Estimation of Nitrogen in Yeast and Brewing Materials

For nearly fifty years now, since the pub lication by Kjeldahl (Medd.Carlaberg Lab., 1883, 2, 1) of the method of digestion of the substance with sulphuric acid, the estimation of nitrogen in yeast and other brewing materials has been carried out by this method in its original form or by the modi fication known as the Kjeldahl-Gunning method.The latter has the advantage of taking much less time than the original method, though in the end both give the same values for nitrogen with the materials under discussion.The confidence of brewers' chemists in the reliability of the Kjeldahl or Kjeldahl-Gunning method remained unshaken until the publication by Christensen and Fulmer {Plant Physiol.1927, 2, 455) of a modified method using hydrogen peroxide, by which they claimed they obtained higher values than those given by the Kjeldahl-Gunning method.Subsequently H. ter Meulen (Rec.Trav.Chim.Pay Bos, 1930, 49) employing his hydrogenation method {ibid 1924, 43) also obtained higher nitrogen values, for yeasts, worts and other materials, than those given by the Kjeldahl-Gunning method.Thome (this Journ., 1932, 23) published results which confirm the work of Christensenand Fulmer and recently Case and Price (this Journ., 1933, 35) have given some figures which seem to support Thome's.