Methods for the recovery of Salmonella spp. from carboxymethylcellulose gum, gum ghatti, and gelatin

Foods analyzed for Salmonella spp, by the procedure in the U.S. Food and Drug Administration's Bacteriological Analytical Manual are preenriched at a 1:9 test portion/broth ratio. Various thickening agents preenriched at this ratio become Viscous and nonpipettable after 24 h incubation at 35 degrees C. The effects of 3 factors (presence of inorganic salts, adjustment of pH, and presence of enzymes) on the viscosity of the test portion/preenrichment mixtures of various thickening agents during incubation were determined. Reduction of the viscosities of these thickening agents was accomplished as follows: carboxymethylcellulose gum, addition of cellulase to a final concentration of 0.10% in lactose broth preenrichment and incubation with no pH adjustment; gum ghatti, addition of NaCl to a final concentration of 0.10% in lactose broth preerichment and adjustment of the pH to 6.5; and gelatin, addition of papain to a final concentration of 0.10% in lactose broth preenrichment and adjustment of the pH to 6.8, With these modified preenrichments, one Salmonella spp. cell/25 g (representing an approximate most probable number value of 0.04 cell/g) was generally recovered from the thickening agents.