Group Comparative Study of VRB-2 Agar in the Recovery of Coliforms from Raw Milk, Ice Cream and Cottage Cheese

The method of Hartman et al. for recovering stressed coliform bacteria was evaluated in a group study. The experimental medium, VRB-2, was more productive than VRB medium by 31% for raw milk, 70% for ice cream and 61% for cottage cheese. Differences in colony counts of coliforms caused by incubating for 48 vs. 24 h and by boiling vs. autoclaving were not statistically significant. Among 40 samples tested in two laboratories, counts obtained at 30 vs. 32 C were not significantly different.