156 CALLOW: THE EFFECT OF CERTAIN SALTS ON FERMENTATION IN DOUGH

The Effect of Certain Salts on Fermentation in Dough

BY R. H. CALLOW, M.Sc., A.I.C.

(Read at the Meeting of the North of EngJand Section, December 2, 1933)

BREAD is defined in this country in the Bread Acts of 1822 and 1836, but the Acts and the definition are practically a dead letter. Nobody puts into bread oats, buck- wheat, Indian corn, peas, or rice, and it is the general practice of those engaged in the trade to add unpermitted ingredients, such as fat, sugar, fruit, chemical improvers, and bleaching agents. A Departmental Committee was appointed in 1923 to consider the addition of chemicals to flour, and published its findings in 1927. The findings are rather indefinite, and, in spite of the fact that the Committee viewed the use of certain chemicals unfavourably, the use of these has increased considerably since the Report was published.

Additions are made to bread for various purposes, and it is, of course, immaterial whether the additions are made by the miller or the baker. Some additions are made in order to alter the colour, the action in this case generally resolving itself into the bleaching of carotene. Some are added to strengthen or weaken the gluten, some to increase the diastatic power. Other substances increase water absorption, some act as yeast foods and activators, and a number of obviously harmless substances are added to improve flavour or nutritive value.

Certain improvers and yeast foods have been known and used for a long time, as, for example, sugar, fat, milk, malt, potatoes, etc., and it has been known for an equally long time that the use of some of these is attended with a certain amount of risk; thus, the use of a large quantity of malt may give a good flavour, but the production of dextrins and the hydrolysis of the proteins will ruin the bread. Also, potato is a very good yeast food, but one is very likely to get the bread infected with “rope ” by its use.

Before considering the effect of certain salts on fermentation in dough it may not be out of place to mention some of the main changes taking place during fermentation and baking. There is a certain amount of fermentable sugar in flour, and, when a dough is made, further sugar is formed by the action of wheat diastase on the starch. If no other sugar or diastatic substance is added, this is the total supply of sugar that is available for the yeast, but often cane sugar or malt extract is added to make up for deficiencies in original sugar or diastase. At the beginning of the dough-stage fermentation is slow, and diastatic action is normal, and, therefore, the sugar-content increases. The fermentation, however, increases continuously in speed, owing to the activation and growth of the yeast, and thus there may come a time when the rate of consumption of sugar by the yeast is equal to the rate of production of sugar by diastase. After this point the rate of fermentation still increases, resulting in a diminishing sugar-content until a shortage of sugar is indicated and the rate of increase of gas-production falls off. Eventually the rate of gas production becomes steady, and then begins to fall.

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CALLOW: THE EFFECT OF CERTAIN SALTS ON FERMENTATION IN DOUGH 157

In order to produce a good bold loaf with a pleasing aspect, it is essential that when the dough goes into the oven the rate of gas production should be vigorous, although not violent, but it must not be falling, otherwise the bread does not spring in the oven, and may actually shrink during the baking process.

The other main change that takes place is in the physical condition of the gluten. When the dough is first made it will not stretch much without breaking. It is said to be short-textured, and this shortness or lack of extensibility is due to the tough condition of the gluten. During fermentation the p , of the dough decreases, owing to saturation with carbon dioxide and the production of a certain amount of lactic and, possibly, other acids, the gluten becomes more dispersed, and the dough becomes softer and more extensible, and yields more easily to pressure or tension. Also, the proteolytic enzymes in the flour act in the same direction. This softening of the gluten, making it easily extensible, is referred to in trade circles as the “maturing” of the gluten. If it goes too far, it is called the “breaking down” of the gluten, but both are essentially the same thing.

When the dough is placed in the oven there is a rapid production of gas, owing to two causes. First, the dough is saturated with carbon dioxide, which is liberated during heating; secondly, the yeast acts more rapidly as the temperature rises to the optimum. It is essential for the production of a good loaf that the gluten should be sufficiently matured to give way and expand under the pressure of the rapidly developed carbon dioxide, but not so matured as to collapse. If the dough is insufficiently matured, it will be too tough and will tear in the oven, giving a rough unsightly loaf. If, on the other hand, it is over-matured, the strength goes out of the gluten and the resulting loaf is very crumbly. These two points may not affect the nutritional value of the loaf, but they do count with the public.

Where the dough is made of flour, yeast, salt and water this loss is from 2.5 to 3 per cent. in processes of about 3 to 5 hours’ duration. In long-process doughs some authors report losses as high as 11 per cent., but this cannot be considered as commercial practice. The highest losses commercially obtained are probably in the neighbour- hood of 5 to 6 per cent. of the total weight of flour and sugar. This loss was generally regarded as a necessary evil. The yeast does the work and demands its price. This view was accepted until about 1916, when Swanson and Willard,l and Kohman, Hoffman’ss and others carried out a series of experiments on the nutritional requirements of yeast.

