INHIBITION OF PSYCHROTROPHIC BACTERIA IN RAW-MILK BY IMMOBILIZED LACTIC-ACID BACTERIA

Cells of Lactococcuslactis or Lactobacillushelveticus were immobilized in calcium-alginate beads, added to raw milk, and incubated 48 h at 7°C. The addition of 2.7×107 immobilized Lc. lactis or 13×107 immobilized Lb.helveticus cells per mL reduced the development of the psychrotrophic bacteria of raw milk by approximately 50%. The pH of the raw milk dropped 0.10 to 0.22 units under these conditions. Periodic agitation of the seeded raw milk increased the inhibitory activity of the immobilized lactic acid bacteria (LAB). Free LAB cells in the system were only of 0.5% of total LAB. The use of immobilized LAB to inhibit psychrotrophic bacteria might be extended to raw milks destined to the manufacture of non-fermented dairy products. © 1990 Kluwer Academic Publishers.