Title: Inhibition effects of vapor phase thymol and modified atmosphere against Salmonella spp. on raw shrimp Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 9, 2012
Publication Date: June 25, 2012
Citation: Zhou, S., Sheen, S., Liu, L.S., Pang, Y.H., Yam, K.L. 2012. Inhibition effects of vapor phase thymol and modified atmosphere against Salmonella spp. on raw shrimp [abstract]. IFT Meeting, June 25-28, 2012, Las Vegas, Nevada. 1:1. Technical Abstract: Salmonella contamination of shrimp is a food safety concern in the U.S. and other countries. Natural antimicrobial compounds (e.g. essential oils) in vapor phase and modified atmosphere (MA) technology can inhibit the growth potential of Salmonella spp. However, each strategy has its limitations, while a stronger antimicrobial effect could be expected by using them in combination. This research evaluated the combinational inhibition effect of vapor phase thymol and MA towards Salmonella spp. on raw shrimp. In addition, linear regression predictive models were developed to describe the microbial growth characteristics (lag time and maximum growth rate) of Salmonella spp. on shrimp. Growth profiles of a Salmonella spp. cocktail (6 strains) inoculated onto raw shrimp treated with vapor phase thymol at three levels (0, 0.8 and 1.6 mg/l), or MA (60% CO2 + 40% N2), both alone and in combination, at three temperatures (8, 12 and 16 degree C), were determined. Lag time and maximum growth rate for each treatment were obtained using Baranyi & Roberts models. Results indicated that combination of vapor phase thymol and MA significantly inhibited the growth of Salmonella spp. For instance, at 8 degree C, the lag time of Salmonella spp. was extended from 54.2 hrs (without treatment) to 143.9 hrs (1.6 mg/l vapor thymol + MA treatment), and the maximum growth rate was reduced from 0.021 log CFU/g/hr (without treatment) to 0.0098 log CFU/g/hr (1.6 mg/l thymol + MA treatment). Synergistic antimicrobial effectiveness was also observed. For instance, at 16 deg C, the lag time of Salmonella spp. was extended 30.6% by the combined treatment (1.6 mg/l thymol plus MA) over that of either treatment alone. Linear regression models for lag time and maximum growth rate under the different stresses were also developed. These models may be used for shelf-life prediction and risk assessments for raw shrimp.