Comparative Study on the Main Chemical Composition of Button Mushrooms (Agaricus bisporus) Cap and Stipe

Using agricultural waste is one of the best ways to reduce the costs and the environmental pollution. Button mushroom´s stipe is a cheap by-product that is rich in nutrients for human nutrition. The
purpose of this study is to compare the nutritional value of cap and stipe of button mushroom (Agaricus bisporus). The caps were separated from the stipes after harvesting and parameters such as moisture, protein, carbohydrates, fat, fiber, ash, minerals (potassium phosphorus, calcium, iron and selenium) and the fatty acid compositions were determined. Atomic absorption was employed to determine Iron, potassium and calcium and hydride generation atomic absorption spectrophotometry and gas chromatography were used to determine selenium and fatty acid composition of the product respectively. The result indicated that the caps on average contained 90.76% moisture and total solid content consisted of 33.65% protein, 20.59% carbohydrate, 2.48% fat, 33.11% fiber and 10.17% ash while the stipes contained 90.01% moisture where the solid content consisted of 19.01% protein, 31.41% carbohydrate, 2.00% fat, 38.08% fiber and 9.5% ash. The analysis of the extracted lipid revealed that the major unsaturated fatty acid was linoleic acid, while the predominant saturated fatty acid was Palmitic acid in both cap and stipe. According to statistical analysis, significant differences (p<0.05) were obtained between the chemical composition of caps and stipes. The results also indicated that the amount of calcium content in the stipe is twice higher than cap (2.08 g/kg) and the amount of iron and linoleic acid in the stipe is significantly higher than cap (p<0.05). The cap of the mushroom has significantly higher concentration of protein (p<0.05) than the stipes. From statistical point of view, button mushrooms stipe, contains higher quantities of fiber and carbohydrate in comparison with cap (p<0.05), that could have useful health promotion effects. Therefore, this valuable product that is often considered as an agricultural waste might be employed as a rich source of nutrients in food industries.