Several types of wheat are grown today. They differ in their protein content and growing habit.
The most common species of bread wheat is Triticum aestivum. This wheat is high in protein and forms a strong gluten. Most of the wheat produced in North America is Hard wheat, which constitutes 75% of the total crop. Soft wheat makes up 20% and have less protein and form weaker gluten. Durum wheat is a different species that is mainly used to make pasta.
The classification of wheat growth habits and kernel color. Spring wheats are sown in spring and harvested in fall. Winter wheats are sown in the fall and harvested in summer. Red wheat gets its color from the presence of phenolic compounds, which the White wheat variety lacks, and it is often preferred for its sweeter taste.
Saturday, March 31, 2012
Gas bubbles
Breads and cakes are aerated to the point that as much as 80% of their volume is empty space. Bakers use yeast and chemical leavenings to enhance the bubbles in their baked goods. It is important to note that leavenings do not create all of the gas present in the batter or dough. In fact, most of the bubbles form from air introduced when the baker kneads the dough, creams the butter and sugar, or whips the eggs. The carbon dioxide produced by leavenings is released into the water phase of the dough, diffuses to the bubbles already present, and merely enlarges them. Therefore, the initial aeration of doughs and batters strongly influence the final texture of the baked goods.
Starch
The word starch comes from a German root that means "to stiffen or make rigid." While starch has been used in paper making and textiles to stiffen, it has also served the same purpose bread making. Gluten proteins make only 10% of flour by weight, whereas starch makes up 70%. Starch granules absorb water, swell, and set to form the rigid bulk. They account for more than half the volume of dough. Though starch provides gives structure to bread, it also tenderizes it by penetrating and breaking up the gluten network. As carbon dioxide is produced, the rigidity of starch-formed walls stops the expansion of the bubbles. Pressure forces the water vapor inside to pop the bubbles and allow carbon dioxide to escape. As it does, a spongy network is left behind. This accounts for the crumbly texture of bread.
Starch is particularly important in batters where gluten proteins are too dispersed in water and sugar to contribute to the solidity of the cake.
Starch is particularly important in batters where gluten proteins are too dispersed in water and sugar to contribute to the solidity of the cake.
Friday, March 30, 2012
Dough, batter, and texture
Wheat flour has characteristic liveliness and cohesiveness that set it apart from other cereal doughs. These characteristics make it possible for light, delicate loaves, flaky pastries, and silken pastas.
There are three basic elements at work: water, the flour's gluten proteins, and its starch granules. When integrated, these elements create cohesive mass.
Mixture of flour and water is called a dough or batter depending on the relative portions of the ingredients. According to Harold McGee, "doughs contain more flour than water and are stiff enough to be manipulated by hand. All the water is bound to the gluten proteins and to the surfaces of the starch granules, which are embedded in the semisolid gluten-water matrix. Batters contain more water than flour and are loose enough to pour. Much of the water is free liquid, and both gluten proteins and starch granules are dispersed in it." Once cooked, the starch granules absorb water, swell, and create a permanent sponge-like structure made up of millions of tiny air pockets.The term crumb refers to this network. Crust is the outer surface.
The texture of breads and cakes is light and tender because the protein-starch mass is divided up by millions of tiny bubbles. Pastries are flaky and tender because the protein-starch mass is interrupted by hundreds of layers of fat.
There are three basic elements at work: water, the flour's gluten proteins, and its starch granules. When integrated, these elements create cohesive mass.
Mixture of flour and water is called a dough or batter depending on the relative portions of the ingredients. According to Harold McGee, "doughs contain more flour than water and are stiff enough to be manipulated by hand. All the water is bound to the gluten proteins and to the surfaces of the starch granules, which are embedded in the semisolid gluten-water matrix. Batters contain more water than flour and are loose enough to pour. Much of the water is free liquid, and both gluten proteins and starch granules are dispersed in it." Once cooked, the starch granules absorb water, swell, and create a permanent sponge-like structure made up of millions of tiny air pockets.The term crumb refers to this network. Crust is the outer surface.
The texture of breads and cakes is light and tender because the protein-starch mass is divided up by millions of tiny bubbles. Pastries are flaky and tender because the protein-starch mass is interrupted by hundreds of layers of fat.
Controlling Gluten Strength
Gluten development and strength varies according to the product desired. For yeast-leavened breads and puffs, bakers need the tough qualities of gluten. For goods such as pastries, griddle cakes, and cookies, gluten needs to be controlled to avoid undesirable toughness. Here are some techniques and ingredients that affect gluten/gluten strength:
- Flour - high protein flour produces strong gluten, low protein and cake flours produce a weak one. Durum semolina produces a strong, plastic gluten preferable for pasta.
- Oxidizing substances - oxygen frees the sulfur groups at the end of glutenin proteins such that they are more available to react and form longer gluten chains that give dough greater elasticity and strength.
- Water - little water underdevelops gluten and forms a crumbly texture; a lot of water makes for less concentrated gluten and a softer, moister dough.
- Stirring/Kneading - mechanical actions stretch and organize the gluten network.
- Salt - the electrically charged ions of salt cluster around charged portions of the glutenin proteins allowing proteins to come closer to each other and form stronger bonds. Salt geratly strengthens the gluten network.
- Sugar - limits gluten development by diluting the flour proteins.
- Fats and oils - weaken gluten by bonding huydrophobic amino acids, thus preventing the proteins from further bonding to each other.
- Acidity - weakens the gluten network by increasing the repulsive forces between chains. This action is somewhat opposite of the effects of salt.
Gluten
Gluten proteins form long chains that stick to each other.
