Floral extract from four clones of Boronia megastigma (Nees) throughout flowering

Abstract

SummaryThe rates at which flowers reach anthesis on four genetically distinct clones of brown boronia grown at different sites in Tasmania were examined. The yield of flower material per plant and the concentration of extract, total volatiles and b-ionone (% dry weight) were assessed throughout the flowering period via small- and pilot-scale extractions. Organoleptic assessment of absolutes was done. The four clones had similar concentrations of extract when harvested at between 50 and 80% open flowers (1.5–2.0% d.w.). The concentrations of total volatiles and b-ionone were reduced in pilot scale extractions compared with small-scale extractions. Inter- and intra-sample variability was high; there were no significant trends in the concentration of total volatiles or b-ionone in any clone. The yield of dry flower weight per plant varied between clones throughout flowering. Clones No. 3 and No. 5 progress through flowering earlier than clones No. 17 and No. 250. Despite the reduction in extract concentration in late flowering in clones No. 3 and No. 5, flower yield per plant was maintained, ensuring good yields of extract per ha even if flowers were harvested later than at the optimum for extract concentration. The organoleptic qualities of the absolutes made from clones No. 3 and No. 5 at 90% open flowers and clones No. 17 and No. 250 at 75% open flowers were most typical of the commercial product, having fruity top notes and an intense floral background. In terms of the yield of flowers and extract, and the organoleptic properties of the extract, clones No. 3 and No. 5 can be harvested until 90% open flowers, whereas clones No. 17 and No. 250 can be harvested at 75–80% open flowers. At many sites, it is likely that the four clones would simultaneously be ready for optimum harvest given the rates at which flowers on each clone open. This work represents the first documentation of the effect of harvest timing on extract concentration and organoleptic properties of extract from different clonal types of brown boronia.