Calcium combined with vacuum treatment improves postharvest storage quality of Agaricus bisporus by regulating polyamine metabolism

Calcium (Ca) immersion treatment has been used for the preservation of Agaricus bisporus (A. bisporus), but the effective dosage of Ca absorption has often been disregarded. In our study, vacuum pretreatment was performed to promote Ca infiltration in A. bisporus. Vacuum pretreatment (−0.1 MPa, 5 min, Vac + Ca group) exhibited a super effectiveness in promoting Ca absorption. The results of Ca diffusion simulation using COMSOL Multiphysics showed that Ca level in the center of the sample in the Vac + Ca group increased from 0.1020 to 0.2028 g kg−1 during a period of 0 to 60 min. Additionally, the effects of Vac + Ca treatment on the polyamine (PA) metabolism during a 3-day room temperature storage of A. bisporus were investigated. Vac + Ca treatment resulted in a reduction of putrescine (Put) level and an elevation in spermidine (Spd) level, suggesting that the treatment may facilitate the conversion of Put to Spd. Interestingly, a negative linear correlation between changes in Spd level and both the browning index and weight loss, while a positive correlation was found with alterations in hardness were observed. Moreover, several amino acids and enzymes involved in PA metabolism, including arginine, methionine, ornithine decarboxylase, arginase, S-adenosylmethionine decarboxylase, and spermidine synthase, were also affected by this treatment. Therefore, the increase in Spd induced by Vac + Ca treatment may be one of the underlying mechanisms responsible for extending the postharvest lifespan of A. bisporus.