A Comparison of Visual Turbidity with Turbidity Measured by Commercially Available Instruments

Abstract

A formulation for visual turbidity standards was developed using uniformly sized latex spheres as the turbidity source. The visual standards were used to determine the turbidity of process samples and punished beer so that visual assessments could be compared with readings obtained using various commercially available laboratory turbidity instruments. All of the commercially available instruments demonstrated good reproducibility and linearity, and most were only slightly affected by beer color or bottle type. However, their response in comparison with visual observations varied. The scatter angle employed in the measurement and the particle type were both significant factors. For a given visual turbidity level caused by many process particles, those instruments employing an 11° scatter angle measurement produced the largest response, followed by smaller responses for 25 and 90° scatter measurements. However, for very small particles, such as the 0.222-μm spheres used in the visual standards, readings were largest at a 90° measurement angle, with lower response at 25 and 11° measurement angles.