胶具有更高的强度和弹性，但在酸性胃环境中，RG凝胶的蛋白质网络链会变得更加紧密，通过扫描电子显微镜成像观察到其孔隙相对较大。这导致RG凝胶比TG凝胶具有更高的消化率。这是第一项使用散射研究模拟胃消化过程中酪蛋白凝胶结构的研究，并强调了中子散射在监测多长度尺度消化过程中结构变化方面的优势。