It had long been known that yeast required sugar, nitrogenous matter, phosphates and potash, and it was known in the brewing trade that water containing fairly large quantities of calcium gave a faster fermentation and made better beer than soft waters.

The work of Kohman, Hoffman and others was, in the first instance, an attempt t o discover why bread made in several bakeries belonging to the one firm, each using the same raw materials, process, formula, and plant, varied considerably in quality, volume, and general characteristics. Suspicion eventually fell on the water supplied, and analysis of the water showed large differences in

Fermentation in dough is always accompanied by a loss of flour solids.

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168 CALLOW: THE EFFECT OF CERTAIN SALTS ON FERMENTATION IN DOUGH

calcium-content. In those bakeries working on a soft-water supply the fermenta- tion was sluggish, whereas in those working on hard water the fermentation was relatively fast. When the waters were treated so as to equalise the calcium differences, the differences in the products of the bakeries disappeared, and the bread was standardised. Gas-production tests showed, however, that if the calcium-content was still further increased, the activity of the yeast was increased. Different calcium salts activate the yeast to different extents, as the anion may have a specific effect as well as the cation. Also, the acid salts will have an accelerating effect in respect of the acidity.

Practically all except calcium compounds show an activating effect on yeast, those having an alkaline reaction, e.g. carbonate and bicarbonate, hydroxide, and normal phosphate, also those salts in which the anion has an antiseptic or preservative action, e.g. benzoate, sulphite, etc. The activation by the addition of calcium salts is, to all intents and purposes, immediate, but the effect on gas- production is relatively larger with a weak yeast than with a strong yeast. The following figures indicate the ml. of gas evolved in 5 hours from doughs made from 56 grms. of flour, 33 grms. of water, 0.8 grm. of salt, and 0.5 grm. of yeast at a temperature of 80" F., without, and with, the addition of 0.075 grm. of calcium sulphate.

Calcium Percentage Control sulphate increase

1. 304 330 8.2 2. 272 298 9.5 3. 240 271 12.9

Somewhat similar figures are obtained with other calcium salts when the acid radicle has no specific effect. I t will be seen, therefore, that the tendency of the addition of calcium salts is to standardise the gas-producing power of yeast in dough.

In addition to stimulating gas-production, calcium salts have an effect on the gluten of dough, by which the gas-retaining powers are increased. Thus, of two doughs showing the same rate of gas-formation in the oven, that containing added calcium salt will give a larger loaf than the one without such addition. Certain results obtained by HoffmanS indicate that addition of a calcium salt to dough increases the rate of reproduction of the yeast. Yeast cells in dough are difficult to count, and the technique, even under the best conditions, must be some- what crude, but the fact that Hoffman always obtained an increased effect lends weight to the results. An an example, the increase found in a dough after six hours was 45.1 per cent., whereas in a similar dough containing calcium sulphate (0.125 per cent. on the flour) the increase in yeast count was 57.6 per cent.

The activity of yeast in dough is only slightly influenced by additions of potassium compounds and phosphate, owing, presumably, to the relatively large quantities of these already present in flour.

The nitrogenous requirements of yeast are normally derived from the proteins and similar bodies in the flour, and thus during fermentation there is a partial destruction of protein, resulting in a reduced amount available for gluten formation. It has been found that if nitrogen is supplied in a more readily assimilable form,

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CALLOW: THE EFFECT OF CERTAIN SALTS ON FERMENTATION IN DOUGH 159

the activity of the yeast is increased. Thus if glutamic acid, prepared by hydro- lysis of gluten with hydrochloric acid, or peptone, is added to a dough, gas- production is considerably increased. It was found by Willard and Swanson that a still simpler nitrogenous body, namely, ammonium chloride, would increase the activity of yeast, but that ammonium phosphate was ineffective, and am- monium tartrate and acetate were detrimental. There appears to have been some fault in the technique, as we and others have tried several ammonium salts and found them all effective, except the alkaline salts.

One feature of the activation of yeast by the addition of ammonium salts, which is quite different from the activation by calcium salts, is that, whereas calcium activates, practically immediately, the action of ammonium salts is delayed for some time and then takes place rapidly. For the first three hours ammonium chloride has practically no effect on gas-production in dough, but the subsequent effect is considerable. Ammonium salts activate all types of baker’s yeast, i .e . strong or weak, old or new, and, as with calcium salts, the relative effect is more marked with the weaker yeasts. The following figures refer to doughs similar to those in the former series, but containing 0.03 grm. of ammonium chloride instead of 0.075 grm. of calcium sulphate:

Ammonium Percentage Control chloride increase

ml. ml. 1 300 325 8.3 2 281 307 9.25 3 278 310 11.5

In these tests the gas-productions have been given up to the time when such a dough would normally be set in the oven.

