Flour is the product of grinding and milling cereal (grain). The main point of harvesting grain is to preserve the starches in the cereal, to be eaten and metabolized into glucose.
When flour is mixed with water, starches dissolve. Yeast, added to the flour and water, consumes some of the starches – it ferments, creating gas, which is trapped in gluten in the dough, which makes the bread rise, after the dough has been kneaded and portioned. Bakerpedia explains:
When yeasted dough ferments rises and increases in volume, and flavor is developed. Yeast converts starch in flour into sugar, carbon dioxide and ethyl alcohol. CO2 gas is trapped by gluten proteins in the flour which causes dough to rise. Fermentation results in a light and airy crumb.
The yeast propogates. Propogation and fermentation accelerate until the living yeast cells run out of starch, or are killed off by high temperature.
Gliadin and glutenin are insoluble proteins in grain and in flour. When water is added to flour, these proteins react by bonding into a strands and sheets of gluten “a composite of storage proteins … found in wheat, barley, rye, oats, related species and hybrids … ” Cereal scientists and commercial bakers know, referring again to Bakerpedia:
Consisting of mainly gliadin and glutenin, wheat gluten is unique among cereal proteins based on its ability to form a cohesive and viscoelastic mass. This rheological property makes it a dynamic material that is able to grow and keep the gasses within the dough during extended fermentation periods. The viscoelastic nature also provides the oven spring (increase in height due to the expansion of gasses) that we see in the oven.
Whole wheat and bread flour weigh the same amount per unit of volume; bread flour milled to US and European standards (and Canadian All-Purpose) from wheat has more of the proteins that bond to form gluten. It is mixed, kneaded and handled differently.
Bakers discovered that working the dough affected the way the dough behaved in the oven. Bakers knead dough, stretching and folding it on itself, repeating the motion for several minutes. This action structures the gluten. A baker can pause after mixing or start kneading. A professional baker will probably use a mechanical mixer; many home bakers may have one. A mechanical mixer or stand mixer uses mixing arms, a paddle or a spiral dough hook in a circular or elleptical motion. A mixer has a range of speeds. The baker uses a slow speed to mix the ingredients and a higher speed to knead. Kneading pulls the gluten into a network of micro balloons. The dough should be tenacious and elastic to hold together, extensible to stretch, and viscous to flow.
Modern professional bakers work with hundred of kilograms of flour and water. Professional bakers have some control over how long to mix, rest, bake and control over temperature. Ingredients are mixed and kneaded in large industrial mixers, fermented, put into pans and put into ovens, turned out and packaged. The dough goes into pans in small irregular lumps. It has to rise and flow to fill the pan, spring when pans go in the oven, but not spring above the limited headspace of the pan. Professional bakers may use 10-15 minutes of “intensive mixing” – the mechanical mixing of yeasted white flour dough was dominant in professional bakeries for French loaves until Raymond Calvel devised the hybid style in the 1960s. Intensive mixing develops gluten in white flour rapidly. Home bakers with stand mixers use slower speeds due to limitations of machinery (see the stand mixer review by America’s Test Kitchen in print and YouTube) or to use a hybrid, modified or improved mixing method.
Overmixing is a risk for professional bakers using industrial mixers. Machine mixing can stretch dough too much or too often, breaking the gluten strands. An overmixed dough cannot hold the gases, and will not rise. Intensive mixing may affect a loaf with effects short of the complete failure caused by overmixing. Home bakers can have the same problem. A variety of mixers are available to the home baker:
- Food processors can mix dough, although a food processor might only handle 3 cups of flour, and may only have one speed – very fast. The mixing time may be less than a minute. Some food processors have a dough speed and/or special blade to mix dough. The risk of overmixing dough in a food processor is well recognized.
- A home stand mixer can handle several cups of flour, at low-medium speed settings. The power output of a Kitchen Aid stand mixer with a 5 quart bowl may be 325 watts. A Bosch Compact Kitchen Machine may output 400 watts into its dough hook in its stand mixer configuration. Larger stand mixers may output 800 watts. They have to be used at the right settings and for a short time.
Gluten gives elasticity to dough, helping it keep its shape and often gives the final product a chewy texture. Gluten relaxes in time which lets the dough flow and rise. As we read at Bakerpedia:
Excessive use of wheat gluten would result in drier doughs that have a hard time with pan flow, and a higher than normal oven spring.
The proteins to form gluten are found in wheat flour. The proteins can be extracted and dried into vital wheat gluten, a powder used as a dough enhancer.
The dough rises in 2 or 3 stages: bulk fermentation, and intermediate and final proof. Dough is knocked or “punched” down to release gas at the end of the bulk fermentation and again when the loaf is shaped. The dough rises again in the baking pan and springs when yeast warm up the pan goes in the hot oven – before the heat kills the yeast.