Gluten is an interconnected network of coiled chains made up of gliadins and glutenin proteins. Each of these proteins is around 1000 amino acids long. Gliadin chains fold onto themselves in a compact mass. These proteins act as ball bearings for glutenin proteins. Glutenins have sulfur-containing amino acids at the end of their chains. Where gliadins only form weak bonds, glutenins form strong sulfur-sulfur bonds with each other, forming long chains. Amino acids in the glutenin chains also form weak temporary hydrophobic bonds that form the coil. The coiled and kinky gluten molecules makes the dough elastic. Thus when dough gets stretched out, the coils extend. When the tension is released, the kinks and coils reform, and the dough shrinks back to its original shape. These properties of plasticity and elasticity allow wheat dough to accomodate carbon dioxide gas without allowing it to escape.
Gluten is an interconnected network of coiled chains made up of gliadins and glutenin proteins. Each of these proteins is around 1000 amino acids long. Gliadin chains fold onto themselves in a compact mass. These proteins act as ball bearings for glutenin proteins. Glutenins have sulfur-containing amino acids at the end of their chains. Where gliadins only form weak bonds, glutenins form strong sulfur-sulfur bonds with each other, forming long chains. Amino acids in the glutenin chains also form weak temporary hydrophobic bonds that form the coil. The coiled and kinky gluten molecules makes the dough elastic. Thus when dough gets stretched out, the coils extend. When the tension is released, the kinks and coils reform, and the dough shrinks back to its original shape. These properties of plasticity and elasticity allow wheat dough to accomodate carbon dioxide gas without allowing it to escape.
Bread 101
What qualifies as bread? On the most basic level, bread is the result from cooking a mixture of milled grains and water. Here is a quick run down of the most common ingredients in bread:
- Flour - Wheat flour is most commonly used in raised bread because it contains two proteins, glutenin and gliadin, which form gluten when combined with water. As the baker kneads the dough, the gluten develops and becomes elastic. This elasticity allows the incorporation of carbon dioxide gas into the dough.
- Starch is a carbohydrate that makes up 70% of the flour by weight. Starch granules release sugars that the yeast feed on. Starch reinforces gluten and absorbs water during baking, helping the gluten contain the carbon dioxide.
- Water is the most important liquid in bread. It dissolves and activates yeast and blends with the flour to create gluten.
- Yeast is a live, single-cell fungus that begins feeding on the sugars in flour and releases the carbon dioxide that makes bread rise. Yeast also adds many of the flavors and aromas associated with bread.
- Baking powder and baking soda are chemical leavenings that participate in the reactions between acidic and alkaline compounds that produce the carbon dioxide necessary to inflate dough or batter. These chemical leavenings act much faster than yeast, and are best used in quick breads.
- Salt slows rising time, which allows the flavor of the dough to develop. Salt also adds structure to the dough by strengthening the gluten, which keeps the carbon dioxide bubbles from expanding too rapidly.
- Eggs add food value, color, and flavor. They also make the crumb fine and the crust tender. Eggs add richness and protein.
- Fat in the form of butter, margarine, shortening or oil add flavor and moisture to bread. Fat slows moisture loss and helps bread stay fresh longer.
- Other liquids such as milk, buttermilk, cream or juice may be added for flavor or to enhance texture. Only add warm liquids to dry ingredients. Too cool liquids slow or stop yeast action. Too hot liquids destroy the yeast and prevent bread from rising.
- Sweetners such as sugar, brown sugar, honey, molasses, jams, and dried fruits may be used to add flavor and color to the crust.
Thursday, March 29, 2012
History of bread
There is no other food as important in the history of humanity as is bread. As Harold McGee expresses in his book, On Food and Cooking, bread took the center stage of life early on as it was "a startling sign of the natural's world hidden potential for being transformed, and [man’s] own ability to shape natural materials to human desires."
Bread and bread-making lore infiltrated language and culture early on. Words such as "Lord" come from the Anglo-Saxon hlaford, which means "loaf ward" or the master who supplies food. The word "Lady" derives its meaning from “loaf kneader.” Even the word "companion" can trace its meaning to “one who shares bread.”
The development of bread in pre-historic times is thought to have come about in two ways: First, by cooking pastes of crushed grain and water to form flatbreads; and second, from setting the paste aside, allowing it to ferment, and baking it in an enclosed oven to form raised breads.
Examples of wheat flatbreads include Middle Eastern lavash, Greek pita, Indian roti and chapatti. Latin American tortilla and North American johnnycake are flatbreads made from maize.
The history of wheat bread dates to 8000 BCE. The earliest record of leaven bread comes from the Egyptians, around 4000 BCE. Yeast production, though not entirely understood, was a notable skill. By 300 BCE, it had become a specialized profession in Ancient Egypt.
The Greeks mark on bread was one of whiteness. The early Greeks developed ways to partly refine grain in a way that it produced white bread. The Romans treasured wheat bread enough that wheat was imported from Africa to satisfy the demand of the Empire.
The 17th century brought improvements in milling and in per capita income that led to a wide availability of whiter bread and the dissolution of the brown guild. The Renaissance gave birth to pastries.
In the 1800s, most bread was still baked in communal ovens. The Industrial Revolution led to bakeries, and adulterated flour with whiteners (alum) and fillers (chalk, ground animal bones). Such developments led to the decline of domestic baking.
Furthermore, some innovations came to leaving. Pearlash, a precursor to baking soda and baking powders, appeared around 1790s. Baking powder and baking soda appeared 1830-1850s. Their development increased the ability to leaven doughs that yeast could not, such as fluid cake batters and sweet cookie doughs.
Twentieth century industrialization and modernization led to a decline in the per capita consumption of bread. As incomes rose, more people had ability to eat meat, and high-fat, high-sugar pastries and cakes. Bread was no longer the staff of life. Bread making became more industrialized in that most bread was made in large central factories, not local bakeries. The result was affordable, white bread with uncharacteristic flavor.
