Preparation Of Glycated Gelatin And Its Application In Algal Oil Microcapsules

Microencapsulation is a common method to improve the oxidation stability and expand the application range of algal oil.With the increasing demand of consumers for algal oil products,higher requirements for product quality are also put forward,so it is urgent to develop algal oil microcapsule wall materials with good functional properties Gelatin was cheap and easy to obtain,but it has poor embedding performance as microcapsule wall material.Glycation modification is an effective method to improve the functional properties of proteins.In order to improve the functional properties of gelatin as the wall material of algal oil microcapsules,glycated gelatin was developed as the wall material of algal oil microcapsules,with a view to extending the shelf life of algal oil microcapsules and improving the bioavailability of algal oil.The following studies have been carried out:（1）To obtain glycated gelatin with excellent emulsifying property and antioxidant activity,glycation of gelatin with maltodextrin and oligomeric mannose was performed at 65℃and 79%relative humidity for 0 h,24 h and 48 h.The grafting degree,color difference,FT-IR（fourier transform infrared spectoscopy）,SDS-PAGE,emulsifying properties（emulsifying activity,emulsifying stability,and emulsion particle size）and antioxidant activities(Fe³⁺reducing capacity,DPPH,and ABTS radical scavenging activity)of glycated gelatin were determined.Results showed that the degree of glycation and browning of glycation gelatin increased with the extension of dry-heating time.Glycation would increase the molecular weight of the gelatin subunit,but also the decomposition of part of the subunit.The secondary structure of gelatin after glycation changed.Theαhelix decreased and theβangle increased.Glycation gelatin significantly increased the emulsion stability（P<0.05）.After dry heating for 24 h,the emulsifying stability of oligomeric mannose-gelatin increased by 37.56%,and its average emulsion particle size was far less than the average particle size of raw gelatin emulsion.Glycation significantly enhanced the antioxidant activity of gelatin.Among the glycation products,maltodextrin-gelatin with drying heat for 48 h had the strongest antioxidant activity.（2）In order to prepare algal oil microcapsules with good performance,In order to prepare algal oil microcapsules with good performance,using Maltodextrin-gelatin glycated products with 48 h dry-heating and mannose-gelatin oligosaccharide glycated roducts with 24 h dry-heating prepare algal oil microcapsules MG and OG by freeze-drying,respectively.Algal oil microcapsule MOG was prepared by mixing two kinds of glycated gelatin with equal mass,and the microcapsule（GE）prepared by the original gelatin was used as the control.Using embedding rate as evaluation index,single factor and orthogonal experiment were used to optimize the preparation conditions of algae oil microcapsules.The freeze-thaw stability and rehydration properties of microcapsules and their emulsions were investigated by optical microscopy,laser confocal microscopy,scanning electron microscopy and emulsion particle size analysis.The water content,water activity,solubility and dispersibility of microcapsules were determined.The results showed that the embedding rates of GE,MG and MOG microcapsules were85.14%,91.15%and 93.45%,respectively,when the solid content was 17.5%,the emulsion dispersion speed was 10000 r/min,and the core-wall ratio was 0.3.The embedding rate of OG microcapsules was 89.75%when the solid content was 12.5%,the dispersion speed was 12500 r/min and the core wall ratio was 0.3.The morphology of algal oil emulsion stabilized by glycated gelatin has little change before and after freezing-thawing,and the mean particle size has little change,which has good freezing-thawing stability.The rehydration emulsion of glycated gelatin and algal oil microcapsules had little difference in particle size and droplet morphology from the original emulsion,good rehydration,and good solubility and dispersion,among which OG microcapsules had the best performance,MOG microcapsules were slightly weaker than OG microcapsules.OG microcapsules had higher water content and water activity,while MOG microcapsules had significantly lower water content and water activity than OG microcapsules.（3）In order to investigate the effects of glycation gelatin as wall material on the storage stability and bioavailability of algal oil microcapsules,the changes of peroxidation value,2-thiobarbituric acid value,DHA retention rate and core material retention rate of algal oil microcapsules over storage time were determined by oven heating method,and the oxidation kinetics and release kinetics were analyzed.The release and digestion of algal oil microcapsules in stomach and intestine were simulated by in vitro digestion experiments.The results showed that the oxidation and release of algal oil could be delayed by embedding microcapsules,and the oxidation and release of algal oil could be further delayed by using glycation gelatin as wall material.The results showed that the oxidation and release of algal oil could be delayed by embedding microcapsules,and the oxidation and release of algal oil could be further delayed by using glycation gelatin as wall material.With the extension of storage time,the peroxide value and 2-thiobarbituric acid value of MOG microcapsules increased the most slowly,and the DHA retention rate and core material retention decreased the most slowly.The predicted shelf life of MOG microcapsules was 323 d.The oxidation process of the four kinds of algal oil microcapsules conforms to the first-order oxidation kinetics,but the release kinetics is complex,which is the synthesis of several kinds of release kinetics.Encapsulation of algal oil by glycation gelatin mainly delayed the release and digestion of algal oil in stomach.During intestinal digestion,the fatty acid release rates of MG and MOG microcapsules were similar to GE microcapsules.The fatty acid release rate of OG microcapsules was always the lowest in the whole digestion process.In general,MG and MOG microcapsules were beneficial to improve the bioavailability of algal oil.