CARBOHYDRATES IN MALTING AND BREWING IV. DETERMINATION OF STARCH IN BARLEY AND MALT

Abstract

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.