Main Phenolic Compounds of the Melanin Biosynthesis Pathway in Bruising-Tolerant and Bruising-Sensitive Button Mushroom (Agaricus bisporus) Strains

Browning
is one of the most common postharvest changes in button
mushrooms, which often results in economic losses. Phenolic compounds,
which are associated with browning, were extracted from the nonbruised
and bruised skin tissue of various button mushrooms with a sulfite-containing
solution and analyzed with UHPLC-PDA-MS. In total, 34 phenolic compounds
were detected. Only small differences in the total phenolic content
between bruising-tolerant and -sensitive strains were observed. The
contents of γ-l-glutaminyl-4-hydroxybenzene (GHB) and
γ-l-glutaminyl-3,4-dihydroxybenzene (GDHB) correlated
with bruising sensitivity; for example, R2 values of 0.85 and 0.98 were found for nonbruised brown strains,
respectively. In nonbruised skin tissue of the strains with brown
caps, the GHB and GDHB contents in sensitive strains were on average
20 and 15 times higher, respectively, than in tolerant strains. GHB
and GDHB likely participate in the formation of brown GHB–melanin,
which seemed to be the predominant pathway in bruising-related discoloration
of button mushrooms.