Magnificent Milk

Milk is unique to the mammal family and has been a source of survival for millions of years. The mammalian families ability to secrete nourishing liquid to their youth has been the reason the mammalian family has strived and succeeded (McGee, 8). Today, milk is still used for nourishment and is found in other products such as cheese, yogurt, and ice-cream. This class of products are called diary (McGee, 10). Milk is comprised of five main components: fat, protein, lactose, minerals, and water (McGee, 13). Since the mineral portion is a small amount, minerals are left out of the composition, leaving four main components of milk. 

The fat content in milk gives milk its creamy taste and will vary depending on the amount the animal secretes into its milk. The fat contains the fat soluble vitamins A, D, E, K and is the primary source of nourishment (McGee, 18). Depending on the amount of fat, milks can be classified as 1%, 2%, whole, or cream. Milk fat exist as fat globules or circular structures that are surrounded by a phospholipid membrane.  Milk proteins are also a circular shape, resembling sun bursts. The two main proteins in milk are curds and whey. The curd proteins are also known as the casein proteins. The proteins, mostly casein’s help stabilize the milk structure. Unlike other products, milk does not destabilize in heat, but acidic conditions do effect the proteins (McGee, 19). The kappa casein is the policeman in milk. Kappa prevents the other casein micelles from growing too large and keeps them separated. Kappa keeps the micelles apart with its negatively end tail. Who knew milk was charged! When milk proteins are exposed to acidic conditions, the negatively charged tail on kappa casein is neutralized and the alpha and beta caseins can bond to one another, curdling the milk (McGee, 20).

Casein Protein

 Lactose is the milk sugar.  Lactose is made of glucose and galactose and gives milk half its calories (and sweetness!). To breakdown lactose, the body needs the enzyme, lactate. The inability to breakdown lactose results in lactose intolerance. Lactose also plays a part in the souring of milk. The bacteria Lactobacilli grows on lactose and converts it to lactic acid. Again, the acidic environment causes milk to sour (McGee, 18). 

Along with the fat and protein content of milk, milk contains calcium which strengthens our bones.  Calcium builds our bone mass since calcium phosphate is the mineralized filler in bones. Osteoporosis is a disease of the bones and their lack of calcium, which effects the bone mass (McGee, 15). Milk on its own is not enough calcium and many women supplement their diet with calcium tablets and eating yogurt for example. 

With all of the ingredient in milk, how is milk one liquid layer? The answer is milk is an emulsion, meaning it is an unstable mixture that will not mix together. The milk emulsion needs an emulsifier to stabilize the liquid so the fat does not separate out from the water content. The fat globules have a phospholipid membrane which acts like the lecithin in eggs and holds the mixture together (McGee, 630).

McGee, A. (2005). On food and cooking, the science and lore of the kitchen. Scribner Book Company.

Bouncin’ Buttermilk Biscuits

Biscuits are a great morning treat for breakfast and are actually quick to make, true to their name quickbreads. The term biscuit comes from the French word, “twice-cooked” and got that name for the baking method. Biscuits are baked until they dry and hard. Well, maybe not hard, because no one wants to eat a rock, so we will say throughly baked (McGee, 549).

Buttermilk biscuits begin with flour, which is the source of gluten. As we know, gluten is the protein in flour and gives breads their structure and elasticity properties. All-purpose flour is used in this recipe and is not high in protein content. Baked goods with all-purpose flour will be lighter. The flour is added to baking powder and baking soda. The powder and the soda act as the leavener's. The B.P. contains the sodium bicarbonate and the acidic ingredient. On the other hand the baking soda cannot act unless it is combined with an acidic ingredient. In buttermilk biscuits, buttermilk is the acidic ingredient. As previously mentioned, buttermilk is acidic because the milk is fermented and releases lactic acid, giving buttermilk that tangy taste. The buttermilk will activate the baking soda so it can release CO2 for rising.

