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Protein Denaturation
Dr. Kiki breaks down the breakdown of proteins.. Food Science Episode “Protein Denaturation” Dr. Kiki: Hi, I am Dr. Kiki Sanford and today on Food Science we are breaking down proteins. One of the most important processes in cooking is protein denaturation, or the breaking of a proteins structure by the application of extreme conditions. Denaturation changes the structure of proteins and therefore the way that they react, without denaturation many delicious foods would never be possible. Proteins are necessary for our survival; we have to eat them to be able to create them in our own bodies. And to proteins structure is everything from their most basic to complex levels, structure determines the function of proteins. Many of the food we eat contain proteins which consist of amino acids. There are hundreds of amino acids found throughout nature, but only instructions for 20 are contained in our genetic code. The amino acids that bio organisms can synthesize differ, some amino acids must be provided by diet and these are called essential amino acids. Proteins are created by creating amino acids end to end, like the links in a chain. Then chemical interactions and bonds within the chain cause the proteins to fold in knot like formations. Proteins have four structural levels, the primary chain of amino acids. Secondary is the formation of patterns within the protein, tertiary are side chain reactions leading to the stability of single protein molecules and quaternary is the association of multiple protein molecules or subunits. So in uncooked foods proteins are normally all folded up, there are an almost infinite number of possible protein structures but the primary structure determines the final folded shape that allows a protein to perform a particular task. Change the amino acid sequence even slightly and it might affect the structure enough to create a new protein with an entirely different function. There are different methods that can be used to break the bonds in proteins and change them from their naturally folded state, like heat or acid or force. Heating proteins increases the kinetic energy or energy of motion within them so that they start vibrating more and more intensely. The amount of heat determines the amount of motion, more heat, and more motion. Eventually if enough heat is applied the molecular motion will cause the bonds that keep the proteins folded to break, the knots unfurl and the proteins denature returning to their primary chainlike structure. Our bodies use this strategy to rid themselves of infection. The temperature that you feel when you get sick is your bodies attempt to denature viral proteins. Hopefully the temperature doesn’t get too high and end up denaturing you. Most proteins denature at 40 Celsius, higher temperatures are necessary to promote further physical changes. Adding acid to proteins, like the citric acid in lime juice causes a change in their ph, and the change in ph causes denaturation very similarly to adding heat. Alternatively, proteins can be denatured through the physical force of stretching. This happens when you use a manual or electric beater to whip eggs against the side of a bowl. When proteins denature it opens up whole new opportunities for bonding. Protein chains become more likely to bond with one another and form a solid network. Water gets forced out from between the chains and a stronger denser association is formed. The bonding of proteins into a solid mass is known as coagulation. In egg whites the change from translucent to opaque is due to coagulation, so is the skin on the surface of curdled milk, or the increase in firmness in custard. I know this is getting a little technical, but remember it is not just food, its science.
The Maillard Reaction
What do steak, coffee beans, caramel, and toast have in common? . Food Science Episode “The Maillard reaction” Dr Kiki: Hi I am Dr. Kiki Sanford, and today on Food Science we are going to show you what coffee beans, Caramel, and toast have in common. So what do steak, coffee beans, caramel, and toast have in common anyway? They all gain special odors and flavors when they are cooked, because of a special process called non-enzymatic browning. There are two kinds of non-enzymatic browning reactions that take place because of the sugars. Carmelization, in the Maillard reaction, carmelization is the reaction of sugars with sugars. But the Maillard reaction is the reaction of sugars with amino acids. The most basic caramelization in the kitchen is the melting of sugar into a syrup. It is easiest caramelize sugar if you use water. The water allows more even heating of the sugar, it reduces the possibility of it burning, and it also helps out the chemical reactions that are taking place. Give it a little mix. White table sugar is made up of sucrose, and gets broken down into glucose and fructose when heat is added. You need to cook it at 170°C Celsius for caramelization to take place. Fructose and glucose are reducing sugars that means that they give some of their electrons the other molecules. As they break apart into smaller components due to heating, their tendency to donate new electrons leads to totally new compounds. Some of the compounds give the developing Caramel its color while others deliver its flavor or aromas. Diacetyl gives off a buttery flavor, Furan is nutty, and Acetaldehyde lends a rum or a sherry component. Caramelization in addition to requiring heat to get started actually produces heat when it develops. The chemical reactions are thermogenic in nature. So is probably a good idea to keep an eye on the temperature of your caramel, so you don’t end up with something all bitter and burnt to the bottom of your pan. But what about other kinds of foods, you have probably heard of or even tried caramelizing onions at one point or another. The truth is that caramelization does take place; this onion is full of sugars. But it also contains amino acids, which means that the Maillard reaction should take some blame. When heat is added to the onion the carbohydrates in it cells start breaking down. The carboneled group, that is carbon atoms that will bond into oxygen, start binding with the amino groups of the amino acids. And then you get caramelization plus the Maillard reaction, and it is messes of Maillard, caramel fun. When you sear a stake it does not seal in the juices, the Maillard reaction is responsible for making it taste better. The high heat causes amino acids in the surface of the muscle to form new compounds in the carboneled groups in the carbohydrates and other compounds in the muscle. Because of caramelization and the Maillard reaction new compounds are formed which are responsible for the delicious odors of seared steak, caramelized onions, or even toasted bread. But remember it’s not just food, its science. What is it? It’s science. I don’t know what is it? It’s science.
