On the use of native corn starch as a standard reference material for falling number

BACKGROUND AND OBJECTIVES: Falling number (FN) is an analytical wheat quality procedure that uses viscometry to indirectly measure starch α‐amylase activity. National grain standards as well as sales contracts often contain specifications on this single‐number value. In recent years, an effort has been underway to define acceptable performance characteristics of the instruments used to measure falling number. Essential to this effort is the reliance on a standard reference material that has similar behavior of wheat, yet is more stable when stored over time. A recent study by one of the authors identified native corn starch among three other botanical starch sources as the most suitable candidate and defined the repeatability precision in the context of one laboratory possessing two identical instrument models. The current study was designed to evaluate corn starch in a network of eight instruments located throughout the continental United States, with the intention of producing guidelines for operational limits for statistical process control in a FN network. FINDINGS: Over a four‐month period, biweekly (fortnightly) FN measurements repeatedly collected on analytical grade native corn starch sourced from a common container resulted in 99th percentile estimates of the coefficient of variation of repeated measurements of 6.0% and 8.1% for two scenarios: five and three successive runs, respectfully. Estimated 1st and 99th percentile FN limits, expressed as percentages for a laboratory's mean value compared to other laboratories in a network, were −10% and 10% for both scenarios. Additionally, the time‐stable nature of corn starch as a reference standard was verified, with seven laboratories showing no statistically significant linear trend with time and the eighth showing a very weak trend. CONCLUSIONS: Native unmodified corn starch may be used as a standard reference material in a network of FN instruments. The material is shelf stable at room temperature and produces intra‐ and inter‐laboratory precision equivalent to that of ground wheat meal, with the added benefit of being stable over time. SIGNIFICANCE AND NOVELTY: The findings may serve as a basis in establishing operational limits for statistical process control in FN networks.