Investigation of Casein Micelle Particle Size Distribution in Raw Milk of Estonian Holstein Dairy Cows

Abstract

The particle size of milk influences its microstructure and defines many properties of dairy products such as colloidal stability, texture etc. Differences in particle size can significantly affect milk processing especially when membrane technology is used. Aim of this investigation was to estimate casein micelle size in the raw milk of Estonian Holstein dairy cows and its variability concerning individual animals. Milk samples were collected during 12 months with the interval of 25 -35 days. DLS analyses were performed using a Malvern Zetasizer Nano ZS (Malvern Instruments Ltd, Malvern, UK). Average mode of casein micelle particles size in raw milk of 44 cows was 171.13 nm with the variation range 70.1 nm and its distribution resembled a normal one. Casein micelles size mode of individual cows varied in a wide range from 148.5 (with variation range 18.2) to 194.1 (with variation range 27.6) nm which may be caused by differences in physiological and health status, stage of lactation and other factors concerning milk production.