Chemical, nutritional, and bioactive compositions of fresh, washed, and blanched shiitake

Abstract

Washing and blanching are two important steps for the processing of fresh good grade small shiitake into casual snacks and prepared foods. This study explored their effects on the dimensions, weights, proximate compositions, taste and bioactive compounds of the shiitake caps and stipes. Results showed that the dimensions and weights of the caps and stipes increased after washing but decreased after blanching. On a dry basis, washing did not affect the nutrients and bioactive compounds contents of shiitake except sugars and polyols compared to fresh samples. However, blanching greatly reduced all the quality contents of the shiitake. The major minerals in the caps and stipes were potassium, magnesium and calcium. The main polyol, sugar, free amino acid, and 5'-nucleotide of shiitake were mannitol, trehalose, glutamine and 5'-adenosine monophosphate, respectively. Equivalent umami concentration (EUC) in the caps was three-fold higher than that in the stipes. Ergosterol, ergothioneine, γ-aminobutyric acid (GABA), and total phenols contents in the caps were significantly higher than those of the stipes, but the polysaccharides showed the reversed. Overall, both caps and stipes contain the necessary nutrients and bioactive compounds, and the blanching significantly affected the above-mentioned components of all tested samples.