Impact of Blue LED Illumination and Natural Photosensitizer on Bacterial Pathogens, Enzyme Activity and Quality Attributes of Fresh-Cut Pineapple Slices

Abstract

Fresh-cut fruits are susceptible for microbial contamination during handling and storage. Hence, there is a need for minimal processing of such foods using non-thermal technology that can inactivate both bacterial pathogens and undesirable enzymes while retaining the quality. In this regard, synergistic effect of light emitting diode (LED) based blue light (BL) and natural exogenous photosensitizer- curcumin (PS) on the inactivation of bacterial pathogens (Escherichia coli, Staphylococcus aureus), and enzymes (polyphenol oxidase, peroxidase, bromelain) of fresh-cut pineapple slices were evaluated. The effect of photodynamic treatment (PS+BL) on quality attributes like color, phenolics, flavonoids, ascorbic acid content and antioxidant activity was also investigated. The PS+BL treatment at optimized conditions resulted in 3 and 4 log reduction of E. coli and S. aureus, respectively. PS(100 μM)+BL treatment led to partial inactivation of polyphenol oxidase (33.5%) and peroxidase (25.7%), synergistically, but preserved desired enzyme bromelain. The PS+BL didn’t show any significant (p<0.05) consequence on color, phenolics, flavonoids and antioxidant activity, while it affected the ascorbic acid content negatively (reduced by ~30%). The current investigation showed that the photodynamic inactivation of E. coli and S. aureus using LED-based photosensitization in fresh-cut fruit slices could be used as a potential method for microbial control although some phytochemical losses.