Purpose: The objective of this study was to develop and determine the efficacy of acidification treatments for reducing Lm counts in brines with (W) and without (NW) whey (2%).
Methods: Model brines formulated with ~25% NaCl and ~0.25% CaCl2 were adjusted to pH 5.2 with lactic acid (LA). Cultures of salt and acid adapted Lm (106 CFU/mL) were allowed to acclimate in model brines for one week at 12°C prior to treatments. Brine pH was then adjusted to pH 2 with either lactic, hydrochloric (HCl), acetic (AA), or citric (CA) acid and held at room temperature for up to 360min. Subsamples were removed and neutralized (NaOH) for enumeration every 15min for 120min, and every 30min thereafter for enrichment.
Results: Overall, counts did not change during the acclimation period. Differences in Lm counts were observed over time between NW and W brines when acidified with CA, HCl, or LA (P≤0.002). Treatment of NW brines with HCl, AA, and LA resulted in rapid reduction in counts to below the detection limit (10 CFU/mL) within 60-90min, whereas treatment with CA took significantly longer (120min; P≤ 0.002). Acidification of W brines with AA and LA reduced counts to below the detection limit more rapidly when compared to other acids (105min; P≤ 0.017). After 90min, Lm were not detectable by enrichment in NW-AA and after 2h in W-AA, NW-HCl, and NW-LA brines. In contrast, HCl-W was the least effective with ~1 log CFU/mL remaining after 120min and detectable Lm after 360min by enrichment.
Significance: Acidification of brines presents a cost-effective and actionable approach for the reduction of Lm in brines as a promising preventive control.