| At present,excessive intake of fat,especially saturated fat,is the main cause of obesity.Among many strategies to reduce obesity,food scientists and nutritionists are attempting to microencapsulate fat in order to inhibit fat digestion.Therefore,a series of new fat delivery systems had been constructed in this paper to reduce the digestion of fats in the gastrointestinal tract.Firstly,single-layer coconut oil emulsions of six proteins with different concentrations were first prepared,and their particle size,potential and stability were analyzed.The type and concentration of proteins were optimized and established.And then singlelayer coconut oil emulsion was mixed with different celluloses to prepare stable doublelayer coconut oil emulsion.Based on this,the microrheological properties and digestive properties of the emulsion were studied,and the effects of different factors on the release properties in vitro were explored.The following conclusions were reached:(1)Taking the particle size,potential and stability as the indicators,the effects of six types of single-layer coconut oil emulsions at a concentration of 0.1%-4% were compared.The results showed that the particle size distribution of SC and WPI was concentrated,and the emulsion system was more stable;at high protein concentrations(1%-4%),The SC,WPI,WPC,and LF emulsions had a small change in the bottom transmittance over time and the overall clarification index,which indicated that emulsions were stable.It demonstrated that SC and WPI could be selected as the ideal wall material for embedding coconut oil.Considering the later economic benefits,the protein content was set at 1%.(2)From the particle size,potential and light transmittance spectrum of the doublelayer coconut oil emulsion,the stability of the WPI-cellulose coconut oil emulsion was better.WPI-CNC emulsion system had obvious viscoelastic characteristics and was more suitable for slow digestion system of fat.In the range of pH 3~7,the particle size of WPI-CNI stabilized coconut oil emulsion at pH 7 was significantly more high than that at pH 3~6.The average particle diameter of WPI,WPI-CMC,WPI-CNC,WPI-MCC stabilized coconut oil emulsion at pH 3 was higher than that at pH 7;at pH 3~7,the negative charge WPI,WPI-CNC,WPI-MCC stable coconut oil emulsion gradually increased,and the repulsion between droplets gradually increased with the incease of pH.WPI-CNI stable coconut oil emulsion had a higher positive charge at pH 3~6,which indicated that the emulsion was more stable.When pH was 7,it had a lower negative charge and the stability becomed worse.The potential of WPI-CMC stabilized coconut oil emulsion at pH 7 was lower than that of emulsion at pH 3.(3)The digestive propertie of five different types of coconut oil emulsions was studied.The results showed that WPI-CNC emulsion had a lowest intestinal release rate and the slowest release rate;following passage through the simulated stomach phase,extensive droplet flocculation was observed except coconut oil emulsion stabilized by WPI-CNC,and the degree of aggregation was increased following exposure to the simulated small intestinal stage;following exposure to the simulated mouth,stomach and small intestinal stage,we observed a ordinal increase in the mean particle size of WPI,WPI-CNC and WPI-CMC emulsions,and the particle size distribution demonstrated that these emulsions exhibited multimodal distribution;Following exposure to the simulated small intestinal stage,we observed a increase in the negative charge of all emulsions.It demonstrated that the microrheological property of coconut oil emulsion significantly affected their digestibility,and WPICNC stabilized coconut oil emulsion has the lowest and the slowest digestibility in vitro.(4)An in vitro simulated gastrointestinal tract was used to investigate the effects of different enzyme concentrations,sample loadings,lipid types and oil contents on the fatty acid release rate of coconut oil emulsions;and the effects was researched of different lipid types on the release rate and fatty acid composition of emulsion.Results showed following passage through the simulated mouth and stomach phase,the fatty acid release rate of WPICMC stabilized coconut oil emulsion was generally low and stable with the increase in enzyme concentration(0.15-1.5 mg/mL),sample loading and oil content;following exposure to the simulated small intestinal stage,with higher trypsin concentration came faster fatty acid release and higher release rate of the emulsion;there was a sharply deline in the fatty acid release rate with the increase of sample or oil content;with the increase in oil content,the viscoelasticity of emulsions increased and the fluidity became worse.The emulsions with coconut oil had the highest release level of fatty acid,followed by those with olive oil,palm oil,rice oil and perilla seed oil;the release rate of long chain triglycerides were slower than medium chain triglycerides,and long-chain polyunsaturated fatty acids were slower than long-chain monounsaturated fatty acid;embedding hardly affected the fatty acids composition of the main components in coconut oil,perilla seed oil and olive oil,but it made the proportion of main fatty acids composition of palm oil decrease,and caused a certain damage to the main fatty acids composition ratio of rice oil;release rate of other fatty acids in coconut oil,perilla seed oil and olive oil were higher than polyunsaturated fatty acids.It demonstrated that the enzyme concentrations,sample loadings and oil contents significantly affected digestibility of fat. |
PDF Full Text Request