Phosphorylation of Egg White Proteins by Dry-Heating in the Presence of Phosphate

Abstract

Food proteins were phosphorylated by heating in a dry state in the presence of phosphate. When casein, whey protein isolate (WPI), and egg white proteins (EWP), which were lyophilized from their solutions in a phosphate buffer, were dry-heated at various temperatures and pH levels for 1-5 days, EWP was more highly phosphorylated than casein and WPI. Phosphorylation of EWP was promoted with a decrease of pH from 7.0 to 3.0 when the incubation temperature was raised from 55 to 100 degrees C. The phosphorus content of EWP increased from 0.08 to 0.64% by dry-heating at pH 3.0 and 85 degrees C for 5 days in the presence of phosphate. The electrophoretic mobility of EWP increased with an increase in the phosphorylation level. The heat-induced polymerization of EWP by dry-heating was not affected by the presence of phosphate. Although the solubility of EWP decreased by dry-heating at pH 3.0-5.5, the phosphorylation depressed the insolubilization at low pH. The phosphate bonds in phosphorylated EWP (P-EWP) were stable at pH 2.0-10.0 and were more acid-labile and base-stable than phosphoesters of egg riboflavin-binding protein (RfBP). (31)P NMR spectral data suggested that besides phosphoesters, phosphodiester and polyphosphate bonds were introduced in P-EWP. Heat stability of EWP was improved, and calcium phosphate-solubilizing ability of EWP was enhanced by phosphorylation.

Phosphorylation of ovalbumin by dry-heating in the presence of pyrophosphate: Effect of carbohydrate chain on the phosphorylation level and heat stability

“…The samples were phosphorylated according to a previous paper (Li et al, 2003). The N-and Re-OVA were dissolved in 0.1 M sodium pyrophosphate buffer at pH 4.0 followed by lyophilisation.…”

“…The solubility of samples was measured according to a previous paper (Li et al, 2003). Protein samples were dissolved at a protein concentration of 1 g/l in 50 mM Tris-HCl buffer (pH 7.0), and then centrifuged at 1000g for 15 min.…”

“…Using the Maillard reaction, egg white and whey proteins were phosphorylated by conjugating glucose-6-phosphate with proteins (Aoki, Fukumoto, Kimura, Kato, & Matsuda, 1994;Aoki et al, 1997;Kato, Aoki, Kato, Nakamura, & Matsuda, 1995). However, these phosphorylation methods have posed some problems (Li, Salvador, Ibrahim, Sugimoto, & Aoki, 2003), making them very difficult to put to practical use. Researchers (Enomoto et al, 2009b;Hayashi et al, 2009;Li, Ibrahim, Sugimoto, Hatta, & Aoki, 2004;Li et al, 2003) have effectively phosphorylated egg white protein by dry-heating in the presence of phosphate, and some functional properties, such as heat stability, emulsifying, foaming, gelling, and the calcium phosphate-solubilising abilities of egg white protein were improved.…”

“…However, these phosphorylation methods have posed some problems (Li, Salvador, Ibrahim, Sugimoto, & Aoki, 2003), making them very difficult to put to practical use. Researchers (Enomoto et al, 2009b;Hayashi et al, 2009;Li, Ibrahim, Sugimoto, Hatta, & Aoki, 2004;Li et al, 2003) have effectively phosphorylated egg white protein by dry-heating in the presence of phosphate, and some functional properties, such as heat stability, emulsifying, foaming, gelling, and the calcium phosphate-solubilising abilities of egg white protein were improved. However, whey protein isolate showed a lower phosphorylation level than egg white protein by dry-heating under the same conditions, presumably due to the absence of a carbohydrate chain (Li et al, 2003).…”

“…Researchers (Enomoto et al, 2009b;Hayashi et al, 2009;Li, Ibrahim, Sugimoto, Hatta, & Aoki, 2004;Li et al, 2003) have effectively phosphorylated egg white protein by dry-heating in the presence of phosphate, and some functional properties, such as heat stability, emulsifying, foaming, gelling, and the calcium phosphate-solubilising abilities of egg white protein were improved. However, whey protein isolate showed a lower phosphorylation level than egg white protein by dry-heating under the same conditions, presumably due to the absence of a carbohydrate chain (Li et al, 2003). So, we attempted to phosphorylate whey protein isolate by glycation with maltopentaose through the Maillard reaction and subsequent dry-heating in the presence of pyrophosphate, with the results that whey proteins were effectively phosphorylated and some functional properties were improved by phosphorylation after glycation (Enomoto et al, 2007(Enomoto et al, , 2008(Enomoto et al, , 2009aLi, Enomoto, Ohki, Ohtomo, & Aoki, 2005a).…”