Effect of d-tryptophan on the psychrotrophic growth of Listeria monocytogenes and its application in milk

Publication date: April 2020Source: Food Control, Volume 110Author(s): Jian Chen, Shuso Kawamura, Shigenobu KosekiAbstractCurrent refrigeration temperatures are inadequate to restrain psychrophilic bacteria capable of survival and growth at low temperatures. Specifically, Listeria monocytogenes is strongly resistant to chilling stress and osmotic stress and tends to be more pathogenic during long-term refrigeration. Here, we demonstrated that d-tryptophan (d-Trp) reduced and delayed the psychrotrophic growth of L. monocytogenes at 4 °C in PYG medium during a 30-day period, and that>30 mM d-Trp further decreased the L. monocytogenes growth rate and extended the lag phase to a maximum of 400 h, which was 4-fold longer than that in the absence of d-Trp. In particular, 40 mM d-Trp alone significantly (P < 0.05) reduced L. monocytogenes growth by 3 log CFU/mL in concentration-dependent manner during a 30-day incubation at 4 °C, and 40 mM d-Trp combined with>3.0% NaCl resulted in an overall greater bacteriostatic effect accompanied by a partial bactericidal effect. Furthermore, 40 mM d-Trp significantly (P < 0.05) inhibited L. monocytogenes growth in artificially contaminated milk samples during extended refrigerated storage and maintained a low bacterial load (~103–104 CFU/mL) of L. monocytogenes throughout the 30-day refrigeration period. These results indicated that d-Trp significantly attenuated the psychrotrophic growth of L. monocytogenes at refrigerat...

Source: Food Control - December 14, 2019 Category: Food Science Source Type: research