Impact of phosphates on heat-induced egg white gel properties: Texture, water state, micro-rheology and microstructure

The impact of phosphates (sodium pyrophosphate, sodium tripolyphosphate and sodium hexametaphosphate) on gelling properties of heat-induced egg white gel were investigated in this study. The hardness and springiness of the gels treated with sodium pyrophosphate and sodium tripolyphosphate were significantly improved compared with the control group. The hardness of sodium tripolyphosphate-treated gel was increased to 768.17 g when heated for 30 min and the springiness of sodium pyrophosphate-treated gel increased to 1.09 when heated for 30 min. The water holding capacity (WHC) of the sodium pyrophosphate-treated gel reached 85.57% when heated for 45 min. This improvement was ascribed to the formation of more ordered network structure. At 30 min of heat induction, the disulfide bond content of the gels treated with sodium pyrophosphate and sodium tripolyphosphate were 0.98 and 0.96, respectively. Moreover, decreasing mobility of water in the phosphate-treated gel was obtained with the heat induction time increased. The results of micro-rheological analysis showed that sodium pyrophosphate and sodium tripolyphosphate had better effects on the gel properties than sodium hexametaphosphate. Scanning electron microscopy showed that dense and uniform network structure and small pores appeared in the phosphate-treated gels. These results provided an important basis for phosphates to improve the heat-induced gel properties of egg production, and further expanded the application of phosphate additives in the food processing industry.