Authentication of Jarrah (Eucalyptus marginata) honey through its nectar signature and assessment of its typical physicochemical characteristics

Abstract

Jarrah (Eucalyptus marginata) is a dominant forest tree endemic to the southwest of Western Australia. Its honey is appreciated for its highly desirable taste, golden colour, slow crystallisation, and high levels of bioactivity, which have placed Jarrah in the premium product range. However, whilst customers are willing to pay a high price for this natural product, there is currently no standard method for its authentication. As honey is naturally sourced from flower nectar, a novel route of authentication is to identify the nectar signature within the honey. This study reports on a high-performance thin layer chromatography (HPTLC)-based authentication system which allows the tracing of six key marker compounds present in Jarrah flower nectar and Jarrah honey. Four of these markers have been confirmed to be epigallocatechin, lumichrome, taxifolin and o-anisic acid with two (Rf 0.22 and 0.41) still chemically unidentified. To assist with the characterisation of Jarrah honey, a range of physicochemical tests following Codex Alimentarius guidelines were carried out. A blend of authenticated Jarrah honey samples was used to define the properties of this honey type. The blend was found to have a pH of 4.95, an electric conductivity of 1.31 mS/cm and a moisture content of 16.8%. Its water-insoluble content was 0.04%, its free acidity 19 milli-equivalents acid/kg and its diastase content 13.2 (DN). It also contains fructose (42.5%), glucose (20.8%), maltose (1.9%) and sucrose (<0.5%). The HPTLC-based authentication system proposed in this study has been demonstrated to be a useful tool for identifying Jarrah honey and might also act as a template for the authentication of other honey types.