Use of Nisaplin to Inhibit Spoilage Bacteria in Buttermilk Ranch Dressing .

Nine commercial salad dressings (spoonable and pourable) were sampled for microbial flora, pH, and total acidity. Bacterial populations ranged from 10 to 10 CFU/g in the salad dressings, but yeasts and molds were largely undetected (<1 × 10 CFU/g). The range of pH (3.3 to 4.1) and titratable acidities (0.63 to 1.34% as acetic acid) indicates that such differences in formulation may lead to varying shelf lives among the dressings, especially in regard to aciduric microorganisms. Nisaplin, a commercial antimicrobial food additive and shelf-life extender, inhibited 27 of 30 bacterial isolates obtained from 6 salad dressings. Nisaplin (200 ppm) was used as a preservative in a shelf-life study with a spoonable buttermilk ranch dressing at pH 3.8, 4.0, and 4.2, challenged with Lactobacillus brevis subsp. lindneri , a ranch dressing spoilage isolate, and maintained at 26°C. In control samples at pH 4.2, both the added Lactobacillus and the indigenous flora increased starting at day 6 to a maximum at 30 days. However, in buttermilk ranch dressing (pH 4.2) containing Nisaplin, initial levels of added inoculum were quickly reduced and no significant growth occurred during the 90-day shelf-life period. The data indicate that the natural preservative Nisaplin may be an effective spoilage inhibitor for spoilage-sensitive refrigerated salad dressings.