Yeast is among the simplest life forms on Earth, yet it is absolutely necessary for at least two major food industries. Photo of leavened bread is from: 3268zauber

Photo of activated dry yeast is from: Ranveig. In bread making, the yeast, Saccharomyces cerevisiae, is often sold as a granulated dry form (A). Some alcoholic beverages, such as champagne, can also be carbonated using the carbon dioxide produced by the yeast.įigure 5.1 Yeast is used in many food processing applications. The other major use of yeast, fermentation, depends on the production of ethanol, which results from the same chemical transformation. Leavened bread is softer, lighter, and easier to eat and chew than unleavened bread. The gas, which is produced in tiny pockets in bread dough, acts as a leavening agent: it expands during baking and makes the bread rise. They convert glucose into carbon dioxide (CO 2) and ethanol (C 2H 5OH) in a chemical transformation that is represented as follows: C 6H 12O 6 (s) → 2CO 2(g) + 2C 2H 5OH(ℓ)īread making depends on the production of carbon dioxide. Yeasts live primarily on sugars, such as glucose (C 6H 12O 6). Some species can cause infections in humans. Other species are used for the fermentation of alcoholic beverages. About 1,000 species are recognized, but the most common species is Saccharomyces cerevisiae, which is used in bread making. Opening Essay 5.1 The Law of Conservation of Matter 5.2 Writing and Balancing Chemical Equations Practice Writing and Balancing Equations 5.3 Quantitative Relationships Based on Chemical Equations 5.4 Some Types of Chemical Reactions (1) Combination (or Synthesis) Reactions (2) Decomposition Reactions (3) Single Replacement (or Single Displacement) Reactions (4) Double Replacement (or Displacement) Reactions Acid-Base Neutralization Reactions Precipitation Reactions Solubility Rules Net Ionic Equations Applications and Examples (5) Oxidation and Reduction (Redox) Reactions Rules for Assigning Oxidation States Combustion Reactions A Closer Look at the Importance of Redox Reactions 5.5 Focus on the Environment – Air Pollution 5.6 Chapter Summary 5.7 ReferencesĪlthough yeast has been used for thousands of years, its true nature has been known only for the last two centuries. This text is published under creative commons licensing, for referencing and adaptation, please click here. This content can also be downloaded as an printable PDF, adobe reader is required for full functionality.

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