Europeans and North Americans began to eat more bread in the 1980s. Traditional bread making returned. Small bakeries began to produce bread with less refined grain, building flavor with long, slow fermentation, and baking small batches in brick ovens that produced small, dark loaves. The Japanese invented the home bread machine. Today, small fraction of bread is artisan. But manufacturers have started to ship partly baked and frozen loaves to supermarkets. These loaves are rebaked locally and sold while still crusty and flavorful. Currently, we are experiencing a return to flavor and texture characteristic of traditional bread.
Bread and bread-making lore infiltrated language and culture early on. Words such as "Lord" come from the Anglo-Saxon hlaford, which means "loaf ward" or the master who supplies food. The word "Lady" derives its meaning from “loaf kneader.” Even the word "companion" can trace its meaning to “one who shares bread.”
The development of bread in pre-historic times is thought to have come about in two ways: First, by cooking pastes of crushed grain and water to form flatbreads; and second, from setting the paste aside, allowing it to ferment, and baking it in an enclosed oven to form raised breads.
Examples of wheat flatbreads include Middle Eastern lavash, Greek pita, Indian roti and chapatti. Latin American tortilla and North American johnnycake are flatbreads made from maize.
The history of wheat bread dates to 8000 BCE. The earliest record of leaven bread comes from the Egyptians, around 4000 BCE. Yeast production, though not entirely understood, was a notable skill. By 300 BCE, it had become a specialized profession in Ancient Egypt.
The Greeks mark on bread was one of whiteness. The early Greeks developed ways to partly refine grain in a way that it produced white bread. The Romans treasured wheat bread enough that wheat was imported from Africa to satisfy the demand of the Empire.
The 17th century brought improvements in milling and in per capita income that led to a wide availability of whiter bread and the dissolution of the brown guild. The Renaissance gave birth to pastries.
In the 1800s, most bread was still baked in communal ovens. The Industrial Revolution led to bakeries, and adulterated flour with whiteners (alum) and fillers (chalk, ground animal bones). Such developments led to the decline of domestic baking.
Furthermore, some innovations came to leaving. Pearlash, a precursor to baking soda and baking powders, appeared around 1790s. Baking powder and baking soda appeared 1830-1850s. Their development increased the ability to leaven doughs that yeast could not, such as fluid cake batters and sweet cookie doughs.
Twentieth century industrialization and modernization led to a decline in the per capita consumption of bread. As incomes rose, more people had ability to eat meat, and high-fat, high-sugar pastries and cakes. Bread was no longer the staff of life. Bread making became more industrialized in that most bread was made in large central factories, not local bakeries. The result was affordable, white bread with uncharacteristic flavor.
Europeans and North Americans began to eat more bread in the 1980s. Traditional bread making returned. Small bakeries began to produce bread with less refined grain, building flavor with long, slow fermentation, and baking small batches in brick ovens that produced small, dark loaves. The Japanese invented the home bread machine. Today, small fraction of bread is artisan. But manufacturers have started to ship partly baked and frozen loaves to supermarkets. These loaves are rebaked locally and sold while still crusty and flavorful. Currently, we are experiencing a return to flavor and texture characteristic of traditional bread.
Lesson 5: Challah (Braided) Bread
This week I am going to explore all things related to bread. The topics include:
- All things bread
- Gluten
- Flour
- Yeast
- Salt
Thoughts on Scottish Raisin Scones
Usually I write these notes prior to the experimentation, but this time I have some after thoughts instead:
1. The pH of water markedly affects the flavor of the tea. I truly recommend acidifying the water if you use tap water. With the right pH, one can truly appreciate the depth of flavors.
2. There is a vast amount of research performed on benefits/effects of caffeine, tea, and coffee. It is too great to mention here. Some findings are controversial. It raises questions about the specific compounds that are harmful (i.e. addictive stimulants) in comparison to the beneficial ones (i.e. antioxidants.) Research further if interested.
3. When making biscuits/scones, the dough stiffens rather quickly. Knead just enough to shape dough, but beware of overdeveloping the gluten.
1. The pH of water markedly affects the flavor of the tea. I truly recommend acidifying the water if you use tap water. With the right pH, one can truly appreciate the depth of flavors.
2. There is a vast amount of research performed on benefits/effects of caffeine, tea, and coffee. It is too great to mention here. Some findings are controversial. It raises questions about the specific compounds that are harmful (i.e. addictive stimulants) in comparison to the beneficial ones (i.e. antioxidants.) Research further if interested.
3. When making biscuits/scones, the dough stiffens rather quickly. Knead just enough to shape dough, but beware of overdeveloping the gluten.
Another scone recipe - Coffeehouse Scones
This is a tested recipe given to me by a friend.
From: http://www.joyofbaking.com/SconesCoffeehouse.html
Ingredients:
Directions:
From: http://www.joyofbaking.com/SconesCoffeehouse.html
Ingredients:
- 2 cups (260 grams) all-purpose flour
- 1/4 cup (50 grams) granulated white sugar
- 1 teaspoon baking powder
- 1/2 teaspoon baking soda
- 1/4 teaspoon salt
- 1/2 cup (113 grams) unsalted butter, cold and cut into pieces
- 2/3 - 3/4 cup (160-80 ml) buttermilk
- 1 teaspoon vanilla extract (optional)
Directions:
- Preheat oven to 400 degrees F (200 degrees C) and place oven rack in middle of oven. Line a baking sheet with parchment paper.
- In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt. Cut the butter into small pieces and blend into the flour mixture with a pastry blender or two knives. The mixture should look like coarse crumbs.
- Add the buttermilk and vanilla extract to the flour mixture and stir just until the dough comes together. Do not overmix.
- Transfer the dough to a lightly floured surface and knead gently. Form into a 7 in (18 cm) round that is about 1 inch (2.5 cm) thick. Use a 2 1/2 inch (6.5 cm) round biscuit cutter to cut the dough into circles.
- Transfer the scones to the baking sheet and brush the tops with a little milk.
