The anatomy of a laser label

Abstract

Laser labeling of fruits and vegetables is an efficient alternative to adhesive tags. In general, the label consists of alphanumerical characters formed by laser-generated pinhole depressions that penetrate the produce’s surface creating visible markings. The depth and morphology of the pinhole depression likely influence parameters such as water loss and clarity of the markings. Given the enormous differences in fruit anatomy, we investigated the anatomical characteristics of laser-generated pinholes on citrus peel. In general, the pinhole depressions are irregular in appearance, of approximately 0.3 mm in diameter and only 1–2 cells in depth. Although the external appearance remains fairly constant during cold storage, cell underlining cells layers below the pinhole depression appear to undergo metabolic changes as evidenced by their increasing darkening. In conclusion, the pinhole depressions on citrus fruits are very superficial I nature and not penetrating below the flavedo, therefore not enhancing the potential for penetration of pathogens or decay organisms.