Breakfast
Dr. Kiki irons out the important ingredients found in cereal.. Food Science Episode “Breakfast” Dr. Kiki: Hi, I am Dr. Kiki Sanford and today on Food Science we are going to play with our cereal. Breakfast cereal is a staple of many American households, from sugar bombs to super nutritious it comes in all shapes and flavors. However so that people can make educated choices about their diet and of their children cereals must state how much of certain required vitamins and minerals that they contain. One to the cereals claims to contain 100% of all of the ire that you need for one entire day it a single serving, nice. Iron is found in nails and is a component of steel so what is it doing in your breakfast cereal? Iron in addition to helping make skyscrapers possible is actually something that we need to eat in our food. Now you can play with magnets and nails and you can even play with a magnet and iron supplements, but have you ever tried playing with a magnet and your breakfast cereal. It takes a little practice but it is fairly easy to move around cereal flakes instead of nails, watch. How much iron do you really need every day? The U.S. RDA is at between ten and 18 mg depending on age and sex. Women are recommended to get 15 mg per day and up to 30 mg if they are pregnant or breastfeeding. Men are recommended to get 10 mg per day. Iron is essential to the proper functioning of your cells and various enzymes; it also makes up a large part of the oxygen caring molecules in our blood, hemoglobin. Hemoglobin is a metalo protein with four globular protein subunits in closing for hem subgroups. The hem groups each contain one iron atom embedded with ring like molecule called porphyrin. The iron is the active bonding portion of hemoglobin. Four iron atoms means that each hemoglobin cell can combine four oxygen’s. Obviously it is important so if you do not get enough iron in your diet it could lead to trouble. Iron deficiency can lead to weakness, fatigue, irritability, and dirty eating, back to the cereal. Did you now that is actually possible to see the iron in your cereal? Well it is and I’m going to show you how. First you take your breakfast cereal and stick it in a blender, a cup or two will work very well, add water just a cover the flakes. Put the lid back on and mix it up really well, you do not want any big flakes remaining. That looks pretty good, take the slurry and put it into a bowl, aah there is the cereal. Then take a magnet and just stir the slurry for about a minute or so. I will be back in a minute. Iron is lost during the processing of most foods though in some foods like flour manufacturers have take to enriching their products with an elemental Iron. Elemental iron is not absorbed by the body as easily as Iron found naturally in foods. You’re likely to eat foods other than cereal that contain Iron so the question is can you get too much? Will the answer is both yes and no. The body has no way to excrete extra higher and its absorption is very tightly regulated so if you can manage to get your body to absorb it you can end up with too much iron in your blood and tissues which can lead to iron toxicity. Ingestion of 60 mg per 1 kg of body weight is lethal, but considering that most people do not even make the RDA of 18 mg per day death from iron poison and for most Americans is unlikely. So now you’re going to want to Ritz your magnet lightly in water and make sure you get all of the cereal off of it. Can you see the iron on the magnet? All of the black stuff that you see are the iron filings from your cereal, but remember is not just food, it is science.