- Bake for 18-20 minutes or until golden brown and a toothpick inserted in the middle comes out clean.
- Remove from oven and transfer to a wire rack to cool.
- Can be stored at room temperature for a few days.
- Makes ten 2 1/2 inch (6.5 cm) or 8 wedge-shaped scones.
Scottish Raisin Scones Recipe
From Ontario Milk Board Calendar, 1980s, as posted in: http://ocw.mit.edu/courses/special-programs/sp-287-kitchen-chemistry-spring-2009/readings/MITSP_287s09_read06_Scones.pdf
Ingredients:
If you don't like raisins, you can add chocolate chips, dried cranberries, almonds, or strawberries.
----
Footnote: When I tried this recipe, the dough was incredibly dry. I added some more liquid to make them work. These scones are not as sweet as I expected. They were okay, but I was a bit disappointed with the recipe.
Ingredients:
- 1 tbsp vinegar
- 1 cup milk
- 4-6 cups unsifted flour
- 3 tbsp sugar
- 1 tsp salt
- 1/2 tsp baking soda
- 1/3 cup butter
- 1/2 cup seedless raisins (see note below)
- 1 egg yolk
- sugar for sprinkling
- Preheat oven to 450 degrees F.
- Stir vinegar into milk, set aside.
- Combine 4 cups flour, sugar, salt, and baking soda in a bowl. Mix well.
- Cut in shortening until mixture resembles coarse crumbs.
- Stir in raisins.
- Add milk mixture to dry ingredients at once and stir with a fork until all ingredients are moisted.
- Add additional flour if mixture is too moist (i.e. you are not able to knead it easily).
- Turn out on a lightly floured board and knead gently about 20 times.
- Make large balls of dough (about the size of small muffins).
- Brush with egg yolk and sprinkle sugar on top.
- Bake in preheated oven at 450 degrees F for 12-15 min or until done.
If you don't like raisins, you can add chocolate chips, dried cranberries, almonds, or strawberries.
----
Footnote: When I tried this recipe, the dough was incredibly dry. I added some more liquid to make them work. These scones are not as sweet as I expected. They were okay, but I was a bit disappointed with the recipe.
Other types of coffee
Expresso is made by forcing water through the grounds with high pressure. Through this process, a higher percentage of the beans oil is extracted, which emulsifies into the brew and gives the drink a velvety texture. The concentration of coffee is three or four times greater in expresso than on unpressurized brews. Expresso also forms a characteristic foam, called the crema, which is the product of carbon dioxide gas and the mixture of dissolved and suspended carbohydrates, proteins, phenolic materials, and pigment aggregates.
Decaffeinated coffee was invented in Germany in 1908. It is made by soaking the green coffee beans in water to dissolve the caffeine, then extracting the caffeine with a solvent, and steaming the beans to evaporate any remaining caffeine. Ordinary coffee contains 60-180 mg of caffeine per cup. Decaff contains 2-5 mg.
Instant coffee is essentially a dry concentrate. It is made by boiling ground coffee in duplicate to obtain maximum extraction of pigments and carbohydrates. Later it is dehydrated and supplemented with aromas. It is used in baking, confections, and ice cream.
Decaffeinated coffee was invented in Germany in 1908. It is made by soaking the green coffee beans in water to dissolve the caffeine, then extracting the caffeine with a solvent, and steaming the beans to evaporate any remaining caffeine. Ordinary coffee contains 60-180 mg of caffeine per cup. Decaff contains 2-5 mg.
Instant coffee is essentially a dry concentrate. It is made by boiling ground coffee in duplicate to obtain maximum extraction of pigments and carbohydrates. Later it is dehydrated and supplemented with aromas. It is used in baking, confections, and ice cream.
Tuesday, March 20, 2012
Brewing and drinking coffee
There are many different methods for brewing coffee. Most methods extract between 20 - 25% of the coffee substance. Standard American filter-drip coffee is the lightest, making a proportion of 1:15 coffee to water. Italian expresso is the strongest at a 1:5 ratio. Brewing coffee is an art, as the results depend on type of drip, temperature, and length of time.
Coffee tastes the best when freshly brewed and consumed. The ideal temperature for sipping is 140 degrees F. It loses aroma and flavor in less than an hour in the pot. It is best to keep hot coffee within its original heat in a preheated, insulated, closed container than on a hot plate, as excessive heat speeds the escape of aroma and flavor.
Coffee tastes the best when freshly brewed and consumed. The ideal temperature for sipping is 140 degrees F. It loses aroma and flavor in less than an hour in the pot. It is best to keep hot coffee within its original heat in a preheated, insulated, closed container than on a hot plate, as excessive heat speeds the escape of aroma and flavor.
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.
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.
Monday, March 19, 2012
Coffee
Coffee trees are native to Africa. They produce a red berry that contains two large seeds or "beans." The history of roasted coffee dates back to the 14th century Arab nations. From then, the coffee tree was taken to India in the 1600s, after which it was taken to Java and then to the French Caribbean. Today Brazil, Vietnam, and Colombia are the largest exporters of coffee.
There are two main trees that produce coffee beans: Coffea arabica, native to the Sudan, produces "arabica" beans; and Coffea canephora, native to West Africa, produces "robusta" beans. About 2/3 of the beans in the international trade are arabica beans. They develop a more complex and balanced flavor than robustas. They also contain less caffeine, less phenolic material, and more oil and sugar. Robustas are only popular because the trees themselves are more disease resistant.
There are two main trees that produce coffee beans: Coffea arabica, native to the Sudan, produces "arabica" beans; and Coffea canephora, native to West Africa, produces "robusta" beans. About 2/3 of the beans in the international trade are arabica beans. They develop a more complex and balanced flavor than robustas. They also contain less caffeine, less phenolic material, and more oil and sugar. Robustas are only popular because the trees themselves are more disease resistant.
