Use of a Ferrous Oxidation-Xylenol Orange (FOX) Assay to Determine Lipoxygenase Activity in Barley and Malt

The objective of this research work was to develop a new high-throughput screening method for lipoxygenase (LOX) activity, which was based on the determination of lipid hydroperoxides by ferrous oxidation-xylenol orange (FOX) assay. The final method employed extraction of a finely ground sample at a grist/buffer ratio of 1:20 for 30 min at 4°C. Extracts were incubated with linoleic acid for 5 min at 25°C, and the hydroperoxides formed were determined with the FOX reagent. Up to 100 samples can be analyzed per day with this method. The new method showed good reproducibility (coefficient of variation = 1.4–6.5%) and accuracy, although there are some disadvantages and limitations compared with the traditional UV assay. The FOX assay principal may be useful to barley breeders for screening large numbers of progeny, and also would have value to maltsters and brewers when conducting research work on LOX or performing routine quality assurance.