Laser Labeling and Its Effects On the Storage Quality of Citrus Fruits

Etching the required information on the skins of fruits and vegetables is an alternative way to label produce. A low energy CO₂ laser beam etches the outermost layer of the epidermis revealing the contrasting underneath layer while forming alphanumerical characters. These etched areas represent breakages of the natural protective barrier and can result in moisture loss and potentially act as an entry site for pathogens. The present study was aimed at determining the water loss, peel stability and potential decay in laser etched citrus fruits namely tangerine (Citrus reticulata) and grapefruit (Citrus paradisi) during storage.  Laser labeled fruit stored at 10 ^oC and two different relative humidities (RH) (95% and 65%) for 5 weeks showed no increase in decay compared to control non-etched fruit, indicating that laser labeling does not promote decay. This was further confirmed by experiments where Penicillium digitatum spores were smeared on the laser etched areas before and after etching. In either case, no decay was observed. Water loss from etched areas and label appearance were determined in both the fruits during storage. Water loss from the etched label area declined sharply, and reached comparable levels to control non-etched fruit within seven days. Waxing the labeled surface reduced water loss by 35-95%, depending on wax formulation. Label appearance gradually deteriorated during storage and was proportional to the laser beam exposure time and ambient relative humidity. These results led to the conclusion that laser labeling could be a safe alternative for existing adhesive labels.