Brewing tea
The quality of brewed tea and coffee is highly influenced by the water used to make them. Very hard water can slow flavor extraction, whereas soft water overextracts flavor and tends to have a salty flavor. Distilled water makes flat brews. The ideal water has moderate mineral content and a neutral pH. The final brew has an acidic pH around 5 that supports and balances flavors the best.
Many cities intentionally alkalinize water to reduce pipe corrosion. Alkalinity reduces the quality of flavor of both tea and coffe. Alkaline brews tend to produce red infusions from both, black and green, tea. Alkaline tap water can be corrected by adding tiny pinches of cream of tartar until it just begins to have a slightly tart taste.
Teas are brewed in various ways depending on the type of tea and the regional preference of the brewer. In the West, a small amount of tea is brewed once for several minutes, then discarded. In Asia, a greater quantity of tea leaves is used per ounces of liquid. It is rinsed with hot water and then infused several times. The temperature of water also varies. For black and oolong teas, use water close to boil, and infuse briefly. Green tea is infused longer and at lower temperatures, around 110-160 degrees F/45-70 degrees C. This limits too much extraction of the bitter phenolics and minimizes damage to the chlorophyll pigment.
The typical 5 minute brew of black tea extracts almost all of the caffeine present.
Once tea is properly brewed, it should be separated from the leaves to stop further extraction. Tea is best when drunk fresh. With time the aroma dissipates and phenolic compounds react with oxygen and each other, causing a change in color and taste.
If milk is to accompany the tea, it is best to add hot tea to warm milk to prevent the milk from curddling. The taste of tea with milk is milder because phenolic compounds bind to milk proteins and render them unable to bind to salivary proteins in the mouth.
Lemon juice is sometimes added to tea. The acidity of the lemon alters the structure of red phenolic complexes in black tea so it lightens the brew.
Many cities intentionally alkalinize water to reduce pipe corrosion. Alkalinity reduces the quality of flavor of both tea and coffe. Alkaline brews tend to produce red infusions from both, black and green, tea. Alkaline tap water can be corrected by adding tiny pinches of cream of tartar until it just begins to have a slightly tart taste.
Teas are brewed in various ways depending on the type of tea and the regional preference of the brewer. In the West, a small amount of tea is brewed once for several minutes, then discarded. In Asia, a greater quantity of tea leaves is used per ounces of liquid. It is rinsed with hot water and then infused several times. The temperature of water also varies. For black and oolong teas, use water close to boil, and infuse briefly. Green tea is infused longer and at lower temperatures, around 110-160 degrees F/45-70 degrees C. This limits too much extraction of the bitter phenolics and minimizes damage to the chlorophyll pigment.
The typical 5 minute brew of black tea extracts almost all of the caffeine present.
Once tea is properly brewed, it should be separated from the leaves to stop further extraction. Tea is best when drunk fresh. With time the aroma dissipates and phenolic compounds react with oxygen and each other, causing a change in color and taste.
If milk is to accompany the tea, it is best to add hot tea to warm milk to prevent the milk from curddling. The taste of tea with milk is milder because phenolic compounds bind to milk proteins and render them unable to bind to salivary proteins in the mouth.
Lemon juice is sometimes added to tea. The acidity of the lemon alters the structure of red phenolic complexes in black tea so it lightens the brew.
Sunday, March 18, 2012
Tea styles
Though there are many styles of tea, the following three account for most of the world consumption:
Green tea preserves some of the original qualities of the fresh leaf. It is made by cooking fresh or briefly withered leaves to inactivate their enzymes, then pressing them to release moisture, and finally drying them via hot air or a hot pan. "Pan firing" gives tea a characteristic aroma of roasted foods. In Japan, the leaves are steamed, so they have a more grassy flavor and green color.
Oolong tea is made by allowing modest enzyme transformation. The leaves are significantly withered, then lightly agitated and bruised. Enzymatic action occurs during the subsequent rest period, usually a few hours long. Once the bruised edges turn red, the leaves are pan-fired at high temperatures. The tea is rolled and dried at moderate temperatures, which gives it a light amber color and fruitful aroma.
Black tea undergoes profound enzymatic transformation. The leaves are withered for hours, rolled repeatedly, and air-dried at around 100 degrees Celsius. The tea develops a deep, dark color.
Other teas tend to be variations or additions to one of the above mentioned styles. For example, white tea is a version of Chinese green tea made almost exclusively from buds that are steamed and dried. Scented teas tend to be Chinese teas held for 8-12 hrs in containers with flowers such as jasmine, cassia bud, rose, orchid, and gardenia. They may include 1-2% flower petals. Other teas vary in the type of heat they receive, such as wood fires, or high temperature roasting.
Herbal tea, also known as herbal tisane, is made from ingredients other than the Camellia sinensis plant. There are three main categories: rooibos tea is primarily made from the South African red bush; mate tea is made from the South American Yerba Mate plant; and finally, herbal infusions are made from spices, fruits, flowers, or a variety of other plants.
Iced tea, the most popular form of tea in the US, is made from any kind of tea that is brewed and cooled. Black tea is most commonly brewed for iced tea. It was introduced by Richard Blechynden, a tea plantation owner who, in an attempt to promote his tea during the summer time, threw ice cubes in the mix and had people sample it during the 1904 World's Fair in St. Louis. Rapid cooling from ice makes the brewed black tea cloudy as caffeine and theaflavin compounds complex and precipitate out. To avoid this, brew the tea at room temperature or colder over several hours. The long process extracts less caffeine and theaflavin, so when chilled, they do not complex and the liquid remains clear. Iced tea is often sweetened or flavored.
Green tea preserves some of the original qualities of the fresh leaf. It is made by cooking fresh or briefly withered leaves to inactivate their enzymes, then pressing them to release moisture, and finally drying them via hot air or a hot pan. "Pan firing" gives tea a characteristic aroma of roasted foods. In Japan, the leaves are steamed, so they have a more grassy flavor and green color.
