I'm a senior at Colorado School of Mines, studying Chemical and Biochemical Engineering. I will be graduating in May 2012. I love science and chemistry, but my true passion in life is cooking.
It has been really great making blog posts during this semester. I have thoroughly enjoyed it! However, this semester is coming to a close and so is our blog project. I would like to be able to say that I will continue to post new things, but that may not be the case. I hope that I do get the chance to write some more because I love food, but if I don’t then I guess this is goodbye. Thanks for reading! But just remember to keep up the cooking and chemistry!
Food is one of the things that I enjoy immensely. Everything just tastes so different from everything else. So how exactly does that work? How can bananas taste so differently than a steak? And how can the brain distinguish between the two?
The tongue is covered with taste buds, and these allow us to sense the different tastes in food when we eat them. These taste buds are chemoreceptors, which are sensory receptors that detect certain chemical stimuli in the environment and convert it into a useable form within the body. This means they translate the chemical signals that food produce when in contact with the taste buds into an electrical signal that can be sent though the body. These electrical signals are called action potentials, and they travel to the brain through the nervous system. When the signal gets to the brain it is identified by the brain and a certain sensation is experienced.
There are five different distinct tastes that the taste buds detect: salty, sweet, bitter, sour, and savory. When food enters the mouth, saliva breaks the food down into ions and other chemical molecules that then enter the pores of the taste buds. Each of these tastes is sensed by the taste buds a little bit differently, based on what molecules the food is broken down into.
Salty and sour tastes are sensed through ion channels that are triggered by ions, or electronically charged particles, that are found in salty or sweet foods. Salty foods contain the ion sodium chloride (NaCl), which is commonly called table salt. This molecule is composed of two ions: the positively charged sodium ion and the negatively charged chlorine ion. When the ions are being sensed, the sodium ion triggers the ion channels in the taste buds, which changes the electrical charge of the taste bud cells, causing an action potential. For sour foods, which contain acids, the positively charged hydrogen ions cause the action potential within the taste buds.
Bitter, sweet, and savory foods are sensed through G-protein coupled receptors, which are a more sophisticated mechanism than the ion channels, and one that is not well understood. Compounds within bitter and sweet foods trigger G-protein coupled receptors to release a messenger protein, gustducin, which triggers molecules to close potassium ion channels, creating an action potential. Sensing savory foods is similar, though it is triggered by the amino acid L-glutamate.
Once the action potential has been created and a signal has been sent through the nervous system, the signal is transferred between nerve cells until the signal reaches the brain where the signal is translated into a taste. The process from ingesting food to having a sensory experience from that food is very fast, happening within a couple of milliseconds, which is good because there are lots of delicious foods out there to try. And the tongue contains an average of 10,000 taste buds that get replaced every two days. That’s a lot of taste buds! Now it’s time to get busy using some!
Water is such an amazing molecule that has many unique features. Without water, life would cease to exist on this planet since life depends on it. Water also has amazing capabilities in the kitchen too. It has great heat transfer properties used when cooking something in boiling water, such as boiling eggs, or when cooling something off with cold water, such as cooling pasta. It is also good for dissolving substances, such as sugar, and for re-hydrating dehydrated foods.
There are two main properties of water that are taken into account in the kitchen: diffusion and osmosis.
Diffusion is the movement of molecules from high areas of concentrations to areas of low concentrations by the random motion of molecules until an equilibrium state has been reached. A good example is the spread of dye within water without being stirred. The random motion of both the water and dye molecules helps the mixture to come to an equilibrium state where the water and the dye are thoroughly mixed.
Osmosis is the diffusive movement of water across a selectively-permeable membrane into a region of higher solute concentration in order to establish an equilibrium of solute to water ratio on both sides of the membrane. A good example is submerging a wilted piece of lettuce in fresh water. The inside of the lettuce leaf has a higher concentration of solute than the water it’s submerged in, so the water diffuses into the leaf in order to equalize the solute concentrations both inside the lettuce leaf and in the water. This essentially causes the wilted piece of lettuce to become rigid again.
