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Bread
One of the main bakery products is bread. Bread include several bakery products and the types vary significantly from country to country.E.g., the Ullmann`s Encyclopedia gives the following description:
In France, about 80% of the bread is still produced in small bakeries. The most common traditionally eaten bread is the baguette. It is produced with four basic materials: flour, water, salt and yeast. It represents more than 50% of the French bread production. Other French speciality breads include the fine wheat bread (pain de gruau), the Viennese bread, and biscottes.
In Germany, baked products are divided into two types: the production of bread allows a maximum of 10 parts sugar and/or fat to 90 parts of flour; products with more than 10 parts sugar and/or fat to 90 parts of flour are called fine bakery wares (Feine Backwaren). Bread is divided into five main groups: wheat breads (at least 90% wheat), mixed wheat – rye breads (min. 50% wheat), mixed rye – wheat breads (min. 50% rye), rye breads (at least 90% rye), and bread specialties. Each of the first four groups were established based on the proportion of wheat and rye in the formula. These groups are further classified into subgroups according to the type of milled raw materials used: low extraction flour bread, meal bread, and wholemeal bread. Speciality breads can be prepared, for example, by adding nonbread grains (e.g., oat, barley, rice, maize), raw materials of plant origin (e.g., oilseeds, germs, raisins), materials of animal origin (e.g., milk, butter, yogurt, whey) or by using special baking techniques (e.g., wood-heated oven, steam oven, stone oven, crisp bread). From the total bread consumption, about 15% is eaten as small rolls and its consumption is further increasing. Recently, the socalled nonbread grain breads have become very popular. Also the production of dark breads such as wholemeal flour breads is on the rise.
The typical UK sandwich-bread has a high volume, soft texture, very fine porous crumb structure and is also characterized by long shelf live properties. Speciality breads comprises germ breads with the addition of 10 – 25% wheat germs, high protein bread with wheat gluten, milk, or sometimes soy protein. Malt bread produced in the UK is a sticky, sweet, dark loaf that might also contain dried fruit pieces. UK rye bread is usually made from a mixture (50 : 50) of white wheat flour and rye flour.
Bread is made by combining flour, water, salt and yeast. Wheat is the most important cereal grain produced and traded in the world for the production of bread and other baked products. Commercial production of bread may also involve the addition of preservatives and additives to improve flavour, texture and prevent microbiological growth.
Production of most baked products containing wheat flour begins by mixing flour, water, and various other ingredients to a form dough. Incorporation of air during dough mixing is necessary to achieve a baked loaf of good volume, structure, and texture. As dough becomes cohesive, it starts to incorporate air and, thus, decreases in density.
There are several methods for making bread. In a straight dough process all the formula ingredients are added together at the start and the mixture is mixed into an optimally developed dough. The dough is then allowed to ferment for 2-3 hours. After fermentation the dough is divided into loaf sized pieces of dough, rounded into a ball, given an intermediate proof time of 10 – 20 min (allows the dough to relax), and then molded and panned.
In the sponge and dough process a sponge is prepared from part of the flour (ca. 65%), part of the water, and the yeast. The sponge is only mixed enough to have a uniform mixture and then allowed to ferment for 3 – 4 h. After fermentation, the sponge is brought back to the mixer and mixed with the rest of the formula ingredients. At this stage the dough is mixed to optimum development. After mixing the dough is given a floor time (15 – 20 min) to allow it to relax.
Utilization of sour dough is the traditional leavening method in bread making. Bread doughs containing higher proportions of flour or meal require more acidification, that is generally achieved by a sour dough process. During sour dough fermentation a typical microflora develops that includes lactic acid bacteria (lactobacilli) and yeasts. Various sour dough processes (multi-, two-, single stage varying from 2 h up to 24 h) were designed to increase the growth of yeast and lactic acid bacteria to give the final sour dough (full sour) proper acidity (especially the lactic acid/acetic acid ratio) and dough consistency. Often, baker's yeast Saccharomyces cerevisiae is added to accelerate the leavening process.
Consequently proof time of sour dough bread is often long, of the order of several hours.For the production of rye bread an acidification is required.
After bulk fermentation, the dough is divided into individual loaf-sized pieces, and is given a floor time. The purpose of this time is to allow the dough to relax. The dough is then ready for molding. The molding operation is essentially sheeting followed by curling, rolling, and application of pressure. As the dough is sheeted (passed between rolls to be flattened) during the various processes, it must be sheeted in different directions. Continued machining in one direction would align the protein fibrils and result in a dough that was strong in one direction but weak in the direction at a 90° angle to the sheeting. After being molded, the loaf is panned.
The dough is then ready for proofing. This is usually accomplished at 30 – 35°C and at 85% relative humidity. Because the dough now has only limited viscous-flow properties, it fills the pan by expansion. Proofing usually takes about 55 – 65 min; the dough increases greatly in volume. After proofing, the dough is ready for baking.
In the UK, the majority of commercial bakers employ the Chorleywood (CBP) process. In this process, dough mixing and development take place in a single operation in the presence of an oxidising agent such as potassium iodate, potassium bromate, or ascorbic acid. This process requires a high quality wheat flour with a protein content of 12.5% dry matter together with a high level of starch damage and hence high water absorption. An oxidising improver, fat or emulsifier, and extra water and yeast are mixed in at this stage. The whole mixing and development process lasts between two and five minutes. All short time systems require high levels of oxidants. The dough ingredients are mixed together with an intensive energy input and transferred to a hopper which is sometimes sprayed with oil. The dough is divided into loaf size pieces. A preliminary rounding is given to the dough at this stage. The dough is then allowed to rest (“first proof”) before being given a final moulding and (normally) placed into tins. The tins may be sprayed with oil before filling. The dough is allowed to ferment a second time (“second proof”) and may be “cut” before baking.
Baking times and temperatures as well as baking temperature profiles vary largely, dependent on the type of bread. For example, a wheat bread is usually baked for 35 - 40 min at 220 - 230°C. In the UK, baking normally takes place at around 220 to 270°C for 21 to 30 minutes. Heat is transferred by direct or indirect heat to the loaf. The most common energy source is the combustion of natural gas although electricity may also be used. Combustion gases and volatiles from the oven are released via a stack. After cooling, the bread may be sliced before being wrapped ready for distribution.
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