In Vitro Digestion Of Chitooligosaccharides

Chitooligosaccharides(COS)were raw food materials,which had good water solubility and various physiological activities.And the physiological activities were related to their degree of polymerization(DP)and content.However,the digestive process would change the DP and content of COS,which further changed their physiological activities in vivo.The digestive process and mechanism of COS with different DP during gastric and intestinal digestion were still unclear.In this study,the digestion mechanism of COS with or without meal and the influencing factors were investigated by in vitro static and dynamic model to provide supportings for the application of COS.Firstly,an established in vitro static digestion model was used to simulate the digestion of COS.The effects of digestive time,pepsin,pancreatin,gastric acid,bile salt and food matrix during the digestion of COS with different DP were studied.The results showed that COS with DP 2 to 5 were indigestible in gastric and intestinal digestion.Meanwhile,COS with DP 6 to 10 degraded over time.The degradation rates after 2-hour gastric and intestinal digestion reached 51.44%and 36.58%,respectively.And the degradation products were mainly COS with DP 2 to 5.Pepsin,pancreatin and lipase were the main factors leading to the decrease of COS with DP 6 to 10.Food matrix could protect COS with DP 6 to 10 from degradation during gastric digestion.However,food matrix also caused bile secretion,which accelerated the degradation of COS with DP 6 to 10 during intestinal digestion and led to the degradation of COS with DP 5.The content of COS with DP 5 reduced to 58.60%.Secondly,based on in vitro static digestion model studies,the in vitro dynamic model was used to investigate the influence of dymatic variables including the release of digestive juice,digestive emptying,digestive time on the regulation of gastrointestinal emptying process and digestion mechanism of COS.Regardless of absorption,COS were emptied gradually,and the cumulative emptying mass curve of chitiobiose to chitopentose were in accordance with the exponential function equation in the gastric and intestinal digestion process:y=Ae-x/5+y0(A<0;t,y0>0);x meant digestive time and y meant cumulative emptying mass of COS with different DP.The digestion time was shortened,and thus,the degradation rate of COS with DP 6 to 10 became lower,which reached 9.63%and 36.07%after gastric digestion and gastrointestinal digestion.Furthermore,COS with DP 5 to 10 degraded largely under the action of bile salt,trypsin and lipase in food matrix.Finally,commercially encapsulated COS were studied by in vitro dynamic model to investigate the digestion situation of encapsulated COS including the fragmentation of capsules,the release and emptying of COS and digestion behaviors of encapsulated COS.The results showed that the capsules could be completely broken within 5-15 min during gastric digestion,and then COS could be completely released and dissolved.The cumulative emptying mass curves of COS with DP 2-5 during 10-50 minutes of gastric digestion were in accordance with the exponential function equation.Encapsulated COS with DP 6 to 10 degraded.And thus,it is necessary to take measures to avoid COS with high DP being digested and degraded before absorption.