Experimental cookery

Proteolytic enzymes. Balls and Hale state that the changes that take place in the quality and behavior of flours after bleaching or storage in air are due to the diminution of proteolytic activity. The Proteins of Flour Osborne in his classical work on the wheat flour proteins reported only a small fraction soluble in water. This fraction contained leucosin and albumin, plus proteose or non-protein nitrogen. A small fraction was ex- tracted by dilute salt solution and this globulin fraction constituted about 0.6 per cent of the wheat kernel. Gliadin, a prolamin, constituting about 40 per cent of the total protein, was soluble in alcohol. The remaining protein, called glutenin, was found to be insoluble except in dilute acids or alkalies. But later work has shown that the terms "globulin" and "albumin" have little meaning in connection with flour proteins and that neither "gliadin" nor "glutenin" may be an individual chemical entity. Blish in "The Wheat Flour Proteins" says, "It seems that as we have become increasingly familiar with the behavior and properties of flour proteins, we have found ourselves progressively more and more hesitant in the matter of making dogmatic assertions and published statements relative to their nature, their identities, and their individualities." Effect of salts on protein extracted. Gortner, Hoffman, and Sin- clair found that N/1 solutions extract the following average percentages of the total wheat flour proteins: KF 13, KCl 23, KBr 37, and KI 64. They showed that the amount of protein extracted varied not only with the nature of the salt used but also with its concentration. Gortner, Hoffman, and Sinclair have found that for increasing peptizing effect on wheat proteins the following anions arrange themselves in a lyotropic series: F < SO4 < CI < tartrate < Br < I. The cations have a 414 FLOUR AND BREAD less distinct effect on solubility of the flour proteins but give the following order of peptization: Na < K < Li < Sr < Mg < Ca. Mangels and Bailey in studying the gelatinizing action of reagents on starch noted a Hoffmeister series as follows: CI < B < I < CNS < salicyl- ate <OH. Rich has shown that the amount of protein extracted or peptized by N/2 MgS04, 10 per cent NaCl, and N/4 NaCl solutions varies directly with increasing ash content of the flour. In general, the maximum peptiza- tion occurred with N/4 solutions. A further increase in salt concentration causes dehydration and eventually salting out of the protein micelle. Is gluten a single protein? McCalla and Rose say that the most soluble 10 to 15 per cent of the gluten protein is probably distinct, but the remainder is a single protein complex which can be divided into a great many progressively different fractions. They suggest the terms ''glutenin" and ''gliadin" should be discarded. Rich states that it is "apparent that the protein of wheat is a single individual and that knowledge of the nature of differences in protein 'quality' between 'strong' and 'weak' flours can best be solved by studying the protein as a whole instead of splitting it into arbitrary fractions and studying each fraction separately." He believes that if the dispersing agent or the method of isolation is changed, even slightly, there is no established limit as to the number, quantities, and character of the protein fraction that can be isolated.