Effect of production process on the amino acid content of frozen and canned Pleurotus ostreatus mushrooms

The aim of the work was to determine the effects of the freezing and canning processes, followed by a 12-month storage, on the amino acid content of Pleurotus ostreatus mushrooms. The pre-treatment involved blanching, or soaking and blanching, in mushrooms in water or in solutions containing sodium metabisulphite, citric acid, l-ascorbic acid and/or low-methylated pectin. Freezing and canning resulted in significant decreases in the levels of alanine, glutamine, cysteine and tyrosine (6–39%), and, in the case of canned mushrooms arginine, glycine, serine, histidine, methionine and threonine (1–31%). Frozen products obtained from blanched mushrooms had significantly higher levels of 12 out of the 17 amino acids examined (4–28%) whereas, in canned mushrooms, only 5 amino acids showed higher levels (3–20%), than those obtained from soaked and blanched mushrooms. With the exception of samples blanched in water, frozen mushrooms had higher levels than canned mushrooms of all the investigated amino acids. Limiting amino acids were not found in mushrooms.