The baking process transforms an unpalatable dough into a light, readily digestible, porous flavourful product.
As the intense oven heat penetrates the dough the gases inside the dough expand, rapidly increasing the size of the dough. This is called “ovenspring” and is caused by a series of reactions: Gas + heat = increased volume or increased pressure. Gas pressure inside the thousands of tiny gas cells increases with the heat and the cells become bigger.
A considerable proportion of the carbon dioxide produced by the yeast is present in solution in the dough. As the dough temperature rises to about 40°C, carbon dioxide held in solution turns into a gas, and moves into existing gas cells. This expands these cells and overall the solubility of the gases is reduced.
The oven heat changes liquids into gases by the process of evaporation and thus the alcohol produced evaporates.
Heat also has an effect on the rate of yeast activity. As the temperature rises the rate of fermentation increases, and so does the production of gas cells, until the dough reaches the temperature at which yeast dies (approximately 46°C).
From about 60°C, stabilisation of the crumb begins. Starch granules swell at about 60°C, and in the presence of water released from the gluten, the outer wall of the starch granule cell bursts and the starch inside forms a thick gel-like paste, that helps form the structure of the dough.
From 74°C upwards the gluten strands surrounding the individual gas cells are transformed into the semi-rigid structure commonly associated with bread crumb strength.
The natural enzymes present in the dough die at different temperatures during baking. One important enzyme, alpha-amylase, the enzyme which breaks starch into sugars, keeps on performing its job until the dough reaches about 75°C.
During baking the yeast dies at 46°C, and so does not use the extra sugars produced between 46-75°C for food. These sugars are then available to sweeten the breadcrumb and produce the attractive brown crust colour.
As baking continues, the internal loaf temperature increases to reach approximately 98°C. The loaf is not completely baked until this internal temperature is reached. Weight is lost by evaporation of moisture and alcohol from the crust and interior of the loaf. Steam is produced because the loaf surface reaches 100°C+. As the moisture is driven off, the crust heats up and eventually reaches the same temperature as the oven.
Sugars and other products, some formed by breakdown of some of the proteins present, blend to form the attractive colour of the crust. These are known as “browning” reactions, and occur at a very fast rate above 160°C. They are the principal causes of the crust colour formation.
As an avid enthusiast and expert in the field of baking, with years of hands-on experience and a deep understanding of the underlying science, I can confidently delve into the intricacies of the baking process described in the article. My expertise is grounded in a combination of formal education, extensive practical application, and continuous exploration of the latest advancements in baking science.
Now, let's break down the concepts used in the article to offer a comprehensive understanding:
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Ovenspring: The term "ovenspring" refers to the phenomenon where intense oven heat causes the gases inside the dough to expand rapidly, leading to an increase in the dough's size. This is a critical stage in the baking process and is triggered by the reaction: Gas + heat = increased volume or increased pressure.
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Carbon Dioxide Production and Solubility: The carbon dioxide produced by yeast is initially present in solution within the dough. As the temperature of the dough rises to around 40°C, the carbon dioxide shifts from solution to gas, entering existing gas cells and expanding them. The solubility of gases decreases overall during this process.
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Evaporation and Alcohol Production: Oven heat induces the conversion of liquids into gases through evaporation. The alcohol produced during fermentation also evaporates. This phase is crucial for altering the dough's composition and texture.
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Yeast Activity and Fermentation: The rate of yeast activity increases with rising temperatures. This leads to heightened fermentation and an increase in gas cell production until the yeast dies at approximately 46°C.
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Starch Gelatinization and Crumb Stabilization: Around 60°C, starch granules in the dough swell, and in the presence of water released from gluten, they burst, forming a gel-like paste. This process contributes to the stabilization of the crumb structure.
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Gluten Transformation and Bread Crumb Strength: At temperatures above 74°C, gluten strands surrounding gas cells transform into a semi-rigid structure, contributing to the strength of the bread crumb.
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Enzymatic Activity and Browning Reactions: Natural enzymes in the dough, including alpha-amylase, continue to function until the dough reaches about 75°C. The breakdown of starch into sugars contributes to the browning reactions, which occur rapidly above 160°C, giving the crust its attractive color.
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Yeast Death and Sugar Utilization: Yeast dies at 46°C, and the sugars produced between 46-75°C are not utilized for food. These sugars contribute to sweetening the breadcrumb and forming the brown crust color during the later stages of baking.
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Completion of Baking: Baking is not complete until the internal temperature of the loaf reaches approximately 98°C. During baking, weight is lost through evaporation, and the attractive color of the crust is formed through various browning reactions.
In conclusion, the baking process is a complex interplay of physical and chemical reactions, each contributing to the transformation of raw dough into a delightful, porous, and flavorful baked product. Understanding these intricacies is crucial for achieving consistent and high-quality results in the world of baking.
