Making bread

There are four main steps in making yeast bread.

Mixing

The first step is to mix the ingredients-flour, water, yeast, and salt-together. During mixing, starch granules absorb water and enzymes digest starch into sugars. The yeast feed on the sugars and produce carbon dioxide and alcohol. Glutenin proteins begin to react into gluten. Mixing can be done by hand, with an electric-mixer, or in a food processor. The later offer the advantage of limited oxygen exposure, which in excess can alter the pigments and flavor of the bread.

Kneading

The second step involves dough development. Through kneading, the dough is stretched, folded over, and compressed over and over. This manipulation strengthens the gluten network. It orients proteins to lay side by side which encourages them to form bonds. Overdevelopment of gluten causes bonds to break and turns the dough sticky and inelastic. Bewrae of overdeveloping the dough when kneading mechanically.

Kneading also aerates the dough. The more air pockets formed, the finer the texture of the final bread. Some breads call for minimal kneading. This results in fewer and larger air cells and their corresponding irregular and coarse texture. The gluten is weak and less developed, but it continues to develop through fermentation and can rise to an airy, tender crumb.

Fermentation (Rising)

The third step is fermentation, where the dough is set aside for yeast cells to produce carbon dioxide. As they do so and the carbon dioxide diffuses into air pockets, the dough rises. Yeast have the highest metabolic activity at 95 degrees F. This produces the greatest amount of carbon dioxide and metabolic by-products, some of which can be sour and unpleasant. For quick rising, it is suggested to keep fermentation at 80 degrees F for a couple of hours. Lower temperatures may extend the fermentation an hour or two, but generally produce more desirable flavors.

The end of fermentation is signaled by the dough's volume and the gluten matrix. Fully fermented dough is about twice its original size and has been stretched to its limit, so a finger impression remains when touched. Fermented doughs feel softer and are easier to handle than freshly kneaded dough.

Fermentation can be retarded by storing dough in the refrigerator. Yeast take 10 times as long to rise bread in cool temperatures. Retarding fermentation not only allows bakers to break up the work of making bread, but it has useful effects too. Long, slow fermentation allows greater flavor development by the yeast and bacteria in the dough. Cold dough handles easier without as much loss of leavening gas. The cycle of cooling and rewarming redistributes gases and promotes the development of a more open and irregular crumb structure.

Baking

The last step is baking. The kind of oven where a bread is baked has an important influence on the qualities of the finished loaf. Traditional bread ovens were made out of clay, stone, or brick. The baker preheated the oven by wood fire to temperatures up to 900 degrees F. The domed roof stored heat and radiated it down onto the loaves. The temperature declines during baking. The dough expands early on. The bread benefits from color and flavor development due to enhanced browning reactions.

Modern metal ovens are not ideal for bread making. The maximum cooking temperature is usually around 500 degrees F. Heat cannot be stored as well within their walls, so modern ovens maintain a heat source of gas or electrical elements. The necessary venting does not allow gas ovens to retain the loaves' steam. Some bakers use ceramic baking stones or ceramic oven inserts that mimic the traditional oven. The oven is preheated to its maximum temperature and provide more intensive even heat during baking.

Steam is important in the early baking stages because it increases the rate of heat transfer from the oven to the dough. As steam condenses onto the dough surface, it forms a thin film of water that temporarily prevents it from drying out into a crust. By doing so, it encourages the initial rapid expansion of the loaf. The hot water film eventually dries into an attractive glossy crust. Professional bakers often inject steam in the first minutes of baking. At home, one can spray water or throw ice cubes into the hot chamber to improve oven spring and crust gloss.

There are three stages of baking plus cooling.

Early baking: Oven Spring refers to the first 6-8 minutes of baking. Heat transfers first from the oven floor to the bottom of the dough, and to the top from the hot air and oven ceiling. Heat moves from the surface through the dough slowly through the gluten matrix; and rapidly through the gas network.  Alcohol and water in the dough vaporize. The gas cells expand, and the dough rises. The better leavened the dough, the faster it cooks.

Mid-baking: The dough begins to transform into a sponge when the interior temperature of the dough reaches 155-180 degrees F/68-80 degrees C. At this range, the gluten proteins form strong cross-link bonds, the starch granules gelate, and the amylose molecules leak out. Gas pressure builds and ruptures the walls, turning the closed network of bubbles into an open network of pores similar to a sponge.

