Effects of washing treatment on microbial and sensory quality of modified atmosphere (MA) packaged fresh sliced mushroom (Agaricus bisporus)

The effects of different washing treatments combined with modified atmosphere packaging (MAP) on the quality and storage life of sliced mushrooms were determined. Trials with anti-microbial treatments involved a disinfectant step followed by a rinse, and investigated the effectiveness of different concentrations, washing times and combinations of chlorine dioxide (ClO2) and hydrogen peroxide (H2O2). Combination trials involved anti-microbial treatments followed by anti-browning treatments involving washing or spraying with sodium d-isoascorbate or H2O2. Hand sliced mushrooms were then packaged within micro-perforated PA-190 film and stored at 4 or 8 °C for 7 days. The most effective ClO2 treatments were washing for up to 60 s at concentrations of 25–50 mg/L. In the case of H2O2, washing for 60 s produced best quality. H2O2 treatments were superior to ClO2 in reducing pseudomonad counts. There were no additional benefits to the sensory or microbial quality from using a two-stage wash versus a single wash of either H2O2 or ClO2. Combination anti-microbial/browning treatments using H2O2 and sodium d-isoascorbate monohydrate had beneficial effects on quality, with better acceptability of appearance and colour and significant microbial reduction. A spray application of sodium d-isoascorbate monohydrate, proved even better than a washing treatment, probably due to minimal water uptake. Spray applications of H2O2 above 1% were damaging. Overall, the most effective treatment was 3% H2O2 for up to 60 s prior to slicing followed by a spray application of 4% sodium d-isoascorbate monohydrate or 1% H2O2. Subsequent storage under modified atmospheres at 4 °C maintained quality and enhanced shelf-life.