Study On The Modification Of Egg White Protein With Guar Gum Hydrolysate

As a functional raw material of food, egg white protein is widely utilized in food processing. It not only has high nutritional value, but also has good functional properties, mainly including the gel property and the foaming property. Development and application of egg white powder with the special functional property are always the research focus in the food industry. Egg white protein and guar gum were used as raw materials to prepare egg white protein-guar gum hydrolysate conjugates through dry heating method of Maillard reaction. Functional properties, physical and chemical properties and structure characteristics of the grafted products were studied, aiming to analyze the differences of functional properties of the grafted products prepared in different grafting conditions, discuss the mechanism of Maillard reaction between egg white protein and guar gum hydrolysate, and provide certain theoretical basis for the industrial production of modified egg white protein powder.First, the best hydrolysis conditions of guar gum were studied and its hydrolysate was analyzed by HPGFC and HPLC. The results showed that the best hydrolysis conditions were enzyme dosage 60 U/g, pH value 5.0, hydrolysis temperature 45℃,hydrolysis time 8h,in which conditions guar gum could get the highest hydrolyze rate,that was 21.76%. Guar gum hydrolysate was made up of many components, of which the main components were manno-oligosaccharides(62.70%), the second components were polysaccharide with more than 10 sugars(31.87%),and the least components were monosaccharide(0.12%).Second, effects of different grafting conditions(weight ratio, pH value, reaction time) on functional properties of egg white protein-guar gum hydrolysis conjugates were studied. The results showed under the conditions of weight ratio 0.5%, pH value 9.0 and reaction time 4 d, the grafted products could get the best gel strength and water holding capacity, of which gel strength could reach more than 1500 g in pH 4.0-10.0, and the grated products had good storage stability. Network structures in the gel of the modified protein powder were more uniform and compact compared to the original protein powder, which were observed under SEM. Under the condition of weight ratio 1%, pH value 9.0 and reaction time 2 d, the grafted products could get the best emulsion activity and emulsion stability. The emulsions prepared by the grated products had good storage stability, and had high stability when changing the pH value, ionic strength or encountering heating treatment. Under the conditions of weight ratio 1%, pH value 7.0 and reaction time 3 d, the grafted products could get the best foaming capacity and foaming stability.Last but not the least, physical and chemical properties and structure characteristics of egg white protein-guar gum hydrolysis conjugates were studied. In the process of grafting reaction, free amino content and the total sulphur content constantly decreased, surface hydrosulfuryl content steadily increased, and surface hydrophobicity firstly increased and latter flattened. DSC showed that the glycosylation modification could enhance the thermal stability of egg white protein. FT-IR, HPLC and SDS-PAGE analysis showed that in the process of the grafting reaction, carbohydrate in guar gum hydrolysis was combined with egg white protein in the form of covalent bond, generating larger molecular weight compounds, confirming the happening of Maillard reaction.