Crosslinking Reaction Of Low Bloom Gelatin Catalyzed By Transglutaminase And The Applications Of Crosslinked Gelatin In Marshmallow And Yoghurt

Gelatin has multiple properties and abilities such as gelling,emulsifying,foaming,film forming,transparency,thermal-reversible,thickening,water-binding,fat mimic etc.and it is a natural protein which protein content is up to 85%.Gelatin is widely used in pharmaceutical,food and photo products.The commercial gelatin in China is mainly extracted from skin and bone of bovine and porcine,and a few is extracted from fish skin or fish scale.In process,the gelatin is extracted repeatedly from materials after they are treated with acid or alkali.Then gelatin solution flow through filters,ion exchanger,evaporator,sterilizer,freezer and extruder,then get dried and crushed to become granular gelatin.When gelatin is extracted repeatedly,the temperature of every extraction is higher than previous extraction.so normally the first three times extracted with lower temperature which yield higher gel strength gelatin,but the 4th or 5th extractions can only yield low gel strength gelatin due to very high temperature is used.The bad quality and properties of low gel strength gelatin limited its application.Transglutaminase is an enzyme which exists widely in nature beings.Now the transglutaminase from microorganisms is industrialized and the price is also suitable.Transglutaminase can catalyze protein molecule crosslinking reaction.It has been widely used in flour products,aquatic products,meat products,dairy products,soybean products etc.The crosslinking reaction of low gel strength gelatin catalyzed by transglutaminase was studied in this article,the index and properties were compared between the un-crosslinked gelatin and crosslinked gelatin to find the potential application advantages of crosslinked low gel strength gelatin.Orthogonal testing method was used to study reaction under different combined conditions of transglutaminase content,reaction time and reaction temperature in 6.67% 120LB(Alkaline process bovine bone gelatin)solution.Gel strength,viscosity,gelling temperature and melting temperature were tested after reaction.The results showed that the gel strength has not changed but the viscosity had a biggest change.There was a strong positive correlation between viscosity and setting temperature or melting temperature,and the results showed the same correlation in this study.Viscosity was chosen to evaluate the reaction and get the best combination A3B3C1.The corresponding best reaction conditions are: transglutaminase content is 0.6%,reaction temperature is 40? and reaction time is 4 hours.To simulate the condition of production line,the granular relatively high viscosity crosslinked gelatin was made by reacted in 40% gelatin solution at 40? for 1 hour with 0.25% transglutaminase.Other indexes were compared between crosslinked gelatin and un-crosslinked gelatin: IEP remained unchanged.Molecular weight distribution test showed that the contents of lower molecular weight sub-units,?-chain and ?-chain were decreased,and the contents of higher molecular weight ?-chain and micro gels were increased.Emulsifying stability,foaming capacity and foam stability were all improved significantly.Marshmallow and yoghurt were chosen to study gelatin in because gelatin viscosity is important in these two products.Compared their application advantage after making final products with crosslinked and un-crosslinked gelatin,the study in marshmallow revealed that the firmness of marshmallow made with crosslinked 120 LB gelatin was lower but the elasticity and heat resistant were better compared with marshmallow made with un-crosslinked 120 LB gelatin.This was mainly because of higher melting temperature and improved foam stability caused by high viscosity of crosslinked gelatin.Yoghurt was made with un-crosslinked 120 LB gelatin and crosslinked X-120 LB respectively.The results showed that with the increasing of gelatin dosage,the water holding capacity,viscosity,break strength,the taste score of yoghurt all increased,and the whey separation rate decreased.These conclusions agreed with which from former studies.Compared the performance of two different gelatins in liquid milk recipe and milk powder recipe respectively,higher viscosity crosslinked X-120 LB gelatin was better than un-crosslinked 120 LB gelatin in yoghurt made with milk powder.The contributions of crosslinked gelatin to viscosity,breaking strength,water holding capacity,whey separation preventing and the taste score of yoghurt are greater than which of un-crosslinked gelatin.