NaHCO3     +     H+     ----->     Na+     +     H20     +     CO2

(soda)         (acid)           (sodium)       (water)        (gas)

Before the buttermilk is added,we need a source of fat. Vegetable shortening is added to the dry ingredient to give a crumbly dough that sticks together. Why does the dough stick together once added? The shortening “shortens” the gluten network by preventing cross-linking between the gluten proteins, interfering with the structure. The shortening effect gives a crumbly dough. Shortening is a solid at room temperature and it made of hydrogenated vegetable oil. Do not let the word vegetable fool you. Crisco, a shortening is a hydrogenated oil, meaning additional H’s are added to a molecule. Hydrogenation extends the shelf life of the product. In partially hydrogenated fats, trans bond’s or trans fat are present. This has a health implication, because trans fats are more favorable because they are a lower energy molecule. Trans fat’s are linked to cardiovascular disease. You should minimize the amount of trans fat’s in your diet, because as mentioned they are linked to CAD and common in high-fat, processed foods (Wikipedia, 2011). Trans-fatty acids raise your LDL’s and decrease you HDL’s. High LDL’s and low HDL’s increase you chance of developing CAD (Mayo Clinic, 2011).

Once all of the ingredients are added, buttermilk was added to achieve a sticky dough. We had mixed the dough with our hands. The dough was rolled out on the counter. Even though, the biscuits are flakey, the dough was too flakey to roll out and get a clean circle shape with the biscuit cutter. In the future, I would add more buttermilk for a softer dough. Since the dough was so flakey, it was hard to roll out the roll. The dough was rolled out and folded over itself 3 times for the layered effect. We cut 1 1/2 inch thick biscuits, because they will rise! Next time, I would only cut the one inch thick biscuits, so they do not topple over. The biscuits baked for 22 minutes and were crispy on the top and flakey and soft in the center. The dough was the perfect consistency, but the dough tasted too salty in my opinion. Next time I will half the salt because I do not like the taste of salt. Also next time, we should brush the tops of the biscuits with buttermilk so they will have a buttery top. This was an easy recipe and definitely something I can do again.

Mayo Clinic. (2011, May 06). Mayo clinic. Retrieved from http://www.mayoclinic.com/health/trans-fat/CL00032

McGee, A. (2005). On food and cooking, the science and lore of the kitchen. Scribner Book Company.

Wikipedia. (2011, November 04). Hydrogenation. Retrieved from ttp://en.wikipedia.org/wiki/Hydrogenation

Yummy Yogurt

Yogurt is my first choice of breakfast’s on the go when I am running out the door to class. I love yogurt for its creamy texture and sweet flavors. Are these attributes common among all yogurt’s or just Yoplait’s?

Yogurt comes from the Turkish word “milk” and also means “thick” (McGee, 48). Common in ancient cultures, yogurt did not hit Europe until the 20th Century. At this time, scientist were able to identify the property of fermented milk and the bacteria produced. It was this bacteria that enhanced the natural bacteria in the gastrointestinal tract and prevented destructive bacteria from infiltrating the body. Yogurt flavors were not always Boston Cream Pie and Wild Strawberry. Up until the 1920’s, only plain yogurt existed. Yogurt is made from fermented milk, bacterial cultures and in some cases, flavorings and sugar. We made plain yogurt from fresh milk and plain yogurt. The plain yogurt was considered our starter and already contained the common bacteria Lactobacillus and Streptococcus. Live cultures can be bought that contain the bacteria, but on our case, we used plain yogurt. The milk was heated which destabilized the proteins (McGee, 48). The heat denatures the whey protein Lactoglobulin. The milk was heated via a double boiler to prevent scalding the milk. A double boiler made it easier to regulate the temperature of the milk to 185 degrees. The milk was removed from the heat and the plain yogurt was added, which means the bacteria was added. At this point, the milk was still liquid and remained the white color. The casein protein was broken down by Streptococcus and allowed to slightly bind with other casein proteins. The casein proteins were able to bind together at a few spots, creating a matrix structure and not chunks as in the cheese. This matrix gives yogurt its thicker texture. The circular structure of Streptococcus allows the bacteria to function at higher temperatures. At this elevated temperature, the bacteria are allowed to grow and ferment the milk by producing lactic acid (Probiotic.org, 2009). The yogurt was covered with plastic wrap to seal in the heat and left untouched for the milk to set. At two hours, the yogurt had not gelled yet, and remained liquid. The finishing appearance of the yogurt is thinner than store bought yogurt because store bought yogurt contains corn starch, which is a thickener. The starch gives the yogurt the creamy texture we know. Greek yogurt is even thicker than normal yogurt because the water the whey are strained out of the yogurt (Greek yogurt vs..., 2011). In the future, I would add more sugar to the yogurt, so it is sweet and the sugar also acts as food for the bacteria.

