Chem181- Topic7, 3.docx - DR DAVID N HARPP Hi Today we're going to talk somewhat about cooking I would say at the outset that the cooking course that

Chem181- Topic7, 3.docx - DR DAVID N HARPP Hi Today we're...

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DR. DAVID N. HARPP: Hi. Today we're going to talk somewhat about cooking. I would say at the outset that the cooking course that edX offers is one that is being produced and taking place now, as far as I remember, at Harvard as a Harvard course. And there's a lot of detail in that course about making sure that the recipe is exactly right. This is going to be a much simpler connection to the topic of cooking. And we'll look at the main highlights. I thought it might be useful to start with this book, Catching Fire by Richard Wrangham. And in this book he indicates how-- well, the subtitle is How Cooking Made Us Human and how, in fact, much more nutritional materials can be pulled into the body by cooking, particularly that of meat. So we're going to talk generally about the various main food items as we go through, trying to serve up something that you hopefully can get a few good points from. I showed this slide a little earlier that is cooking sometimes in older times, this painting by van Gogh-- the Potato Eaters. That was all that they were eating in some families in Holland at that particular juncture around the 1880s. Many people have concerned themselves with what goes on when materials are in fact cooked-- boiled, fried, and sizzled. Well, the chemical change is extremely significant, and it's extremely complicated. I don't think we can get too far with this. It has a bearing on diet and cancer eventually. But some of the simple changes we've already looked at, at least a little bit-- the Maillard reaction, where bread, with carbohydrates and protein materials buried within that bread, are heated to a significant temperature. And when they're toasted, they combine, losing water in the case of the combination of the carbohydrates and the proteins, one end of one kind of protein with an NH2 ending to it. So when it's cooked up in the toaster, of course, we're all familiar with the browning aspect. And that means chemicals have interacted and have changed. There is no question about that. And is it harmful? Generally speaking, probably not. Acrylamides are formed in this particular reaction, and we'll talk more about that in the diet and cancer section, as that simple molecule has been implicated in that regard. Bigger, more powerful changes take place when meats are cooked. The fat drips from the meat. It is immediately vaporized. It comes back up in an altered form and in many cases
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sticks to, by way of this mechanism-- the loss of water. That's one of the major features of these chemical reactions, that water is lost from OH groups adjacent to a hydrogen, making a double bond, then making more changes and more changes. And some of that material is deposited as the charcoal-like look that this particular piece of meat has on the surface.
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