Oolong tea is made by allowing modest enzyme transformation. The leaves are significantly withered, then lightly agitated and bruised. Enzymatic action occurs during the subsequent rest period, usually a few hours long. Once the bruised edges turn red, the leaves are pan-fired at high temperatures. The tea is rolled and dried at moderate temperatures, which gives it a light amber color and fruitful aroma.
Black tea undergoes profound enzymatic transformation. The leaves are withered for hours, rolled repeatedly, and air-dried at around 100 degrees Celsius. The tea develops a deep, dark color.
Other teas tend to be variations or additions to one of the above mentioned styles. For example, white tea is a version of Chinese green tea made almost exclusively from buds that are steamed and dried. Scented teas tend to be Chinese teas held for 8-12 hrs in containers with flowers such as jasmine, cassia bud, rose, orchid, and gardenia. They may include 1-2% flower petals. Other teas vary in the type of heat they receive, such as wood fires, or high temperature roasting.
Herbal tea, also known as herbal tisane, is made from ingredients other than the Camellia sinensis plant. There are three main categories: rooibos tea is primarily made from the South African red bush; mate tea is made from the South American Yerba Mate plant; and finally, herbal infusions are made from spices, fruits, flowers, or a variety of other plants.
Iced tea, the most popular form of tea in the US, is made from any kind of tea that is brewed and cooled. Black tea is most commonly brewed for iced tea. It was introduced by Richard Blechynden, a tea plantation owner who, in an attempt to promote his tea during the summer time, threw ice cubes in the mix and had people sample it during the 1904 World's Fair in St. Louis. Rapid cooling from ice makes the brewed black tea cloudy as caffeine and theaflavin compounds complex and precipitate out. To avoid this, brew the tea at room temperature or colder over several hours. The long process extracts less caffeine and theaflavin, so when chilled, they do not complex and the liquid remains clear. Iced tea is often sweetened or flavored.
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.
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.
Saturday, March 17, 2012
Brief history of tea
The word "tea" comes from the Chinese word "cha" which refers to a drink prepared from the green leaves of the Camellia sinensis plant. The history of tea in China dates back more than 2,000 years. It became a staple of the Chinese diet around 1000 CE. By the 17th century, China began trading with Europe and Russia. Tea took a particular stronghold in England, where consumption rose from 20,000 pounds in 1700 to over 20 million pounds in 1800.
Until the 19th century, all the tea in the world trade was Chinese green tea. In the 1840s, the Chinese developed "black" tea by intensive pressing of the leaves. Black tea is the type most common in the West today.
Around the same time, China began to resist the British practice of paying for tea with opium. Britain in return intensified its tea production in British colonies, particularly in India. The warm regions were better suited for Assam tea, which has more phenolic compounds and caffeine than Chinese tea and produces a stronger, darker black tea. Today, three quarters of tea produced is black. India is the world's largest producer. China and Japan still consume more green tea than black.
Until the 19th century, all the tea in the world trade was Chinese green tea. In the 1840s, the Chinese developed "black" tea by intensive pressing of the leaves. Black tea is the type most common in the West today.
Around the same time, China began to resist the British practice of paying for tea with opium. Britain in return intensified its tea production in British colonies, particularly in India. The warm regions were better suited for Assam tea, which has more phenolic compounds and caffeine than Chinese tea and produces a stronger, darker black tea. Today, three quarters of tea produced is black. India is the world's largest producer. China and Japan still consume more green tea than black.
Quickbreads
Quickbreads are named so for two reasons: they are quick to prepare and are best if eaten shortly after baked. These breads stale quickly.
There are regional differences for quickbreads such as biscuits and scones.
The term "biscuit" originated from French, and it refered to goods that were baked until dry and hard. Biscotti, though of Italian origin, is an excellent representation of the original meaning of a biscuit. It is made from a lean dough leavened with baking powder, baked, cut crosswise into thin pieces, and rebaked to dry at low temperature. Modern French and English biscuits refer to long-keeping sweets or cookies.
American biscuits are entirely different. In the US, biscuits contain no sugar, and often no eggs. They are made from a moist dough of milk or buttermilk, flour, fat (butter), and baking soda. Minimally handled, the dough is briefly baked into a soft bread.
The term "scone" is just as ambigous. Originally scones come from Scottland. Scottish and English scones are similar to American biscuits. Both are flaky and moist, except that scones are sweeter and often incorporate dried fruit. Different areas of the US have their own versions of scones.
Scones are usually accompanied by tea or coffee.
There are regional differences for quickbreads such as biscuits and scones.
The term "biscuit" originated from French, and it refered to goods that were baked until dry and hard. Biscotti, though of Italian origin, is an excellent representation of the original meaning of a biscuit. It is made from a lean dough leavened with baking powder, baked, cut crosswise into thin pieces, and rebaked to dry at low temperature. Modern French and English biscuits refer to long-keeping sweets or cookies.
American biscuits are entirely different. In the US, biscuits contain no sugar, and often no eggs. They are made from a moist dough of milk or buttermilk, flour, fat (butter), and baking soda. Minimally handled, the dough is briefly baked into a soft bread.
The term "scone" is just as ambigous. Originally scones come from Scottland. Scottish and English scones are similar to American biscuits. Both are flaky and moist, except that scones are sweeter and often incorporate dried fruit. Different areas of the US have their own versions of scones.
Scones are usually accompanied by tea or coffee.
Lesson 4: Scottish Raisin Scones
This week the topics include:
Quick bread - scones
Tea
Coffee
It should be short and sweet. Hope you join me!
Quick bread - scones
Tea
Coffee
It should be short and sweet. Hope you join me!
