Bacteriocin production by protective cultures

Bacteriocinogenic Lactococcus lactis CSCC 146 and Pediococcus pentosaceus ATCC 43200 can be used to improve the safety of extend shelf-life cook-chill foods, however, the information on their growth and bacteriocin production rate at refrigeration temperatures was lacking. These cultures were inoculated at 105–108 cfu/mL in TPGY broth and grown at 10°C. Their populations were enumerated and bacteriocin titre was measured using well diffusion assay. The bacteriocins' identity produced by L. lactis and P. pentosaceus was confirmed as nisin and pediocin A, respectively, by their enzyme sensitivity pattern. Nisin (>100 IU/mL) was detected between the third and fifth day of storage when the populations of L. lactis reached 108 cfu/mL. Pediocin A (35 AU/mL) was detected on the fourth day when the population of P. pentosaceus reached 109 cfu/mL. Freeze-drying of the cultures did not reduce the speed of the production of bacteriocins. Colour, mouth-feel, texture, flavour and the overall acceptability of commercial sous vide meals was not affected by the presence of the cultures.