Colour quality assessment of commercial white Agaricus bisporus mushrooms

This study evaluated mushroom colour quality characteristics in terms of L*, a*, b* and Δ E ab * values for commercial white Agaricus bisporus (Lange) Imbach mushrooms from three different flushes and six different growers. The results indicated that there was a very significant effect of grower on mushroom colour quality (P < 0.0001), with some growers producing consistently higher quality than others. Colour characteristics for 900 mushroom samples were L*, 81–97, a*, −1.6 to +2.1 and b*, 6.5–15.1. There were moderate but significant differences in colour quality between flushes (P < 0.0001), but this was not replicated at the farm level where some growers produced consistently high colour quality across three flushes. Data from the top 25% of mushrooms with the highest L* values (reflecting brightness/whiteness) were used to calculate average L*, a* and b* values of high-quality commercial white mushrooms (CWM) which were L* = 96, a* = −1 and b* = 8. These values were used as standard reference values for L 0 * , a 0 * and b 0 * in the calculation of Δ E ab * , to give Δ E CWM * , which measures the colour difference between samples and a standard. Δ E CWM * values were compared to Δ E Ajlouni * values for white mushrooms, which were calculated using different reference values for L 0 * , a 0 * and b 0 * . Δ E Ajlouni * values for mushrooms in this study were all >7, whereas Δ E CWM * values were frequently close to 0. Mushroom colour characteristics L* and a* correlated more strongly with Δ E CWM * than Δ E Ajlouni * . We propo