USE OF YEAST CRUDE EXTRACT FOR SEQUENTIAL INJECTION DETERMINATION OF CARBOHYDRATES

A sequential injection procedure for enzymatic-potentiometric determination of non-structural carbohydrates content (sucrose, fructose and glucose) in forrage plants was developed. In the proposed methodology, a yeast crude extract (Saccharomyces cerevisae) solution was employed as source of invertase to promote the sucrose hydrolysis. Periodate reduction monitoring was used as quantitative parameter. The periodate remained from reduction reaction between IO-4 ions and sugar reducing units was monitored using a periodate tubular selective electrode. Agreement results were obtained when the developed procedure was compared with the spectrophotometric method used for carbohydrate determination (anthrone). Detection limit of 0.13% (m v-1) sucrose, relative standard deviation <2.0% (n = 10) and analytical frequency of 24 samples h-1 could be observed when 280 µl of sample and yeast crude extract with activity around 5,000 I.U. were employed. The use of crude extract solution associated with sequential injection approach was easy to perform and presented reproductive results.