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By Joseph Amendola Nicole Rees
John Wiley & SonsISBN: 0-471-40546-9
Chapter OneWHEAT AND GRAIN FLOURS
Any discussion of baking must begin with its most elemental ingredient: wheat flour. Not only is wheat the heart and soul of bread but its special properties allow bakers to produce an astonishing array of products, from pastry to cakes and cookies. This will be the longest chapter in the book, as understanding this primary ingredient is vital to baking.
Wheat (and to a much lesser extent rye) flours do one thing extremely well that the flours of other grains cannot: create a gluten network. Gluten is the substance formed when two proteins present in flour, glutenin and gliadin, are mixed with water. Gluten is both plastic and elastic. It can stretch and expand without easily breaking. A gluten structure allows dough to hold steam or expanding air bubbles, so that yeasted dough can rise and puff pastry can puff.
As with many discoveries, the domestication of wheat and the making of risen bread was as much accident as intent. A truly remarkable series of fortuitous, mutually beneficial interactions between wheat and humankind helped to guarantee the success of both species.
Today's wheat is descended from wild grasses. Our hunter-gatherer ancestors certainly supplemented their diets with large-seeded wild wheat grasses for thousands of years, perhaps even cultivating the stands sporadically. Necessity,however, seems to have been the impetus for domestication of these wild grasses. A climatic shift about 10,000 years ago in the southern Levant (modern Jordan and Israel) brought warm, dry summers. Heat-resistant adaptive grasses thrived as other vegetable food sources diminished. Humans harvested the grasses more frequently, especially favoring the large-seeded, nutrient-packed wild wheats like einkorn and emmer.
Wild wheats are self-sowing. That is, the upper portion of the grass stem that bears the seeds, the rachis, becomes brittle upon maturity. It breaks apart easily in a good breeze or upon contact, scattering the seeds that will become next year's plants. Archeologists and agricultural scientists theorize that when humans gathered the wheat, most of the seeds fell to the ground. The seeds that made it home, attached by an unusually tough rachis, were mutants. Inadvertently, humans selected wheat that would not have survived natural selection: If the stem and kernels remain stubbornly intact, the grass is no longer self-sowing. Perhaps this new wheat was easier to transport back to camp in quantity, meaning a bit of leftover grain could then be planted conveniently close by. In a span of what archeologists estimate to be less than thirty years, humans and this now co-dependent strain of wheat set up housekeeping. Hunter-gatherers became farmers.
Further selection by the farmer, combined with accidental crosses with wild grasses and new mutations, soon produced new wheat varieties. Selection continued to occur not only for obvious boons like bigger kernels and greater yields but also for ease of processing. The advent of a free-threshing wheat, where the seed or kernel separates relatively easily from the husk by mere agitation, was a critical step in the evolution toward bread wheat. Previously, parching-or heating the grain on a hot stone-was a favored method for removing the tightly attached husk from the kernel. The more palatable naked kernels were then softened in boiling water and the resulting gruel was eaten plain or baked later into flatbreads. And flat was most likely the name of the game: Parching at least partially denatures or cooks the gluten-forming proteins in wheat, as well as destroys critical enzymes that help yeast convert sugar into starch. With free-threshing wheat, raw wheat kernels sans husk could be dried and ground, and the resulting "flour" had the potential to consistently produce risen loaves.
Wild yeasts had probably colonized grain pastes on occasion, but it was the availability of a wheat flour that could form a gluten network which made leavened bread feasible. The baker could replicate yesterday's loaf by saving a bit of the old risen dough to use as leavening for the next day's batch. The risen loaves had an appealing texture and aroma, as well as providing a more easily digestible form of nutrients. The Egyptians were using baked loaves of risen bread to start the fermentation process in beer by 5000 B.C.E. The brewery's use of malted grain (usually barley or wheat, sprouted and then lightly toasted) in the beer ferment (wort) attracted the species of yeasts and their symbiotic bacteria that produce bread humans find most appealing. The yeasty dregs of the beer provided bakers with a reliable, predictable yeast variety that is the ancestor of commercial yeast used today. The species of wheat we refer to as bread wheat, Triticum aestivum, was the most favored grain throughout the Roman Empire. During the Dark Ages and up until the nineteenth century, wheat waned a bit, perhaps because it required more effort and time than its more self-sufficient cousins like rye and oats. Wheat returned to preeminent stature early in the twentieth century.
