3.3. 50-Nucleotides
MSG, 50 -IMP and 50 -GMP are mainly contributed to the umami flavour of meats. In particular, 50-IMP was first obtained from dried bonito tuna, while 50-GMP was isolated from Shiitake black mush- room in the 20th century (Maga, 1994). Chen (1986) described fla- vour 50 -nucleotides as 50 -GMP, 50 -IMP and 50 -XMP. Content of total 50 -nucleotides and flavour, which were represented by 50 -GMP only in this study, were in the range of 15.51–26.82 mg/g and 0.39–0.88 mg/g, respectively (Table 2). It is obvious that contents of 50-CMP were higher than other 50-nucleotides in P. eryngii, accounting for more than 80% of global contents. Mau et al. (1998) also reported that content of total and flavour 50-nucleo- tides, in FZ P. eryngii, were 28.80 mg/g d.b. and 1.63 mg/g d.b., respectively, with the highest content of 50 -CMP (23.00 mg/g d.b.), lowest of 50-IMP (0.42 mg/g d.b.) and no 50-XMP.
Total content of fresh mushroom got the highest value and the HA product got the lowest one. Besides, FZ and VA products were also in the high range as fresh mushroom. Meanwhile, content of flavour 50-nucleotides was significantly (p < 0.05) higher in FZ than that of fresh mushroom and other dried products. Liu and et al. (2014) showed that total content of 50-nucleotides and flavour in fresh Agaricus bisporus were slightly higher than those of the FZ product, while canning and salting process caused a great loss. It is known that the moisture in mushrooms was frozen initially, and then the ice sublimated from the solid to the vapour phase directly at a low temperature (