Baking process

Author: [British] Stanley P. Cauvain,
Publisher:
Publish Date: 2004-01-01
Features: [Excerpt:] The function of DATA in yeast-leavened wheat flour doughs can be easily confirmed by practical baking tests and many standard dough rheology methods. The function of DATA esters is primarily that when they are added to almost any type of yeast-leavened wheat flour-based dough, they can increase gas retention. The addition amount has a fairly direct relationship with the increase in gas retention until an optimal dosage is reached, followed by a flat phase beyond the optimal dosage, and then a slight decline in efficiency. The final level of improved bread quality far exceeds that of fat. As for the mechanism, only one suitable for empirical observation can be selected from the literature. Strong evidence suggests that when DATA esters are added to bread dough, they quickly and completely combine with hydrated gluten networks. As a result, the gluten network not only becomes stronger but also more extensible and exhibits more elastic characteristics. The gas network produced by this dough has small pore sizes, strong and extensible pore walls. This property can be utilized in three main areas: white bread, breakfast products (such as rolls), and whole wheat rough meal, whole wheat flour, multigrain, and seed-added bread.
① Application of DATA esters in British white bread When used in bread where the flour's protein content is insufficient or the quality is below ideal, adding DATA esters helps stabilize the dough at the end of normal proofing and ensures reasonable oven spring. The baked bread has a higher specific volume and a more uniform appearance. The internal crumb structure is finer, with thinner pore walls, making the bread core appear whiter with a more delicate and uniform structure, feeling softer and more elastic. The addition amount does not exceed 0.3% of the flour weight.
② Application of DATA esters in high-specific-volume bread and breakfast products The term high-specific-volume bread also includes hard and soft rolls, baps, and Britain's "Danish" bread. The goal is to produce high-specific-volume products while maintaining a finer and more uniform structure. These properties are primarily achieved by increasing the proofing volume beyond normal standards. The proofing time for these products is 50–60 minutes, but the formulation contains a higher amount of yeast. After proofing, they exhibit considerable but well-controlled oven spring. These products require high-quality bread flour as the base to allow emulsifiers to play a greater role in improving gas retention. Due to the improved proofing stability provided by emulsifiers, the dough benefits, especially during the transition from proofing to the oven and in the early stages of baking. The quality characteristics of the baked products benefit in a manner similar to that described above for white bread production, except that better-quality flour is used, resulting in fundamentally higher quality and thus improved final product quality.
③ Bread and breakfast products with extended proofing time These products include everything from (loaf bread) to Scottish breakfast rolls, as well as overnight-proofed rolls. For these products, DATA esters are needed to provide proofing stability over a period of 2–16 hours at low proofing temperatures. The entire range of flour quality varies greatly in these products, from low-protein flour used for (loaf bread) to high-protein flour (sometimes with added gluten) used for overnight-proofed Scottish breakfast rolls. All these products require the dough to remain stable under extended and often variable proofing conditions. For (loaf bread), it must be possible to cut the dough without it collapsing at the end of proofing. In all cases, stability is needed to ensure significant changes in the oven, especially for (loaf bread) to achieve good "spring" at the cut points (Collins, 1978).
3.6.1 Where does yeast come from? The use of yeast in bread making dates back at least 6,000 years, believed to have originated with the ancient Egyptians. At that time, dough fermentation may have been done using a mixture of natural yeast and lactic acid bacteria. Bakers would retain a portion of the dough as a starter for the next batch, a practice that continued until the 19th century. In the Middle Ages, European bakers developed a form of brewer's yeast, a more liquid fermentation, often starting with brewing yeast from hops. Louis Pasteur's research contributed to the understanding and development of yeast cultures. Commercial baker's yeast began in the mid-19th century with the Vienna process. The foundation of this process was introducing air and a small amount of steam during fermentation. The development of the Vienna process increased production and allowed for quality control. At that time, yeast grew on grains. In 1915 (during wartime Europe), grain shortages led to the commercial use of molasses for yeast production.
3.6.2 Main forms of yeast Today, baker's yeast is produced in various forms to meet specific needs related to climate, technology, products, methodologies, transportation, and storage. Baker's yeast is available in many different forms, including compressed yeast, granular yeast, emulsified yeast, dry granular yeast, instant yeast, capsule yeast, and frozen yeast. The variations are primarily related to the physical form of the yeast, with the main difference being the moisture content. The development of different strains is based on the properties required for the intended use of the yeast, which will be discussed later.
(1) Compressed yeast This form is often supplied as blocks wrapped in paraffin paper. The standard for this product is a dry matter content of 28%–30%. In the UK, each block weighs 1 kg (2.2 lb); in many other parts of the world, blocks of 0.5 kg are common. The market also offers small household blocks of 42 g (1.5 oz).
