Salmonella Does Not Penetrate Citrus Peel through Natural Light Labels

Michelle D. Danyluk, Preeti Sood, Lisseth Proano, Loretta M. Friedrich, Ed Etxeberria


In natural light labeling of fruit and vegetables, the desired information is etched onto the produce surface using a low-energy carbon dioxide laser beam (10,600 nm). Etched characters are formed by surface depressions in the epidermis that seemingly facilitate entrance of decay and pathogenic organisms. The objective of this study was to determine the effect of natural-light labeling and different postharvest treatments on Salmonella’s ability to survive/grow and penetrate into citrus fruit. A five-strain cocktail of Salmonella was spot inoculated onto ‘Valencia’ orange peels in different application sequences with wax and laser etching. Inoculated samples were stored at 10 or 26 °C. Etched peels and corresponding juices were extracted and enumerated for Salmonella. No set of conditions promoted the growth of Salmonella on the fruit surface or allowed penetration into the juice. Survival of Salmonella populations on the peel surface did not differ between any of the treatment and control (unlabeled samples). In all cases, Salmonella declined between 1.5 and 3.0 log colony forming units (cfu)/orange after 30 d, with faster decline noted at 10 °C. Based on the data obtained from all treatments and under conditions extremely unfavorable and unrealistic in terms of fruit storage, natural light labeling citrus fruit peels and subsequent waxing in any order does not allow for the growth nor influence the natural decline of Salmonella populations on citrus fruit surfaces as compared to controls.


Citrus sinensis, citrus postharvest, citrus juices, food safety, fruit wax


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Proc. Fla. State Hort. Soc.     ISSN 0886-7283