Study On The Nutrition Quality,functional Properties And Gastrointestinal Digestive Properties Of Selenium-enriched Egg White

The trace mineral selenium is an essential nutrient element that plays a vital role in the life activities of the human body.Selenium-enriched eggs have become one of the most popular selenium-enriched foods due to their high selenium conversion rate,short production cycle,and low cost of selenium enrichment,etc.Egg white is widely used in food field because of its nutritional value,functional properties and biological activity.It has been reported that selenium may affect the material composition and functional activity of foods.However,there are few studies on the basic ingredients composition and biological activity of selenium-enriched egg white.Therefore,this paper used selenium-enriched eggs(EW-2)as raw materials and the ordinary egg white(EW-1)as control,the nutritional quality,functional properties and gastrointestinal digestive properties of EW-2 were studied.The main results are as follows:(1)This paper studied the quality properties of EW-2,such as freshness and nutrient composition.According to the results,no apparent difference was observed between the Haugh units,but the protein index of EW-2(88%)was significantly higher than that of EW-1(68%)(p<0.05).The total protein content of EW-2 is 77.66%,which is slightly higher than that of EW-1(75.39%);the fat content is 0.79 mg/100g,which is significantly lower than that of EW-1(0.93 mg/100g)(p<0.05);the total sugar content is 12.84 g/100 g,which is 3 times than that of EW-1;the contents of total selenium,organic selenium,and inorganic selenium has been significantly increased by 4 times,and the contents of Zn and Ca have been significantly increased by 1?2 times.After selenium enrichment,the content of ovomucin in egg white has been increased significantly from 2.1%to 4.5%(p<0.05),while the contents of ovotransferrin and ovoinhibitor get decreased(p<0.05),the contents of ovalbumin,ovomucoid and lysozyme did not change significantly.There also was no significant difference in the amino acid composition between EW-1 and EW-2.(2)This paper studied the functional properties of EW-2,such as solubility,oil absorption,foaming and gelling.The results showed that the solubility of EW-2 was 66.06%,slightly higher than that of EW-1(62.78%);the oil absorbability absorption of EW-2 was 2.22g/g sample was significantly lower than that of EW-1(2.65 g/g sample)(p<0.05);the foaming ability of EW-2 was 81.87%,significantly higher than that of EW-1(72.82%)(p<0.05),and the foaming stability of EW-2 was 70.86%,slightly lower than that of EW-1(74.98%);there is no significant difference between the emulsifiabilities.The results of TPA analysis showed that the heat-induced gel of EW-2 performed significantly better than EW-1(p<0.05)in terms of hardness,adhesiveness,gumminess,chewiness and cohesiveness.The surface microstructure of heat-induced gel of EW-2 was flatter and denser by SEM.The results of DSC showed that the T_d of EW-2 wass 94.7?,which was higher than that of EW-1(82.5?).(3)In this study,the molecular weight changes of EW-2 protein and the antioxidant activity of EW-2 gastrointestinal digestive products(EWI-2)were studied by simulated gastrointestinal digestion in vitro.No significant difference exists between the degree of hydrolysis of the two samples,the yield of soluble peptide of EWI-2 is significantly increased from 47.30%to 68.10%(p<0.05),and the content of free amino acids was significantly increased(p<0.05).HPLC results demonstrated that EWI-2 contained a higher proportion(85.57%)of small peptides(Mw<2k Da)than EWI-1(71.11%),indicating that egg white was more gastrointestinally digestible after selenium enrichment.As for the Fe³⁺reducing power and the ABTS free radicals scavenging ability,no discrepancy was detected.In the test of erythrocyte hemolysis,EWI-2 had a significantly higher inhibition rate(p<0.05)at the same concentration level.And the results of ORAC and CAA presented that EWI-2 had better antioxidant activity.In conclusion,the freshness,nutritional quality and gel properties of EW-2 were better than those of EW-1.EW-2 protein was easier to be digested into small molecular peptides and amino acids in the gastrointestinal tract,and EWI-2 had better antioxidant activity.