Effect Of Resistant Starch As Fat Replacer On Function Properties Of Low Fat Cheese

Cheddar cheese usually contains about 30%fat and is a semi-hard natural cheese.High intake of fats is considered unhealthy to human and may increase risks of chronic diseases.Therefore,reduced-fat dairy products have attracted increasing interest because of their potential health benefits.In recent years,low fat cheese with healthy function is recognized by consumers,but the scale of commercial production is low,due to consumers'inability to accept the taste and texture of low-fat cheese.Researchers are exploring the use of fat substitutes to improve the shortcomings of low-fat cheese,but the current shortcoming is that common fat substitutes cannot completely replace the functional properties of fat and endow mature low-fat cheese(natural cheese)with the original quality.Therefore,it is necessary to further explore new types of fat substitutes to make low-fat cheese commercial production.Resistant starch(RS)has many health benefits such as prebiotics,low lycemic index(low GI)and promotion of the absorption of mineral elements.Therefore,there have been some good applications in dairy products such as yogurt and processed cheese.It has great potential in natural cheese applications,and low-fat cheese containing RS will be a very beneficial food for human health.In this paper,six commercial resistant starch samples were selected,and then their functional properties were evaluated to clarify their health benefits and application potential.Then the interaction mechanism of the 6 kinds of RS and milk protein were evaluated by Isothermal Titration Calorimetry(ITC)and Differential Scanning Calorimetry(DSC),in order to clarify the interaction mechanism of RS and milk protein,and the property of RS in the process of sterilization and cooling(program temperature control),and form theoretical support and guidance for its subsequent effective use.In order to promote RS efficient use in low-fat cheddar cheese processing,the coagulation mechanism of RS and skim milk were investigated.Two kinds of RS sui Tab.as fat substitutes for natural cheese were screened out and used i n the processing of low-fat Cheddar cheese.During the 240d ripening period,in order to understand the mechanism and biological function changes of RS as a fat substitute in low-fat natural cheese,the effect of RS as a fat substitute on low-fat Cheddar cheese were evaluated.The main results were as follows:(1)Research on the functional characteristics of RSSix commercial RS samples were selected,and the composition,RS content,GI and microstructure of all samples were evaluated.The results showed th at the total starch content of all samples was above 92%,the ranges of RS content,RS in total starch content and GI value were28.3%-58.73%,30.7%-63.02%,47.35-61.60,respectively.The GI value of C4-PRS,M6-PRS and S5-PRS samples was the lowest,and the GI value of all samples was lower than that of potato starch GI value of 85.46,indicating that they can significantly reduce calorie intake.The SEM test results showed that the shape,size distribution,particle aggregation form of all samples were completely different.The microscopic particles of the B3-CRS and C4-PRS showed multiple small granular aggregates and most of them were larger than 10?m.The particle sizes of N1-CRS,P2-CRS,S5-PRS and M6-PRS were among 5?m to10?m,which were closer to the size of milk fat globules.From the structural point of view,these four RSs are sui Tab.as fat substitute.(2)Research on the interaction between RS and skim-milk,the mechanism of coagulation and the screening of fat substitutesThe interaction mechanism of the 6 kinds of RS and milk protein were evaluated by ITC and DSC.The results showed that the initial p H has a significant difference in the interaction force between RS and skim milk,and the driving mode(enthalpy or entropy driving)(P<0.01).It is found that some reactions have more configuration changes based on hydrogen bonds.The interactions between all starch samples and skim milk were exothermic processes(?H<0),and there were hydrogen bonds and hydrophobic forces involved in the interaction(?H<0,-T?S<0),and only M6-PRS has no configuration change at p H 6.5,and it is relatively stable,which is conducive to its participation in the enzymatic milk coagulation process.The control temperature analysis(20-80?)showed that the enthalpy change(?H)of C4-PRS and M6-PRS experimental groups was significantly affected by the addition amount of RS and p H value(P<0.01).The reaction of N1-CRS(or P2-CRS,C4-PRS,M6-PRS)and skim milk have heat flow peaks(T_onset<T_peak),and the initial temperature(T_onset)and peak temperature(T_peak)of those RS and skim milk were increased with RS dosages increasing and the p H decreased(P<0.01).It was showed that those four starches and skim milk have a heat-sensitive reaction properties.It can be inferred that thoes RS interact with milk protein to form a polymer or starch gelation.The T _onset and T_peakincrease significantly after the use of RS(P<0.01),and?H basically remains unchanged.Starch gelation was more likely to produce a heat flow peak,and it may form di fferent polymers and different polymerization modes after being heated.N1-CRS with the weakest effect on the formation of curd,and the strongest was the M6-PRS resistant starch,and hen 2.50%of M6-PRS is added,the curdling time can be reduced by 70%compared to the control.The results showed that the G'value of all samples curd was greater than its G"value at 45min,and with the increase of used various RS dose,the G'value increased significantly while G"decreased significantly,indicating that a vis coelastic curd was formed due to RS added.As the RS dose(range 0-2.5%)increased,the binding rate of curd increasesd significantly,it can be inferred that RS is combined together with milk solids and formed a curd,rather than as lost in the whey.The results of screening with cheese yield and starch utilization rate as evaluation indicators show that C4-PRS resistant starch and M6-PRS resistant starch are more sui Tab.as fat substitutes.