A protein concentrate (NPC), obtained by alkali extraction of navy beans, was used as a model medium for microbial growth. Only three among eight bacterial cultures (Pediococcus spp, Pseudomonas spp and Streptococcus spp) grew better on mediums with NPC than on the control nutrient broth. Retail ground beef with and without 5%, lo%, and 15% NPC was wrapped with plastic film and stored up to 6 days at 4°C. Aerobic plate count, psychrophiles, coliforms, yeasts and molds were determined at 0, 3, and 6 days. All levels of NPC added to ground beef had a significant influence on aerobic plate count and coliforms. Growth of psychrophiles and yeasts and molds was not affected by NPC. Lactobacillus spp was a dominant part of the microflora of all samples.