Contribution of wheat and wheat protein fractions to the colloidal haze of wheat beers

The contribution of wheat and wheat protein fractions to the desired permanent colloidal haze in Belgian white beers was investigated using two fractionation-reconstitution experiments. In the first approach, wheat was milled into flour and bran. The flour was separated into starch, gluten, and water-extractables. The bran was further fractionated into a major water-unextractable fraction and a minor water-extractable fraction. Different laboratory-scale brews were made with a grist containing barley malt (60%) and either reconstituted wheat fractions or wheat itself (40%). The nephelometrically determined haze of the all-malt (reference) beers was significantly higher than that of the beers brewed with wheat and reconstituted wheat. The gluten fraction, containing more than 80% proteins, had a strong negative effect. In a second fractionation-reconstitution experiment, wheat whole meal was submitted to an Osborne type of fractionation. The haze readings of the experimental beers brewed with different combinations of the obtained fractions showed that the water-extractable fraction had a negative effect and the combination of the water- and ethanol-extractable fractions had an extremely negative effect on the haze intensity of the beer. It was concluded that, under the experimental process conditions used, including a 60:40 ratio of barley malt to wheat, wheat has a strong negative effect on the permanent haze intensity of Belgian wheat beers and that this effect is predominantly caused by water-soluble or (as a result of brewing) solubilized gluten proteins.