A COMPARISON OF GLUTENIN AND GLIADIN PREPARED FROM ONE FLOUR BY VARIOUS METHODS

Abstract

Gliadin and glutenin were prepared from gluten of hard red spring wheat flour by five different methods and analyzed by the Van Slyke procedure. The gliadin preparations gave very similar results, indicating that differences in manipulation have little effect on this protein. The glutenin preparations showed very great differences in nitrogen distribution, the greatest being in ammonia nitrogen and in basic nitrogen. There is considerable evidence that these two nitrogen fractions tend to be inversely proportional. This is particularly applicable to preparations made by methods involving use of alkaline solutions. Glutenin isolated by use of Blish and Sandstedt's acetic acid method, using 0.007 N acid appeared to be purer than the other preparations and contained the highest percentage of ammonia nitrogen. This protein, when dissolved in 0.025 N sodium hydroxide solution and allowed to stand for one week, lost 4.8% of its nitrogen in the form of ammonia, but the basic fraction was unchanged. It seems likely that any method for isolating glutenin involving use of alkaline solutions would involve loss of nitrogen in the course of the preparation and the nitrogen distribution obtained by the Van Slyke analysis would therefore be in error. The use of very dilute acetic acid is recommended but exposure to even dilute solutions of the strong alkalies should be rigorously avoided in the preparation of glutenin.