Preparation,Characteristics And Application Of Ovalbumin-dextran Conjugates Under Single-mode Microwave Induction System

With the homogenization competition of egg processing industry becoming increasingly fierce,the development of high value-added egg products is the main strategy of current enterprises.Ovalbumin is a fully reactive protein with high reactivity,which is easy to react with polysaccharides through grafting to enhance its functional properties.The focused single-mode microwave has the advantages of precise temperature control and high energy density,which can regulate the temperature by microwave radiation at a lower power and in a shorter time,thus to induce the grafting reactions to occur quickly and uniformly.Therefore,we have chosen ovalbumin as raw material to explore the influence of single-mode microwave assisted wet grafting on the structure and physicochemical properties of ovalbumin-dextran conjugates;And then the intrinsic molecular mechanism of grafting reaction was analyzed based on high precision Ethcd MS/MS technology;Finally,explore the effects of ovalbumin-dextran conjugates on the stability and digestibility of?-carotene emulsion.The main research contents and conclusions are as follows:(1)The effects of single-mode microwave heating time and traditional water bath heating on the structure and physicochemical properties of ovalbumin–dextran conjugates was studied to reveal the correlation between the physicochemical properties and structure of conjugates.The results showed that microwave and traditional water bath heating increased the content of?-sheet by 2.7%–9.4%and2.1%,the content of?–helix by 11.1%–30.7%and 15.7%,the surface hydrophobicity by 130.09%–334%and 194.34%,respectively;In addition,grafting reaction based on the above two heating modes can significantly improve the emulsification and rheological properties of ovalbumin(p<0.05),especially the ovalbumin–dextran conjugates,prepared by microwave heating for 20 min.When microwave heating lasted for 0 to 20 min,the emulsifying activity and emulsifying stability of the ovalbumin–dextran conjugate increased from 224.04 m~2/g and 47%to 311.05 m~2/g and 82.26%,respectively.The results of correlation analysis showed that emulsifying activity was positively correlated with surface hydrophobicity,and emulsifying stability was positively correlated to surface hydrophobicity(P<0.01)as well as the secondary structure content of?-sheet(P<0.01).In summary,compared with traditional water bath heating,single-mode microwave heating could make the structure of ovalbumin more loser,which would induce the rapid occurrence of grafting reaction,and significantly improve the emulsifying activity and emulsifying stability of ovalbumin.(2)The high-precision bio mass spectrometry?HPLC-MS/MS was used to determine the grafting sites and glycan chains of ovalbumin–dextran conjugates,revealing the molecular mechanism of grafting between ovalbumin and dextran under microwave and water bath heating modes.The results showed that there were two grafting sites(Thr 37 and Ser 385)in native OVA protein.For ovalbumin-dextran conjugates,prepared by water bath heating,we had detected eight grafting sites and seven types of glycan chains.While for ovalbumin-dextran conjugate obtained by microwave heating,there were twelve grafting sites and five types of glycan chains.Furthermore,the?-elements,including?-sheet and?-turn,of ovalbumin showed higher reaction activity during grafting reaction.To sum up,the types of grafting reaction were different under single-mode microwave heating and traditional water bath heating,and compared with traditional heating,more grafting sites were exposed under microwave heating,which was conducive to the grafting reaction.(3)The ?-carotene emulsions were prepared by using ovalbumin and ovalbumin-dextran conjugates as emulsifiers,and then analysed the effect of different emulsifiers on the physical and chemical stability,digestibility and bioavailability of?-carotene emulsions.As a result,ovalbumin-dextran conjugates emulsions showed higher pH stability,thermal stability,salt-resistant stability and storage stability,especially the ovalbumin–dextran conjugates prepared by microwave heating,which was consistent with the apparent viscosity characteristics of the emulsion.The results of in vitro digestion showed that the fat in the emulsion prepared by ovalbumin–dextran conjugates was basically digested at 23 and 26 min respectively,while ovalbumin was basically digested at 28 min;the bioavailability of?-carotene was48.38%,47.68%and 48.72%,respectively.In summary,the ovalbumin-dextran conjugate,induced by single-mode microwave,was the most effective in improving the physicochemical stability and digestibility of fat in the emulsion.While there was no significant difference between in protein digestibility and bioavailability of?-carotene in vitro among different emulsions.