Effect of Lecithin Addition and Homogenization of Bulk Starter on Agglutination

¹ University of Kentucky, Lexington 40546

Effect of lecithin addition and homogenization of bulk culture on agglutination was studied. Proteinase-negative Lactococcus lactis ssp. cremoris UC310 was grown in internal pH control medium containing 0, .5, 1.0, and 2.0% deoiled lecithin. After incubation, one-half of each medium was homogenized at 176 kg/cm², dual stage. Skim milk was pasteurized (63°C for 30 min), homogenized (176 kg/cm²), and inoculated (10%) with bulk starters. The pH was measured at 5-cm increments (5 to 40 cm) through the depth of the skim milk at 2-h intervals to determine agglutination. Homogenization of bulk culture prevented agglutination and increased colony-forming units per milliliter by approximately .9 log₁₀. Bulk culture containing lecithin reduced agglutination and increased colony-forming units per milliliter greater than .3 log₁₀; however, with homogenization and lecithin the increase in colony-forming units per milliliter was over 1 log₁₀. In other experiments, where bulk starters were homogenized at 0, 35, 106, 176, 246, and 317 kg/cm², a pressure of 176 kg/cm² or greater was most effective in increasing colony-forming units. Bulk culture homogenized at 176 kg/cm² three and six times was equally effective in reducing agglutination, but the 6x treatment resulted in a decreased rate of acid production suggesting some cellular destruction. Increase in colony-forming units per milliliter was due to decreased chain length of the lactic culture.

Key Words: agglutination • bulk starter • homogenization

Submitted on June 14, 1989
Accepted on March 14, 1990