British Food Journal Volume 48 Issue 8 1946

Abstract

The shortage of grain, reflected by an increase in the rate of extraction in milling and then by the rationing of bread, has fully aroused the attention which it warrants. Avoidance of wastage, always important, now becomes imperative. In view of this, notes in connection with the occurrence of “rope” in bread which were recently made available to members of the baking industry by the Ministry of Food may be even more important than the warnings issued in previous years. The disease is associated with warm weather and develops most rapidly at about 100°F. The first of the symptoms is usually the development in the bread of a faint fruity odour, resembling that of an over‐ripe pineapple, which becomes more intense as the bread gets older. Discolouration and softening of the crumb next occurs, so that on attempting to cut the bread it tends to stick to the knife. When the crumb is pulled apart, fine gelatinous threads may be formed. Although an outbreak of “rope” is unpleasant, there is fortunately little or no evidence that such an occurrence is dangerous to health. The disease can of course occur in cakes and similar bakery products, but outbreaks are practically always confined to bread. The comparative immunity of cakes is probably due to a generally lower moisture content, which does not encourage development of the disease. Another possibility is that fruit, where present, may cause the development of a certain amount of acid, and acid conditions discourage the activity of the organism responsible for the trouble. “Rope” in bread is caused by the spore‐forming bacterium B. mesentericus. It has been suggested the disease is due to the decomposition of the starch by amylase, in which the organism is rich. There are several strains of this bacterium, which is of widespread occurrence—it is found, for example, in the soil. All kinds of flour, whether of high or of low extraction, and including those derived from cereals other than wheat, are possible carriers of the disease. However, carefully‐conducted experiments have shown that the “rope” spore content of the flour, unless particularly high, is of minor significance when outbreaks of “rope” occur. Far more important are the conditions under which the bread is made and under which it is treated after baking. It has been found that “rope” formation is more likely to develop in the dense crumb associated with under‐fermentation than in loaves in which the crumb is well‐developed. Use of sufficient yeast to cause the fermentation to be vigorous has also been found to be beneficial. The initial development of the organism appears to be at the expense of the soluble nitrogen compounds, sugars, etc., present in the bread. When these materials are exhausted, attack upon the protein of the loaf proceeds. A possibility is that prolonged fermentation causes a partial transformation of the gluten into nitrogenous substances which are more easily assimilated by the bacteria, whereas in a short, vigorous fermentation the formation of such substances may not occur to the same extent. Occurrences of the disease may be expected to be more severe with high extraction flours or whole‐meals, since higher extraction gives a medium which is better suited for the growth of the “rope”‐causing organism. All the members of the mesentericus group are characterised by the formation of spores which are extremely difficult to destroy by heating. For example, the spores can resist the temperature of boiling water for hours on end. Since the interior of a loaf probably does not exceed this temperature whilst in the oven, many of the spores will escape destruction. The spores will thus pass through the operation of baking and, if conditions are favourable, the development of the disease will start at or near the middle of the loaf. Since the damp, soggy crumb associated with an under‐baked loaf is conducive to the development of “rope,” thorough baking is a definite advantage. Owing to the fact that the “rope” organism requires warmth for its growth, rapid and thorough cooling of the bread in well‐ventilated cooling rooms is an important preventative factor. Spacing upon the racks should be such that the loaves do not touch, and the latter should not be packed whilst warm into delivery vans. Cleanliness is also of vital importance. Odd scraps of bread, dried dough, etc., may contain the spores of the organism and contact of the loaves with such material will lead to contamination which may bring to nought the preventative efforts made in other directions. Since the “rope” organism does not like acidity, addition to the bread dough of acidic substances is a useful deterrent. Acetic acid and acid calcium phosphate are particularly useful in this connection, since the requisite concentrations of these substances do not cause deterioration in bread quality. Bakeries with sackages below 100 per week may obtain without permit acetic acid solution of strength suitable for immediate addition. For larger users, the acid is supplied in a more concentrated form against a permit obtainable from the Directorate of Molasses and Industrial Alcohol, and is diluted before adding to the mixing. Though acetic acid or acid calcium phosphate may be used to suppress outbreaks or as preventatives during exceptional conditions, supplies of these agents are insufficient to enable them to be used continually as general preventatives during hot weather. For this purpose, the “acid dough” process of the British Arkady Co. Ltd., which requires no special materials, is recommended by the Ministry of Food. A small batch of “starter” dough is first prepared and is then incorporated into a larger mixing of “acid dough.” Portions of the latter are then added to the main mixing of bread dough, no alteration in the other constituents of the latter being required. Once the “acid dough” has been prepared, daily supplies may be kept up for months. A portion of the dough from the previous day is used as a starter for the new mixing, and from the second day onwards the “acid dough” becomes a fairly‐stabilised producer of acid.

Citation

(1946), "British Food Journal Volume 48 Issue 8 1946", British Food Journal, Vol. 48 No. 8, pp. 189-198. https://doi.org/10.1108/eb011414