Survival and Growth of Probiotic Lactic Acid Bacteria in Refrigerated Pickle Products

We examined 10 lactic acid bacteria that have been previously characterized for commercial use as probiotic cultures, mostly for dairy products, including 1 Pediococcus and 9 Lactobacilli. Our objectives were to develop a rapid procedure for determining the long-term survivability of these cultures in acidified vegetable products and to identify suitable cultures for probiotic brined vegetable products. We therefore developed assays to measure acid resistance of these cultures to lactic and acetic acids, which are present in pickled vegetable products. We used relatively high acid concentrations (compared to commercial products) of 360 mM lactic acid and 420 mM acetic acid to determine acid resistance with a 1 h treatment. Growth rates were measured in a cucumber juice medium at pH 5.3, 4.2, and 3.8, at 30 degrees C and 0% to 2% NaCl. Significant differences in acid resistance and growth rates were found among the 10 cultures. In general, the acid resistant strains had slower growth rates than the acid sensitive strains. Based on the acid resistance data, selected cultures were tested for long-term survival in a simulated acidified refrigerated cucumber product. We found that one of the most acid resistant strains (Lactobacillus casei) could survive for up to 63 d at 4 degrees C without significant loss of viability at 10(8) CFU/mL. These data may aid in the development of commercial probiotic refrigerated pickle products. Practical Application The development of probiotic pickled vegetable products will be facilitated by identifying probiotics that can survive in acidified vegetable products with a proposed shelf life of 2 or more months. We analyzed the growth and acid resistance of 10 probiotic lactic acid bacterial cultures and found that cultures selected for acid resistance had superior long-term survival (up to 2 mo) in a simulated refrigerated probiotic vegetable product that included a fermentation step. These data may be useful to aid the development of a commercial process for the manufacture of probiotic pickles.