On the Large - Scale Isolation of Water - Insoluble Cell Wall Material from Wheat Flour

Nonstarch polysaccharides (NSPs) are believed to have an influence on the baking performance of wheat flours due to their high water-binding capacity. Much attention has been given to the isolation and characterization of water-soluble NSPs. The chemical structure as well as the physicochemical and baking properties of the water-insoluble NSPs have been less well characterized. In order to study the relation between chemical structure and physicochemical and baking properties, large amounts of water-insoluble cell wall material (WIS) are necessary. Various procedures have been reported for the isolation of WIS. Most isolations involve centrifugation of flour-and-water suspensions (Yamazaki 1955, Markwalder 1975, Kim and D'Appolonia 1976, Abdel-Gawad 1982) or dough washings (D'Appolonia and MacArthur 1975), resulting in a sludge layer that is further purified. In order to get a distinct sludge layer, high centrifugation speeds must be applied, which means that only small volumes can be centrifuged at a time. Alternative isolation methods are based on wet-sieving and ultrasonication in aqueous ethanol (Mares and Stone 1973) or removal of starch and intracellular protein by organic solvents (Selvendran and Du Font 1980). Most of the isolation methods yield cell wall material that contains large amounts of intracellular protein and/or starch. Usually quantities up to 5 g of cell wall material are obtained. The centrifugation of large amounts of material as a first step of the isolation procedure hinders rapid upscaling of the procedure. Therefore, when larger quantities of WIS are required these methods become very labor-intensive. Recently we reported the isolation of highly purified WIS based on dough washing followed by wet sieving (Gruppen et al 1989). This method circumvents the labor-intensive centrifugation as a first step of the isolation procedure. In this study we describe the upscaling of our method to yield 100-g quantities of WIS.