Proofing (baking technique)
Proofing (also called proving or more rarely blooming), as the term is used by bakers, is the final rise of shaped bread dough before baking. It refers to a specific rest period within the more generalized process known as fermentation. Fermentation is a step in creating yeast breads and baked goods where the yeast is allowed to leaven the dough.
Fermentation rest periods are not always explicitly named, and can appear in recipes as "Allow dough to rise." When they are named, terms include "bulk fermentation," "first rise," "second rise," "final proof" and "shaped proof".
Proofing yeast (as opposed to proofing the shaped bread dough) refers to the process of first dissolving yeast in warm water, a needed hydration step when using active dry yeast.[note 1] Proofing can also refer to testing the viability of yeast by dissolving it in water and feeding it sugar or carbohydrate. If the yeast is viable, it will feed on the sugar and produce a visible layer of bubbles on the surface of the water mixture.
The process of making yeast-leavened bread involves a series of alternating work and rest periods. Work periods occur when the dough is manipulated by the baker. Some work periods are called mixing, kneading, and folding, as well as division, shaping, and panning. Work periods are typically followed by rest periods, these occur when dough is allowed to sit undisturbed. Particular rest periods include, but are not limited to, autolyse, bulk fermentation and proofing. Proofing, also sometimes called final fermentation, is the specific term for allowing dough to rise after it has been shaped and before it is baked.
Some breads begin mixing with an autolyse. This refers to a period of rest after the initial mixing of flour and water, a rest period that occurs sequentially before the addition of yeast, salt and other ingredients. This rest period allows for better absorption of water and helps the gluten and starches to align. The autolyse is credited to Raymond Calvel, who recommended it as a way to reduce kneading time and thereby improve the flavor and color of bread.
Proofing the yeast is a hydration or dissolving process that occurs when dry yeast is mixed with warm water and allowed to rest for a short time. The minimum weight of water required may be calculated: yeast weight x 4 = water weight.
Yeast viability can be tested by mixing yeast in warm water and sugar, and following a short rest period during which it first dissolves then begins to grow, a layer of foam is developed by the action of the yeast, a sign of primary fermentation and live yeast. Typically, using US customary volume units, ¼ cup (≈ 59.1 mL) water at 105–115 °F (41–46 °C) and ½ teaspoon (≈ 2.5 mL) of sugar are used, or expressed differently, a sugar weight of about 3.5% of the water's weight. While this sugar may be sucrose or table sugar, instead it may be glucose or maltose.
Fermentation typically begins when viable baker's yeast or a starter culture is added to flour and water. Enzymes in the flour and yeast create sugars, which are consumed by the yeast, who in turn produce carbon dioxide and alcohol. Specifically, the grain enzyme diastase begins to convert starch in the grain to maltose. The baker's yeast enzyme maltase converts maltose into glucose, invertase converts any added sucrose to glucose and fructose, and zymase converts glucose and fructose to carbon dioxide gas which makes the dough rise, and alcohol which gives the baked bread flavor. Sourdough starters also produce lactic and acetic acids, further contributing to flavor. When the yeast cells die, they release high quantities of a protease which snip protein strands, and in large dieoffs result in soft, sticky dough, less baked volume and a coarse crumb, but in smaller dieoffs, increase dough extensibility and baked volume.
Different bread varieties will have different process requirements. These are generally classified as either straight or sponge dough processes. Straight doughs will require only a single mixing period. During bulk fermentation straight-dough recipes may instruct a baker to "punch down" or "deflate" the dough, while artisan bakers will use terms like "stretching," "folding," and "degassing," meaning to expel gas from the carbon dioxide bubbles that have formed. Sponge doughs will need multiple mixing periods.
Overproofing occurs when a fermenting dough has rested too long. Its bubbles have grown so large that they have popped and tunneled, and dough baked at this point would result in a bread with poor structure. Length of rest periods, including proofing, can be determined by time at specific temperatures or by characteristics. Often the "poke method" is used to determine if a dough has risen long enough. If the dough, when poked, springs back immediately it is underproofed and needs more time. Some breads are considered fully proofed if the indent left by the poke springs back slowly, while others are considered fully proofed when the indent remains and does not spring back.