Wheat is the second largest cereal crop in the United States; corn, with its myriad uses in industrial food and even nonfood applications, ranks first. Worldwide, however, wheat or rice, depending on the region, is the dominant food grain. It is wheat's gluten-forming proteins, so inextricably linked with the development of baking, that, when combined with a willingness to adapt to new environments and new demands, help to explain its enormous popularity. It grows well over a wide range of moderate temperatures. It is relatively easy to cultivate and consistently produces high crop yields. The wheat kernel has high nutritional value and good keeping qualities. Wheat can be processed with very little waste; what is not sold as flour is used for animal feed.
Genetically, wheat carries seven chromosomes to a cell. In diploid wheats like einkorn, there are two sets of chromosomes per cell. In tetraploid wheats-durum wheat being the best known example-there are four sets of chromosomes per cell. Hexaploid wheats have six sets of chromosomes and include bread wheat (Triticum aestivum), club wheats, and spelt wheats. Triticum aestivum accounts for 92 percent of the American wheat crop. Of the remaining percentage, about 5 percent is Triticum durum, or durum wheat, and 3 percent is Triticum compactum (red and white club wheats). Durum wheat is used almost exclusively in pasta making, and the club wheats are used in crackers and other products requiring flour with a low protein content.
Classes of Bread Wheat
Of the types of bread wheat grown here in the United States, 5 primary classifications are of major importance: hard red spring wheat, hard red winter wheat, soft red winter wheat, hard white wheat, and soft white wheat. Hardness, growing season, and color are the three criteria used to draw the distinctions among these classes.
Hard and soft refer not only to the actual hardness of kernel of wheat (i.e., how hard it is to chew) but more specifically to the kernel's protein content: The hardest wheats genetically contain more protein and fewer starch granules. Hard wheats contain a layer of water-soluble protein around the starch granules; in soft wheats this trait is far less prominent. For the baker, this means that hard wheat flours produce doughs capable of the greatest gluten development. These hard or "strong" flours are ideal for bread. Hard wheats are grown where rainfall is low and the soil is more fertile, generally west of the Mississippi River and east of the Rocky Mountains up into Canada. Hard wheats account for about 75 percent of the American crop, but only a tiny amount of the Western European crop. This factor requires some juggling of flours when, for instance, adapting a classic French baguette recipe for American flour.
Generally, soft wheats have a high starch yield on milling and a low protein content. They are grown in areas of high rainfall and lower soil fertility, primarily east of the Mississippi River. Low-protein southern flours are deployed to their best advantage in their growing region's specialties-biscuits, pies, and cakes where tenderness is prized over strength. Beyond wheat's given genetic quotient of hardness or softness, environmental conditions determine the hardness of any given crop. Not only the overall protein content but also the quality and specific amounts of each protein present can be affected by seasonal variations.
Winter and spring refer to the two growing seasons for wheat. Winter wheats are planted in the fall. They grow for a very short period of time, become dormant during winter, resume growing in the spring, and are harvested in early summer. They are usually grown in areas that have relatively dry, mild winters, like Kansas. Winter wheat is generally higher in minerals. Spring wheats are planted in the spring and harvested in late summer. They are usually grown in areas with severe winters, such as Minnesota and Montana. Spring wheat usually contains more gluten than winter wheat of the same variety.
Color is the final determining criterion in classifying wheat. A slightly bitter red pigment is present in the seed coat of red wheats, similar to the tannins in tea; this trait has been bred out of white wheats. Hard white wheats are used primarily in whole wheat products where the bitter taste is undesirable, but a relatively strong flour is desired. Tortillas and bulgur are examples. Hard white wheat flour is also becoming popular with artisan bread bakers. Its higher mineral (ash) content makes it ideal for long fermentation periods, and it has a slight natural sweetness. Red wheat generally has more gluten than white wheat.
