Interactions between tea catechins and casein micelles and their impact on renneting functionality

•The association of tea polyphenols (EGCG) with casein micelles were quantified.•The presence of EGCG affected the primary stage of renneting.•The presence of EGCG hindered the formation of a casein micelles network.•Above saturation concentrations, gelation, as measured by rheology, did not occur. Many studies have shown that tea catechins bind to milk proteins. This research focused on the association of tea polyphenols with casein micelles, and the consequences of the interactions on the renneting behaviour of skim milk. It was hypothesized that epigallocatechin-gallate (EGCG), the main catechin present in green tea, forms complexes with the casein micelles and that the association modifies the processing functionality of casein micelles. The binding of EGCG to casein micelles was quantified using HPLC. The formation of catechin–casein micelles complexes affected the rennet induced gelation of milk, and the effect was concentration dependent. Both the primary as well as the secondary stage of gelation were affected. These experiments clearly identify the need for a better understanding of the effect of tea polyphenols on the processing functionality of casein micelles, before milk products can be used as an appropriate platform for delivery of bioactive compounds.