CaCl₂ treated irrigation water applied to mushroom crops (<i>Agaricus bisporus</i>) increases Ca concentration and improves postharvest quality and shelf life

Abstract

Four crops of off-white hybrid mushrooms, Agaricus bisporus, irrigated with regular tap water (controls) and four crops irrigated with 2.8 × 10-2 M CaCl2 (DowFlake® Process Grade, 77–80%) added to tap water (treatments) were grown. Addition of CaCl2 to the irrigation water significantly improved color of mushrooms at harvest without reducing crop yield. Dry matter content and size of mushrooms were not affected by the treatment. Ca concentration of fresh mushrooms was significantly increased (P<0.05) by the treatment in both the second and third flush of the crop cycle. Ca concentrations were approximately doubled (~100 to 200 mg/kg, dry weight). Cu was found in lower concentrations than Ca within the mushroom and was not affected by addition of CaCl2 to irrigation water. Ca concentration was found to be significantly increased in all tissues of second flush mushrooms except in the outermost layer of the cap tissue. Cu was found to be distributed more evenly than Ca in different tissues of the mushroom. Postharvest browning was significantly reduced in mushrooms from the second flush (P<0.05) and the third flush (P<0.10). Color of mushrooms during storage was significantly improved by the CaCl2 irrigation treatment but maturation, as measured by cap expansion, and weight loss of stored mushrooms were not reduced by the treatment. Ca concentration was found to have a significant positive correlation (r = 0.39) with color at harvest. A significant negative correlation (r = -0.45) was observed between Cu concentration in fresh mushrooms and color (L-value). The ratio of these two minerals, Ca to Cu, was found to have the most significant positive correlation (r = 0.58) with color (L-value) at harvest.