FORMATION OF BROWNSTAIN IN INOCULATED WESTERN HEMLOCK SAP

Hemlock brownstain is a discolouration which periodically causes serio us economic losses in Canadian high-value export hem-fir lumber market s. As one working hypothesis suggests that fungi are involved in the p roduction of hemlock brownstain fungi, previously isolated from browns tained and stain-free western hemlock logs, were evaluated for their c apacity to induce browning in western hemlock sap samples. Dark-pigmen ted fungi were demonstrated to induce sap browning and the development of browning was normally accompanied by an increase in pH, a decrease in total soluble phenols and oxidation of phenols. Specific sap compo unds seemed to be required to support the occurrence of browning in we stern hemlock sap samples. Catechin was confirmed to be one compound i nvolved in sap browning. Further research investigating the effect of heat, pH and oxygen is underway to better understand the mechanisms of sap browning.