“What is this?” The professor asks the group as he shakes a pot full of what looked like pure fat in front of us. There were many responses (one “disgusting!”) but we came to a consensus that it was some kind of fat and, for the most part, we were right. What it really was though, was chicken skin. He had just unthawed it today after it was frozen for quite a while. So why was he showing us this? We had just started the day talking about fats and about how they were made of a glycerol and fatty acid chains (three in the case of triglyceride seen below), and so the chicken skin was a way to look at this fat in a food. The skin of the chicken is mostly made up of water (50 %) and fat (40 %) and collagen protein (3 %) and it acts as an envelope around the bird, holding a layer of fat beneath it. This is why the skin tastes so good when eating it off of a cooked chicken.
Next, it was announced that we were going to be making chicken gribenes. Basically we would be heating the skin to the point where all the water contained in it would boil off and that the skin itself, made largely of collagen proteins, would fry in its own fat. The resulting fried skin would be separated from the fat (or schmaltz) and would be salted and left to crisp up for a delicious treat.
The picture above shows what the skin looked like after being heated for only a couple of minutes and the temperature was 100 oF, and as you can see the fat has begun to separate from the skin.
Here it is evident that water has started to boil off, however at a temperature of 220 oF it is not yet hot enough for the skin to begin browning.
At 265 oF the water has continued to boil off as evident by the level in the pot and also there is a considerable amount of browning occurring on the skin.
By 340 oF almost all of the water has boiled off and the skin is seriously browning.
The finished product! After straining off the skin, adding kosher salt ground to a fine powder with a mortar and pestle, and allowing it to crisp up for a couple minutes, the final product was ready. The crunchy, salty taste of the skin was to die for!
The chicken was not to be rushed, so while we waited for the chicken to brown what else was there to do except make scrumptious chocolate chip cookies! Two batches of chocolate chip cookies were made, one using oil and the other using butter. Oil and butter are two fats that are often substituted for each other in cooking and baking. Some swear by butter, others by oil. So which one is really better? What difference does it make in the product?
Since both of them are fats, they perform the same desired function as a tenderizer, keeping cookies nice and soft. Fats and sugar prevent a strong gluten network from forming, thus preventing cookies from being too dense and over-chewy.
A baguette is an example of a baked good with minimal fat and sugar; the lack thereof causes it to harden easily and be much chewier. Mixing water and flour without fat causes gluten to form because hydrophobic fat-like groups along the flour molecules bind with each other, holding the proteins together and excluding water. The presence of a fat source like oil or butter prevents this from happening; fat molecules bind to these groups and prevent them from binding to each other. This keeps cookies from hardening like a baguette.
So the question still stands of why two different batches were made? Cookies are cookies and they’re always yummy, so why does it matter?
It matters because one of them creates a sort of illusion, while the other is literally melting in your mouth.
When fat and sugar are beaten together, air gets incorporated into the mix. As a semisolid fat, butter allows the air to stay in the mixture, whereas oil does not. Air introduced by the sugar and the beater becomes suspended in the mixture of crystalline and liquid fat in butter. This is possible because butter forms larger fat crystals than oil. The structure of butter is shown in the photo below, illustrating the air-trapping fat crystals.
You’ll notice that there are water droplets in the photo. This is not because our butter was wet- butter is actually made up of approximately 15% water. The fat crystals shown in the photo allow air to stay trapped in the dough. Oil, on the other hand, has no air-holding ability. It tenderizes products because it is never a solid to begin with. The two photos below show the cookie dough with butter (left, pre-chocolate chip addition) and with oil (right, post-chocolate chip addition).
You’ll notice that the cookie dough made using butter is visibly fluffier and has a much lighter color, while the dough made with oil is gooey and darker. This is because of the air that is caught in the dough. Light reflects off of the increased surfaces created by the air, causing the batter to appear lighter.
The moist feel of a baked good made with oil is simply an oily residue that stays in your mouth, an illusion. Butter, on the other hand, is literally melting in your mouth, with a melting point just below body temperature.
Butter’s semisolid state at room temperature also causes the dough to be more solid before it goes in the oven, then spread out much more after being in the oven. Cookies made with oil do not change in size nearly as much between pre and post-bake. The photo below shows the two finished products side by side. Can you guess which is which? The ones with butter are slightly more flat and you can almost see the melting action of the butter, whereas the ones made with oil are chunkier
The question of which recipe makes better cookies is almost impossible to answer. Tasting just one of each type was practically just a tease, and certainly insufficient evidence to draw a conclusion about the relationship between recipe and yumminess. The only solution to this issue is to increase the sample size, therefore many more cookies must be made. Try it yourself at home and you can decide for yourself! Do you prefer the ever-moist oil option? Or the melt-in-your-mouth buttery option?
Our homework for this week was incredible, to say the least. The assignment was to make caramel (yum!). We made three types of caramel sauce, varying the cooking time and therefore the color of the caramel: a traditional, a light caramel, and a burnt caramel. Photos of the three are shown below, respectively.