Late baking: Starch continues to gelate thoroughly. Continued cooking encourages surface browning reactions that improve color and flavor. Though limited to the crust, these reactions affecte the flavor of the whole loaf because their products diffuse downward. Bread is done when its crust has browned and the inner structure has set. Fully cooked bread feels light and hollow.

Cooling

The temperature varies inside a loaf immediately after being removed from the oven. During cooling, the differences even out.  Most moisture loss occurs at this stage as moisture in the interior diffuses outward. Small rolls dry out the most, while large loaves the least. As temperature declines, starch granules become firmer, which later allows even slicing. This firming continues over the next day and starts the process of staling.

Making coffee

Coffee beans are prepared in the following manner:

First, the ripe berries of the coffee tree are picked and the seeds cleaned by one of two methods. In the dry method, berries are exposed to the sun to dry and ferment, then the fruit is mechanically removed. In the wet method, most of the pulp is rubbed off by machine, and the remainder is liquified by fermenting microbes. Then, the seeds are washed and dried to 10% moisture. The parchment shell is removed, sugars and minerals are leached out, and finally the beans are roasted.

Raw green coffee beans are hard. Roasting transforms them into fragile pockets of flavor. Coffee beans are roasted for 15 minutes or less at temperatures between 375 to 425 degrees F. As the temperature approaches the boiling point of water, the moisture inside the beans turns into steam and puff up the bean (similar to popped corn). At the higher temperatures, proteins, sugars, and phenolic materials break and react with each other in typical Maillard (browning) reactions. The roasted aroma, dark pigment, and flavor develop. At 320 degrees F, the Maillard reactions become self sustaining. The molecular breakdown gnerates more water vapor and carbon dioxide gas. If roasting continues, oil escapes the damaged cells and provides a visible gloss to the surface of the beans. Medium roasts give the fullest brews. The darker beans tend to be more bitter from resulting browning reactions. Once the desired roasting is achieved, the beans are cooled off rapidly.

Coffee keeps reasonably well for a couple of weeks at room temperature and a couple of months in the freezer. Once the beans are ground, the shelf life is only a few days at room temperature.

The key to grinding coffee is to obtain a standard particle size. Too large of a particle makes it hard to control the extraction. Too small particles have a larger surface area that comes in contact with the water, which often leads to overextraction and a bitter flavor. Grinders that allow small pieces to escape before getting too small give more consistent particle sizes and better brews.

Making tea - an enzymatic transformation

The fresh tea leaf has a bitter and astringent taste due to the abundant phenolic substances present. Aromatic molecules are locked up in nonvolatile compounds with sugar. The key to making tea is encouraging the leaf's own enzymes to transform these austeric molecules into pleasant ones.

The best tea is made from a plant's young shoots and unopened leaf buds as they contain the highest concentration of phenolic compounds and related enzymes. These young leaves are harvested and allowed to wither. Withering causes a shift in their metabolism that accounts for a change in flavor and physical fragility. The fragile leaves are rolled or pressed to break down tissue structures that contain cell fluids. Enzymes spill, react with oxygen, and break the aroma-sugar complexes apart. Simple phenolic compounds such as catechin react into larger compounds. The browning enzyme, polyphenoloxidase, uses oxygen to join small phenolic molecules into large complexes that are brown and not astringent at all. The deep, complex of tea is developed by this enzymatic transformation, often referred to as "fermentation," even though no significant  microbial activity is involved.

Once the desired flavor is developed, the leaves are heated to inactive their enzymes. Furthermore, dry heat is used to develop different depths of flavor and to preserve leaves for long keeping. The dry leaves are sieved and graded, and prepared for packaging and consumption.

Maple syrup

North American Indian tribes, notably the Angonquins, Iroguois, and Ojibways, extracted the maple tree sap long before Europeans colonized America. To the colonists, maple sugar was chaper than the tax-laden cane sugar. After the Revolution, some Americans preferred maple syrup on the moral ground that it did not require the work of slaves to produce it. Demand for maple syrup, however, declined steeply once cane and beet sugar became cheap. Today the production of maple syrup is almost isolated to the Eastern Candadian provinces and the American Northeast.

Humans make syrup in a process that mimics the bees' production of honey: Extraction of dilute juices from plants and water evaporation to concentrate the sugars. Tree syrups, such as maple syrup, are similar to honey in that the retain nearly all the original contents of the sap and are not further refined like cane sugar. The Acer saccharum maple tree produces the greatest quantity and quality of sap, and accounts for most of the syrup currently produced.

