Changes in metabolite concentrations detected by C-13-NMR in the senescing mushroom (Agaricus bisporus)

Extracts of the cap, gill and stipe of the fruiting body of the mushroom (Agaricus biporus) were studied by C-13-NMR spectroscopy. This technique enables changes in the main metabolite pools to be studied simultaneously as a function of storage time, temperature and postharvest development. An earlier reported reduction in dry weight of the stipe could be explained by a decrease in mannitol content. At 1 degrees C storage temperature, no postharvest development occurred, yet mannitol content decreased. It is concluded that mannitol is probably used as a respiratory substrate in gill tissue. Proteolytic breakdown was apparent, even during storage at 1 degrees C, but occurred preferentially in the stipe. The products are most probably used by the gill and to a lesser extent by the cap to maintain metabolic activity as demonstrated by urea-cycle activity. Changes in the content of four amino acid pools (glutamate, glutamine, alanine and aspartate) proved to be tissue-specific, as were changes in the content of mannitol, fumarate and malate. (C) 1997 Elsevier Science B.V.