The Story of a Loaf of Bread

by T. B. Wood

Fig. 15. A pair of reduction rolls. They are smooth, and the cog-wheels being nearly of the same size the speed of the two rolls is nearly equal

These large particles, semolina, are next passed between one or more pairs of smooth rolls known as reduction rolls (Fig. 15). These are set rather nearer together than the break rolls, and the difference in speed between each roll and its partner is quite small. The object of reduction is to reduce the size of the large particles of semolina and to produce thereby finely divided flour. The stock from the first pair or pairs of reduction rolls contains much finely ground flour mixed with coarser particles of kernel with or without adherent husk. It is at once submitted to the separation and purification processes as above described. This yields a large quantity of finished flour which is very white and free from husk. It represents commercially the highest grade of flour separated in the mill and is described technically as patents. A small amount of finished offal is also separated at this stage.

The coarse particles of kernel with adherent husk from which the flour and offal have been separated are now passed through a second pair of break rolls more finely fluted than before, known as the second break. These are set closer together than the first break rolls. Their object is to rub off more kernel from the husk. The stock from them is again separated, the flour and finished offal being removed as before. The coarser particles are again reduced by smooth reduction rolls, and a second large quantity of flour separated. This is commercially high grade flour and is usually mixed with the patents already separated. The coarse particles left after this separation are usually subjected to a third and a fourth break, each of which is succeeded by one or two reductions. Separation of the stock and purification of the flour take place after each rolling, so that as soon as any flour or husk is finely ground it may be at once separated without further grinding. The last pair of fluted rolls, the fourth break, are set so closely together that they practically touch both sides of the pieces of husk which pass through them. They are intended to scrape the last particles of kernel from the husk. This is very severe treatment, and usually results in the production of much finely powdered husk which goes through the sifting silk and cannot be separated from the flour. The flour from the fourth break is therefore usually discoloured by the presence of much finely divided husk. For this reason it ranks as of low commercial grade. The later reductions too yield flours containing more or less husk, which darkens their colour. They are usually mixed together and sold as seconds.

The fate of the germ in the process of roller milling is a point of considerable interest, both on account of the ingenious way in which it is removed, and because of the mysterious nutritive properties which it is commonly assumed to possess. The germ of a grain of wheat forms only about 1½ per cent. by weight of the grain. It differs in composition from the rest of the grain, being far richer in protein, fat, and phosphorus. Its special feeding value can, however, scarcely be explained in terms of these ingredients, for its total amount is so small that its presence or absence in the flour can make only a very slight difference in the percentages of these substances. But this point will be discussed fully in a subsequent chapter. Here it is the presence of the fat which is chiefly of interest. According to the millers the fat of the germ is prone to become rancid, and to impart to the flour, on keeping, a peculiar taste and odour which affects its commercial value. They have therefore devised with great ingenuity a simple method of removing it. This method depends on the fact that the presence in the germ of so much fat prevents it from being ground to powder in its passage between the rolls. Instead of being ground it is pressed out into little flat discs which are far too large to pass with the flour through the sifting silks or wires, and far too heavy to be blown away by the air currents which remove the offals. The amount which is thus separated is usually about 1 per cent. of the grain so that one third of the total quantity of germ present in the grain is not removed as such. Considerable difficulties arise in attempting to trace this fraction, and at present it is impossible to state with certainty what becomes of it. The germ which is separated is sold by the ordinary miller to certain firms which manufacture what are known as germ flours. It is subjected to a process of cooking which is said to prevent it from going rancid, after which it is ground with wheat, the product being patent germ flour.

CHAPTER VI
BAKING

In discussing the method of transforming flour into bread it will be convenient to begin by describing in detail one general method. The modifications used for obtaining bread of different kinds, and for dealing with flours of different qualities will be shortly discussed later when they can be more readily understood.

Bread may be defined as the product of cooking or baking a mixture of flour, water, and salt, which is made porous by the addition of yeast. It is understood to contain no other substances than these—flour, salt, water and yeast.

In the ordinary process the first step is to weigh out the flour which it is proposed to bake. This is then transferred to a vessel which in a commercial bakery is usually a large wooden trough, in a private house an earthenware bowl. The necessary amount of yeast is next weighed out and mixed with water. Nowadays compressed or German yeast is almost always used at the rate of 1 to 2 lbs. per sack or 280 lbs. of flour. For smaller quantities of flour relatively more yeast is needed, for instance 2 ozs. per stone. Formerly brewers’ yeast or barm was used, but its use has practically ceased because it is difficult to obtain of standard strength. Some people who profess to be connoisseurs of bread still prefer it because as they say it gives a better flavour to the bread. The water with which the yeast is mixed is warmed so as to make the yeast more active. The flour is then heaped up at one end of the vessel in which the mixing is to take place, and salt at the rate of 2 to 5 lbs. per sack is thoroughly stirred into it. A hollow is then made in the heap of flour into which the mixture of yeast and water is poured. More warm water is added so that enough water in all may be present to convert all, or nearly all, the flour into dough of the required consistency. When dealing with a flour with which he is familiar the baker knows by experience how much water he requires per sack. In the case of an unaccustomed brand of flour he determines the amount by a preliminary trial with a small quantity (Figs. 16 and 17). Flour from the heap is then stirred into the water until the whole of the flour is converted into a stiff paste or dough as it is called. By this method a little dry flour will always separate the dough from the sides of the vessel and this will prevent the dough from sticking to the vessel and the hands. The dough is then thoroughly worked or kneaded so as to ensure the intimate mixture of the ingredients. The vessel is then covered to keep the dough warm. In private houses this is ensured by placing the vessel near the fire. In bakeries the room in which the mixing is conducted is usually kept at a suitable temperature. The yeast cells which are thoroughly incorporated in the dough, find themselves in possession of all they require to enable them to grow. The presence of water keeps them moist, and dissolves from the flour for their use sugar and salts: the dough is kept warm as above explained. Under these conditions active fermentation takes place with the formation of alcohol and carbon dioxide gas. The alcohol is of no particular consequence in bread making, the small amount formed is probably expelled from the bread during its stay in the oven. The carbon dioxide, however, plays a most important part. Being a gas it occupies a large volume, and its formation throughout the mass of the dough causes the dough to increase greatly in volume. The dough is said by the housewife to rise, by the professional baker to prove.