(2) Granular yeast Granular yeast typically consists of small granules with a dry matter content of 30%–33% and is packaged in multi-layer paper or plastic bags. Due to its much larger surface area compared to compressed yeast, it is more sensitive to temperature increases that damage yeast quality. Granular yeast has largely been replaced by emulsified yeast but was used in brewing processes and automatic feeding systems in bread making.
(3) Emulsified yeast Emulsified yeast is a pumpable form with a consistency similar to cream. Typically, emulsified yeast replaces compressed yeast at a ratio of 1.5:1, although some emulsified yeast is labeled with a replacement ratio of 1.7:1, which reflects a focus on quality and price. When using emulsified yeast in baking, additional water must be compensated in the formulation.
(4) Dry granular yeast This is an early form of dry yeast, consisting of very low-moisture, off-white granules. Compared to compressed yeast, its advantages lie in easier transportation, storage, and longer shelf life after packaging (sometimes filled with gas) at room temperature. When used in baking, dry yeast needs to be rehydrated in water five times its weight. Production is available in various packaging sizes, from 1-ton containers for repackaging by others to 12.5 kg (27.5 lb), 20 g (0.7 oz) cans, plastic containers, and small bags. Dry granular yeast has largely been replaced by baker's and household instant yeast.
(5) Instant yeast This form of yeast was developed in the 1960s; it has a very low moisture content and fine granules. The main advantage of using instant yeast over dry yeast is that the moisture in the flour does not affect yeast activity. Instant yeast is widespread across the UK and is used in premixes for bread and pizza. Instant yeast is primarily used in the baking industry in some regions where compressed yeast is unavailable or considered less convenient.
(6) Capsule yeast This is a specialized yeast for premixes and does not require the flour to be dried beforehand. Due to its high cost, capsule yeast is rarely used today.
(7) Frozen yeast This can be compressed yeast frozen under special conditions and needs to be thawed slowly when used. There is also a specialized yeast for frozen dough, which has a moisture content lower than compressed yeast but higher than instant yeast, with an appearance similar to instant yeast, yet it can flow freely despite being frozen.
(8) Discussion The above explains the various physical forms and appearances of yeast. Drying, freezing, and encapsulation are all methods of preserving yeast. Yeast producers have developed various strains and growth methods to produce yeast for different baking methods and fermented products. The culture and growth methods affect many factors of yeast properties, such as activity, acid tolerance, osmotic pressure resistance, temperature stability, response to mold inhibitors, and shelf life. Some properties will be discussed later when considering the use of yeast in baking.
3.6.3 Other yeasts Such as beer yeast and koji can also be used in bread production, but they are not specifically developed for this purpose and are therefore unsuitable due to their low activity and lack of specialized tolerance for bread yeast. The following are examples of other yeast products.
- Pizza yeast: This is a low-activity instant yeast type that offers advantages for pizza production, such as reduced shrinkage.
- Inactive yeast: Another type of instant yeast product with other properties, such as replacing L-cysteine to help relax the dough.
- Non-active yeast: Provides flavor and is used as a flavor carrier in products like fried potato chips.
- Yeast extract: Used in food coatings and soup seasonings.
5.5.2 Shorter proofing time Another method to reduce proofing time is to start proofing with dough already at the optimal temperature of 35–40℃ (95–104°F). This is based on experimental evidence: one approach is to make the dough using traditional dough-making equipment and then preheat it in a microwave oven; the other is to use special dough-making equipment to operate on dough that has already reached the desired temperature. However, no method has yet proven sufficient to achieve perfect production conditions.
5.6 From the proofing room to the oven The transfer from the proofing room to the oven is a critical step in bread production. The dough is close to its final volume but remains a completely flexible structure, maintained by continuous gas production within the semi-porous bubbles formed by hydrated protein films. The primary concern is to protect the immature dough from physical damage, as even minor collisions can destroy the fragile structure if the bubble stability is poor. The structure can be particularly weak in certain cases, such as when the flour quality is poor or if the dough has been overmixed, truly testing the capabilities of the product handling system.
5.7 Baking process
5.7.1 Structure and organization of the bread core The center of the bread does not change significantly when it enters the oven. Due to the excellent thermal insulation of the surrounding dough, it is insensitive to any changes in the first few minutes of baking and continues to experience a peak in gas production. In practice, the bread core receives additional proofing time, compensating for the slower fermentation at the beginning of proofing.
Later, the bread core begins to heat up, and as the temperature rises, the dough undergoes a series of complex physical, chemical, and biochemical changes, which are independent of the exact conditions in the oven and thus beyond the control of the baker. From a thermodynamic perspective, the situation in the bread core is relatively simple. The driving force of heat transfer is the temperature gradient from the bread crust near the boiling point of water to the center. The heat transfer mechanism is conduction along the pore walls, with the center temperature rising gradually to approach the boiling point, regardless of the oven temperature. There is no significant movement of moisture, and the moisture content at the end of baking is essentially the same as at the beginning. Figure 5.10 shows the temperature of the bread core during baking (LCT) for three different pan sizes, with smaller cross-sectional area pans baking faster.