Turbidimetric Behavior of Colloidal Particles in Beer Before Filtration Process

Abstract

The effect of colloidal particles and yeast on turbidity of Pilsen beer before the filtration process was studied in this work. The colloidal particles are mainly composed of polysaccharides, representing 96.89 %, in second place proteins with a concentration close to 2 %, and polyphenols less than 0.3 %. There is also a very low concentration of yeast (;lt;0.25 %). The presence of different types of particles in the sample caused multimodal histogram in the particle size distribution and four distinct zones were identified: (1) very small individual particles (D = 0.06μm),(2) yeast(D = 3μm) (3) colloidal aggregates (D = 17μ), and (4) a zone with a high dispersion of size, with two D Values (101 and 200 μm). Particles size counts well correlate with both the scanning electron microscopy (SEM) digital image analysis, and the turbidity determination. The fractal dimension (Df) of the aggregates was determined by analyzing the SEM images with the Variogram method, obtaining Df > 2.4 values. Those values are typical of aggregates formed by rapid flocculation or diffusion limited aggregation. Results of this study support the formulation of a model valid for the prediction of colloidal particles concentration in beer.