title: Survival of Salmonella in home-style mayonnaise and acid solutions as affected by acidulant type and preservatives.
abstract: Mayonnaise made from contaminated eggs has been linked to outbreaks of Salmonella infections. This study was undertaken to determine the fate of salmonellae in home-style mayonnaise and acid solutions with or without chemical preservatives. Egg yolks were inoculated with different  levels of a three-serotype (Typhimurium, Heidelberg, and Enteritidis [untypeable phage type]) mixture of Salmonella or a three-phage-type (4, 8, and 13) mixture of Salmonella Enteritidis. The inoculated yolks were used to make mayonnaise with 2, 3, or 4 teaspoons of a commercial  wine vinegar or lemon juice. The mayonnaise was sampled for salmonellae over a 15-day period at 4°C, and negative samples were tested further by a three-tube most-probable-number assay. The same Salmonella mixtures were respectively inoculated into six acid solutions including wine  vinegar, lemon juice, and acetic or citric solutions with or without chemical preservatives. The Salmonella populations of the Salmonella Enteritidis mixture were more persistent than those of the other Salmonella mixture in mayonnaise. Both Salmonella mixtures  survived longer in mayonnaise made with vinegar than with lemon juice during storage at 4°C. In the acid solutions, however, the populations of the two  Salmonella mixtures were not significantly different. The numbers of the two Salmonella mixtures in acetic or citric acid  solutions with the preservatives were significantly lower than those in vinegar, lemon juice, and the solutions without the preservatives. Results suggest that Salmonella in contaminated egg yolks could survive the mayonnaise-making process. The inhibition of Salmonella by vinegar  and lemon juice is due to the hurdle effect of organic acids and chemical preservatives.
authors.affiliation: Research Institute of Food Science and Biotechnology, Zhejiang Gongshang University, 149 Jiao Gong Road, Hangzhou 310035, People's Republic of China.
authors.forename: Junli
authors.initials: J
authors.lastname: Zhu
authors.forename: Jianrong
authors.initials: J
authors.lastname: Li
authors.forename: Jinru
authors.initials: J
authors.lastname: Chen
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology*; D019343:Citric Acid / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004530:Egg Yolk / Q000382:microbiology*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D012034:Refrigeration; D012475:Salmonella / Q000254:growth & development*; D012477:Salmonella enteritidis / Q000254:growth & development; D012486:Salmonella typhimurium / Q000254:growth & development
chemical_list: D019343:Citric Acid; D019342:Acetic Acid