The physiological and biochemical consequences of water uptake by the barley grain are reviewed, and their significance in malting assessed.

Laboratory investigations of the quality of worts produced from green malt, from mixed grists of green malt and unmalted cereals, and by the action of commercial enzymes on barley starch are described. Green malt alone gives sweet worts which are very highly fermentable and contain much nitrogenous material but are of very reduced anthocyanogen content. Satisfactory yields of extract are obtained in the conversion of unmalted cereals by green malt if they are finely ground. Additional treatment such as presoaking or gelatinization usually further increases the extract and is essential where certain enzyme preparations are employed.

To provide a detailed picture of wort composition, values for the concentration of individual compounds present in wort have been collated. Information on the compounds is grouped into sections covering total solids, carbohydrates, nitrogenous substances, hop substances, lipids, tannins, sulphur compounds, dissolved oxygen, phosphates, inorganic constituents and other substances. Wherever possible, the effects of variation of grist composition and of mashing and boiling conditions on wort composition are given. Brief notes on the fate of individual constituents during fermentation are also included.

Glucan, mannan, chitin, protein, phosphate and lipid are found in the walls of all brewing yeasts so far examined although the contents and composition of each varies, as does the content of wall in the cell. Both glucan and mannan have branched structures and are linked to protein. Chitin is probably also bound to protein and phosphate to mannan. Some of the enzymic activities present in the wall are associated with the mannan‐protein fraction. This fraction is located on the outer surface of the wall and appears to play a part in the appearance of flocculence in brewing yeast during fermentation.

A comparison has been made of methods of determining the starches in barley and malt, and satisfactory procedures have been worked out. Analyses were usually carried out on materials in which the enzymes had been inactivated and from which the simpler carbohydrates had been removed by means of aqueous ethanol and water. Starch in this material was gelatinized with hot water and then dispersed With chloral, perchloric acid, sodium hydroxide, formamide or ammonium carbonate or with enzymes. Although each of the first four reagents proved to be excellent for dispersion, the procedure which was also most rapid and which gave precise and accurate results involved the use of aqueous perchloric acid. The starch was recovered quantitatively from each of the extracts by precipitation with iodine and was estimated as glucose directly with anthrone‐sulphuric acid reagent. The determination of glucose after hydrolysis of the starch with dilute acid was found to be less satisfactory, in that appreciable degradation of the sugar occurred during hydrolysis.