Percentage & Conversion

Several cookbooks for home bakers refer to baker percentage (B%), a mathematical method of managing the production of bread. For instance Peter Reinhardt devotes pages 40-45 of The Bread Baker’s Apprentice to this topic.

It is a tool taught to professional bakers, and addressed in culinary texts such as Daniel T. DiMuzio’s Bread Baking; An Artisan’s Perspective. For the baker-manager, it is a calculation to scale inputs up or down to  create 2, 10, 100 or 1,000 consistent loaves of bread. The assumptions are consistency of ingredients, equipment, energy, working space, and time.  For managing production, every ingredient is put into the formula.  The formula can be use to build dashboard indicator of the use of a bakery.  It is as precise as it needs to be, for how it is used. Bakers tinker with the applications of the method. B% is explained:

Total flour weight is determined.  Flour does not include all dry ingredients. It is flour which has plant proteins and starch that form dough and ferment when mixed, hydrated and stretch and folded. It includes the ground product of grains, including flour and meal. All flour is counted even when flours differ in density and protein content. It is conventional to express the relative amounts of flour as a percentage of the total flour weight (e.g. 50% bread flour and 50% whole wheat; or 90% bread flour and 10% rye flour). 

The weight of every other ingredient is expressed as a percentage of the weight of the flour.

Fluid is weighed – the main fluid that yields water.  Milk is nearly all water and almost the same density as water.  Oils don’t count.  The fluid percentage is called the hydration rate, a scale of how wet, sticky and messy the dough is.  Eggs, honey and other ingredients that contain water are not counted but may be noted to see if a dough has a higher hydration rate than the fluid percentage accounts for.

The ingredient that mean a product is bread is yeast. Yeast means, normally, one of the strains of yeast commercially grown and distributed as a leaving agent. Salt is a chemical control on yeast, and vital to a stable process. It weighs what it weighs.  Granularity matters in baking,  but not for B%.

Bread recipes for the home baker usually list ingredients measured by volume: cups, tablespoons etc.  The measurement of ingredients introduces discrepancies. Recipes can be misinterpreted.  A cup may mean the amount that fits in the cup used by the recipe writer and tester, rather than a standard measuring cup.  A US cup is .87 of a an Imperial (U.K., many other English speaking countries) cup.  An Imperial cup is 1.2 US cups.  A metric cup is a quarter liter (250 millilitres) which is .88 Imperial cups or 1.06 US cups. The amount of flour in a cup by volume depends on how the cup is scooped or filled.   

A recipe for a 1 lb. loaf of bread typically requires 2 cups of white bread flour or whole wheat flour.  For 1-3 cups of flour,  2% salt and 1% yeast means fractions of a gram of salt and yeast.

Measuring by weight is more exact – but converting volume to weight is fuzzy. The Bread Lover’s Bread Machine Cookbook suggests 1 cup of bread flour or whole wheat flour converts at 5 oz.  Panasonic suggests, in its bread machine recipes, measuring bread flour and whole wheat flour by weight at the conversion rate of 1 cup = 4.9 oz.  Reinhart (The Bread Baker’s Apprentice, and other books) say 4.5 oz.; he measures differently.  4 and 7/8 oz. (4.875) or 4.9 reconciles to recipes in BLBMC and other recipes that use flour as scooped into a measuring cup.  Scales in ounces go down to 1/8 oz, but not necessarily to decimal fractions.  Metric kitchen scales go to the nearest gram; there are some scales that go down to the nearest .1 gram  Conversions of 1 cup for white bread flour and whole wheat flour:

  • 4.875 (4 and 7/8) oz. = 138 g.
  • 4.9 oz. = 139 g.
  • 5 oz. = 141 g.

The volume to mass conversion for other flours varies. Millers have conversions for their products – e.g.  King Arthur. There are generic conversion calculators and tables but these have to used with care.

A US cup of water reliably converts to 236.6 grams.  (An Imperial cup of water reliably converts to 284 grams. A Canadian cup is 224 grams. A metric cup of water is 250 grams.)  Engineers deal with variation of the density of water with temperature in some applications.  Bakers are not as precise.

A US cup of milk converts to 245 grams.

Table salt 1 tsp = 5.7; but some table salts are fine-grained and more dense

Instant dry yeast 1 tsp = 2.8 g. 

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