The following video is a good example of both diffusion and osmosis. It shows both of the examples that I used above: the diffusion of dye in water, and the osmosis of water into a wilted lettuce leaf.
Perhaps the dessert that I am best known for making is the cheesecake. I started making cheesecakes for family events a few years ago, and they have become legendary in my family. Along the way I have picked up a few tips about making cheesecakes and have started coming up with my own recipes and flavor combinations.
Most common cheesecake recipes have a common list of ingredients: a crust, cream cheese, sugar, eggs and vanilla. The differences between cheesecakes come mainly from flavorings. Some recipes call for other ingredients like sour cream or ricotta cheese, and some recipes use other types of cheeses too. I prefer to stick with cream cheese, although I will sometimes add sour cream or ricotta cheese on occasion to make the cheesecake a little bit fluffier. Personally, I’m not a big fan of adding ricotta to cheesecakes since I think it makes the texture a little grainy.
The key to a good cheesecake is to not over-beat the batter. With cheesecakes, unlike with traditional cakes, you don’t want to have too much air in the batter. Air in the batter will cause the cake to swell in the middle while in the oven and then deflate once it is cooled, leaving a depression in the middle of the cake. There are a few ways to ensure that over-mixing doesn’t occur. First, make sure off of the ingredients are at room temperature. Also, only set the mixer to medium or slow speed rather than high and only mix until the batter is just well blended. Eggs should always be added one at a time and the batter should be mixed after each addition.
Now I’m not all that big on how my cheesecakes look; I’m more interested in how they taste. But if you’re worried about presentation, here are a few tips to make a perfect looking cheesecake. Bake the cheesecake at a lower temperature to prevent cracking because a gentle cooking process will not cause drastic changes to the chemistry of the batter. Also, cool the cake slowly as well. To prevent cracking as the cake cools, run a thin knife around the edge of the pan to loosen it from the sides immediately after it is done baking.
There are also three different baking methods when it comes to cheesecakes. The first is the traditional method where the cheesecake is baked at moderate temperature (300-325°F) until the edges are set and the middle is still jiggly. Another method is the New York method which involves baking the cake at 500°F for 15 minutes and then decreasing the temperature to 200°F for an hour, after which the oven is turned off and the cake is cooked in the oven with the door open. The final method is the water bath method where the bottom of the cheesecake pan is coated in aluminum foil and placed in a larger pan with boiling water that covers about an inch of the base of the cheesecake pan. These pans are then placed in the oven and the cheesecake is baked as in the traditional method.
Personally, I have only ever used the traditional method, but most of my cheesecakes do have cracks that appear on the top of the cake. If you wish to make a pretty cheesecake, I hear that the water bath method is very good for this. I usually never have the patience or equipment to do the water bath method, and I’m more concerned with the taste than the appearance.
The movie below is a movie that was made with our chapter (Mu Pi) of Alpha Phi Omega National Service Fraternity for our Regional Conference in 2010. It’s pretty silly and mostly a lot of fun, but it doesn’t really have anything to do with science other than we are a bunch of engineering student eating cheesecake. Anyways, I made the cheesecake featured in this video.
Have you ever wondered why some people throw salt into their boiling water when they are cooking pasta or vegetables? The answer to this is very simple: salt causes a phenomena called boiling point elevation to occur when it is added to water.
So what does this mean? Well, the salt causes the temperature at which the water boils to increase, meaning that the water is hotter when it is boiling with the salt than it is without it.
Essentially what happens when salt is added to boiling water is that the molecules of salt interact with the water molecules, causing the water molecules to not change phase from liquid to gas, which is what happens when water boils, until a higher temperature has been reached and the interactions between the salt and water molecules can be overcome.
Salt also has an effect on the freezing point of water as well. This effect is called the freezing point depression. This means that the temperature at which water normally freezes at is lower when salt is added than without the salt. This phenomena is often taken into account when making ice cream in some household ice cream makers. This is also why people often throw salt out onto frozen sidewalks in the winter.
