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Origins of the Poor Filtration Characteristics of Wheat Starch Hydrolysates

¹Agrotechnological Research Institute DLO, P.O. Box 17, 6700 AA Wageningen, The Netherlands. ²Netherlands Institute for Carbohydrate Research TNO Rouaanstraat 27, 9723 CC Groningen, The Netherlands. ³Corresponding author. Phone: +31 50 3694628. Fax: +31 50 3128891.

The effects of wheat starch components on the filtration characteristics of wheat starch hydrolysates were investigated with a model-based approach. The filtration rate was not affected by the removal of the pentosans or by altering the conformation of the protein. On the other hand, the filtration rate increased when a hydrolysate was defatted with chloroform or butanol. Some commercially available enzymes also increased the filtration rate. The filtration rate of potato starch hydrolysates decreased when gluten, pentosans, solubles, or propanol extract from defatted wheat starch were added. The latter had by far the largest effect. The composition of this extract was 65% lipid and 11% protein. The main lipid in wheat starch is lysophosphatidylcholine (LPC). This single-chain lipid forms micelles above a concentration of 0.025 g/kg. The filtration rate decreased when LPC was added to potato starch hydrolysates or glucose solutions at concentrations above the critical micelle concentration. This effect of LPC on glucose solutions proves that the filtration characteristics are not related to the formation of amylose-lipid complexes. Therefore, micelle formation must be responsible for the effect of LPC on the filtration rate. The critical micelle concentration is only 2.5% of the amount of lysophospholipids in wheat starch hydrolysates. Thus, almost all of these lipids have to be removed from wheat starch hydrolysates to increase the filtration rate.