Impaired or accelerated aggregation of proteins in sterilised milk by adding surfactants

The effect of small-molecule surfactants on the stability of sterilised milk (with added sterol esters) was determined by measurement of the sensitivity towards renneting, and of particle size upon freeze-thaw treatment. Water-soluble surfactants like diacetyl tartaric esters of monoglycerides and sodium stearoyl lactylates reduced freeze-thaw stability and the rate of renneting. Oil-soluble surfactants, like monoglycerides and citric acid esters of monoglycerides had an opposite effect. Water-soluble surfactants could coat the proteins and render casein micelles more dense; hence they could reduce age gelation through reduced access by enzymes. The same surfactants, however, also coated the outside of the micelles and rendered them more hydrophobic, which resulted in reduced colloidal stability. The oil-soluble surfactants had an opposite effect: they accelerated renneting, and improved colloidal stability. Because of the latter they are alternatives to polyphosphates or carrageenan. We also found indications that polyphosphates increased protein-enzyme repulsion.