Once again the salt molecules interact with the water molecules, causing the restriction of water molecules from making a phase change from liquid to solid, which occurs when water freezes, until the solution has reached a lower temperature and the interactions between the salt and water molecules are overcome.
However, the temperature differences in boiling and freezing of water with salt are not equivalent on both ends. The freezing point depression is greater than the boiling point elevation. Water normally boils at 100°C, but with the addition of salt the boiling point of water increases based on the concentration of salt added to the water (about a 0.17°C increase for every teaspoon of salt added to a quart of water). On the other hand, water normally freezes at 0°C, but when salt is added it freezes at -18°C.
For such as small and common molecule, salt sure does have a lot of power in the kitchen, and not just for flavoring.
This week, as part of our assignment, we were instructed to make a 2 minute video to post on our blog. Here is the one that I filmed with the help of my three roommates.
I know the idea of a cookie scoop as a necessary piece of equipment in the kitchen seems kind of silly, and it probably is to those of you who don’t do much baking like I do. For those of us who are more pastry chef or baker than cook, a cookie scoop is a pretty nifty piece of equipment. It not only makes the cookies the same size so all of the cookies cook the same amount, it also makes the cookies look really nice and pretty. Of course the secret to cooking excellent cookies is to not over-bake them, but the cookie scoop helps.
The cookie scoop also helps by decreasing the time it takes to make cookies. Rather than have to deal with two spoons to make uneven cookie dough balls where the cookie dough sticks to the spoons or comes off in an oddly shaped blob, the cookie scoop is fast, efficient and makes perfectly round pieces of dough. And since the pieces of dough are pretty much the same size, the rate of heat transfer into each of the pieces of dough to cook it is exactly the same. The area of heat transfer for both conduction and convection are exactly the same for each piece of dough, meaning the cookies come out with the exact same amount of doneness.
Now with these perfect cookies all you need is a big glass of milk to go along with it!
One of my favorite pieces of technology that I use in the kitchen is my slow cooker, also commonly referred to as a crock pot. Since some of my classes tend to run late into the night, I find that once I get home I don’t want to prepare myself food. With my slow cooker, I can simply throw something into the slow cooker earlier in the day, set it to low and let it cook for the rest of the day while I’m away at class or work. It is such a modern miracle much like the microwave is.
So how exactly does a slow cooker cook something so slowly? Here is what I found.
A slow cooker has three components: an outer casing, an inner container, and a lid. The outer casing is metal and contains low-wattage heating coils. These coils are surrounded by the outer casing. The inner container, also called a crock, is usually made of glazed ceramic and fits into the metal outer casing. Some crocks can be removed from the outer casing, while others are permanently attached. The lid is domed and fits tightly onto the crock.
When the slow cooker is turned on, heat is produced in the outer casing via the heating coils. This heat is then transferred to the crock by means of convection (see my previous post for more information on this). The heat that was transferred to the crock heats up the liquid in the slow cooker, causing the contents in the slow cooker to simmer at a low temperature for several hours until everything is cooked thoroughly.
When food is put into the slow cooker and it is sealed and turned on, any moisture added to the slow cooker or moisture that naturally exists within the foods in the cooker becomes steam as the cooker is heated. The food in the slow cooker releases moisture in the form of steam, the condensation from which collects and acts like a baster.
As steam is released during the cooking process, the lid traps it, and as it condenses, it creates a vacuum seal between the lid and the rim of the crock, which ensures that all of the moisture remains in the slow cooker. This essentially adds moisture to the food while aiding in the cooking process. The lid is the key component of the slow cooker that allows it to cook food the way it does. Without the lid, the moisture would simply boil off and the food would burn.
Most slow cookers have three heat setting on them: low, high and off. Some cookers have a warm setting just to keep the food warm. Some advanced programmable cookers will automatically switch to the warm setting once the food is thoroughly cooked to keep the food at the proper temperature.
Now the picture is not of my cat. I just thought it was an amusing picture and wanted to share it with you all.
