There is quite a general belief among millers, bakers, and the laity that flour improves on ageing. However, there is no definite information as to the time requisite for this improvement nor whether it reaches a maximum and then deteriorates. The information is no more exact as to the changes which occur during the ageing process or the conditions which govern them. We have found no reference in the literature where bad effects have resulted from storage, provided a highly-milled, sound flour is stored in dry, well-ventilated rooms free from odors (20). The results which have been reported point to the conclusion that the same improvement occurs whether grain or flour be stored (8, 14). When the grain is stored the time necessary for the change to become perceptible is greater than when flour is stored (14, 15).
Greaves, J. E. and Hirst, C. T., "Bulletin No. 194 - The Influence of Storage on the Composition of Flour" (1925). UAES Bulletins. Paper 159.