Influence of spectral distribution on bacterial inactivation and quality changes of fresh-cut watermelon treated with intense light pulses

The application of intense light pulses (ILP) is an emerging technology with interesting prospects regarding food preservation. However, information concerning the factors affecting the inactivation of microorganisms and their impact on the quality of fresh-cut fruit is scarce. In this study, the effects of spectral ranges on inactivation of Escherichia coli and Listeria innocua in fresh-cut watermelon were determined. In addition, the effect of ILP on the quality parameters of fresh-cut watermelon was evaluated. The effectiveness of ILP was significantly affected when the UV-portion of light was blocked, which resulted in lower log reductions for both microorganisms. Full-spectrum treatments with an overall fluence of 12 J/cm2 reduced the E. coli populations by more than three log cycles. On the other hand, the initial loads of L. innocua were reduced by 2.79 log, demonstrating that this microorganism is less sensitive to ILP treatment than E. coli. The entire spectral range of ILP had a higher negative effect on the color, texture and headspace gas composition in comparison to treatments without UV light. This work demonstrates that a slight modification in the spectrum of ILP treatments, mainly in the UV portion, may have a negative impact on the effectiveness of the treatment.

► The effectiveness of intense light pulses (ILP) on fresh-cut watermelon depended on the spectral range.
► ILP treatments with full spectrum reduced Escherichia coli by more than three log cycles.
► E. coli inactivation was greater than that of Listeria innocua.
► A modification of the UV profile had a negative impact on treatment efficacy.
► Full spectrum-light pulses had a greater effect on quality parameters than visible-light pulses.