Determination of the influence of starch sources and mashing procedures on the range of the molecular weight distribution of beer using field-flow fractionation

摘要

To produce experimental beers, different mash mixtures (barley malt, barley malt + 30% pre-cooked maize, barley malt + 30% nonmalted spelt) and distinct mashing procedures (infusion and decoction) with variations of the rest time and initial temperatures were evaluated. The range of molecular weight distribution (MWD) of the resulting beers was determined using asymmetrical flow field flow fractionation coupled to multiangle laser light scattering and refractive index. There were no differences on the range of MWD among the beers, according to infusion or decoction, using similar raw materials and initial temperatures (45 and 55℃). However the range of MWD was higher (p < 0.005) when using infusion at an initial temperature of 63℃, regardless of the raw material. The use of maize did not alter structural properties of the beer, while mash containing nonmalting spelt caused an elevation on the MWD (p < 0.001) and a lower (p < 0.05) apparent degree of fermentation. Therefore the range of the MWD of the beers was influenced by the quality of the raw material and the initial mashing temperature, whereas apparent degree of fermentation values were affected only by the type of starch source. Thus the determination of the MWD is an important tool for monitoring the production of beer.