Enzyme-assisted extraction enhancing the umami taste amino acids recovery from several cultivated mushrooms

Umami is recognized as the fifth basic taste after sweet, salty, bitter, and sour, and is described by its pleasant savory or meaty flavors naturally present in many plant and animal based foods. The sodium salt of glutamic acid (Glu), monosodium glutamate (MSG), is well-known to exhibit umami-type flavors and is widely used in the food industry .The salt of aspartic acid (Asp), aspartate, also imparts umami taste in foods. The umami taste can also be achieved with the 5′-ribonucleotides such as inosinate and guanylate.

Mushrooms are widely used as raw food, functional food, and seasoning particularly due to their complex flavor and are good a source of proteins, carbohydrates, vitamins, minerals and other nutrients. They also possess a wide range of biological properties including antioxidant, antimicrobial, anticancer and immuno-modulating activities, and are also good sources of umami substances. A comprehensive review on umami based ingredients of edible mushrooms was published recently, which clearly suggests that significant amounts of free Glu and Asp are present in a wide variety of mushrooms, and their extracts found to elicit umami flavor. Among many other mushrooms, champignons (Agaricus bisporus, produced in three varieties: white champignons, cremini/brown champignons and Portobello), shiitake (Lentinus edodes) and oyster (Pleurotus ostreatus) mushrooms are the most widely cultivated edible mushrooms across the globe.

In a recent study, enzyme-assisted extraction was performed to extract umami taste and total free amino acids (FAAs) from the six different mushrooms including shiitake (Lentinus edodes), oyster (Pleurotus ostreatus), tea tree (Agrocybe aegerita) and, white, brown and portobello champignons (Agaricus bisporus). β-Glucanase and Flavourzyme® were used as the enzymes for cell wall and proteins hydrolysis, respectively. It was found that β-glucanase treatment alone did not enhance the extraction efficiency, however in combination, β-glucanase and Flavourzyme® enhanced the extraction efficiency significantly up to 20-fold compared to conventional HCl mediated extraction, depending on the mushroom species. The optimal conditions for the enzyme treatment were: water as extraction solvent (initial pH = 7), enzyme concentration of 5% v/w each of β-glucanase and Flavourzyme®, temperature 50 °C and an incubation time of 1 h. White and brown champignons were found to be the richest source of umami taste FAAs (26.75 ± 1.07 and 25.6 ± 0.9 mg/g DM, respectively).

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