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

Sicun Fan, Robert Price, Ilenys Pérez-Díaz
Journal of food science 2017 v.82 no.1 pp. 167-173
Lactobacillus casei, Pediococcus, acetic acids, acid tolerance, acidity, brining, cucumbers, dairy products, juices, lactic acid, lactic acid bacteria, microbial growth, pH, pickled vegetables, probiotics, refrigeration, sodium chloride, survival rate, viability
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 °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 °C without significant loss of viability at 10^8 CFU/mL. These data may aid in the development of commercial probiotic refrigerated pickle products.