A bread that is properly proofed will balance gas production with the ability of the bread's gluten structure to contain it, and will exhibit good oven spring when baked. A bread that is under- or overproofed will have less oven spring and be more dense. An overproofed bread may even collapse in the oven as the volume of gas produced by the yeast can no longer be contained by the gluten structure.
Retarding may occur at any time during fermentation and is accomplished by placing the dough into a dough retarder, refrigerator, or other cold environment to slow the activity of the yeast. The retarding stage is often used in sourdough bread recipes to allow the bread to develop its characteristic flavor. A cold fermentation stage is sometimes used to develop flavor in other artisan breads, with a part of the dough ("pre-ferment") before the final mixing, with the entire dough during bulk fermentation, or in the final fermentation stages after shaping.
To ensure consistent results and maintain baking schedules, specialized tools are used to manipulate the speed and qualities of fermentation.
A dough proofer is a warming chamber used in baking that encourages fermentation of dough by yeast through warm temperatures and controlled humidity. It is also called a proofing box, proofing oven or proofing cabinet. The warm temperatures increase the activity of the yeast, resulting in increased carbon dioxide production and a higher, faster rise. Dough is typically allowed to rise in the proofer before baking, but can also be used for the first rise, or bulk fermentation. Desired proofer temperatures can range from around 70F / 21C up to about 115F / 46C (cooler temperatures are achieved in a dough retarder, see below). Commercial bakers typically use large, temperature- and humidity-controlled proofers, whereas home bakers employ a variety of methods to create a warm, humid environment for dough rising. Examples include a home oven with a bowl of water and the pilot light on, a box with a bowl of hot water in it (the water is replaced periodically to maintain warmth), or a counter top proofer (an electric appliance) designed for home use.
A dough retarder is a refrigerator used to control the fermentation of yeast when proofing dough. Lowering the temperature of the dough produces a slower, longer rise with more varied fermentation products, resulting in more complex flavors. In sourdough bread-making, cold decreases the activity of wild yeast relative to the Lactobacilli, which produce flavoring products such as lactic acid and acetic acid. Sourdough that is retarded before baking can result in a more sour loaf. To prevent the dough from drying, air flow in the dough retarder is kept to a minimum. Home bakers may use cloth or other cover for dough that is kept for a longer period in the refrigerator. Commercial bakers often retard dough at approximately 50F / 10C, while home bakers typically use refrigerators set at about 40F / 4C or below.
A banneton is a type of basket used to provide structure for shaped loaves of bread during proofing. Banneton baskets are also known as Brotform or proofing baskets. It is normally used for doughs that are too soft or wet to maintain their shape while rising. Proofing baskets are distinct from loaf pans in that the bread is normally removed from these baskets before baking. Conventionally, these baskets are made out of wicker, but some modern proofing baskets are made out of silicone or plastic. A banneton will sometimes have a cloth liner to prevent dough from sticking to the sides of the basket. Bannetons become more non-stick with use as a small amount of flour accumulates in them. These baskets are used both to provide the loaf with shape and to wick moisture from the crust. Bannetons come in round or oblong shapes.
Alternatively, a couche (pronounced koosh) or proofing cloth can be used on which to proof dough. Couches are generally made of linen or other coarse material to which the dough will not readily stick and are left unwashed, so as to let flour collect in them, increasing their non-stick properties. A couche is typically used for longer loaves, such as baguettes. The loaves are laid on top of the couche, and folds are placed in the linen to separate and support the loaves.
Breads such as sandwich loaves and brioche are normally proofed in the bread pan in which they will be baked.
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- Instant dry yeast may be placed directly into flour undissolved.
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Proofing yeast involves letting the yeast sit in warm water for about five minutes before it is ready to mix with other ingredients.
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... active dry yeast is grown on larger grains of nutrient that have to be dissolved first in warm water (this is called proofing the yeast).
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Active dry yeast ... must be resuscitated in 4-5 times its own weight in warm (100-110°F) water, which is then subtracted from the quantity of total water in a bread formula. The time for blooming or proofing the yeast in warm water is around 10 minutes....
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