Culture Agglutination as Affected by Homogenization of Skim Milk

¹ Food Science Section, Department of Animal Sciences, University of Kentucky, Lexington 40546

Skim milk was homogenized at 0, 7, 14, 21, 28, 71, 106, and 176 kg/cm² and inoculated with a lactic culture to determine effect of homogenization on culture agglutination. Top to bottom pH differentials were determined hourly; sediment depth and top to bottom total solids differentials were determined after 4 h of incubation. Top to bottom pH differentials decreased as homogenization pressure increased. Culture agglutination increased with time in skim milk homogenized at pressures less than 176 kg/cm². Acid production in the upper portion of skim milk increased as homogenization pressure increased. Top to bottom total solids differentials in skim milk homogenized at pressures of 0, 7, and 14 kg/cm² were greater than the differential from that homogenized at 176 kg/cm². When skim milk was homogenized at pressures greater than 7 kg/cm², visible sediment depth decreased linearly. Sediment depth was 2.9% of the total volume for skim milk homogenized at 0 kg/cm², peaked at 3% when homogenized at 7 kg/cm², and decreased to .34% when homogenized at 176 kg/cm². Time from inoculation to the first sign of agglutination (lag time) as measured by pH differential increased as homogenization pressure increased.

Key Words: culture agglutination • homogenization • skim milk

Submitted on March 30, 1992
Accepted on July 21, 1992