The first step in maple syrup production is the sap run. The sap is collected in the spring between the first major thaw and the burst of leaf buds. Sap production is affected by four external factors: severe winter that freezes the roots; snow cover that keeps the roots cold in the spring; extreme variation in tempreature from day to night; and good exposure to the sun. The Canadian provinces meet all of these conditions favorably. Sap runs in other trees, but maples produce the most due to a unique mechanism by which they force sugars from the previous season out of storage.

Up until the 20th century, sap was collected by punching a small hole in the tree bark, inserting a spout, and hanging a bucket to catch the sap. Modern methods have improved the efficiency of collecting the sap from multiple trees into a central holding tank. Becasue the sap consists of mainly water that must be evaporated to concentrate the sugar, it takes about 40 parts sap to make 1 part syrup. Currently manufacturers use reverse osmosis to remove up to 75% of the water content without heat. They boil the concentrated sap for flavor development and sugar concentration. Ideally, maple syrup is 65% sugars, with 62% in the form of sucrose and 3% glucose and fructose. The remaining 35% is mainly water with some malic acid and other impurities.

The flavor of maple syrup comes from sugars, acids, vanillin (a wood by-product), and the products from sugar caramelization and browining reactions. The longer and hotter the syrup is boiled, the darker the color and heavier the taste. Maple syrups are graded based on color and flavor. Garde A maple syrup is to be consumed directly whereas Grade B is used mainly in cooking. Maple syrup is expensive, so most supermarket syrups contain little or none, but rather are artificially flavored.

Chemical leavenings

Chemical leavenings are a fast-acting source of gas. They exploit the reaction between acidic and alkaline compounds that result in carbon dioxide production.

Baking soda, also known as sodium bicarbonate (NaHCO3), is the most common alkaline component in chemical leavenings. When mixed with an acid (H+), it reacts in the following way:

Fig 1:

If the dough or batter contains acids, only baking soda is necessary as a chemical leavening. Common acids in baking include: sourdough cultures, buttermilk, yogurt, brown sugar, molasses, chocolate, cocoa (not Dutch processed), fruit juices, and vinegar.

Baking powders are complete leavening systems. They contain baking soda and an acid in the form of solid crystals. Ground dry starch is added to prevent premature reactions with moisture and add bulk to the mix. The timing of gas production varies according to the type of acid crystal used. If the acid is soluble (like cream of tartar), then the reactions occur quickly. If the acid is not very soluble, the reactions take longer. The acid remains in crystal form until the cooking temperature is high enough to dissolve it and promote the reaction with sodium bicarbonate.

"Double acting" baking powders inflate an initial set of gas bubbles upon mixing into the batter, and then a second set during the baking process. Baking powder for commercial purposes contains slow-release acids so that the leavening power is not lost during storage.

Chemical leaveners affect taste and color. Improper measuring and mixing can leave behind unreacted acids and bases that alter flavor. In slightly alkaline conditions, color changes occur as a result from enhanced browning reactions. Observable examples are chocolate turning red or blueberries turning green.

Sugar substitutes

Sugar alcohols, or polyols,  provide bulk without being digested like sugars. Examples are sorbitol, mannitol, other sugars ending in -itol. They are derived from an altered sugar molecule which makes them hard to absorb and use. They only cause a slow rise in insulin levels. In addition, sugar alcohols lack the aldehyde group that initiates browning reactions, making them resistant to discoloration and flavor changes.

Intensive sweeteners can have a sweetness of 50 to 8000 times greater than table sugar. Examples include stevia, saccharin, and aspartame. Their advantage is that only small amounts are needed to attain sweetness, therefore the caloric content is negligible. The disadvantages are flavor differences with lingering after-tastes and heat instability.

Sweetness inhibitors, such as Lactisole, block the taste receptors for sweetness. They are used in roasted coffee, confectionery, and snacks. A tiny amount can reduce the apparent sweetness of sugar by two-thirds.

Kinds of sugar

White sugar is purified sucrose. It is obtained from sugar cane or beets that have been made into a juice, clarified, and converted into a dark syrup. The sucrose is later crystallized and centrifuged to remove impurities (molasses). Table sugar is around 99.85% pure sucrose. The differences in white sugars are attributed mostly to size and purity. Standard granulated table sugar has an approximate length of 0.3 to 0.5 mm.