Lactobacillus

Streptococcus

Double Boiler

Adding the plain yogurt

Example of Bacteria in yogurt

Lactic Acid

Finished Product

Greek yogurt vs. regular yogurt [Web log message]. (2011, May 13). Retrieved from http://eyeitryit.com/2011/05/13/greek-yogurt-vs-regular-yogurt/

McGee, A. (2005). On food and cooking, the science and lore of the kitchen. Scribner Book Company.

Probiotic.org. (2009). Streptococcus thermophilus . Retrieved from http://www.probiotic.org/streptococcus-thermophilus.htm

Blue-ribbon Buttermilk

Buttermilk is the liquid residue after separating butter from fresh milk. Buttermilk can be used in soda bread and scones or for enjoying like milk. The issue with buttermilk, is most people do not consume enough buttermilk to justify buying buttermilk at the store, but when the pancakes call for 1/2 cup of buttermilk what do you do? You can make your own buttermilk with milk and vinegar and it only takes 15 minutes! For quick buttermilk, the milk is combined with the vinegar. Since the vinegar is added, buttermilk will be more acidic than fresh milk and smell like the milk has gone bad. The vinegar is the “starter” like the cultured buttermilk. The vinegar lowers the ph and the casein protein will precipitate out, similar to the cheese recipe. The milk mixture is now thicker. The cultured buttermilk is made from the buttermilk, which acts as the starter and fresh milk. The buttermilk will turn the fresh milk’s lactose into lactic acid (the acidic taste). As the mixture becomes more acidic, the ph will drop. We know that under acidic conditions, enzymes are no longer optimal. The casein milk proteins are destabilized, giving cultured buttermilk that thick texture (Fankhauser, 2007). True buttermilk is made during the process of whipping heavy cream into butter. The buttermilk is the left over liquid. True buttermilk is low fat and has a less acidic taste since vinegar is not added and this buttermilk is not fermented. Since buttermilk is acidic, it can last longer than fresh milk. The acidic conditions kill potential bacteria (McGee, 50).

	Quick Buttermilk	Cultured Buttermilk	Buttermilk from butter
Flavor	More acidic than fresh milk due to the vinegar. Flavor is slightly sour. Consistency is still liquid similar to fresh milk.	This buttermilk has a tangy flavor from the fermentation process. Consistency is thicker, similar to cream.	Consistency is similar to fresh milk and the taste is not as acidic as quick or cultured. Creamy taste from the fat globule remnants.
Chemical	This buttermilk is not as good as a leavener as true buttermilk.	Left to sit to acquire bacteria, giving the milk a tangy flavor.	Good for preparing smooth textured foods from ice-cream to baked goods. It is a good emulsifier.

Lactic Acid

Quick Buttermilk

Cultured Buttermilk

Fankhauser, D. (2007, June 14). Making buttermilk. Retrieved from http://biology.clc.uc.edu/fankhauser/cheese/buttermilk.htm

McGee, A. (2005). On food and cooking, the science and lore of the kitchen. Scribner Book Company.

Say Cheese!

Mozzarella is a type of cheese originating from the Southern tip of Italy. This cheese was first made with Buffalo’s milk and is still considered a delicacy. Today, Mozzarella is made with cow’s milk around the world (Zonis, 2006). Mozzarella’s name is derived from the Italian verb, “mozzare,” meaning”to cut off”. This name was given to the cheese because of the action of cutting the curd into smaller pieces. Mozzarella is normally a white cheese that is very moist. The trick to making Mozzarella, is not in complex ingredients, but the complexity of heating and cooling the cheese several times throughout the process (New England Cheesemaking Suppy, 2011).