Components of the Wheat Kernel
A wheat kernel consists of three basic parts: the bran, the germ, and the endosperm. The bran consists of several layers of protective outer coverings. The aleurone layer of starch-free protein that surrounds the endosperm is not truly a part of the bran, but usually comes off with it during the milling process. The bran, comprising 13 to 17 percent of the weight of the wheat kernel, contains relatively high amounts of celluloses (fiber), protein, and minerals. The endosperm, the part of the kernel beneath the bran covering, acts as a food reservoir for the growing plant. It composes 80 to 85 percent of the grain's weight, including the aleurone layer removed with the bran. The endosperm consists of starch granules embedded in a matrix made up of gluten-forming proteins. In its center, near one end, is the germ. The germ, composing 2 to 3 percent of the kernel's weight, is the embryonic wheat plant. It contains high levels of proteins, lipids, sugars, and minerals.
Milling is the mechanical process in which wheat kernels are ground into a powder or flour. Beginning with simple crushing in a mortar and pestle, humans rapidly devised more and more efficient ways to accomplish this feat. The ancient Egyptians advanced to grinding the grain (grist) between two large flat stones (grooved or dressed to let the fine flour particles escape), moving in opposite directions and driven by animal power. Grist mills soon employed the power of running water to drive wheels. Stone-ground flour is de facto whole-grain flour; only when the flour is bolted or sifted will it become white stone-ground flour. The finer the sieve, the whiter the flour will be; it will, however, always contain some of the finely crushed wheat germ. Flour was usually produced in just one session of grinding-only with the advent of new harder wheat varieties was it necessary to pass the grist through again, this time with the stones set closer together. Stone-ground flour is generally produced without generating excessive heat, which is thought to be beneficial to both flavor and performance of the flour in breads. Also, the presence of small amounts of finely ground wheat bran (with its relatively high amounts of pentosans) is believed to increase moisture content in breads and helps prevent staling. Wheat germ provides a nutty, pleasant taste and aroma to the baked loaf.
Flour must be oxidized before it is ready to use (see oxidizing and bleaching, pages 14-15). This can be done by adding a chemical to the flour or it can be done naturally by letting the flour age. Natural aging, or oxidizing, takes three to six weeks. In whole-grain or stone-ground white flours, natural aging of flour can be problematic since both the thiol groups and the fats (wheat germ oils) oxidize. When fats oxidize, they become rancid; therefore, the aging must be done at a cool temperature. Once purchased, naturally aged whole-grain flours must be stored in the refrigerator if they are not used in a timely fashion. Use freshly milled whole-grain flours promptly-or, even better, grind the grain as needed if you work on a very small scale-to prevent off flavors from developing.
For the past hundred years, roller milling has been used to produce the majority of flours. It is especially suited for producing white flours. Roller milling, in addition, creates the capability to produce hundreds of "streams" of flour from one single grain stock. Flour producers can combine various streams to produce flours of a desired protein content or particular makeup.
In either grist or roller milling, the kernel is first cleaned in a series of operations designed to remove dust and any foreign particles. In roller milling, the wheat kernel is then dried and rehydrated to a specific moisture content designed to optimize the separation and grinding processes that follow. At this point, different strains of wheat can be blended to produce a stock with the desired characteristics. The first pass between heavy ridged metal rollers revolving toward one another serves to break the kernel into its component pieces; this first break roll produces some flour, chunks of endosperm (termed variously "shorts," "overtails," or "overs"), bran, and germ. The process is repeated another four or so times, using rollers with successively smaller grooves that are set closer and closer to one another. These are all break rolls, designed to separate the endosperm from the bran. The germ is quite plastic owing to its high oil content and is easily flattened into a single plug on the first couple of passes. It is usually removed by the third break roll (despite its high nutritive content of lipids or fats) because it easily becomes rancid and will cause spoilage in the resulting flours. The bran is somewhat flexible and progressively detaches from the endosperm in large flakes.
Excerpted from Understanding Baking by Joseph Amendola Nicole Rees Excerpted by permission.
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