A method relying on the Dumas Combustion Principle for the determination of total nitrogen in barley, malt and beer has been collaboratively tested by the Analysis Committee of the Institute of Brewing. "Kjeldahl" procedures were used for comparison. The Committee approved the adoption of the Dumas procedure as the reference method for barley and malt. Precision values were independent of total nitrogen content for barley and malt, over the range 1.17 to 1.71 %m/m and 1.45 to 2.03 %m/m (as is) respectively. Repeatability {rgs) and reproducibility {Rg 6 ) values were 0.030 and 0.070 respectively for barley and 0.036 and 0.065 respectively, for malt, over the given ranges. Slightly higher values were obtained for total nitrogen by the Dumas method, compared with those given by Kjeldahl procedures.
A method employing gas chromatography for the determination of ethanoi in beer has been collaboratively tested by the Analysis Committee of the Institute of Brewing. It was judged that precision values were independent of concentration over the range 0.93 to 6.05% V/V ethanoi. Repeatability (r8S) and reproducibility (/?.») values of 0.061 and 0.136 respectively, were obtained over this range. At a mean level of 9.17% V/V, the r9B and fls5 values were 0.154 and 0.284 respectively. This was probably due to dilution errors as the sample had to be diluted to bring it within the linear range of the method. A comparison of the precision values given by the gas chromatographic method, with those obtained in 1991/1992 by 8 laboratories in a major brewing company using 12 sample pairs, for the IOB Rec ommended Distillation Method, revealed that there is no significant difference between the precision data for the two methods.
Pilot scale trials have been carried out to determine the nature and patterns of evolution of com pounds present in condensates obtained from boiling worts at atmospheric pressure.Analytical procedures involving gas chromatography and gas chromatography-mass spectrometry have been used to identify 70 compounds in condensates from unhopped ale worts. Over 30 of these volatile compounds have been classified according to one of three patterns of evolution. The rate of evolution for one class remained constant throughout the boiling period, for the second class decreased gradually towards the end of boiling, and for the third was sufficiently rapid to lead to the removal of most of a component during the early stages of boiling. Many of the com pounds identified in the condensates are highly flavour-active.
This review describes the developments in barley and malt analysis since 1960, the suitability of analyses commonly used at present, and changes which are likely to occur in future. The review is not restricted to analyses suitable for brewers and distillers but also discusses methods used in the control of malting and in the selection of barley for malting.
A survey of haze meters that are currently available has been carried out to find out whether an instru ments) can be recommended for use by the brewing industry. There is a marked difference between values measured by instruments reading at 13s and 90°scatter. There are very minor differences in the haze values obtained using the various 90°instruments. Overall the Hach meter is recommended as a replacement for the Radiometer.Suspensions of styrene divinylbenzene beads were judged to be suitable as an alternative to Formazin for standardising haze meters.Key words: calibration, haze meters, brewing. IntroductionProduction of the Radiometer haze meter7 has ceased, and the manufacturer does not intend to offer a replacement. Even though this instrument is very widely used, it has never been officially recommended by either the Institute of Brew ing or the European Brewery Convention, although they have adopted a preparation of Formazin, which is used in the Radiometer, as a haze standard.Il2>5 The preparation described is the basis of the definition of the E.B.C. Forma zin Haze Unit. Instruments that are currently being used or evaluated rely on light scattered at either 90°or 13°. Some beers which appear bright to the eye give substantial read ings in haze meters which depend on light scattered at 90°. Such beers are said to contain the so called 'invisible haze', or 'pseudo haze'. Measurements on beers containing these hazes, using 13°instruments give low values, which arc in agreement with visual assessments.A survey has been carried out to find whether any alterna tively available haze meters can be recommended as a stan dard to give realistic assessment of beer quality. In addition alternative materials, such as polymer and latex beads have been evaluated, in an attempt to find a more realistic TABLE I. Details and specifications of haze meters standard to Formazin for calibrating haze meters. Current understanding of haze measurement suggests that although accurate determination of particle size and particle disper sion can be achieved, this will not be accomplished in any single, economically priced quality control instrument. Haze MetersIn the search for an alternative to the Radiometer haze meter for the measurement of beer clarity, the following instruments were evaluated at the Brewing Research Details and specifications For the instruments evaluated are given in Table I. Results and DiscussionThe evaluation was designed to assess the reliability, ease of operation, stability and linearity, i.e. the meter response to corresponding additions of haze material made in water, lager and pale ale. In addition the effect of colour, particle size and different types of haze material was studied. Further more, instrument response was compared with a visual assessment of the samples under test. LinearityAs an arbitrary value the instruments were standardised against a Forrnazin solution of 2-0 E.B.C. units. The Formazin additions were made to distilled water, a lager (colour 11°EBC) and a pale ale (colour 25°EBC...
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