In this article we will discuss about the preparation, types and abnormal fermentation of bread.
Preparation of Bread:
Flours and meals for the preparation of bread are usually made from wheat or rye, occasionally from maize or barley. They are all high in starch, and the first two contain a considerable proportion of protein, commonly designated as ‘gluten’.
In addition, there are traces of sugar and some diastase enzyme. Flour is mixed with water to form a dough. For some types of bread, little sugar is also added. The series of changes which occur in the flour and other constituents of the dough before baking into bread is termed ‘panary fermentation’.
An alcoholic fermentation by yeast is an essential step in the production of bread; this process is known as the ‘leavening of bread’. A product of action of microorganisms is involved in the production of bread.
Types of Bread:
However, there are following three basic types of rising breads, which are the following:
(i) White or Common Bread:
In this bread preparation the moistened flour is mixed with yeast, Saccharomyces cerevisiae, and is allowed to stand for several hours in a warm place.
Flour itself contains little free sugar, but there are sufficient quantities of starch splitting enzymes in it to produce some sugar during the leavening process. The sugar is rapidly fermented by the yeast with the production of alcohol and carbon dioxide, the latter causing the rising of the bread. During the baking process the alcohol is driven off.
(ii) Sour Bread:
This bread is a sour dough, from which a ‘starter’ is saved to inoculate the next batch. The organisms appear to be Escherichia coli and Enterobacter species which produce a mixed lactic acid fermentation, i.e., accompanying the gas there is always some lactic acid which tends to make the bread taste sour.
(iii) Salt-Rising Bread:
This type of bread is dependent upon the spontaneous fermentation by (probably) wild yeasts and common contaminating bacteria, E. coli and Enterobacter types. In this case, salt is added to the bread which cuts down some of the extraneous contamination and allows the bread to rise during fermentation.
Abnormal Fermentation of Bread:
The most common abnormal fermentations in bread are the following:
(i) Undesirable High Acidity:
Too high acidity may develop as a result of the growth of lactic bacteria for too long a period in the dough before baking and the bread thus becomes unpalatable as a result of the development of sourness in it.
Ropiness results in from the growth of certain highly resistant spore-producing bacteria after baking. Several such species have been described which are mostly the varients of Bacillus subtilis. They are probably present in most bread, but do not develop and cause ropiness except when there has been too little development of acid in the leavening process and the bread has been stored at a relatively high temperature.
In other words, in order to prevent rapid deterioration of the bread after baking, it is necessary that a certain amount of acid be present in the dough. This is usually formed as a result of the growth of certain lactic acid species.
(iii) Bloody Bread:
Some bacteria may form coloured spots or areas in the bread. Serratia marcescens (sometimes termed Bacillus prodigiosus) produces a red pigment. The red spots were interpreted before the development of modern science as spots of blood, hence the name bloody bread.