Monday, March 5, 2012
Thoughts on buttermilk pancakes
I am curious to try the recipe before noted. This section made me realize how many imitation products I have consumed in the past, mainly chosen for their cheaper price. One often hears that natural is better, and this lesson puts that theory to the test. I am curious to see if I can truly appreciate a palatable difference between true cultured milks and their cheap imitations. I am most anxious to test:
- cultured sour cream versus acidified sour cream.
- true buttermilk
- probiotic yogurt
Buttermilk pancakes with blueberry compote
Recipe from from Bon Appétit, March 1999, as noted in http://ocw.mit.edu/courses/special-programs/sp-287-kitchen-chemistry-spring-2009/readings/MITSP_287s09_read04_pancakes.pdf
Ingredients:
Blueberry compote (optional)
Ingredients:
Ingredients:
- 2 1/2 cups of all-purpose flour
- 1/4 cup sugar
- 2 tsps baking powder
- 2 tsps baking soda
- 1 tsp salt
- 2 cups buttermilk
- 2 cups sour cream
- 2 large eggs
- 4 tsps vanilla extract
- 3 tbsps unsalted butter
- additional butter or cooking spray
- Whisk first 5 ingredients in large bowl (the dry ingredients). Whisk buttermilk, sour cream, eggs and vanilla in another large bowl. Add to dry ingredients. Stir until batter is just blended but still lumpy (do not overmix).
- Melt 1/2 tablespoon butter on griddle over medium heat. Pour batter by 1/3 cupfuls onto griddle, spacing 2 inches apart. Cook until bubbles break on surface, about 3 minutes. Turn pancakes over. Cook until bottoms are golden, 3 minutes. Transfer to plates. Repeat with remaining batter, adding butter to skillet as needed.
- Serve pancakes immediately with butter and syrup/blueberry compote.
Blueberry compote (optional)
Ingredients:
- 2 1/2 cups frozen blueberries, unthawed
- 1/3 cup sugar
- 1/3 cup water
Directions:
Combine 1 1/2 cups blueberries, sugar and 1/3 cup water in heavy small saucepan. Simmer over medium heat until berries burst, stirring often, about 10 minutes. Add remaining 1 cup berries. Cook until compote coats spoon, stirring often, about 8 minutes. (Can be made 3 days ahead. Cover and chill.) Serve warm.
Combine 1 1/2 cups blueberries, sugar and 1/3 cup water in heavy small saucepan. Simmer over medium heat until berries burst, stirring often, about 10 minutes. Add remaining 1 cup berries. Cook until compote coats spoon, stirring often, about 8 minutes. (Can be made 3 days ahead. Cover and chill.) Serve warm.
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.
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.
Sunday, March 4, 2012
Buttermilk
True buttermilk is composed of the low-fat portion of milk that remains after the cream has been churned into butter. Traditionally, its thickness and flavor develop by mild fermentation. It has remnants of fat globules that make it an excellent emulsifier like lecithin; a characteristic that make it valuable in the preparation of finely-textured foods. True buttermilk is slightly acidic and has a subtle, complex flavor. Regrettably, it is prone to spoilage and off-flavors.
A shortage of true buttermilk after World War II led to the development of imitation “cultured buttermilk.” It is made from ordinary skim milk that is fermented. The process follows that of yogurt, but the fermentation is stopped abruptly by rapid cooling. The gelled milk is then agitated to produce a thick, smooth liquid. Most buttermilk sold in the US is not true buttermilk but rather imitation cultured buttermilk.
Bulgarian buttermilk has yogurt cultures that have replaced the cream cultures. It has increased acidity by fermentation also at higher temperatures; thus it resembles yogurt.
Sour cream
Sour cream is a leaner, firmer version of crème fraîche. It contains 20% milk fat and enough protein to curdle when cooked. It appears to have originated from Central and Eastern Europe and brought to the US in the 19th century. Since then, Americans have added a small amount of rennet, which contains enzymes that cause protein coagulation. The result is a heavier, firmer sour cream than its European counterpart.
Acidified sour cream is made by coagulating milk with acid instead of through fermentation. It is therefore also known as non-fermented sour cream. Manufacturer versions of low fat and non-fat sour cream replace butterfat with starch, plant gum, and dried milk protein.
Crème fraîche
Crème fraîche is 30% milk fat pasteurized at moderate temperatures. It is not made from UHT (Ultra High Temperature) pasteurized or sterilized milk. Two versions are available: liquid and thick. The liquid crème fraîche is unfermented. It has a shelf life of 15 days. The thick version is fermented with a typical cream culture. It has a shelf life of 30 days.
A home-made version of crème fraîche is made by adding cultured buttermilk or sour cream to heavy cream (1 tbsp per cup) and letting it stand at cool room temperature for 12 to 18 hrs or until thick.
Cream cultures
Cream cultures such as sour cream, crème fraiche, and buttermilk are indigenous to Western and Northern Europe. These products result from the slow fermentation produced by the mesophilic bacteria Lactococci and leuconostoc species. These bacteria have three important characteristics that make them ideal for production of creams and buttermilk: 1. They grow best at moderate temperatures. The process of fermentation can be kept at lower temperatures than those that produce yogurt. 2. They are moderate acid producers. Again, it prevents the formation of yogurt from too acidic a condition. 3. They complement flavor by turning citrate into diacetyl; a compound which gives the fermented milk product a characteristic buttery flavor.
Yogurt
Yogurt originated in the warm climates of Southwest Asia and the Middle East. Though it has been produced for thousands of years, it only gained popularity in Europe in the early 20th century. By the 1920s, yogurt attained factory-scaled production. Broader popularity for yogurt came after the French developed a means to give it a creamy texture and added fruit flavors.