(3)Process optimization of low-fat Cheddar cheese with RSAfter optimization experiments of single factor experiment and response surface experiment design,the optimum parameters showed that the addition amount of starch was 1.50%,the coagulation time was 50min,the addition amount of rennet was 0.035‰,and the brewing of p H was 5.40.The addition of RS reduces the fat content(?56%-63%),salt-to-moisture ratio(S/M)and protein content of cheese,and can also significantly increase the starch content,RS content,and the ratio of RS to non-fat solids in cheese(RSNFS),cheese yield,and moisture content of cheese sampls.The possible reason is that C4-PRS and M6-PRS have a certain water retention capacity and increase the water content.The starch content of all cheeses was directly correlated with its usage dose.The change trend of RS content of cheese is linearly related to the change of total starch content of cheese.However,it is found that there are several cheeses of obvious increase phenomena,indicated that C4-PRS and M6-PRS were affected by process adjustments such as heating and cooling during cheese processing,and the content of resistant starch of the cheese sample were significantly increased after this process..(4)Effects of RS on the function properties of low-fat Cheddar cheese during maturationThe analysis of texture found that reducing the fat content of milk increased the hardness,fracturability,resilience,cohesiveness and springinessof the Cheddar cheese,and the raw milk contained more than 1.5%RS reduced the hardness(?235N),fracturability(?159N)and springiness(?1.31mm)of low fat Cheddar and its close to the control full-fat Cheddar cheese(P<0.01).The results indicating that the use of more than 1.5%RS in the raw skim milk can improve the texture defects of Cheddar cheese due to fat reduction,and reduce the strength of internal bonds in the cheese structure.After continuing to mature,the hardness,fracturability,cohesiveness,resilience and springiness of all samples showed a decreased trend(P<0.01).Comprehensive analysis of C4-PRS and M6-PRS resistant starch can significantly improve the texture defects of low-fat Cheddar cheese and make it more close to full-fat Cheddar cheese.In the early stage of maturation(2d),the meltability and free oil of the low fat Cheddar(LFC,control)are lower than that of the full-fat Cheddar(FFC),while the stretchability of LFCwas higher than that of FFC(P<0.01).After a certain amount of RS is added,the melting and stretchability of the sample cheese decrease,while the free oil value remains unchanged,the meltability of cheese sample contained 2.0%C4-PRS or M6-PRS is closer to that of full-fat Cheddar(P<0.01).Research on the rheology of cheese found that the complex viscosity of low-fat Cheddar cheese increased with fat content reducing,while the addition of two types of RS could reduce the complex viscosity of low-fat cheese(P<0.01).It was found that the use of RS could significantly reduce the G'and G"of low fat Cheddar at the same ripening time(P<0.01).After added C4-PRS and M6-PRS starch,their T_gel-sol is significantly reduced and both are lower than the low-fat cheddar cheese(control),indicating that the addition of RS can reduce Tgel-sol and the vale close to FFC(P<0.01).At 120d,the study of the microstructure experiment found that cheeses(S1-LRFC,S1-MRFC and S1-HRFC)contained M6-PRS still had a large number of"mechanical holes".C4-PRS has no discrete phenomenon in cheese,and the formed cheese(especially after 240d maturation)has a tighter texture and a structure similar to full-fat cheese.Flavour research experiments showned that cheese samples had the highest FAA content(?6714mg/kg),when they were processed with 1.50%(or 2.0%)C4-PRS or M6-PRS,and that is higher than FFC(?5554mg/kg)(P<0.01).It shows that the addition of RS increases the degree of proteolysis.The results showed that all cheese samples did not contain Pro.Principal component analysis found that the analysis model is highly significant,and the changes in amino acid content can significantly reflect the differences in flavors of each group to explain(distinguish)the amino acid hydrolysis of cheese samples in each group(P<0.01).The addition of C4-PRS and M6-PRS can reduce the production of fat hydrolysates in all cheese samples.Principal compone nt analysis results show that the analysis results can well explain the flavor changes formed by the fatty acids in each group of cheeses,and the changes in the fatty acid content of the model can significantly reflect the flavor differences of each group to explain about 80.868%of the fat of each group of cheese samples fat hydrolysis(P<0.01).On the basis of the instrument-assisted analysis results,the artificial sensory evaluation found that compared with the FFC(control sample),the cheeses added with C4-PRS or M6-PRS showed yellowness,gloss,pore size,color consistency,no graininess,odor intensity,Fatty taste of samples are relatively reduced,while rancid taste,nutty taste,taste intensity,sour taste of samples are relatively increased,and salty taste,sweet taste,bitter taste index difference is not significant difference.The RFC has relatively high elasticity and hardness(P<0.01).At 240d,the taste intensity and sourness of the samples added with two kinds of RS were relatively increased compared with the FFC(control sample)(P<0.01).The cheese samples added with two kinds of RS overcome the defect of relatively high elasticity and hardness of the LFC(control)(P<0.01).The principal component model shows that the analysis results can explain the flavor of each group of cheeses to explain(distinguish)the flavor of each group of cheese samples.During maturation period,the whiteness value of low-fat cheese contained RS(C4-PRS or M6-PRS)were significant decreased,which is more similar to the FFC(control sample)(P<0.01).At the same ripened time,adding two kinds of RS has no obvious change trend to the above phenomenon due to resistant starch samples is pure white.At 2d,evaluation of the effect of hypoglycemia——Glycose Index(GI)study found that,the GI groups of the samples of the experimental groups with 1.5%and 2.0%RS were not significantly difference,and the GI value reached the maximum:?40.61,and GI values remain unchanged when they continue to mature,and the GI of each group of cheeses added with RS are significantly lower than other foods(P<0.01).The results indicating that the low-fat Cheddar cheese prepared by replacing fat with RS has the nutritional characteristics of low energy intake.The study found that the number of lactic acid bacteria(LAB)in each group of cheese samples decreased during the maturation process and was not affected by fat content,resistant starch types and added amounts(P<0.01).Further analysis found that the amount of Non-fermenter lactic acid bacteria(NSLAB)in low-fat cheese increased significantly after adding RS in raw skim milk(P<0.01).NSLAB reached a peak at 60d,and continued to mature significantly decreased(P<0.01).