A review of chemical composition and nutritional value of wild-growing and cultivated mushrooms.

Fruit bodies of about 200 mushroom species are consumed throughout the world, preferably as a delicacy. Knowledge of their chemical composition, nutritional value and health-promoting effects has expanded dynamically during the last few years. Dry matter (DM) is low: commonly about 100 g kg⁻¹ . The usual contents of protein, lipids and ash are 200-250, 20-30 and 80-120 g kg⁻¹ DM, respectively. Various carbohydrates form the remaining DM. Nevertheless, great variations occur both among and within species. Energy is low, usually 350-400 kcal kg⁻¹ of fresh fruit bodies. The nutritional contribution of mushroom protein derived from earlier data seems to be overestimated. Fat content is low with markedly prevailing in linoleic acid and oleic acid, while the proportion of n-3 fatty acids is nutritionally marginal. The main carbohydrates are chitin, glycogen, trehalose and mannitol. Information on fibre content and composition is limited. Health-promoting β-glucans are an auspicious group of polysaccharides. High potassium content is characteristic of mushrooms. Several species can accumulate very high levels of both detrimental trace elements, particularly cadmium and mercury, and radiocaesium isotopes if growing on heavily polluted substrates. Mushrooms seem to be a considerable source of ergosterol, provitamin D₂, and phenolids with antioxidative properties. Hundreds of flavour constituents have been identified, particularly with eight-carbon aliphatic chains. Data on changes of mushroom components under various preservation conditions and culinary treatments have been fragmentary. Even more limited is knowledge of nutrient bioavailability.