Large grain sugars, such as coarse and sanding, measure 1 - 2 mm. These sugars are exceptionally pure batches of sucrose. They have been further washed with alcohol to remove impurities and sucrose dust to give them their characteristic sparkle and crystalline appearance.

Extra fine sugars like English caster sugars and baker's special are smaller than table sugar, measuring 0.1 to 0.3 mm. These sugars provide crystalline surfaces that can be used to introduce air into fat during the creaming stage of cake-making.

Powdered sugars offer no roughness to the tongue and measure 0.01 to 0.1 mm. These sugars contain 3% starch to absorb moisture and prevent caking.

Brown sugar is soft and clingy due to hygroscopic glucose and fructose molecules found in its molasses film. It contains a significant amount of water so keep in airtight container. At the same time, it traps air between groups of adhering crystals, so it is important to  pack it down before its volume is measured. When exposed to air, brown sugar dries and becomes hard. To resoften, place a moistened cloth or an apple inside its container. The sugar absorbs the moisture from the cloth or fruit.

Brown sugars are divided into two subgroups:

Factory brown sugars are produced during the initial processing of the cane juice into unrefined sugar. These include demerara, turbinado and muscovado. These sugars retain a coating of the syrup from which they were crystalized.

Refinery brown sugars are produced at the refinery using raw sugar as the starting material, not the cane juice. Ordinary brown sugar is made this way. Some are dissolved and recrystalized, while others are made into white sugar and coated with a thin film of syrup or molasses.

Whole sugars are crystalline sugars still enveloped in the cooked cane juice. These sugars are usually found in international markets. Examples are jaggery (Indian) or piloncillo (Mexican/Latin America).

Molasses, also known as treacle (UK), is the syrup left over after the sugar cane sucrose has been removed. Most molasses today are blends of molasses and syrups obtained at various stages of sugar-making. The darker the molasses, the more its sugars have been caramelized by browning reactions. Therefore, the darker the molasses, the more bitter and less sweet. Their pH is unpredictable, usually between 5 and 7. It can sometimes react with baking soda and produce a leavening effect in baked goods. Molasses also help retain moisture and have antioxidant capacities. Unsulfured molasses refer to molasses that are dark in color and have not been treated with sulfur dioxide.

High-Fructose Corn Syrup is produced by adding enzymes to plain corn or potato syrups to convert some of the glucose sugars into fructose. The ratio then becomes 53% glucose and 42% fructose, with the same sweetness of table sugar. Its acidic pH (3.5 to 5.5) allows it to react with baking soda to produce carbon dioxide and act as a leavening tool. High-fructose corn syrup has long carbohydrate molecules that become tangled and result in a thicker consistency than any other sucrose syrup. This prevents crystallization and moisture loss. It also prolongs storage life.

Vanilla

Vanilla, though one of the most widely used flavorings in the world, is only second to saffron in its cost of production. Most of the vanilla flavoring used today is synthetic.

Vanilla comes from the pod fruit of a climbing orchid native to Central and northern South America. Cultivated for more than a 1,000 years, the Aztecs used it as a flavoring for their chocolate. The Spaniards were introduced to it during colonization, and gave it its name. In the 19th century, Charles Morren, a Belgian botanist figured out how to pollinate vanilla flowers by hand. This discovery allowed for production of vanilla in areas that lacked the pollinating insects of Central America. The French took it to the islands of the coast of Africa, which now supply much of the world's Bourbon vanilla.  Indonesia and Madagascar are today's largest vanilla producers.

The process for making vanilla is long and complex. Long after pollination, the vanilla orchids produce green pods that contain thousands of tiny seeds embedded in a mixture of sugars, fats, amino-acids, and phenolic-sugar storage compounds. The pods are exposed to high heat in order to prevent the pod from using up its sugars and amino acids, and to damage the pods' cells such that the phenolic storage compounds and browning enzymes (polyphenoloxidases) react. Phenolic compounds cluster into colored aggregates causing the vanilla pods to change color from green to brown. The pods are exposed to the sun for several days, then wrapped and allowed to "sweat." This process frees vanillin and related phenolic molecules from their sugar molecules, and develops the vanilla flavor. Finally, the pods are dried for several weeks, and aged to further develop their flavor. It takes 3-5 lbs of fresh pods to make 1 lb of cured beans.

