Antilisterial effects of hop alpha and beta acids in turkey slurry at 7 and 37°C

Abstract

Chemical components of hop resins effectively inhibit the growth of L. monocytogenes in microbiological culture media. This study was conducted to investigate antilisterial activities of hop α- and β-acid in turkey slurry. Turkey slurries were inoculated with L. monocytogenes, formulated with hop α- or β-acid from 0 to 1,000 ppm, and incubated at 37°C for 24 h or at 7°C for 12 days. During storage at 37°C for 24 h, L. monocytogenes populations were reduced from 2.40 log CFU/g to non-detectable (<1 log CFU/g) in α-acid at ≥750 ppm and β-acid at 1,000 ppm, whereas the control (0 ppm) allowed the pathogen to grow to 8.0 log CFU/g. During storage at 7°C for 12 d, the slurry treated with α-acid at ≥100 ppm and β-acid at ≥500 ppm showed listeristatic effects, while listericidal effects were observed in the slurries at 1,000 ppm, regardless of hop acid type. Hop α-acid ≤ 50 ppm and β-acid ≤ 100 ppm failed to inhibit L. monocytogenes, and the pattern of bacterial growth was similar to that of control with no significant difference (P > 0.05). Based on these results, the concentration of α-acid > 100 ppm or β-acid > 500 ppm is minimally required to inhibit L. monocytogenes when turkey batters are formulated with hop acids as a single antilisterial agent prior to cooking and storage at 7°C.