Experimental cookery

The hydration of a gluten and hence its tenacity or cohesiveness, and its elasticity or extensibility, may be altered, that is increased or decreased, by: (1) over-grinding, (2) bringing the dough to a certain acidity or alkalinity and subsequent neutralization, (3) treating with alcohol, (4) salts, (5) alkalies, (6) acids, (7) proportion of water used, (8) added substances, (9) temperature, (10) time of standing, (11) mechanical treatment of the dough, and (12) fermentation. Over-grinding has been considered. The effect of mechanical treatment of the dough and fermentation upon gluten will be considered with the discussion of bread making. The effect of proportion of water used has been considered and that of added substances will be considered under dough structure. Bringiriff the dough to a certain acidity or alkalinity and subsequent neutralization. The quality of the gluten can be altered by increasing the acidity or alkalinity. Gortner and Johnson have found that "doughs brought to /)H 3.0 or 11.0 by the addition of acid or alkali and in which the acid or alkali has been subsequently neutralized, have lost their bak- ing strength." Treating with alcohol. Gortner and Johnson have found that flour treated with 70 to 85 per cent alcohol, from which the alcohol is evapo- rated, and the flour dried and remilled, when used in bread has lost its bak- ing quality. They attribute this to a loss in colloidal properties brought about by action of alcohol on the glutenin of the flour. Salts. The imbibition of water by gluten, and thus the swelling, may be depressed considerably by salts. This may be brought about by the salts found in the flour, by the addition of salts like baking powders to flour mixtures, or by the addition of the so-called flour improvers to weak flours. The inhibiting effect may be due to the cation or the anion of the salt. Different salts depress the hydration capacity of the gluten in different proportions, that is, in the order of a lyotropic series. See also the section on proteins. Bailey and Le Vesconte have reported that the addition of monocalcium phosphate to a dough effected a slight increase in the extensibility of gluten. They find no increase in extensibility of the dough, as measured in the Chopin extensimeter, when calcium sulfate and magnesium sulfate are added in the proportions used in commercial practise. Alkalies. The hydration capacity of gluten on the alkaline side of the isoelectric point reaches its maximum capacity at a pYL 11.0. Beyond a /)H 11.0 the gluten dissolves very rapidly with increasing alkalinity. Since gluten proteins tend to imbibe water and disperse in a weakly alkaline HYDRATION CAPACITY 421 medium, doughs with a slight alkaline reaction are sticky. With excess alkali they become yellow and develop a soapy taste. Since the proteins are peptized readily with alkali, a product with a pH higher than 7 is quite tender. Thus chocolate cakes and gingerbread with excess alkali (soda) are very tender, though the cell walls are very thick.