Department of Food Science, University of Guelph, Ontario, Canada N1G 2W1.
Food Funct. 2019 Dec 11;10(12):7687-7696. doi: 10.1039/c9fo01994d.
This work compared in vitro and in vivo digestion of breakfast cereal with milks containing high protein concentration (9.3 wt%) and the normal protein ratio (80 casein : 20 whey) or a modified ratio (40 casein : 60 whey) and with a water-permeate control. The in vivo study indicated that high protein concentration and modified ratio in milks delays the postprandial appearance of blood glucose (BG) and amino acids due to delayed gastric emptying and hormonal responses. However, the role of viscosity and/or protein structure during digestion was not examined. Therefore, milks and the control were digested in vitro (oral (O, 2 min), gastric (G, 62 min) and duodenal (D, 92 min)) to determine viscosity, particle disintegration, protein solubility and hydrolysis, and the bioaccessibilities of sugars and total amino acids (TAA). The normal ratio (80 : 20) treatment demonstrated higher structural viscosity during digestion (P < 0.05) due to the formation of casein aggregates and interaction with cereal and greater TAA (mg per g protein of undigested breakfast) caused by gastric hydrolysis (DH%; P = 0.01). Overall, there were no treatment differences for disintegration, solubility and d-glucose. Protein-containing treatments inhibited amylolysis and lowered reducing sugars (mg g-1 available carbohydrates of undigested breakfast) compared to the control. Similar trends were observed between higher viscosity (Pa s) during gastric stage and slower in vivo gastric emptying (paracetamol, mmol L-1). Also, protein treatments inhibited amylolysis and lowered reducing sugar (mg g-1 of carbohydrates) and may have contributed to lowered BG (mmol L-1 g-1 of carbohydrates) after the duodenal phase. However, increased viscosity, elicited by higher proportions of casein, did not inhibit starch hydrolysis and appearance of BG. In vitro systems provide similar trends in biomarkers to in vivo studies and can be used to answer specific physiological questions.
这项工作比较了含有高蛋白浓度（9.3wt%）和正常蛋白比例（80 酪蛋白：20 乳清）或修改比例（40 酪蛋白：60 乳清）的早餐麦片在体外和体内的消化情况，以及与水渗透物对照物的消化情况。体内研究表明，高蛋白浓度和牛奶中的修改比例会由于胃排空和激素反应延迟而延迟餐后血糖（BG）和氨基酸的出现。然而，在消化过程中，粘度和/或蛋白质结构的作用尚未得到检验。因此，体外消化了牛奶和对照物（口腔（O，2 分钟）、胃（G，62 分钟）和十二指肠（D，92 分钟））以确定粘度、颗粒分解、蛋白质溶解度和水解以及糖和总氨基酸（TAA）的生物可利用性。正常比例（80：20）处理在消化过程中表现出更高的结构粘度（P<0.05），这是由于酪蛋白聚集的形成和与谷物的相互作用以及胃水解（DH%；P=0.01）导致的更大 TAA（未消化早餐每克蛋白质的毫克数）。总体而言，在分解、溶解度和 d-葡萄糖方面，处理之间没有差异。含蛋白质的处理抑制了淀粉水解并降低了还原糖（未消化早餐每克可利用碳水化合物的毫克数），与对照相比。在胃阶段，较高的粘度（Pa s）和较慢的体内胃排空（扑热息痛，mmol L-1）之间观察到类似的趋势。此外，蛋白质处理抑制了淀粉水解并降低了还原糖（碳水化合物每克的毫克数），并可能导致十二指肠相后 BG（碳水化合物每克的 mmol L-1 g-1）降低。然而，由更高比例的酪蛋白引起的粘度增加并没有抑制淀粉水解和 BG 的出现。体外系统提供与体内研究相似的生物标志物趋势，可用于回答特定的生理问题。