Mozzarella cheese begins with adding citric acid to water. The citric acid causes the milk to instantly curdle. Without citric acid, the curd would not be able to be stretched to achieve the milky-smooth texture of Mozzarella. To aid in stretching the milk, the milk proteins casein’s must be broken down. The citric acid is the first attempt to break down the proteins into amino acids. Since the citric acid is slow, rennet will come in and finish the job (Maranowski, 2008). The acid will not add flavor or color to the cheese. Citric acid is the acid found in citric fruits like lemons and lime. It has a white appearance and salt like texture. The taste is sour, hence why lemons are sour!

Citric Acid

Citric Acid in Water

The next step is to add the rennet. The word “Rennet” was derived from the German word “rennen” which means to “run-away” or “coagulate”. In the kitchen, we use rennet, but the biologically correct term is chymosin. Ending in “sin” indicates rennet may be a enzyme... (Fankhauser, 2009).

That’s correct!

Rennet is a natural occurring enzyme found in the stomach of a young cow, goat, or sheep. It causes curdling of the milk producing the curds and whey. Rennet is also known to coagulate the milk in the terms that the milk yields chunks (curds) and liquid (whey) (Pav, 2010). The mechanism by which rennet works is destabilizing the casein protein in the milk, encouraging the proteins to join together, forming a gel. The rennet targets the kappa casein, rendering it inactive. Since kappa casein prevents the alpha and beta from bonding to one another, once kappa casein in inactive, the alpha and beta caseins can be precipitated by the calcium in the milk. The act of precipitation causes casein proteins to become solid or the curds (McGee, 56).

Thistle Plant for vegetable rennet

For our Mozzarella cheese we used the Rennet tablets by Junket. These tablets are made vegetable or plant materials and will still curdle milk. This is for vegetarians and vegans (McGee, 57). The thistle flower is used for rennet instead of a young calf’s stomach lining. Vegetable rennet is intended to work as well as animal base rennet.

Rennet and Water

Curds forming

The next steps in cheese making is the delicate balance between heating and cooling. The citric acid was added to the milk and heated to 90 degrees. The milk mixture began to thicken at this point and chunks formed.The high temperature aids the acid in its act of destabilizing the proteins. The milk mixture was removed from the heat (cooling) and the rennet was added at this point to pick up where the acid left off. The milk mixture continued to thicken. The rennet was gently stirred in to ensure even distribution, but slowly to prevent disturbing the curd formation. The cheese was left to sit for 40 minutes. During this time the curds where forming and a chunky, white layer formed on top of the whey, which was a yellowish color. After 40 minutes, the curds were cut into small chunks, hence the name Mozzarella. The curds and whey were again heated to 105 degrees. The second heating killed bacteria and encouraged flavor in the cheese. Heating also promotes the whey separating form the curds (McGee, 61). Again, the cheese was removed from the heat and cooled. With a metal colander, the curds where strained to remove excess whey. This was repeated twice to collect more curds (more curds=more cheese). At this time, the curds were white chunks. To achieve the smooth cheese, the curds where reheated to 130 degrees. Measuring the temperature was difficult at this time because the cheese was not liquid. The temperature was carefully watched to prevent the cheese from getting too hot. The final step in cheese making is kneading and stretching the cheese till the Mozzarella is smooth and creamy. Our cheese did not get to the stage of creamy. We microwaved the curds twice and continued to knead the cheese. Other students mentioned microwaving the curds 4-5 times for the creamy texture. The Mozzarella was very moist and did not have a strong flavor as expected. The texture was soft and gummy like. We did not add salt, which we should have for flavor and preservation (McGee, 61). Overall, the cheese was a success.

Curds forming

Cutting the Curds

After 40 minutes

The Whey

The Curds

Before the final heating

Stretching the Cheese

End Product

In other cheeses, they are aged for days to years. During this time the cheese is exposed to bacteria and mold to intensify the flavor of the cheese. The growth is regulated by the humidity and temperature of the storage facility. This process results from the breakdown of casein proteins and the milk fat. The cheese may be wrapped in wax, natural rinds, or wraps. The key to the environment is it must be kept dry! Today, prepared bacterial cultures are prepared to give consistent results in cheese. For example, blue cheese is from a prepared bacterial culture (McGee, 61).

