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Antilisterial effects of different hop acids in combination with potassium acetate and potassium diacetate at 7 and 37 °C
- Sansawat, T., Lee, H.C., Zhang, L., Ryser, E.T., Kang, I.
- Food control 2016 v.59 pp. 256-261
- Listeria monocytogenes, acetates, alpha acids, antibacterial properties, beta acids, exposure duration, heat, minimum inhibitory concentration, potassium, salts, synergism, temperature, yeast extract
- This study was conducted to assess the effect of eight hop acid extracts (α-acid, β-acid, acid-iso, acid-tetra, potassium-iso, potassium-hexa, potassium-tetra, and potassium-rho) with/without potassium acetate/potassium diacetate salts (PAPD) on inhibition of Listeria monocytogenes in trypticase soy broth with yeast extract (TSBYE). Following overnight incubation at 37 °C, 50 ppm α-acid decreased Listeria from 6.0 to <1.0 log CFU/mL, with significant reduction to 3.6–3.8 log CFU/mL using β acid, acid-tetra, K-tetra, or K-hexa.No inhibition was seen for acid-iso, K-iso, K-rho and the control. After incubating Listeria with the five hop acids (α-acid, β-acid, acid-tetra, K-tetra, and K-hexa) at 25 ppm with/without 0.5% PAPD, Listeria population decreased from 5.7 log CFU/mL) to < 1.0 log CFU/mL in PAPD/α-acid, PAPD/β-acid, or PAPD/acid-tetra, with reduction to 1.8–4.2 log CFU/mL for the remaining except the control. When the hop acids at 25 ppm were exposed to 85 °C up to 30 min, α-acid maintained the most effective antilisteiral activity by reducing Listeria from 5.0 to <2.9 CFU/mL, regardless of heat exposure time. The minimal inhibitory concentration was 6.3 ppm for α-acid, β-acid and acid-tetra, with 12.5 ppm seen for K-tetra and K-hexa. During the incubation of hop extracts at 5 ppm/7 °C for 6 days, listeristatic effect was observed in the hop/PAPD mixtures and PAPD at 0.5 and 1%, with no listeristatic effect seen for a single addition of hop acids except β-acid. These findings indicated that the combination of hop/PAPD provided both stable and synergistic effects against Listeria growth compared to any single addition, regardless of incubation temperature and addition amount.