Experimental cookery

Is gluten composed of distinct groups or individual proteins? The greatest difficulty in fractional precipitation of the flour proteins can be traced to the agents used to disperse them, for no solvent has been found from which all the protein can be recovered without loss or irreversible change in original properties. Blish says that "irreversible and destructive hydrolytic changes occur almost at once, and proceed at a relatively high rate when gluten is dispersed in weak alkali." On the other hand, in dilute acetic acid, an appreciable amount of hydrolysis is detectable after a few hours standing, but at ice temperature hydrolytic changes are slow. Addi- tion of an equal volume of alcohol to dilute acetic acid protects against hydrolytic change, but may split off other components. Urea is used for peptizing proteins, but because it gelatinizes starch must be used on washed gluten. Salicylate is one of the anions in the lyotropic or Hoffmeister series caus- ing greatest peptization of flour proteins. Sodim salicylate appears to peptize the flour proteins with no observable hydrolysis or denaturation. Blish states that it is probable that only a few components or component groups constitute the flour proteins and that they may be precipitated as mixtures containing progressively varying proportions of these few com- ponents. "We can merely summarize our present viewpoint, which is as follows: There is a considerable portion of flour protein that does not enter into the formation of gluten, but it is not yet possible to distinguish a sharp GLUTEN 415 and definite boundary-line between the gluten and non-gluten portions. With reference to gluten, itself, we recognize a definite fraction consisting of approximately 10-12 per cent that is extremely resistant to dispersion. We recognize the 'gliadin' fraction, which accounts for 50 per cent or more of the gluten, and which may or may not be a mixture of components having very similar properties. The remaining portion we regard as doubt- ful, but until proven otherwise we prefer to look upon it as a mixture of a 'glutenin' and a lipoid-protein complex." Work with flour proteins **is peculiarly a problem in which any new discovery is likely to invalidate much that has gone before and to necessitate an entire re-examination of the whole situation." Lecithio-protein. Flour may contain a lecithio-protein somewhat sim- ilar to that found in egg yolk. Blish says that alcohol added to acetic acid solutions in fractioning flour proteins may cause irreversible splitting off of an important gluten component, a "lecithio-protein" or some similar lipoid-protein complex. Blish adds that he suspects the ''lecithio-protein" is a very important gluten constituent and that its importance and amount in flours have been underestimated. "At present we feel that a thorough study and understanding of the nature and properties of the lipoid-protein complex will contribute greatly to the solution of several flour problems that are of the greatest fundamental interest and importance."