Abstract：
Sheep\'s milk (SM) is known to differ from cow\'s milk (CM) in nutritional composition and physicochemical properties, which may lead to different digestion behaviours. This work aimed to investigate the impact of the species (cow vs sheep) and the structure (milk vs yogurt) on the digestion of dairy products. Using an in vitro static gastrointestinal digestion model, CM, SM, cow\'s milk yogurt (CY) and sheep\'s milk yogurt (SY) were compared on particle size evolution, microscopic observations, degree of lipolysis, degree of proteolysis, specific protein degradation and calcium bioaccessibility. Species and structure affected particle size evolution during the gastric phase resulting in smaller particles for yogurts compared to milks as well as for CM products compared to SM products. Species impacted lipid composition and lipolysis, with SM products presenting higher short/medium-chain fatty acids content and higher intestinal degree of lipolysis. Proteolysis was influenced by structure, with milks showing higher intestinal degree of proteolysis compared to yogurts. Caseins were digested faster in CM, ⍺-lactalbumin was digested faster in SM despite its higher concentration, and during gastric digestion β-lactoglobulin was more degraded in CM products compared to SM products and more in yogurts compared to milks. Lastly, SM products released more bioaccessible calcium than CM products. In conclusion, species (cow vs sheep) impacted more the digestion compared to the structure (milk vs yogurt). In fact, SM was different from CM mainly due to a denser protein network that might slow down the accessibility of the enzyme to its substrate which induce a delay of gastric disaggregation and thus lead to slower the digestion of the nutrients.
摘要：
已知羊奶（SM）在营养成分和理化性质上与牛奶（CM）不同，这可能会导致不同的消化行为。这项工作旨在研究物种（牛vs羊）和结构（牛奶vs酸奶）对乳制品消化的影响。使用体外静态胃肠消化模型，CM,SM,比较了牛乳酸奶(CY)和羊乳酸奶(SY)的粒度演变，微观观察,脂解程度,蛋白水解程度，特定的蛋白质降解和钙的生物可及性。物种和结构影响胃部阶段的粒度演变，导致与牛奶相比，酸奶的颗粒更小，与SM产品相比，CM产品的颗粒更小。物种影响脂质组成和脂解，SM产品表现出较高的短链/中链脂肪酸含量和较高的肠道脂解程度。蛋白水解受结构的影响，与酸奶相比，牛奶显示出较高的肠道蛋白水解程度。酪蛋白在CM中消化得更快，尽管SM的浓度较高，但其在SM中的消化速度更快，在胃消化过程中，与SM产品相比，CM产品中的β-乳球蛋白降解更多，与牛奶相比，酸奶中的β-乳球蛋白降解更多。最后,SM产品比CM产品释放更多的生物可及钙。总之,与结构（牛奶与酸奶）相比，物种（牛与羊）对消化的影响更大。事实上,SM与CM不同，主要是由于蛋白质网络较致密，可能会减慢酶对其底物的可及性，从而导致胃解聚的延迟，从而导致营养物质的消化速度较慢。
