Measuring, Conversion

Bread recipes for the home baker usually list ingredients by volume: cups, tablespoons etc.  A recipe for a 1 lb. loaf of bread requires 2 cups of white bread flour or whole wheat flour. 

Most recipes round flour and water to the nearest quarter cup. The Bread Lover’s Bread Machine Cookbook (Harvard Common Press, 2000; by Beth Hensperger) goes to the nearest 1/8 cup.   Too much water is cited by BLBMC and others as a source of some kinds of failure – weak and sunken loaves.  Too much is in relation to the amount of flour that is being hydrated, and the mixing or kneading action of the machine. An extra 30 grams (1/8 cup = 2 tbsp.) of water into 3 cups of flour means a wet sloppy dough.  The goal is tenacious and somewhat elastic (i.e. that pulls back to its original size and shape) dough that is also extensible – it relaxes.  Too much water can make the gluten too slack.

Small measurement errors can affect the loaf.  If the recipe rounded the wrong way, being precise may lead to an unsatifactory outcome.Errors in conversion factors and mistakes in arithmetic – even in putting numbers into a calculator can lead to the extra tablespoon of water (15 ml = 15 g.) that changes the dough and the loaf.

Usually, recipes refer to a standard measuring cup. A US cup is .87 of 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 depends on how the cup is scooped or filled.

Measuring by weight is more exact. It is the standard for commercial baking, and useful for bread machine making. 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.  Reinhart (The Bread Baker’s Apprentice, and other books) says 4.5 oz.; he measures loosely scooped bread flour scooped in a scoop and poured into the measuring cup. Flour scooped with a measuring cup is lightly packed, and weighs in at 4 and 7/8 oz. (4.875) or 4.9 oz. There is a range of weights for a cup of bread flour – milled high protein wheat flour:

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

I weigh white bread flour (Canadian All Purpose) and whole wheat flour at 139 g. per cup in a recipe. Scales in ounces go down to 1/8 oz, but not necessarily to decimal fractions.  Metric kitchen scales go to the nearest gram. That is close enough for flour.

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.

Books for home bakers may refer to baker percentage (B %), a 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 used to build dashboard indicator of the use of a bakery.  It is as precise as it needs to be, for how it is used. B % is explained:

Flour has plant proteins and starch. Water and protein make dough sticky and stretchy. Starch feeds yeast – some is fermented. Starch is the carbohydrate in bread – the thing that makes it food. Flour is the ground product of grains, including flour and meal. All flour is counted to determine Total flour weight, 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). It is conventional to count all dry ingredients – which works better for a bakery manager than for a home baker.

The weight of every other ingredient is expressed as a percentage of the Total flour weight. The fluid percentage is called the hydration rate, a scale of how wet, sticky and messy the dough is. Conventionally, only the main fluid counts for the hydration rate. Water or milk.

Milk is nearly all water. Butter has water. Maple syrup, honey and other syrups have some water. Eggs have water. ingredients that contain water are not necessarily counted directly – it involves conversions and extra math. Wet ingredients that contain water may be noted to see if a dough has a higher real hydration rate than a simple calculation implies.

A cup of water, USA standard is 236.6 grams (in the metric system one milliliter of water is one gram). (An Imperial cup of water converts to 284 grams. A metric cup of water is 250 grams.)

Water content of baking ingredients can be calculated by referring the USDA Food Composition Databases. For a Canadian product, the Canadian Nutrient File may have the value. Using the databases takes some practice. Not all of the water reported in the data is released from the source ingredient and incorporated into dough. It may be necessary to use a teaspoon or two more water to get the hydration right (for 2 cups of flour in bread machine).

A cup of fluid cow’s milk is 244-245 grams according to USDA averages. Whole milk should be 3.25% butter fat. 2% milk, 1% milk, and non-fat (or skim) milk are reduced fat milk products. In grams, the water/total weights, per cup:

  • Skim 223/245
  • 1% 219/244
  • 2% 218/244
  • Whole 215/244
  • Buttermilk (whole) 215/245

1 + 1/4 cups of skim milk has 1 + 3/16 cups (1 cup + 3 tbsp) of water.

The home baker’s trick is reduce water in a recipe by 1/4 cup for 1 cup of honey, when honey is used to replace sugar. The average for honey in the US and Canada is 17 g water per 100 g of honey.

A typical pure maple syrup for sale in the US or Canada is 32 grams of water per 100 grams of syrup.

A large egg, in the Canadian egg grading system is about 57 g.  A large egg contributes 40 g. to hydration – nearly 3/16 of a cup of water.

Yeast means yeast organisms that have been commercially grown, preserved, packaged, and distributed as a leavening agent. Commercial yeasts changed. The smaller grained instant dry yeast and quick-rise/rapid-rise yeasts entered the market.

Volume to weight conversion is simple and direct if a recipe refers to instant dry yeast or an equivalent small grain yeast. I convert from measuring spoon units to mass units with the factor 1 tsp = 2.8 g.

Recipes published up to about 1999-2000 tend to refer to active dry yeast and could refer to active dry yeast in packets. A recipe might say a packet or a tablespoon of active dry yeast. Active dry yeast was sold in foil packets containing .25 oz. of yeast, which was apparently a tablespoon until late in the 20th century. Active dry yeast became somewhat denser and finer grained, although it remained distinct from the instant dry yeasts. A modern packet of active dry yeast is about 2.25 teaspoons, but is still .25 oz. = 7 grams.

7 grams of modern active dry yeast is equivalent to 5.6 grams of instant dry yeast.

Salt is a chemical control on yeast. Recipes refer to standard table salt.

B% descriptions of a recipe may have 2% salt and 1% yeast. For 2-3 cups of flour,  this means fractions of an ounce of salt and yeast. Recipes univerally refer to ordinary table salt. For conversion from a recipe teaspoon to weight, 1 tsp of table salt = 5.7 g.

Some 21st century table salts are fine-grained and more dense. This does not affect measurement by weight, but a baker measuring by volume will notice that 1 tsp of fine grained salt is different than 1 tsp of ordinary table salt.

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