FACTORS AFFECTING THE PRECISION OF DIETARY FIBER MEASUREMENTS IN POTATOES

The measurement of dietary fiber in foods is becoming increasingly imp ortant. In the widely accepted gravimetric methods for measuring fiber , a common feature is the use of crucibles, with sintered glass frits, to collect insoluble and precipitated material; in this laboratory, P 2 crucibles are used in insoluble fiber determinations. Evidence from 3 experiments indicated a significant among-crucible variance componen t (P < 0.001) that was at least 50% larger than the residual variation ; this component may be as large as the commonly encountered among-tim e component. The crucible effect has implications with respect to expe rimental design, data analysis, and measurement of insoluble fiber in particular materials such as biological reference materials.