Monosodium glutamate equivalents and B-group vitamins in frozen mushrooms

In mushrooms the dominant taste is umami, which is created by monosodium glutamate (MSG)-like amino acids and 5'-nucleotides. In this research, the levels of 5'-nucleotides, free amino acids (liquid chromatography with mass spectrometry; LC-MS), and vitamins from the B-group (high-performance liquid chromatography; HPLC) in frozen white and brown Agaricus bisporus were determined. Before freezing, the mushrooms were blanched in water, and then in a sodium erythorbate and citric acid solution; next these were vacuum impregnated in a sodium metabisulphite and citric acid solution and blanched again in water. The varieties of mushrooms under analysis responded to the pretreatment, freezing, and frozen storage to different degrees. The equivalent concentration of umami was in the range of 0.293-1.709 g MSG/100 g dm and was higher by 26-444% in brown than in white mushrooms. After frozen storage, in the white variety, there was a higher synthesis of 5'-nucleotides and in the brown variety, of free amino acids. The main components responsible for the umami taste in both varieties were 5'-TMP, 5'-UMP, and L-glutamic acid. The white variety contained a higher level of vitamin B-2 and a lower level of vitamins B-1 and B-6.