Shedding light about the use of photosensitizers and photodynamic treatments during postharvest of fruit and vegetables: Current and future state

Abstract

Photosensitizers are organic compounds which can generate reactive oxygen species in the presence of light. Such photodynamic reactions have been paid attention due to their effectiveness to inactivate microorganisms. The purpose of this study was to analyze progresses already known about the effect of postharvest application of photosensitizers on the quality of fruit and vegetables. First of all, the generalities of this technology are reviewed and a number of photosensitizer compounds potentially useful are described. Later, the main results achieved in those studies evaluating such strategy in postharvest are discussed. Some compounds consistent with food, such as some vitamins and natural additives, are photosensitizers, while others correspond to plant-derived secondary metabolites, potentially compatible with food. Compounds mostly studied have been curcumin and chlorophyllin and, to a lesser extent, riboflavin, pheophorbide a, hypericin, carvacrol and menadione, while other compounds are still to be evaluated. Different combinations of photosensitizers and light have achieved microbial control, rot reduction and extension of postharvest life in strawberry, cherry tomato and grape; and P. digitatum and B. cinerea control in orange and apple, respectively. In some cases, the induction of defense enzymes has been reported. In minimally processed products, treatments with photosensitizers have controlled the microbial development, reduced enzymatic browning and improved texture. The great efforts carried out to date have yielded promissory results. However, our knowledge about the use of this technology in postharvest is far from fully understood. Thus, different questions and lines of investigation for further research are posed. We therefore hope to foster further studies to enlarge our knowledge concerning the use of this emerging technology to reduce losses and preserve the postharvest quality of vegetables and fruit.