Protein Content of Shiitake Mushroom Grown on Nitrogen Soaked Sweetgum Logs

Shiitake mushrooms are used as a source of protein and meaty flavor in many vegetarian diets. While substrate and geographical location are two factors affecting nutrient content, little research has been done on the nutrient content of shiitake grown in north Alabama. The purpose of this study was to compare the protein and amino acid contents of the ‘West Wind’ strain of shiitake mushrooms grown on sweetgum logs soaked in tap water, versus the protein and amino acid content of the same strain grown on logs soaked in tap water amended with different nitrogen (N) solutions (urea, sulfur-coated urea, and ammonium sulfate), at different rates (0, 3, and 6 g N/L water), and harvested from three successive soakings. Chemical analysis was conducted on samples for protein and amino acids. Analysis of variance showed there was no significant difference in the protein content of shiitake grown on sweetgum logs based on type of nitrogen treatment, rate, or soak period. However, urea showed indications that it may increase protein levels. There was no significant difference in amino acid content based on treatment or rate. Although not statistically significant, there was a trend showing mushrooms from logs soaked at a rate of 3 g N/L water had the highest levels of each amino acid. There were significantly lower levels of amino acids in mushrooms harvested during the summer months. Nitrogen soak solutions did not increase protein or amino acid content, but protein and amino acid contents of shiitake in north Alabama are better understood.