The Effect of Sodium Metabisulphite on the Whiteness and Keeping Quality of Sliced Mushrooms

The effect of sodium metabisulphite on the whiteness of sliced mushrooms was investigated. Mushrooms soaked whole in 1, 2 or 4 g/L sodium metabisulphite for 30 s or 10 min prior to slicing, were no whiter than those soaked in water. The effect of soaking whole mushrooms in 1 g/L sodium metabisulphite solution for 10 minutes on the keeping quality of slices at 4°C was quantified. No differences were found between the sulphite-soaked mushrooms and the water-soaked mushrooms with regard to their colour, texture and number of pseudomonad bacteria, irrespective of the flush or compost phase from which the mushrooms were harvested. The minimum inhibitory concentration (2 g/L) of sodium metabisulphite for a pseudomonad strain was twice the concentration used in industrial processing, and sulphur dioxide was undetectable in sliced mushrooms after 18 h at 4°C. The ineffectiveness of the sodium metabisulphite treatment, based on these tests, indicates the need for alternative treatments in the sliced mushroom industry.