Chemical equations Yeast is used for the leavening of bread. Yeast uses the sugars and oxygen in dough to produce more yeast cells and carbon dioxide gas. This is called multiplication. The carbon dioxide makes the dough rise which gives the bread a light and spongy texture. Yeast also works on the gluten network. Yeast uses sugars by breaking them down into carbon dioxide and water. The yeast needs lots of oxygen in order to complete this type of fermentation. In a bread dough, oxygen supply is limited and the yeast can only achieve partial fermentation and instead of carbon dioxide and water being given off, carbon dioxide and alcohol are produced.
This is called alcoholic fermentation. To live and grow, yeast needs moisture, warmth, food and nutrients. Commercial yeast is manufactured on an aerated suspension of molasses. Molasses, a form of sugar, provides the food for the yeast so it can reproduce. The molasses is mixed with water and sterilised to kill off unwanted bacteria, clarified by removal of sludge and then held in vats. Once it has been through this process it is called wort.
Yeast has a phenomenal growth rate and can duplicate itself every 90 minutes by a process called budding. During budding, a mature yeast cell puts out one or more buds, each bud growing bigger and bigger until it finally leaves the mother cell to start a new life on its own as a separate cell.
The yeast spores can then withstand long periods of drought, cold and high temperatures until conditions are right for reproduction and it starts to bud all over again. Salt not only provides its own flavour in bread but also helps to bring out the natural flavours of ingredients associated with it. Bread made without salt is extremely bland and virtually inedible. Salt assists with improving dough consistency so that it is easier to handle in the bakery. It helps the fermentation rising process by strengthening the protein network so that it traps more gas.
This makes for a larger loaf. Sugar and sweeteners. Sugar is added primarily to dough to aid the fermentation process. During fermentation rising the yeast acts upon sugar to produce alcohol and carbon dioxide gas.
The alcohol produced evaporates during baking and the carbon dioxide remains to inflate the dough. The presence of sugar in the loaf helps to keep it moist, because sugar attracts moisture. Its ability to caramelise can improve crust colour and a small amount of sugar also improves the flavour of bread. Acidity regulators. To help control dough fermentation or leavening and reduce spoilage. Their main purpose is to prevent mould or bacteria growth in the loaf. Examples of these include vinegar, acetic acid the acid from vinegar , citric acid and sodium diacetate.
Fats and emulsifiers improve the volume, texture, crumb, colour, and softness of bread. They can also improve slicing characteristics, the amount of oven spring how much the dough jumps in height and therefore volume when it is put in the oven , and improve the keeping quality of the bread.
An example of a bread emulsifier is lecithin, which is produced commercially from the soya bean. Lecithin may be added to bread recipes to help combine the mixture of water and vegetable oils present in the dough which otherwise would not form stable mixtures. Fats have the power of controlling how fast the essential protein gluten network develops during bread making and can also make the dough easier to work with.
They also add flavour and are used in almost all products. Milk and milk powder. Milk helps keep a loaf moist and gives buns a soft crust. It is also added to improve the nutritional value and protein level in bread. Malt flour and malt extracts. Malt flour is made from carefully sprouted, then kiln dried barley kernels.
Some malt extracts are used to give taste and colour to bread, especially grain and wholemeal breads. Other malt flours can be used to produce sugar from the starch in flour so that the yeast has more sugar to work on.
They also help bread to stay soft and moist. Flour treatment agents. A major flour treatment agent used in New Zealand is ascorbic acid Vitamin C. The addition of this agent helps to strengthen the dough so it can retain more of the gas produced by the yeast. This helps to produce loaves of better volume and texture. Enzymes are used to speed up the breakdown of starch into sugars that the yeast can use, which helps the dough rise more quickly. They improve the volume and crumb softness in bread.
A common enzyme naturally present in flour is alpha-amylase. Soyabean flour. Soyabean flour used in bakeries usually contains fats and enzymes.
One of the enzymes reacts with oxygen present in air and bleaches any yellow colour and proteins that are present. This produces a whiter bread crumb. The addition of soyabean flour improves loaf volume, crumb softness and the keeping quality of bread.
Gluten flour. Gluten is the protein present in flour which is responsible for the structure and stickiness of bread dough. It is mainly used by professionals as it is highly perishable and must be used within a short time of opening. Open Package — Active dry yeast will keep well beyond its expiration date printed on the package for one 1 year if unopened at room temperature. It will keep longer if frozen. Place directly in the freezer in its vacuum sealed container. If frozen, you can use it directly without thawing.
Unopened Package — If opened, active dry yeast will keep 6 months in the refrigerator and 12 months in the freezer. Keep yeast in its original container with the opened flap folded closed in a resealable plastic bag. I use Instant Active Dry Yeast in all my breads. I use 1 teaspoon of instant yeast per cup of flour. If the recipe calls for over 3 cups of flour, I still use only 3 teaspoons. See Conversation Measurements below. Instant or Rapid Rise Yeast does not require warm liquid to be activated.
This type of yeast has been genetically engineered from different strains of yeast to produce breads. Rapid rise yeast is also more finely granulated than active dry yeast, so it does not need to be dissolved in water first.
It can be added directly to the dry ingredients, making it a popular choice for use with bread machines. Instant active or rapid rise yeast is added to the dry ingredients. When using Instant Active Dry Yeast, the bread recipe only needs one 1 rise. The second rise takes place after the dough has been shaped into a loaf. It will take approximately one hour in a warm place longer in the refrigerator as a slow rise until the dough is just about doubled in bulk.
Storage of Instant Yeast: Instant yeast will keep a year at room temperature if unopened. If opened, it will keep 6 months in the refrigerator and 12 months in the freezer. Sourdoughs were originally produced by wild yeasts. The wild yeasts in the San Francisco area produce a unique flavor in breads. Some sourdoughs are over a hundred years old. The dough becomes a veritable ferment of reactions. Yeast has help in producing flavorful compounds. Bacteria are important flavor builders as well.
But when bakers chill a dough and slow down its rise, the cold dramatically reduces yeast activity. The bacteria, on the other hand, function well even in cold temperatures, so they now have an opportunity to thrive, producing many more marvelously flavorful acids. I have question about sourdough starter. Already a subscriber?
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Classic Bread Stuffing Recipe. Yeast makes dough rise The essentials of any bread dough are flour, water, and of course yeast. Yeast cells thrive on simple sugars. As the sugars are metabolized, carbon dioxide and alcohol are released into the bread dough, making it rise. Scott Phillips. Yeast strengthens bread dough When you stir together flour and water, two proteins in the flour—glutenin and gliadin—grab water and each other to form a bubblegum-like, elastic mass of molecules that we call gluten.
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