Fungi Associated with Softening of Bisulfite-Brined Cherries

Softening of sound, calcium bisulfite-brined cherries was induced fairly quickly by brining them with cherries rotted by Aspergillus niger, Cytospora leucostoma, and Penicillium expansum, but not with cherries rotted by a variety of other microorganisms, including Alternaria sp., Aspergillus oryzae, Aureobasidium pullulans, Botrytis cinerea, Cladosporium sp., Mucor racemosus, Rhizopus stolonifer, and Sclerotinia fructicola. Rapid softening was correlated with the presence of a bisulfite-stable polygalacturonase, as demonstrated by a cup-plate test. A survey of naturally rotted cherries suggests the involvement of a bark-canker fungus, C. leucostoma, in softening of commercially brined cherries in the Pacific Northwest.