Abstract
5´-Nucleotides, especially 5´-GMP, and free amino acids are major umami components in mushrooms. While raw mushrooms contain little 5´-GMP, the results of our study revealed that the content was significantly increased by heating, and further increased by freezing and heating. In this study, three commercial mushroom varieties: nameko (Pholiota nameko), bunashimegi (Hypsizigus marmoreus), enokitake (Flammulina velutipes) were evaluated. The mushrooms were divided into four treatment groups: raw, heated, frozen, and frozen/heated, and 5´-GMP and free amino acid contents were determined. Additionally, sensory evaluation was performed on the cooked mushrooms subjected to heating alone or heating after freezing. The following results were obtained.
(1) All mushrooms contained high 5´-GMP when subjected to freezing/heating. Under this treatment, 5´-GMP content was the highest in P.nameko and lowest in H.marmoreus.
(2) Free amino acid content exhibited only small changes under the treatments.
(3) Sensory evaluation of P.nameko heated after freezing indicated high palatability. Thus, it was concluded that P.nameko is suitable for freezing. The frozen/heated H.marmoreus sample showed decreased chewiness and palatability, and was therefore determined to be unsuitable for freezing. Additionally, F.velutipes did not exhibit differences between heated and frozen/heated samples, and was thus found to be suitable for freezing.
