Some kits sold for manual enzymatic analysis of L-malic acid can’t be used effectively in an auto-analyser format, as they either lack linearity at higher substrate concentrations, on-machine stability, or the reagents are not present in optimal ratios, leading to significant wastage and thus increased cost per analysis. This kit has, however, been specifically developed for auto-analyser applications, and offers linearity up to 80 μg/mL of L-malic acid (in the final reaction solution), excellent on-machine stability and contains optimal amounts of each reagent. Polyvinylpyrollidone (PVP) has also been incorporated into the assay format to prevent performance inhibition by polyphenolic compounds (tannins). At the same time, the biochemical principle behind this assay format remains the same as all other L-malic acid kits (see equations 1 and 2 below).