Citric acid, hydrogen peroxide extend sliced mushroom shelf life.

Much research has focused on improving the quality and extending the shelf life of whole mushrooms. But there has been less research into optimizing the quality and shelf life of sliced mushrooms. As more consumers demand more prepared ready-to-use vegetables, the market for sliced mushrooms will grow.

Extending the shelf life of sliced mushrooms is desirable because a short shelf life restricts distribution and export potential. One or two additional days of shelf life would compensate for time in transit. An extended shelf life would give more flexibility to processors, retailers and consumers.

Mushroom processors already use some techniques to improve sliced mushroom shelf life. For example, treating mushrooms by adding sulphites to the wash water has been widely used, but a wash in 1 g/L of sodium metabisulphite has been shown to be deleterious for mushroom shelf life. Stabilized chlorine dioxide offers antimicrobial properties. However, its effectiveness in maintaining mushroom whiteness is variable.

Although consumers might prefer the use of different packaging techniques to improve shelf life instead of chemical treatments, chemicals are often simpler and less expensive for processors to implement.

Scientists at Teagasc (The National Food Center, Dunsinea, Castleknock, Dublin 15, Ireland) investigated methods for extending the shelf life of sliced fresh mushrooms. Specifically, they looked into the effects of citric acid and hydrogen peroxide treatments on the quality of sliced mushrooms during storage.

Whole fresh mushrooms were soaked for 10 minutes in solutions of citric acid or hydrogen peroxide. Then they were sliced, packed and stored at 4 C for up to 19 days. Compared with water-soaked slices, both treatments reduced the number of pseudomonad bacteria and improved the keeping quality of the sliced mushrooms. The treatments also extended shelf life by about 50%. Treatment effectiveness varied with different mushroom batches. The citric acid treatment had no deleterious effect on the sensory properties of the sliced mushrooms.

The main improvements in quality occurred after nine days of chilled storage. Therefore, citric acid or hydrogen peroxide treatments would not be of benefit for mushrooms sold and consumed within one week. But the extension of shelf life could allow producers to ship sliced product further distances than before.

Further information. Martine Brennan; phone: [phone]; fax: [phone]; email: [e-mail].