Pseudomonas aeruginosa, a common spoilage microorganism on fresh catfish products, can grow rapidly at temperatures above 4°C during storage and transportation. To protect against temperature abuse and extend the shelf life of catfish, an antimicrobial packaging system examined in this study. Allyl isothiocyanate (AIT), an extract of horseradish oil, is a well-known antimicrobial agent, which has been proved to have an excellent antimicrobial capability on various microorganisms. The packaging system consists of combing AIT with modified atmosphere (MA), a common antimicrobial method, to inhibit the growth of P. aeruginosa. The objectives of this research were: 1) to investigate the antimicrobial effects of AIT in vapor phase and MA on P. aeruginosa in fresh catfish fillet; 2) to develop models to predict the lag phase and shelf life of fresh catfish products as a function of AIT and MA. Three concentrations (0, 18 and 36 μg/L) of AIT in vapor phase were used to inhibit the growth of P. aeruginosa cocktail (3-strains) at 8, 15 and 20°C. In addition, the antimicrobial capability of MA (49% CO2, 0.5% O2 and 50.5% N2) and MA combined with AIT were also investigated. Our results showed that temperature has the most significant impact on the growth rate of P. aeruginosa. Lowing temperature could decrease the maximum growth rate of P. aeruginosa and extend its lag phase and shelf life. Increasing gaseous AIT concentration could elongate lag phase and reduce growth rate of P. aeruginosa effectively. In addition, AIT alone reduced P. aeruginosa counts within the initial several hours. The application of MA had a similar antimicrobial effect as AIT under low storage temperature. Moreover, to attain a longer shelf life of fresh catfish fillet, the combination of AIT and MA was included in this study. The synergistic effect of AIT and MA could extend the shelf life of fresh catfish from 4 days (control) to 23 days at 8°C. Models developed from this study may be applied to estimate the lag phase of P. aeruginosa and shelf life of catfish under abuse temperature conditions. The results could assist food industry to predict the shelf life of catfish products, which may be further optimized with appropriate AIT concentration in a MA packaging.
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Food Science
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Rutgers University Electronic Theses and Dissertations
Rutgers University. Graduate School - New Brunswick
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