Abstract: The antibacterial activity of 4-hexylresorcinol against the spoilage bacteria Carnobacterium maltaromaticum, Shewanella putrefaciens and Aeromonas salmonicida from Pacific white shrimps and its effect on the quality of Pacific white shrimps was assessed in this study. The results of Oxford cup method and the growth inhibition curves for the bacteria indicated that 4-hexylresorcinol showed a strong inhibitory effect on the three spoilage bacteria. The determination of electrical conductivity and flow cytometric analysis showed that 4-hexylresorcinol led to increased permeability of the cytoplasmic membrane of S. putrefaciens cells. When 0.25 mg/mL 4-hexylresorcinol was applied in shrimps, melanization was inhibited according to the low melanosis score and high whiteness value during cold storage at 4 ℃. However, a significant inhibitory effect on the increase of psychrotrophic bacterial counts and total volatile basic nitrogen was only observed in the first 4 days in comparison with the control. At the end of storage, the bacterial count of 4-hexylresorcinol-treated samples was 0.14 (lg(CFU/g)), which was higher than that of the control. These results showed that though 4-hexylresorcinol was effective in inhibiting the growth of the three spoilage bacteria in vitro, it was preferred to be used as a melanosis inhibitor for shrimps rather than as an inhibitor against the growth of spoilage bacteria in shrimps.

Key words: Litopenaeus vannamei, 4-hexylresorcinol, antibacterial activity, Shewanella putrefaciens, Aeromonas salmonicida, Carnobacterium maltaromaticum