Bourbon vanilla is considered to be the finest type, with the richest flavor. Indonesian beans are lighter and the pods contain less vanillin. Mexican beans contain about half the vanillin of Bourbon vanilla (though the process to develop the vanilla can last several months longer). Rare Tahitian vanilla beans have much less vanillin but carry unique flowery flavors.

Vanilla extracts are made by chopping vanilla beans, repeatedly exposing them to rinses of alcohol and water over the course of several days, and aging them to develop flavor. Artificial vanilla flavoring contains synthetic vanillin made from industrial by-products, such as wood lignin. Though the flavor is not complex like whole vanilla, the cost of production is about 100 times less than real vanilla.

The sticky, resinous material and tiny seeds of the vanilla bean can be easily scrapped and dispersed in food preparation directly. The fibrous pod wall can also be used to flavor dishes but must be soaked in either fat or alcohol to extract its flavor. Prepared vanilla extracts can be dispersed throughout a dish instantly. Keep in mind that they are best added toward the end of cooking as any time spent at high temperatures reduces their aroma.

Chocolate Production

There are three groups of cacao trees: the Criollos, Forasteros, and Trinitarios. The Criollos produce some of the finest flavors, but are disease prone and low-yielding trees. They account for less than 5% of the world crop. The Forasteros provide full-flavored beans and are high-yielding. They account for most of the world crop. Trinitarios are hybrids of the other two.

On plantations and farms, the cacao pods are opened and their contents exposed. The sweet pulp is fermented for 2-8 days. Fermentation of the pulp is a key step in making chocolate flavorful. Three phases occur during fermentation: First, yeasts convert sugars to alcohols and metabolize some of the acids in the pulp. Next, as the oxygen supply in the pods diminishes, lactic acid bacteria attack the pods. Some of these lactic acid bacteria are the same species found in fermented dairy. Last, acetic acid bacteria consume the alcohol produced by the yeast and convert it into acetic acid. The acetic acid then penetrates into the beans, making the cacao beans less astringent. Digestive enzymes within the beans break down proteins and sucrose, which will later produce more aromatic molecules during roasting. The beans soak in some of the flavor of the fermented pulp, which makes the beans more flavorful.

The beans are dried to about 7% moisture, at which point they are resistant to further microbial spoilage. The beans are cleaned and shipped to manufacturers.

The next step is roasting. Manufacturers roast beans to develop their flavor. The roasting needs of cacao beans are milder than those of coffee beans because cacao has an abundance of reactive amino acids that participate in Maillard browning to generate flavor. Therefore, roasting helps preserve the rich flavors within the beans acquired during fermentation.

The shells and nibs are separated after roasting. The nibs are ground into cocoa liquor. After that, the process varies according to the ultimate product desired. For cocoa powder, the cocoa liquor is pressed to remove the cocoa butter, then pulverized. For chocolate, other ingredients are added to the liquor (sugar, milk, vanilla, etc.) and then subjected to conching-a process of extended agitation and added heat. The physical friction breaks up particles of the other ingredients so that they coat the cocoa butter evenly. It also mellows the strong flavor of cocoa by means of aeration. Volatile compounds present in the cocoa evaporate, including acids and aldehydes. Favorable volatiles, such as pyrazines, furaneol, and maltol, become concentrated. These compounds make up much of the characteristic aromas in chocolate. At the end of conching, cocoa butter and lecithin are added to create the creamy texture of chocolate.

Following conching, the liquid chocolate needs to be tempered. Tempering is a process that involves heating and cooling the liquid chocolate to ensure that cocoa butter crystals stabilize and become uniform in size.
Lastly, chococolate is molded and cooled off.

Enzymatic Browning

Ever wonder what happens when a fruit or vegetable discolors soon after being cut? Here is the answer from On Food and Cooking, The Science and Lore of the Kitchen, p. 269:

"[The] discoloration is caused by three chemical ingredients: 1- and 2-ring phenolic compounds, certain plant enzymes, and oxygen. In the intact fruit or vegetable, the phenolic compounds are kept in the storage vacuole, the enzymes in the surrounding cytoplasm. When the cell structure is damaged and phenolics are mixed with enzymes and oxygen, the enzymes oxidize the phenolics, forming molecules that eventually react with each other and bond together into light-absorbing clusters."

It is a similar principle to when people react to sun exposure and become tan. 

So why does lemon juice prevent browning?

Browning enzymes work very slowly in acidic conditions. Aside from its acidity, lemon juice also has ascorbic acid (Vitamin C) which has antioxidant properties.