Effects of UV-B and UV-C combination on phenolic compounds biosynthesis in fresh-cut carrots

The single and combined effects of UV-B (1.5 kJ m−2) and UV-C (4.0 kJ m−2) radiation treatments were studied on the phenylalanine ammonia-lyase (PAL) activity, phenolic content and antioxidant capacity (TAC) of shredded fresh-cut carrots during 72 h at 15 °C. Non-irradiated samples were used as control (CTRL). PAL activity of UV-B and CTRL samples was increased by approximately 760% after 72 h while increases of 120-140% in the remaining radiation treatments were found. Chlorogenic acid represented 70% of the sum of phenolic compounds of initial samples. UV-B treatment showed the highest phenolic accumulation with 498% after 72 h, regarding its initial value, while single and combined UV-C treatments achieved an accumulation of 440%, which was similar to CTRL samples. Such phenolics data were highly correlated (R2 = 0.82) to total antioxidant capacity throughout storage. Conclusively, UV-B treatment achieved the highest phenolic compounds accumulation and related antioxidant capacity in shredded carrot during 3 days at 15 °C. Furthermore, the use of UV-C treatment with sanitizing purposes combined with UV-B radiation did not negatively affect the accumulation of bioactive compounds, achieving similar enhancements to CTRL samples.