Microbiology Of Starch And Sugars by A C Thaysen & L D Galloway

Author:A C Thaysen & L D Galloway
Language: eng
Format: epub
Tags: Biology
Publisher: Oxford University Press
Published: 1930-06-17T16:00:00+00:00

Basing their efforts on this assumption, Bailey and Johnson have attempted to evolve a reliable method of ascertaining when a dough has matured sufficiently to be proofed and

made ready for baking. They argue that, since at a given stage there is a rapid loss of carbon dioxide, it should be possible to determine this stage by measuring the carbon dioxide evolution of the dough at intervals. They do this by absorbing the gas given off with a dilute solution of alkali possessing a hydrogen ion concentration corresponding to a pH value of 7-8. The time takers for this pH value to decrease to 7-0, as indicated by the changes in phenol red from pink to yellow, is taken as a measure of the rate of carbon dioxide evolution.

In their experiments Bailey and Johnson found that a sharp increase in gas evolution from a dough was indicated by this method and coincided with the time of ripening of the dough. A somewhat similar method has been advocated by James and Huber 61 for flour and water suspensions. Here the fermentation is allowed to proceed in a flask and the carbon dioxide given off is collected in an inverted tube in which it moves a registering arm recording the changes. Either of these methods appears to be superior to that by which the ripening of a dough is correlated with changes in hydrogen ion concentration.

Since Jessen-Hansen 63 first drew attention to the connexion between changes in the hydrogen ion concentration and the ripening of a dough, the view has gained ground that once the optimum pH value of 5-0 has been established, the gas evolution of a dough has reached its maximum and the fermentation should therefore be arrested (Brewster Morison 37 ). It was suggested that a simple measurement of the hydrogen ion concentration of a dough would suffice to show when proofing could be commenced. It is not surprising to hear that more recent investigations have had to revise this view.

The various flours used in bread-making, even various types of wheat flour, differ too markedly in chemical composition, notably as regards their protein content, to justify the conclusion that the establishment of a given hydrogen ion concentration in a given time is unaffected by the nature of the flour. This is clear from the observations of Bailey and

Sherwood, 6 who found that the hydrogen ion concentration of a dough made with wholemeal flour increases more slowly than that of a dough prepared from patent flour. Bailey and Johnson 48 recorded that, in the case of a wholemeal dough which is allowed to ferment until its optimum pH value of 6-0 has been reached, the resulting bread was inferior, the protracted fermentation having rendered the crumb wet, and having greatly increased the loss of dry matter. As a contrast these writers record that, where the fermentation of a patent flour which for some reason or other had acquired an abnormally high acidity, was arrested through the hydrogen ion concentration of the dough had reaching its optimum, the resulting loaf was harsh and 'unfinished'.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.