Effects of Carvacrol, (E)-2-hexenal, and Citral on the Thermal Death Kinetics of Listeria monocytogenes

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Abstract
Carvacrol, (E)-2-hexenal, and citral at sublethal concentrations combined with isothermal heating between 55 and 68°C were assessed for their effects on Listeria monocytogenes 56LY. Experimental survival curves were obtained and fitted to the Weibull equation to estimate parameters describing their shape and rate. These parameters were further used to assess the impact of this combination of treatments on the cell resistance distribution during inactivation. The sublethal concentrations of the aroma compounds used (i.e., 50 mg/liter citral, 65 mg/liter (E)-2-hexenal, and 30 mg/liter carvacrol) did not prevent the growth of L. monocytogenes at 37°C but did enhance inactivation. Between 55 and 63°C, the presence of the aroma compounds reduced by about two-thirds the time needed for a 5-log reduction of the microbial counts, e.g., from 145.75 h in the control treatment (at 55°C) to 40.84 h in the presence of carvacrol (at the same temperature). The mean and variance observed in the frequency distribution of resistance were reduced as the temperature increased. The results obtained at isothermal temperatures and with single aroma components provide basic information regarding components frequently found in essential oils, which can be used in combination with less extreme thermal treatments to provide energy conservation and improve food quality.

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