The way mushrooms are cooked influences their nutritional quality and their antioxidant capacity. Spanish researchers have shown that preparing mushrooms by boiling, in the microwave or on the grill allows this food to be preserved as well as possible.

Rich in fiber, sources of vitamins (B1, B2, B12, C, D and E) and trace elements such as zinc or selenium, low in calories and fat, mushrooms are an important source of compounds biologically assets with potential medical value (such as beta-glucans). They are usually cooked before being eaten. The results of a study, published in May 2017 in the International Journal of Food Sciences and Nutrition, revealed that the way they are cooked changes their composition to varying degrees.

4 tested cooking methods

Which cooking method should be used to preserve all these nutritional values? This is the question addressed by the group of scientists from the “Center for Technological Research on Mushrooms of La Rioja” (CTICH, a public body in this Spanish autonomous community where mushroom cultivation is important). They assessed the influence of four common cooking methods (boiling, microwaving, grilling and frying) on ​​the immediate composition, beta-glucan content, and antioxidant activity of four of the most widely consumed cultivated mushroom species. in the world: Agaricus bisporus (button mushroom), Lentinula edodes (shiitake), Pleurotus ostreatus (oyster mushroom) and Pleurotus eryngii (Panicaut oyster mushroom). They were collected in the culture rooms of the CTICH facilities. After the cooking process, the raw and cooked mushrooms were freeze-dried, then their composition and antioxidant activity were analyzed.

Frying greatly reduces the protein content

The results showed a decrease in the protein and mineral content (ash) in cooked mushrooms compared to raw materials. It is cooking by frying that induces the most severe losses in proteins and carbohydrates: “This decrease [in proteins] is explained by the high temperatures during frying because the oil can reach up to 175 ° C. It is well known that heat treatment can reduce the amount of protein and destroy certain amino acids, changing the quality of the protein composition in food, ”explains Irene Roncero, author of the study. Conversely, the researchers found an increase in energy and fat. This increases from an average of 2.1% of dry matter before frying to between 45 and 60% after frying, depending on the species.

The benefits of microwave and grilling on antioxidant activity

A significant decrease in antioxidant activity was detected, especially after boiling, but also after frying, unlike grilling or microwave cooking. In this case, the boiled and fried mushrooms had the lowest values, probably due to leaching, that is, the loss of compounds soluble in water or in oil. In the microwave or grilled, the mushrooms reached higher values ​​of antioxidant activity: “The polyphenol and antioxidant content then increased significantly”, specifies Irene Roncero. However, only boiling interestingly increases the total glucan contents, improving the beta-glucan fraction in button mushrooms by up to 30%. Grilling and microwaves mean a slight change in beta-glucan content: respectively + 11% and + 4% beta-glucans in button mushrooms, and -5% and -3.5% in Panicaut oyster mushrooms. Thus, there would not be an ideal method to preserve the composition of mushrooms. Boiling, microwaves and grilling have little influence on the caloric value of food after cooking; frying, however, is not to be recommended. The ideal could therefore be found in varying cooking methods: boiling to get the most out of beta-glucans and microwave or grilling to get the most out of the antioxidants