A MEANS TO REDUCE FORMATION OF PRECURSORS OF 2-TRANS-NONENAL IN BREWING*

A method is described whereby the precursors of 2-trans-nonenal may be estimated in worts and beers. Treatment of malt grist or malt with a variety of polar substances is shown to reduce or eliminate the production of nonenal precursors during mashing. Beers made from worts so treated have enhanced flavour stability over those made conventionally.     

THE DETERMINATION OF GERMINATED GRAINS IN BARLEY

A method for determining germinated grains in barley by detecting the presence of α-amylase activity in individual corns is recommended.     

ANALYSIS OF N-NITROSODIMETHYLAMINE IN MALTED BARLEY

Various methods for extracting nitrosodimethylamine (NDMA) from malt, prior to measurement using a Thermal Energy Analyser, have been assessed by the Working Party, and two methods have been evaluated in a collaborative trial. A total coefficient of variation of 14% at the level of 3μg kg^?1 was obtained with a procedure involving cold-aqueous extraction of malt followed by partition against organic solvent. This is satisfactory for present purposes. In view of continuing developments the method is not issued formally as a Recommended Method of the Institute of Brewing but laboratories are recommended to use the method if they are entering this field of analysis or as a referee method in the case of dispute.     

CALCULATION OF CALORIFIC VALUE OF BEER

It is recommended that the calorific value of a beer should be calculated from estimations of the alcohol, total carbohydrate and protein content.     

OXYGEN LEVELS IN AIR-SATURATED WORTS

The dissolved oxygen contents of air-saturated worts and sucrose solutions determined with an internally calibrated polarographic oxygen electrode show a linear decrease in the gravity range 1.016–1.075. The level at S.G. 1.040 is 8.5 mg/litre at 20 °C.     

SEPARATION OF NITROGENOUS CONSTITUENTS OF MALT,WORT AND BEER USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

High performance liquid chromatography has been used to separate groups of soluble nitrogenous compounds in malt. Malts are extracted with water at 5°C and the nitrogenous components separated using a column packed with a material designed specifically for the analysis of proteins and peptides. The procedure is suitable for routine use and can be readily adapted to study changes in the development of nitrogenous compounds during the brewing process.     

MEASUREMENT OF RESIDUAL CARBOHYDRATE IN BEER

No standardized method exists for the determination of total or individual carbohydrates in beer and this could cause difficulties in view of regulatory requirements for labelling. A comparative study of known methods likely to be most suitable for the measurement of total carbohydrate in beer was therefore undertaken. Methods were also examined for estimating other important residual carbohydrates in beer, such as residual fermentable carbohydrates, β-glucan, total fructose and fructosans, and total pentose and pentosans. The beers analysed covered a wide range of carbohydrate levels and, as expected, the different methods gave different values for the carbohydrate content of the same beer. We consider that the colorimetric anthrone-sulphuric acid procedure (Yadav's version) is to be preferred for estimating the total residual carbohydrate content of beer. It is less prone to interference, relatively simple, rapid and gives more accurate results than acid or enzymic hydrolysis in combination with reductometric procedures. The within-laboratory coefficient of variation is 1.68%.     

APPARATUS AND PROCEDURE FOR REPRODUCIBLE,HIGH-RESOLUTION GAS CHROMATOGRAPHIC ANALYSIS OF ALCOHOLIC BEVERAGE HEADSPACE VOLATILES

A readily established method is reported for concentrating headspace volatiles on a bed of the porous polymer, Chromosorb 105. The trapped components are transferred by a desorption technique onto a small plug of SF96 coated support material. The volatiles can then be injected onto a high-resolution gas chromatographic column by a simple process. The apparatus required and the steps involved in the procedure are discussed in detail. The precision of the method for the quantitative determination of alcoholic beverage headspace volatiles is assessed for a range of typical compounds. Examples are given of applications of the technique to the analysis of alcoholic spirits and beverages.