Influence of chemical agents on interactions in dairy products: Effect of SDS on casein micelles

The addition of SDS during skim milk reconstitution is an original approach to study the effect of an ionic amphiphilic molecule on the milk system and particularly on the casein micelle component. SDS-induced changes in casein micelles were investigated by turbidimetry, rheology, scanning electron microscopy (SEM) and biochemical measurements (including soluble proteins analysis). This study shows that casein micelles were able to interact together to form micellar aggregates or milk gel without coagulating agents addition, when milk was reconstituted in the presence of SDS. This micellar aggregation, depending on the SDS concentration, is confirmed by SEM observations showing that the general aspect of casein micelles was affected by SDS treatment. Biochemical analysis indicated that SDS induced micellar casein dissociation. SDS-induced milk gel formation required a defined level of casein dissociation which could be also related to a particular micellar state.