Study On Properties And Application Of Whey Protein Emulsified Lard With Different Contents Of Water

Lard is widely used as a shortening in baking food because it has good foaming capacity,nutritional and has a good taste.However,lard also has many disadvantages,such as coarse crystal grain,soft texture,poor oxidative stability and so on.With the food industrial development and higher demand of food,low and animal fat has become a new alternative ingredient instead of the traditional hydrogenated oil.In order to prepare low-fat lard,and improve its processing quality,we modified lard by emulsification.Low content lard(50%)was emulsified by adding transglutaminase(TGase)cross-linking whey protein concentrate(WPC)to modify interface characteristics,and then it was subjected to ultrasound technique to improve crystallization of the emulisified lard with high content lard(80%).The physical characteristics,digestive properties,oxidative stability of modified lard were tested and the application of modified lard was studied.The main results are as follow:Firstly,different contents of WPC(2%wt,4%wt)were used to emulsify lard Furthermore,lard emulsion was treated by ultrasound technique and TGase.The solid fat content(SFC),average particle size,crystallization behavior,hardness,storage modulus,viscosity and interfacial protein content were used as parameters to study the effects of ultrasonic treatment,TGase crosslinking on physicochemical properties of modified lard with different contents protein.The results showed that in the emulsified lard with 80% lard by ultrasonic,with the extension of storage time,the SFC of ultra-sounded group increased by 7% compared to the controls and closed to the pure lard(42%).However,there were no significant differences between the different ultrasound time.The crystal acted more fine and orderly arrangement.The storage modulus(G')and the average particle size of emulsified lard increased,the viscosity and interfacial protein content decreased.And compared with pure lard,with adding WPC,the hardness decreased from 58.5 g to 11.5 g.After 2 month storage,the hardness of the emulsified lard with WPC 2% increased to 40.8 g,but for the WPC 4%,the increase of hardness was lower than WPC 2%.With the increase of protein content in the system,the G' decreased 15 times.The emulsified lard with 50% lard is flowing,after adding TGase,the viscosity and interfacial protein content increased.And the G' of the emulsion with WPC 4% is 4 times of WPC 2%,reaching the same level of the emulisified lard with 80% lard and WPC 4%.The ultrasonic technology promoted the crystallization of emulsified lard with high oil content,decreased crystal and increased hardness;while TGase increased the viscosity and G 'of emulsified lard in low oil content group,and improved its coating propertySecondly,for investigating the biochemical characteristics,emulsion stability and interfacial integrity of emulsified lard after ultrasonic treatment and TGase cross-linking,a digestion model was used.We determined the average particle size,?-potential,free fatty acid(FFA)content and microstructure in vitro digestion experiments of lard emulsion.The results showed that emulisified lard with 80% lard by ultrasonic treatment,the FFA released and average particle size was bigger than the controls group.And the ?-potential was lower than the controls group.However,the released amount of FFA and the average particle size in TGase group were decreased.Ultrasonic treatment increased the digestion rate of emulsified lard,while the TGase slowed down the digestion rate.Thirdly,we tried to improve the oxidation stability of emulsified lard and prolong the shelf life.The gallic acid(GA),glycyrrhizic acid(GlA),glabridin(G)and licorice extract(LE)were added in emulsified lard,using electron spin resonance(ESR)and Schaal oven method to evaluate the antioxidant effect of this four kinds of antioxidants.The results of ESR showed that the highest free radical scavenging rate of LE reached 80%.The minimum clearance rate of GlA was about 40%,and the antioxidant effect was the worst.The results of Schaal oven method showed that the antioxidant capacity of the four additives was LE>G>GlA>GA.LE as the best antioxidant at 4°C,the theoretical shelf life of emulsified lard was changed from 224 ~ 267 d to 249 ~ 312 d.Finally,in order to verify the practical application of emulsified lard,the emulsified lard was applied to the pound cake.The effect of rheological properties,microstructure,cake texture,cake physicochemical properties and cake microstructure network on cake were studied.The results showed that the the emulsified lard with 80% lard by ultrasound or the emulsified lard with 50% lard by emulsify with TGase cross-linking protein could reduce the lard content of pound cake without causing the collapse of the cake and the decline of the quality.