Impact of non-thermal technologies and sanitizer solutions on microbial load reduction and quality factor retention of frozen red bell peppers

The effect of non-thermal technologies (ozone in aqueous solution, ultrasounds and ultraviolet C radiation) and washings with chemical solutions (sodium hypochlorite and hydrogen peroxide) on Listeria innocua survival was studied in red bell peppers. Quality attributes such as total colour difference, firmness, pH and ascorbic and dehydroascorbic acid content were also evaluated. The treatments were applied before product storage under frozen conditions (- 7 and - 30 C). Pre-washings with hydrogen peroxide solutions allowed obtaining frozen shred red bell peppers with lower microbial loads, when compared to the results obtained with the remaining treatments. However, those washings had a negative impact on colour and firmness. Alternatively, ozonation provided microbial reductions significantly higher than water-washings and improved, or at least allowed to preserve, all quality parameters analysed under both storage conditions. Storage at - 7 C provided higher microbial reductions in red bell peppers. However, this temperature implied higher colour alterations and ascorbic acid losses. Industrial relevance The native microbial flora of fresh fruits and vegetables may include pathogens which are dangerous threats to consumers. Thermal treatments are conventionally used to attain safety standards; however, overall quality may be negatively affected by heat. Chemical treatments (environmental friendly) or non-thermal processes such as ozone, UV-C radiation and ultrasonication are promising technologies. From an industrial point of view, these processes may have potential application if safe and high quality produce is to be attained.