The tannoid content test, introduced by Chapon, is accepted as a recommended MEBAK analytical method for the detection of haze-forming polyphenols in beer and other intermediates. Under certain conditions, the results can be used directly for predicting the colloidal stability of beer. Its disadvantage is that it does not provide detectable results for beers stabilized by high doses of polyvinylpolypyrrolidone (PVPP). A test modification is proposed that increases the test sensitivity and gives non-zero results, even for highly stabilized samples that are not measurable by the standard test. The modification is based on adding saturated ammonium sulphate solution (SASS) to the sample to reach 9% saturation (0.5 mL of SASS to 5 mL sample volume) before the actual test performance. The results of the modified test can simply be converted to results obtained by the standard method. Tannoid content correlates linearly with the content of haze-forming polyphenols and with chill haze produced after defined accelerated aging. In a set of beer samples of one brand having different degrees of stabilization, a high correlation was determined between test results and long-term colloidal stability. The modified test can be used as a rapid and simple test for checking the stabilization process. It is particularly suitable for Pilsner type beer of long (more than 6 months) colloidal stability controlled by stabilization on the side of polyphenols.

No abstract

Abstract. Density of supercooled water at elevated pressure is interesting because of the strong anomalies which can be explained by existence of a liquid-liquid critical point in the region of supercooled water. In order to provide accurate data for density at these conditions a procedure was developed to calibrate the course of the inner cross section of a capillary along its length. Further, the image analysis for the sub-pixel evaluation of meniscus postion is described.

A rapid high-throughput test for prediction of beer colloidal stability has been developed and evaluated. The method is based on the procedure of aging accelerated by high temperature (60°C). The aging process is accelerated through decarbonization and defined oxidation of the sample. A significant correlation was observed between the results of this rapid test and a standard accelerated aging test. The method can be used as a rapid and simple test for checking the efficiency of the stabilization process. The duration and sensitivity of the test can be modified by adjusting the test parameters.

We describe here a newly developed method for a contact-free optical pH measurement in yeast suspensions supplemented with glucose, and containing the pH sensitive triphenylmethane dye bromocresol green. It is suitable for performing the acidification power test (based on measuring the rate of pH drop of yeast suspension caused by active extrusion of acidity from cells after glucose addition) used for assessing yeast vitality in fermentation industries. Using this methodology we monitored the pH in yeast suspensions in the course of acidification in the pH range of 3.5-5.3. Optical pH measurement allows simultaneous testing of several samples, minimizes the sample volume, simplifies sample handling and reduces the hands-on time in sample processing.