Yogurt production follows the common path of fermented milks: heat and fermentation. First, the milk is prepared by heating it to concentrate proteins and denature the whey protein lactoglobulin. This treatment improves the consistency of the yogurt. A denatured lactoglobulin allows casein proteins to bond and form a fine matrix that retains liquid in its small interstices instead of coagulating into semi-solid curds. The milk is then cooled to a warm temperature optimal for bacterial production of lactic acid.
The bacteria used for the fermentation of yogurt are very thermophilic. Industrially, these bacteria include Lactobacillus delbrueckii, subspecies bulgaricus, and Streptococcus salivarius, subspecies thermophilus. These bacteria stimulate each other and in combination acidify milk rapidly. They are also notable for their production of flavor compounds dominated by acetaldehyde, which gives yogurt its fresh, tart flavor.
Fermentation of yogurt at high temperatures of 40 to 45 degrees Celsius (104-113 degrees F) grow bacteria that multiply quickly and produce large amounts of lactic acid. Milk proteins set in 2-3 hrs, but produce a coarse protein network. The proteins assemble in thick strands which give it firmness but leak whey protein readily. In comparison, fermentation of yogurt carried out at 30 degrees Celsius (86 degrees F) grows bacteria more slowly and produces a finer, more intricate network that better retains whey. Yogurt prepared at this lower temperature takes 18 hours to set.
Reduced fat milk yogurt is firmer than the regular kind due to the addition of milk proteins used to mask the lack of fat. The extra milk proteins add density to the coagulated protein network. Manufacturers also add gelatin, starch and other stabilizers.
Frozen yogurt is somewhat of a misnomer. Commercial frozen yogurt is made from iced milk with small dose of yogurt in it, usually in a ratio of 4:1.
Saturday, March 3, 2012
Health benefits of lactic acid bacteria in fermented milk
Lactic acid bacteria do more than just pre-digest lactose and produce yogurt. Back in the early 1900s, the Russian immunologist Ilya Metchnikov proposed that lactic acid bacteria in fermented milks help eliminate toxic microbes in our digestive system. To support Mr. Metchnikov’s prescient claim, research in recent decades suggests that Bifidobacteria, fostered in breast milk, colonizes the infant intestine and keep it healthy through acidification and production of antibacterial substances. Once the infant is weaned, the Bifidobacteria recede in favor of a mixed population of Streptococcus, Staphylococcus, E. coli, and yeasts.
Bacteria such as L. fermentum, L. casei, L. brevis, and L. acidophilus adhere to the human intestinal wall. Their presence shields it from other microbes by the secretion of antibacterial compounds, and by boosting the immune response to infection. Furthermore, research suggests that these bacteria also dismantle cholesterol and reduce the production of carcinogens.
The consumption of fermented milks for health purposes, however, is debatable. At the time of Mr. Metchnikov’s claim, milk fermentation involved a dozen or more microbes. Industrial versions nowadays usually limit it to two or three. This biological narrowing does not only affect flavor and consistency, but its health value as well. In addition, live cultures in industrial buttermilk and yogurt grow well in milk but cannot survive in the human body. Some manufacturers are adding "probiotic" Lactobacilli and Bifidobacteria to their cultured milk products in an attempt to mimic the original fermented milks. Such products are advertised for the health benefits afore noted.
Bacteria such as L. fermentum, L. casei, L. brevis, and L. acidophilus adhere to the human intestinal wall. Their presence shields it from other microbes by the secretion of antibacterial compounds, and by boosting the immune response to infection. Furthermore, research suggests that these bacteria also dismantle cholesterol and reduce the production of carcinogens.
The consumption of fermented milks for health purposes, however, is debatable. At the time of Mr. Metchnikov’s claim, milk fermentation involved a dozen or more microbes. Industrial versions nowadays usually limit it to two or three. This biological narrowing does not only affect flavor and consistency, but its health value as well. In addition, live cultures in industrial buttermilk and yogurt grow well in milk but cannot survive in the human body. Some manufacturers are adding "probiotic" Lactobacilli and Bifidobacteria to their cultured milk products in an attempt to mimic the original fermented milks. Such products are advertised for the health benefits afore noted.
Lactic acid bacteria and fermented milk
Lactose is almost uniquely found in milk. Few bacteria can break down lactose into usable forms of energy. Lactic acid bacteria, also known as Probiotic bacteria, use the enzyme lactase to break down the disaccharide lactose into the more usable monosaccharides glucose and galactose. The bacteria produce lactic acid as a by-product of lactose digestion. The low pH preserves the milk as other microbes cannot survive in acidic conditions. In addition, casein proteins come together in semi-solid curds. The flavor and texture favorably change in a process referred to as milk fermentation.
The history of milk fermentation dates back at least 2,000 years. In the early years, people believed that the fermentation was a spontaneous process. Later, the process was managed by the inoculation of fresh milk with fermented milk. By the late 19th century, bacteria had been identified as a causative agent, though the process was not entirely understood. By the 1900s, starter cultures of unknown mixed bacteria became commercially available. By the 1930s, pure single-strain cultures had evolved for the specific production of sour creams, yogurts, and cheese.
Fermenting lactic acid bacteria include species in the genera Lactobacillus, Lactococcus, Streptococcus, Leuconostoc, and Pediococcus. Some of these species also colonize the mouth, intestine, and vagina of mammals as normal flora.
The history of milk fermentation dates back at least 2,000 years. In the early years, people believed that the fermentation was a spontaneous process. Later, the process was managed by the inoculation of fresh milk with fermented milk. By the late 19th century, bacteria had been identified as a causative agent, though the process was not entirely understood. By the 1900s, starter cultures of unknown mixed bacteria became commercially available. By the 1930s, pure single-strain cultures had evolved for the specific production of sour creams, yogurts, and cheese.
Fermenting lactic acid bacteria include species in the genera Lactobacillus, Lactococcus, Streptococcus, Leuconostoc, and Pediococcus. Some of these species also colonize the mouth, intestine, and vagina of mammals as normal flora.
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