It does not by any means follow that if two substances will activate an organism, both together will doubly activate it. There is generally a limit to what the organism can do. With calcium and ammonium salts, however, the activating action is cumulative. For example, a set of doughs was made somewhat similar to those previously mentioned but containing 0-425 grm. of yeast instead of 0.5 grm., and also containing 0~03grm. of ammonium chloride. To one was added, in addition, 0-075 grm. of calcium sulphate. The average gas-productions after 5 hours were

1. Without calcium sulphate . . 262 ml. 2. With calcium sulphate .. 285.6 ml.

Percentage increase .. 8-97

It has already been pointed out that when the dough goes to the oven a vigorous gas-production (but not a violent one) is necessary, as otherwise the loaf will not expand rapidly enough to accommodate the gas production. It is, there- fore, necessary, if the yeast is highly activated, to reduce the quantity of yeast used. Curves of the hourly rates of gas-production in doughs containing (i) no additions; (ii) 0.03 grm. of ammonium chloride and 16 per cent. less of yeast; (iii) 0.03 grm. of ammonium chloride plus 0.075 grm. of calcium sulphate and 15 per cent. less of yeast; (iv) 0.03 grm. of ammonium chloride plus 0.075 grm. of calcium sulphate, and 25 per cent. less of yeast have been constructed.

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160 CALLOW: THE EFFECT OF CERTAIN SALTS ON FERMENTATION IN DOUGH

These show that the control dough has the more rapid gas-production in the early stages, but that the dough containing ammonium chloride with a 15 per cent. yeast reduction passes it between the fourth and fifth hours. As, in the final stages of bread-making, it is the rate of gas-production that is important, the use of these salts leads to a considerable economy in yeast.

The control curve cuts the curve with ammonium and calcium salts and 25 per cent. yeast reduction at 4.1 hours. By this time the control dough had developed 216 ml. of gas, whereas the treated dough had developed only 178ml. Further, the rate of gas-production in the control dough is falling slowly, whilst that in the treated dough is rising rapidly. A dough of this composition should go to the oven at about 4% hours, and it will be seen that to bring the rates of fermentation to the same value at this point, the yeast would have to be still further reduced, thus further reducing the total gas- production in the treated dough. As it is, the losses in the treated dough are roughly 82 to 83 per cent. of those in the control dough at the time when therates of gas-production are equal, and, taking the average losses during fermentation as 3 per cent., this will give 0.6 per cent. conservation of carbohydrate.

Two other very important factors are the rate of gluten maturing, and the gas-retaining capacity of the dough. Without dealing in detail with maturation of gluten it suffices to say that traces of potassium bromate and iodate influence to a remarkable extent the elastic properties of gluten in the same direction as yeast fermentation, and that, therefore, by the use of a small quantity of potassium bromate (e.g. 0.001 per cent. by weight of the flour), the amount of fermentation required to ripen the gluten satisfactorily is very considerably reduced.

It has been mentioned that a strong gas-production is necessary in the final stages. This is really an incomplete statement. Actually the rate of gas- production should be considerably higher than the rate of loss of gas from the dough. Under these conditions the loaf will rise well in the oven and make a good loaf; otherwise it will not. If the gas-retaining power of the dough can be increased, thus reducing the rate of loss of gas, the rate of gas-production may be correspondingly reduced. Both calcium salts and salts of bromic and iodic acids act in this way, and thus a further conservation of carbohydrate becomes possible. Actually, we find in large-scale tests that, by the addition of 0.251b. of calcium sulphate (CaSO4,2KO), 0.1 lb. of ammonium chloride and 0-003 lb. of potassium bromate to a dough made from 280 lbs. of flour, the fermentation losses are reduced by at least 50 per cent.

Another point is worthy of consideration.

The rate of gas-production, however, is not the only factor.

REFERENCES 1.

2.

3. 4.

C. 0. Swanson, J. T. Willard and L. A. Fritz, Kansas Agr. Expt. Stat., Bull. No. 202,

H. A. Kohman, C. Hoffman, T. M. Godftey, L. H. Ashe and A. E. Blake, J . Ind. Eng.

H. A. Kohman, Amer. Food J. , 1917, 12, 35; Chem. Abst., 1917, 11, 373. C. Hoffman, Chem. Age (N.Y.), 1924,32, 261; Chem. Abst., 1924, 18, 2771.

1916; Chem. Abst., 1916, 9, 2272.

Chem., 1916, 8, 781; Chem. Abst., 1916, 10, 2776.

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