Fankhauser, D. (2009, November 23). Rennet for making cheese. Retrieved from http://biology.clc.uc.edu/fankhauser/cheese/rennet/rennet.html

Maranowski, M. M. (2008, December 1). How far can you stretcha the mozzarella: The science of making cheese!. Retrieved from http://www.sciencebuddies.org/science-fair-projects/project_ideas/FoodSci_p041.shtml

McGee, A. (2005). On food and cooking, the science and lore of the kitchen. Scribner Book Company.

New England Cheesemaking Supply. (2011). Ricki's 30 minute mozzarella . Retrieved from http://www.cheesemaking.com/howtomakemozzarellacheese.html

Pav. (2010, July 19). Understanding coagulants. Retrieved from http://www.wacheese.com/index.php?option=com_content&view=article&id=73:understanding-coagulants&catid=47:starter-cultures&Itemid=67

Zonis, S. (2006, May). Get to know marvelous mozzarella. The Nibble, Retrieved from http://www.thenibble.com/reviews/main/cheese/cheese2/whey/2006-05.asp

Information Used

SOURCES:

McGee, A. (2005). On food and cooking, the science and lore of the kitchen. Scribner Book Company.

http://en.wikipedia.org/wiki/Starch

http://food.oregonstate.edu/learn/cake.html

http://www.joyofbaking.com/cocoa.html

http://www.squidoo.com/the-creaming-method

http://pastrychefonline.com/blog/2008/11/03/the-creaming-method/

Cream Puffs and Filling

 Choux translates to cabbage in French and pate also means head or ball. Pate Choux is cabbage-like balls that is a light pastry dough. Pate Choux dough is hollow allowing to be filled. This dough is different in that it is cooked twice. Once on the stove and again in the oven. The cream puffs were made by adding water, salt, and butter to a slight boil. The flour was slowly added. The flour is the gluten source that will create the structure for the cream puff. The flour was rolled into a ball. This dough’s consistency was very sticky and a cream color. The dough was sticky from the liquid ingredients outnumbering the flour. The dough was removed from the heat to prevent from over cooking and cooking the eggs. Eggs were added one at a time to transition the dough into smooth textured dough. The eggs were the source of glue  to hold the dough together. After six eggs were added, the dough was more of a paste. The paste was transferred to a bag and piped onto a baking sheet. In the case of the cream puff’s, air is the leavener. A cream puff is one large air pocket. The end product was a light, hollow dough. The inner structure of the dough was light and string-like. The dough has a different taste than other pastries. It is not sweet, but more of a buttery flavor. The cream puffs cooked for 30 minutes. The dough is not cooked until the ridges and valley’s are a golden brown (McGee, 552). 

Melting Butter

Adding the eggs (sticky dough)

After eggs have been added, more paste like.

Ready to pipe!

Cream Puffs pre-baking

Inner Structure

The pastry cream for the cream puffs was similar to the vanilla pudding made earlier in the semester. The sugar was added to the cornstarch. Cornstarch is a thickening agent and is made up of pure starch from a corn grain. When the cornstarch is added to the eggs, the starch absorbs the water from the eggs and clumps up. In another pan, boil the milk and vanilla. The egg mixture is slowly added to the milk as to not scramble to eggs. Keeping stirring the mixture while tempering the egg mixture. Pour the combination back into the saucepan and continue heating till the mixture thickens. At this point, the filling is a thick cream. Whipped whipping cream will be added to give the filling the light and fluffy consistency. The filling took three tries to end up with a successful product. The first attempt resulted in scrambled eggs and the second try ended when the milk was burned. The filling is an excellent example of the precision required for baking and pastry making.

Finished Product

Corn Starch

Cream Filling

Tempering the Egg Mixture

Filling thickening

McGee, A. (2005). On food and cooking, the science and lore of the kitchen. Scribner Book Company.