Laser labeling has become an alternative means of fruit labeling in many areas of the world (e.g., New Zealand, Australia, and Pacific Rim countries), approved in others (e.g., South Africa, Mexico, Canada, Argentina, Chile, and the European Union), and is currently in final approval stages by the U.S. Food and Drug Administration. The technique consists of etching the required information on the produce surface using a low-energy carbon dioxide laser beam (10,600 nm) (Drouillard and Rowland, 1997). Etched markings are formed in dot matrix-style letters and numbers, each dot created by a pin-hole depression. The advantages of laser labeling have been described previously (Etxeberria et al., 2006), yet some reservations linger about potential adverse effects during storage. The pinhole depressions applied after washing and waxing disrupt the natural cuticular barrier and the protective commercial wax cover, seemingly creating open cavities that would allow for increased water loss and facilitate the entrance of decay organisms.
In previous anatomical studies using tomato (Solanum lycopersicum) and avocado (Persea americana) (Etxeberria et al., 2006), it was demonstrated that cells under the affected area of a laser pinhole developed a protective layer mostly of lignin and phenolics when stored for 4 d at 10 °C and 95% relative humidity (RH). This rapid healing response, accompanied by phenolic deposition, has been observed in ‘Valencia’ orange (Citrus sinensis) (Brown et al., 1979). When ‘Ruby Red’ grapefruit were damaged by friction with sandpaper, penetration by Penicillium digitatum was inhibited where cells at the surface produced lignin before fungal entry (Brown et al., 1979). In a related study, Yuk et al. (2007) challenged tomato fruit with Salmonella immediately after labeling and observed no migration into the tissue by the organism, suggesting that some protection is supplied by the labeling process itself.
Little information is available on the impact of this new technology on the overall quality of labeled produce, especially its effect on water loss and decay during prolonged storage. In Florida, grapefruit represents 43% of the citrus fresh market (Florida Citrus Mutual, 2008), a condition that requires extended storage, especially when transported to international destinations. The present study determined the effects of laser labeling on water loss and decay susceptibility during prolonged storage.
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