Laser labeling of fruit and vegetables is an alternative means of labeling produce in which a low-energy carbon dioxide laser beam etches the surface and reveals a contrasting underlying layer. These etched surfaces can promote water loss and may increase the number of entry sites for decay-promoting organisms. The long-term effects of laser labeling on produce quality during storage have not been examined. We conducted experiments to measure water loss, peel appearance, and potential decay in laser-labeled grapefruit (Citrus paradisi) during storage. Laser-labeled fruit stored at 10 pC and two relative humidities (i.e., 95% and 65%) for 5 weeks showed no increase in decay compared with nonetched control fruit, suggesting that laser labeling does not facilitate decay. This was confirmed by experiments where Penicillium digitatum spores were coated on fruit surfaces before and after etching. In either case, no decay was observed. In agar plates containing a lawn of P. digitatum spores, the laser etching reduced germination of spores in contact areas. Water loss from etched areas and label appearance were determined during storage. Water loss from waxed etched surfaces reached control levels after 24 h in storage. Label appearance slowly deteriorated during 4 weeks in storage and was proportional to laser energy levels and ambient relative humidity. Waxing the labeled surface reduced water loss by 35% to 94%, depending on the wax formulation used. We concluded that laser labeling provides the grapefruit industry a safe alternative to adhesive sticker labeling without enhancing decay susceptibility.
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