Synergistic Interactions Of Endogenous And Exogenous Emulsifiers And Their Effects On In Vitro Digestion Of Lipids In Macromolecular Media

The human body often intake a variety of lipids in daily life,and the digestion and absorption of lipids played an important role in body's metabolism.However,we often need to add a certain amount of exogenous emulsifiers in food processing and production to ensure taste,flavour,the quality of food and other specific features.The digestion of the lipids in body requires identification and emulsification with the naturally occurring endogenous emulsifiers such as sodium cholate.Then,the exogenous emulsifiers in these emulsions will encounter the bile salts as endogenous emulsifiers in body.The effect of the synergistic interactions between amphiphilic molecules will change the interface of the emulsions,subsequently affecting the in vivo digestion of lipids.In addition,there are many macromolecules in human body,which can build an crowding environment that affects the structures of many materials and biochemical reactions in body.Therefore,the digestion of lipids in the intestine must be carried out in such crowding environment.In this paper,we have built crowding environment with polyethylene glycol(PEG)and dextran with different molecular weight and concentration.Then,the effect of the synergistic interactions between an exogenous emulsifier(Tween80)and the endogenous emulsifier on the lipid digestion in crowding environment have been studied,which is aimed to understand the in vivo digestion of lipids as real as possible.(1)The effect of the crowding environment on the simulated in vitro digestion of lipidsIn the in vitro lipid digestion experiment,we found that both the hydrolysis rate and hydrolysis degree of soybean oil and glycerol trioleate(C18:1)were increased when the crowding environment builded by different varied molecular weight and concentration of PGE was included.Such increasing trend is proportional to the concentration of PEG.However,when it comes to the crowding environment of dextran,both the hydrolysis rate and hydrolysis degree of soybean oil and C18:1 were decreased,and such descending tendancy was proportional to the concentration of dextran.(2)The synergistic interaction between endogenous and exogenous emulsifiersTween 80 and sodium cholate were chosen as the endogenous and endogenous emulsifier respectively to study their synergetic interactions,which was measured by fluorescence spectroscopy.It was found that when the concentration ratio of Tween 80 and sodium cholate was 3:7,the endogenous and exogenous emulsifiers had the strongest interactions.Further study on the emulsions prepared by different emulsifiers showed that the emulsions prepared by the both kinds of emulsifiers were better than that prepared by single emulsifier in particle size,?-potential and in vitro digestion degree.The same trends in the in vitro digestion of the emulsions of glycerol octanoate(C8),C18:1 and soybean oil were observed.(3)The synergistic effect of the macromolecular crowding and endogenous and endogenous emulsifiers on the digestion of lipidsBased on the results of the previous and present studies,we found that the coexistence of macromolecular crowding environment and endogenous and endogenous emulsifiers would further improve the hydrolysis rate and hydrolysis degree of C8 and C18:1,and this trend was proportional to the concentration of PEG.By employing differential scanning calorimetry,we found that the macromolecule crowding and endogenous and endogenous emulsifiers improved the denaturation temperature of lipase,which made the structure of the enzyme more stable.The change of the surface tension during the hydrolysis process of lipids revealed that the macromolecule crowding and endogenous and endogenesis emulsifiers could slow down the decrease degree of the surface tension of emulsions during the hydrolysis and also prolong the time for the contact between lipids and enzyme.In this paper,the effects of macromolecular crowding environment and endogenous and endogenous emulsifiers on the digestion of different lipids were studied systematically,and the mechanism behind these hydrolysis was interpreted.Our results would provide important guidance for controlling the digestion of the lipids and reflect the real situation of lipid digestion in human body.