Postharvest and postmilling changes in wheat grain and flour quality characteristics

Background and objectivesSoft red winter (SRW) wheat grain immediately after harvest and flour after milling were stored for 26weeks and analyzed for comprehensive milling and baking quality characteristics at different time points to examine the consistency of the quality test results. FindingsIncreases in falling number (FN) of grain during postharvest storage were observed for nine of ten varieties, in which FN ranged from 62 to 264 at 2weeks after harvest and increased by 18-109 during storage for 21weeks at 23 degrees C. Wheat grain exhibited evident fluctuations in refined flour characteristics during the first 4weeks of storage and then lesser changes with further storage. The storage time of grain did not significantly influence the milling yield, FN, and water SRC of refined flour. For refined flour during postmilling storage, storage time significantly affected all the flour characteristics, which showed evident fluctuations especially in the first 4weeks of storage. The refined flour FNs of all four tested varieties increased from 373-405 to 377-417 during the first 8weeks and then sharply to 427-474 with further storage for 26weeks. Flour pH decreased slightly for the first 2weeks after milling, was stable for the next 8weeks, and then decreased again to 5.74-5.90 at 26weeks. Small but steady decreases in both lactic acid SRC and SDS sedimentation volume were also observed for refined flour during storage. Postmilling storage induced relatively small changes in the solvent retention capacity and cookie diameter of flour. ConclusionsPostharvest and postmilling changes must be considered to achieve a reliable determination of the FN of wheat grain and flour, and pH, SDS sedimentation volume, and lactic SRC of flour. A storage time of 4weeks would reduce the variation in wheat grain and flour quality test results, allowing reliable and reproducible evaluation. Significance and noveltyThe FN of both wheat grain and flour significantly increases during postharvest and postmilling storages. The pH and protein strength of flour show small decreases during postmilling storage with even smaller changes in water retaining capacity and cookie-baking quality.