| Trans fatty acids(TFA)is one of the safety risk factors and caused the chronic metabolic diseases(such as cardiovascular disease,diabetes,obesity and other diseases)with gradually rise in recent years.Therefore,developing the oils and fats with excellent nutrition,desirable plasticity and without TFA has become a hotspot in the industry.Enzymatic interesterification prepare zero-TFA plastic fats by vegetable oils and high-melting-point fats,which converts liquid oil into plastic solid fat by restructuring the fatty acid molecular structure of triglycerides.In this study,the enzymatic interesterification was carried out with camellia oil(CO),beef tallow(BT)and palm stearin(PS),and the products were purified by liquid-liquid extraction deacidification to obtain enzymatic interesterified plastic fats(IF).The physicochemical properties and storage stability of the products were analyzed.In addition,the functions of the products in improving lipid metabolism and regulating the structure of intestinal microflora were explored in combination with animal growth experiments.The main research contents and results are as follows:(1)Preparation of IF was carried out.The IF were synthesized by interesterification of CO,BT and PS using specific immobilized lipase Lipozyme RM IM,and the sliding melting point(SMP)as a reference index.The optimal conditions for IF were obtained by single factor and response surface test design(The response value during the optimization test was optimized at 37?),and as follows: the ratio of substrate was 7.55:2.45:4.00(BT:CO:PS),in the concentration of 3.65% Lipozyme RM IM,reaction 3.85 h at 72.6?.The SMP of IF is 36.8? under this condition,which is close to the theoretical value,and the error is less than 1%.The IF was deacidified and purified by liquid-liquid extraction,and could removed by-products such as free fatty acids and monoglycerides effectively.(2)The physicochemical properties include fatty acids and TAG profile,SFC,melting and crystallization behavior,polymorphic forms of IF were systematically characterized.The results showed that the content of OOO,PSS/SPS,LLL and SSS in the triglyceride of IF was lower and the content of PSO/POS/SPO,POO/OPO,POP/PPO,PLO/PLP/PPL increased compared to physical blends.Melting and crystallization behavior of IF has changed,while the contents of various fatty acids did not change significantly.Compared with raw solid fats and physical blends,IF exhibiteda wider plastic range with the lowest SFC at 0-40?,drops to 0-0.49% at 40? and with desirable ?' type crystals,and could be suitable for plastic fats use.The storage stability of physical blends and IF was comparative analyzed by Schaal oven accelerated oxidation experiment,and the shelf life of IF was predicted.The results showed that the acid value(AV),carbonyl value(IV)and peroxide value(PV)of IF rised more obviously than physical blends with the increase of accelerated oxidation time,and SMP also showed instability.The oxidation kinetics equation were derived from the peroxide values of IF,and the shelf life was predicted to be 352 days.(3)The effects of IF on lipid metabolism in rats were preliminarily evaluated by SD rats feeding for 6w.The results showed that the body weight of IF group was significantly lower than that of physical blends group(PB),and there was no significant difference in liver index between the groups,indicating that IF could control the increase of body weight,inhibit the accumulation of fat,and cause no organ hypertrophy.Liver biochemical indicators showed that IF did not cause fat accumulation and hepatotoxicity in the liver.The results of blood lipid levels in rats indicated that IF has an effect of improving the disorder of negative lipoprotein metabolism in SD rats.Adipose factors analysis showed that IF could effectively reduce leptin level and increase adiponectin level,which further illustrated the potential value of IF in improving lipid metabolism.Histopathological observation of liver tissue showed that similar results in IF group and NC group,and no histopathological liver injury was found,and indicating that IF does not cause liver damage.(4)The effects of IF on intestinal microflora in rats were preliminarily evaluated by SD rats feeding for 6w.The results showed that the IF group showed a similar structure of intestinal microflora with higher similarity to the model CO group.Intake of IF could effectively reduced the ratio of Firmicutes to Bacteroidetes and decreased the relative abundance of Proteobacteria,and the composition of intestinal microflora of rats was more balanced.The relative abundance of Bacteroidales_S24-7_group,Bacteroidaceae,Prevotellaceae in IF group was significantly higher than that in PB group;The levels of Bacteroides and Lachnospiraceae_NK4A136_group,Lactobacillus and Lachnospiraceae_uncultured were higher and significantly lower in the IF group,respectively.However,they were positively correlated with the relative abundance of Bacteroidetes and Firmicutes,and negatively correlated with the relative abundance of Firmicutes,respectively.Overall,IF has a certain effect in in regulating the structure of intestinal microflora. |
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