IMMUNOGLOBULINS IN SKIMMILK AND MODEL SYSTEMS AND THEIR EFFECT ON BACILLUS CEREUS

Abstract

Immunoglobulins isolated from milk by ammonium sulfate fractionation were added to skimmilk and the rate of Bacillus cereus spore germination and subsequent vegetative cell growth was determined. At 1 hr incubation at 35 C, 96.6, 96.8, 91.4, and 74.3% of the spores bad germinated in pasteurized (62.8 C - 30 min) skimmilk without added immunoglobulins, skimmilk pasteurized with immunoglobulins added, pasteurized skimmilk supplemented with unheated immunoglobulins, and nonheated unsupplemented skimmilk, respectively. With respect to vegetative cell growth, the number of generations at 4 hr in these systems was 5.9, 5.6, 4.4, and 2.3. Nonheated skimmilk without added immunoglobulins depressed B. cereus spore germination and vegetative cell growth to a greater extent than did pasteurized skimmilk supplemented with unheated immunoglobulins. In model systems composed of protein-free skimmilk dialysate and heated or unheated immunoglobulins, the system with unheated immunoglobulins lowered spore germination by 20% and subsequent cell growth by one-half in comparison with the heated system indicating that vegetative cells of B. cereus 7 are more susceptible to the immunoglobulins than spores.