| This paper evaluated and compared the effects of five cooking methods (steaming, high pressure cooking, microwave cooking, frying and boiling) on the nutritious and antioxidant activities of four fresh Boletus species, which are Boletus luridus, Boletus edulis, Boletus pinophilus and Boletus aereus, collected from Yunnan province.The samples of the four Boletus sp. without cooking were defined as control groups. For the control groups, the moisture contents were86.79-89.69%, ash6.97-8.59mg/gFW, crude fat0.12-0.39g/100g FW, crude protein3.96-4.72g/100g FW, soluble protein1.11-2.09g/100g FW, insoluble dietary fibre1.15-3.10g/100g FW, soluble dietary fibre0.44-0.86g/100g FW, Vitamin C26.1-65.5mg/100g FW, available carbohydrates11.99-48.31mg/g FW, total free amino acids472.87-1357.98mg/g FW, total phenolics150.5-220.0mg/100g FW. The monosaccharide compositions of Boletus sp. showed no significant differences, and glucose was the most important part of Boletus sp.. The amino acid compositions varied significantly, and threonine showed the highest content.the phenolic compositions also showed significant differences, and gallic acid was the most important part. The contents of trace elements K, S, P, and Mg showed much higher than those of Fe, Zn, Cu, Mn, Ca.The weight of samples decreased for different degrees during the cooking processes, and frying and microwave treatments led the greatest decrease of the fresh weight. Boiling treatment significantly (p<0.05) decreased the ash content, while, frying significantly (p<0.05) increased the ash content. Frying treatment also significantly (p<0.05) increased the crude fat content, while, other cooking methods showed little effects. Frying and boiling treatments significantly (p<0.05) decreased the crude protein contents, while, steaming and microwave cooking treatments showed little effects. The effects of microwave, steaming and high pressure cooking treatments on the soluble protein contents showed little differences, while, frying and boiling significantly (p<0.05) decreased the soluble protein contents. Frying and steaming could increase the contents of soluble dietary fibre, while, high pressure cooking, microwave cooking and boiling treatments decreased that. The insoluble dietary fibre contents increased after all cooking treatments, and frying and steaming showed significant (p<0.05) effects. Steaming and microwave cooking showed little effects on the contents of ascorbic acid, while, frying and boiling treatments significantly (p<0.05) decreased it. After frying, steaming, and high pressure cooking treatments, the available carbohydrates contents of some Boletus sp. significantly (p<0.05) increased, while, boiling decreased it. Frying and boiling treatments affected the monosaccharide compositions sharply, while, steaming and microwave cooking showed little effects. Frying could increase the total amino acid contents and amino acid compositions of Boletus sp.. Frying and boiling significantly (p<0.05) decreased the total phenolic contents. Different cooking methods showed different effects on the phenolic compositions. After frying, the contents of trace elements were increased. Steaming, high pressure cooking, microwave cooking, and boiling treatments decreased those.The antioxidant activities of80%methanol extract of Boletus sp. with or without cooking treatments were also evaluated and compared, by DPPH radical scavenging activity assay, reducing power assay, hydroxyl radical scavenging activity assay and lipid peroxidation ability assay. Effects of cooking methods on DPPH radical scavenging activity varied according to the species of Boletus samples, however, boiling decreased the DPPH radical scavenging activity of Boletus sp.. Cooking treatments decreased the reducing power of Boletus sp.(except for Boletus pinophilus), and the influences showed greater by boiling and frying treatments. The effects of cooking treatments on hydroxyl radical scavenging activity varies between different kinds of Boletus sp.. Frying treatment significantly (p<0.05) decreased lipid peroxidation ability, while, boiling and high pressure cooking treatments affected it little. |
