Decontamination of fresh-cut broccoli with a water–assisted UV-C technology and its combination with peroxyacetic acid

Abstract

The effectiveness of a water-assisted UV-C (WUV) technology for the decontamination of fresh-cut broccoli from conventional and organic agricultural practices was evaluated as an alternative to chlorine sanitation. Several WUV doses (0.3-1.8 kJ m-2) were tested alone or combined with peroxyacetic acid (PAA). Results showed that 0.5 kJ m-2 was sufficient to reduce natural total aerobic mesophilic microorganisms by 2 log 10 in conventional broccoli without 2 negative consequences on the physical quality. However, in order to achieve the same effect on organic broccoli, a combined application of at least 0.3 kJ m-2 and 50 mg L-1 PAA was required. Total antioxidant capacity (TAC) was enhanced by 42, 90 and 81% in conventional broccoli 24 h after treatment with 0.3, 0.5 and 1.8 kJ m-2 , respectively, compared to watercontrol. A similar trend was observed in organic broccoli, although the increase in TAC (by 22%) compared to the water-control was only significant when a dose of 1.8 kJ m-2 was used. Similarly, 0.5 kJ m-2 enhanced the sulforaphane content in conventional broccoli by 1.5 and 4fold compared to water and chlorine-controls, respectively. WUV is a promising alternative technology to improve the microbiological and nutritional quality of fresh-cut broccoli.

Decontamination of Listeria innocua from fresh-cut broccoli using UV-C applied in water or peroxyacetic acid, and dry-pulsed light

“…In contrast, we observed no change in the headspace composition or in the chlorophylls contents in samples treated with WUV (0.5 kJ m -2 ) or PL (15 kJ m -2 ) compared to the water control during storage for 8 or 15 d, respectively. These results agreed with our previous results in this matrix (Collazo et al, 2018). In contrast, increased respiration and negative changes in color parameters were eventually observed in chlorine-treated samples, implying that both WUV and PL technologies contributed better to preserve color and overall quality than chlorine sanitation.…”

“…In fresh-cut broccoli, continuous UV-C at a dose of 8 kJ m -2 increased total antioxidant activity as well as phenolic compounds and ascorbic acid contents. We observed that total phenolic content was maintained after PL treatment compared to water-washing while it was reduced after chlorine sanitation as it was observed in previous experiments performed by our work group in fresh-cut broccoli using the same technology (Collazo et al, 2018). Furthermore, we observed and enhanced accumulation in total antioxidant capacity in PL-treated samples during the first 24 h, as measured by DPPH method, showing certain hormetic effect as has been previously reported in this commodity (Martínez-Hernández et al, 2011).…”

“…Contrastingly, when using PL, increases in the UV-C dose from 0.5 to 2.0 kJ m -2 (corresponding to total fluences from 5 to 20 kJ m -2 ) resulted in no significant inactivation of this microorganism or of native microbiota. In previous experiments, we observed that increasing the WUV dose from 0.3 to 0.5 kJ m -2 increased the efficacy of WUV for the decontamination of total mesophilic microbiota in fresh-cut conventional broccoli, whereas no improvement was obtained for the same purpose in organic one (Collazo et al, 2018). In agreement with our results regarding WUV, other researchers have reported that the dose-responses for the inactivation of foodborne pathogens on fresh-cut broccoli using dry-UV-C in a range below 2.0 kJ m -2 , fitted a Weibull model (Martínez-Hernández, Huertas, et al, 2015).…”

“…Two opposite lamps or the four lamps can be activated in order to change irradiance. Different doses were assessed by combining 120 s of exposure with two (2.46 W m -2 ) or four lamps (3.98 W m -2 ), based in previous dose evaluation (Collazo et al, 2018). Doses were calculated as: the mean values of irradiance (W m -2 ) * time of exposure (s).…”

“…In previous experiments our work group assessed the effect of a water-assisted UV-C (WUV) technology on the populations of natural mesophilic bacteria, yeasts and molds as well as on the accumulation of antioxidant compounds and glucosinolates in fresh-cut broccoli (Collazo et al, 2018). Results from those experiments showed a significant reduction of native mesophilic microbiota upon treatments as well as a hormetic increase in the contents of bioactive compounds without negatively affecting the physical quality.…”