Effects of Ultra-High Temperature Processing on Size and Appearance of Casein Micelles in Bovine Milk

Effects of ultra-high temperature treatment by falling-film-steam-infusion on the size and appearance of casein micelles in bovine milk were examined by electron microscopy.Preheating and homogenization at 65.6 or 82.2°C for approximately 150 s did not alter mean micelle size as compared to raw milk, although a narrower size distribution and increased tendril formation was in the treated milk.Samples of uhra-high temperature milk treated for 3.4 s exhibited larger mean micelle diameters and greater tendril formation than those treated for 1.5 or 9.0 s.Increased numbers of small diffuse particles were in samples treated for 9.0 s.Samples preheated at 82.2°C and treated at temperatures above 121.1°Cshowed increasing micelle diameters with increasing temperatures with the exception of those heated at 146.1°C.Initial heart-induced micellar growth was followed by micellar disintegration or disaggregation.Studies on samples stored for 3 mo atroom temperature revealed no general trends.However, the pattern of micellar growth followed by development of a large number of small diffuse particles was discerned.