Effect of green tea extract on heat-induced protein interactions and rennet coagulation in milk

Abstract

The impact of green tea extract (GTE) on heat-induced milk protein interactions and enzymatic coagulation of milk was investigated. GTE addition affected the renneting process, more apparent for heat-treated samples. The enzymatic phase of rennet coagulation was negatively affected by GTE, with a significantly lower amount of κ-casein hydrolysis for intense heat-treated samples. Gel characteristics of raw milk were unaffected by GTE, but mild heat-treated samples with GTE displayed decreased gel firmness and increased water holding capacity compared with control samples. Model studies conducted with purified β-lactoglobulin A and κ-casein revealed that GTE caused a significant impact on interactions between denatured β-lactoglobulin A and κ-casein. Heat-induced large aggregate/complex formation between β-lactoglobulin A and κ-casein in milk samples was not significantly affected, highlighting the importance of the reaction medium. The presence of casein micelles in milk, which are strong candidates for phenolic binding, may ultimately impact protein–protein interactions.