Salt controls yeast which affects fermentation. Fermentation affects flavour but it also affects rise, which affects the size of the loaf and the production line. Salt affects the development of gluten. Salt also has a chemical effect on the taste buds (Lallamand Baking Update, Volume 2, No. 6). A few bread styles, such as Tuscan bread, are made without salt. Salt is part of the process for most bread sold by grocery stores and bakeries large and small. Bread is high in sodium, as an effect of the baking process.
Mark Kurlansky’s excellent book Salt: a World History (2002) tells of the use of salt to bake bread in Egypt (3,000 BCE), The production of salt may have started about 8,000 years ago. Salt is a standard and necessary ingredient in most formulas and recipes. The right ratio of flour to salt and yeast means a loaf that will rise on time, and not overproof or balloon.
Professional bakers and some home bakers express ingredient lists or recipes as formulas expressed in baker’s percentage (B%). Bakers use consistent processes to manufacture a consistent product. A formula with salt needs more yeast to ferment and rise properly. Reducing salt changes the process. Professional bakers may use 2 pounds of salt and .77 pound of instant dry yeast per 100 pounds of flour. The B% for salt is 2%; instant yeast is .77%. This works out to .3 ounces = 8.5 grams = 8,500 mg. salt per 3 cups (15 ounces) of flour. A normal loaf of bread has 3,400 milligrams of sodium per loaf – several hundred milligams per slice or serving.
Salt can be reduced , with a reduction in the amount of yeast. A few books and some internet pages unwisely suggest eliminating salt and but list the same amount of yeast that would be used if there was salt in the recipe! Every reduction in salt in a bread formula has to be balanced with a reduction of yeast. The accepted method is reducing yeast by the same percentage as salt. Please Don’t Pass the Salt has recipes for yeasted breads and a note on the general adjustment for yeasted bread recipes.
Artisan bread baking writers suggest that adjusting the salt in formulas leads to unsatifactory results – e.g. Peter Reinhart, Artisan Bread Every Day (Ten Speed Press, 2009) at p. 15 suggests not reducing by more than 10%. This approach warns the aspiring baker that salt is important to baking what consumers and food critics regard as good bread. This approach does not help much for someone avoiding sodium. It is easy to get to 50%. It is possible to go further if final proofing can be extended to let the dough ferment and rise longer. Conversely, working in the kitchen, a baker may detect and arrest an active fermentation by knocking down the dough or getting the loaf in the oven.
Home bakers work with small amounts of salt and yeast. Measurement by weight is desireable, in theory. Few home bakers have scales precise enough. And what is the conversion?
For table salt: 1 tsp = 5.7 grams (round to 6 grams) or .20 oz. There is contradictory information in some publications, which I do not pay attention to because I think the table salt sold in Canada is what I said.
- America’s Test Kitchen/Cooks Illustrated The Science of Good Cooking (2012) lists several brands of kosher salt and sea salt and compares them to table salt, suggesting that Morton’s brand is the standard for table salt at 1 tsp = 7.15 g.
- Peter Reinhart, The Bread Baker’s Apprentice (Ten Speed Press, 2001) says on p. 28 that 1 tsp of table salt = .25 oz which converts to 7 grams.
Some fine crystal table salt on the market in the US weighs 7 grams per teaspoon. A recipe or bread formula ought to read as referring to conventional table salt. The size of the salt crystals affects solubility, which can affect the distribution of salt in the dough, and effect of salt on yeast. Density, as such, doesn’t matter when adding salt by weight. Home bakers can normally read a recipe in terms of level teaspoons of table salt, and should adjust when using coarser (eg. kosher salt, some sea salt), or finely ground salt measured by volume.
Most sources say for instant dry yeast: 1 tsp = 2.8 grams = .10 oz. This is what I use, and verify with the yeast I use. Peter Reinhart, The Bread Baker’s Apprentice (Ten Speed Press, 2001) says on p. 28 that 1 tsp instant dry yeast = .11 oz which converts to 3.1 grams.
Commercial bakers use chemical leaveners for some bread. Home bakers use baking powder and baking soda for corn bread, soda bread, cakes and other baking. Baking powder is baking soda mixed with cream of tartar. Kraft Foods Magic Baking Powder does not provide Food Facts on the labels of small jars in Canada. The published information is that 1 tsp has 300 mg. of sodium. Substitutions for baking powder involve 1/4 tsp of baking soda plus some acid (e.g. vinegar, cream of tartar) for each tsp baking powder.
Baking soda is sodium bicarbonate. It has 1,259 mg. of sodium per teaspoon, which explains the food facts for baking powder.
The science of substitution for baking soda and baking powder is to use potassium bicarbonate, or to use natural bubbles, if possible e.g. whipped egg whites. Potassium bicarbonate is the key ingredient of Featheweight, but is not a grocery product. It is available as a supplement but has a list of side effects and do not use if taking medication warnings.