An evaluation of the protein quality of some macedonian edible Boletaceae mushrooms

Abstract

The nutritional quality of mushroom protein varies and is strongly affected by the relative proportion of each amino acid. Thus, the purpose of this study was to estimate the concentration of the amino acids present in mushroom proteins in order to evaluate the protein nutritional value. In this investigation fifteen field-collected mushroom samples of the Boletaceae family from various parts of Macedonia were included. After acid hydrolysis and pre-column derivatisation with phenyl isothiocyanate (PITC) determination of seventeen amino acids was carried out by the HPLC method. Tryptophan was determined spectophotometrically in the alkaline hydrolysates. The dietary protein quality of the investigated mushrooms was evaluated by comparison of the essential amino acid content with the reference FAO/WHO pattern. Essential amino acids made up 47-75 % of all determined amino acids depending on the origin and the species of the fruit body. Lysine was the most often found limiting amino acid in the investigated mushrooms samples. The nutritional value of proteins calculated by biological value, protein ratio, chemical score and essential amino acid index was very high in the majority of mushrooms studied. The biological value of the mushroom protein varied from 51.3 to 78.9 %. Protein amino acids accounted for about 66.7 % of the total nitrogen, suggesting that a practical nitrogen to protein conversion factor for this Macedonian edible Boletaceae mushroom may be considered to be about 4.17 on average.