Heat stability of yak micellar casein as affected by heat treatment temperature and duration

Abstract

International audienceHeat treatment is one of the essential operations widely used in most dairy processes, and heat stability is one of the essential properties of milk. Casein micelles are the major component in milk responsible for the heat stability of milk during processing. This study assessed the effects of heat treatment temperature and duration on the average size, turbidity, polydispersity index and heat stability of casein micelles in yak skim milk and distilled water. The results showed that whey protein had an important role in influencing the heat stability of casein micelles. The average size, polydispersity index and turbidity of micelles in skim milk were higher than those of micelles in distilled water in all cases while the heat stability of casein micelles in skim milk was lower than those in distilled water. As a result of the heat treatment, the size of micelles in skim milk increased due to complex of casein/whey protein formed via covalent bonds, whereas it decreased in distilled water attributed to the change of hydrophobicity in micelles. The size distribution of particles broadened with increasing heating temperature, resulting in the increase in turbidity and polydispersity index of casein micelles both in skim milk and distilled water. The micelles in skim milk combined with whey protein during heating. These findings will help processors design appropriate heating conditions for yak milk and yak casein products and help identify new opportunities for product development

Influence of succinylation on the conformation of yak casein micelles

“…The size of yak casein micelles obtained by ultracentrifugation was larger than that in yak milk, which was 211.3 nm (Yang, Zhang, et al, 2014). It has been reported that the size of casein micelles became more slim with increase of pH whereas it also increased after heat treatment (Erdem, 2006;Yang, Zhang, et al, 2014).…”

“…It has been reported that the size of casein micelles became more slim with increase of pH whereas it also increased after heat treatment (Erdem, 2006;Yang, Zhang, et al, 2014). Although the size of casein micelles reduced by ultracentrifugation (Sandra & Dalgleish, 2005), it became loose under heat treatment at 40°C with pH 7.0, higher than native pH of milk (6.7), which induced the increase of micellar size.…”

“…Furthermore, the amino acid sequence of yak caseins is different than that of other caseins (Cui et al, 2012;Zhang et al, 2010). Additionally, yak casein micelles have different composition, size and hydration compared to cow casein micelles (Wang et al, 2013;Yang, Zhang, Wen, Zhang, & Liang, 2014).…”

Succinylation of sodium caseinate and its effect on physicochemical and functional properties of protein

“…Succinylation is one of the frequently used modification method, which enhances solubility, emulsification, foaming characteristics and other functional properties of protein (Gruener & Ismond, 1997;Kohara, Kanei, & Nakajima, 2001;Mirmoghtadaie, Kadivar, & Shahedi, 2009;Yang, Zhang, Wen, Zhang, & Liang, 2014). Succinylation involves chemical derivatization of 3-amino group of lysine in proteins with succinic anhydride.…”

Effect of microbial transglutaminase crosslinking on the functional properties of yak caseins: a comparison with cow caseins

“…The high content of β-casein (more than 45%) and consequently the lower proportion of αs-casein (about 40%) together with the high content of κ-casein (15%) in yak milk make it with a good proportion of individual caseins, which is similar to the proportion found in human milk and more favorable for infant nutrition (Li et al 2010). It also found the high content of minerals and micellar size of yak milk (Wang et al 2013;Yang et al 2014b). To develop yak caseins for use as good ingredients in the food industry, their physicochemical and functional properties must be improved.…”