A Chemist Bakes the Perfect Cookie

Food Scientist Shirley Corriher's tips for baking perfect cookies seem to be everywhere at the moment. On National Public Radio, her advice for crumbly cookies is to add a tablespoon of water to a cup of flour. That will make the proteins — glutenin and gliadin — hold together. In the New York Times she's one of several culinary experts weighing on why you must keep butter cool.

Butter is basically an emulsion of water in fat, with some dairy solids that help hold them together. But food scientists, chefs and dairy professionals stress butter’s unique and sensitive nature the way helicopter parents dote on a gifted child.

Although I have not heard of Corriher before, I am tempted to check out her new book Bakewise: The Hows and Whys of Successful Baking with Over 200 Magnificent Recipes. Amazon customers give it some rave reviews.

And I like the chemistry angle too.

Cake in a Mug mug

When I couldn't get carbon snakes to work, I made exploding cake in a mug. And for a last-minute holiday gift, I just put the barebones recipe on a mug, complete with crudely drawn illustrations. You can order them too from Cafe Press. Order by Monday for holiday delivery.

Homemade Ice Cream

We had homemade ice cream for dessert on Thanksgiving. (My dad, never having seen our machine, asked, "Whose home was the ice cream made in?") But the machine we have uses a cooling pan with some kind of chemical sealed inside. You put the pan in the freezer before using it, then just add the ingredients and let the machine stir them up. Not much to it.

Meanwhile, over at Socks and Books, homeschoolers "Moomintroll" and "Snufkin" recently made ice cream the old-fashioned way, using rock salt and ice cubes. We did this years ago using two plastic bags, but they used a metal pot, which I think looks way more dramatic.

Go to their post to see how its done, complete with chemistry explanation. I'm saving this link for future reference!

Peeps Chemistry

There is a long and glorious tradition of torturing leftover Easter candy. At the site Peep Research, the fear response of a Marshmallow Peep is measured through exposure to heat in a microwave. But many of the more sophisticated Peeps experiments can probably not be done at home. While you can replicate the vacuum experiment above (by Seaford, NY chemistry teacher Edward Kent, who has many other interesting demonstration videos on his website) by using an ordinary Kitchen Vacuum Packer as shown on the Steve Spangler website, the explosive liquid oxygen video should be only be done under laboratory conditions.

More Peepy links at Peep-O-Rama including Martha Stewart's recipe for fresh, homemade Peeps (sort of an oxymoron). Also solubility tests by a stuffed chemistry mascot mole.

Oh, and here's the chemistry explanation, from the Exploratorium's Science of Cooking website:

Marshmallows are mostly sugar and water wrapped around a bunch of air bubbles. When you cook marshmallows in your microwave oven, several things happen at once. The microwave makes the water molecules vibrate very quickly—which makes the water heat up. The hot water warms the sugar, which softens a little. The hot water also warms the air bubbles.

When you warm air in a closed container, the gas molecules move around faster and push harder against the walls of the container. As the air in the bubbles warms up, the air molecules bounce around faster and faster and push harder against the bubble walls. Since the sugar walls are warm and soft, the bubbles expand, and the marshmallow puffs up. If it puffs up too much, some air bubbles burst, and the marshmallow deflates like a popped balloon.

When you take the marshmallow out of the microwave and it cools off, the bubbles shrink and the sugar hardens again. When the microwave marshmallow cools, it’s dry and crunchy. We think that’s because some of the water in the marshmallow evaporates when the marshmallow is hot. If you cook your marshmallow for too long, it turns brown or black inside. That happens when the sugar gets so hot that it starts to burn [known as caramelizing].

Baking soda vs. baking powder

Apricot, Poppy, and Chocolate Kiss filled Hamantaschen

We made Hamantaschen cookies for Purim and the question came up about the difference between baking soda and baking powder. We have done the baking soda and vinegar thing many times, so we already know that mixing sodium bicarbonate with an acid releases carbon dioxide. When you bake, those little bubbles of CO2 make the bread puff up. The acid needed to start the reaction in a batter can come from yogurt, buttermilk, lemon juice, or even molasses or honey.

Baking powder is baking soda with the acid already mixed in, in the form of cream of tartar. When moistened, powdered acid combines with the baking soda and produces the requisite bubbles. Some baking powder is "double acting," meaning it releases most of the bubbles when heated, so that the leavening action doesn't expend itself while the dough is waiting on the counter to bake.

Baking powder and water fizzing

There are many explanations on the web about this topic, but I like this one from something called Wally's Food Company. Scroll down to read the chemical explanation of why baking soda absorbs odors in the refrigerator.

Tartaric acid

Breaking Molecular Bonds - Jello and Pineapple

Lesson: Breaking molecular bonds in protein using enzymes

What Happened: We disintegrated Jello using pineapples

(With help from Anthony)

The ingredients









Before we added the pineapple







The Jello started to melt after a minute










The Jello was half dissolved by now








Ewwwwwwwwwwwwwww









The Jello is almost fully dissolved by now










It's fully dissolved now



Warning: Do not add pineapple




Why did it do that?

(From Chempedia)

Jell-O gelatin was first patented in 1845 by Peter Cooper of Cooper Union.

Gelatin is a processed version of the protein collagen, a simple protein that makes up one-third of all proteins in the human body. The main source of the collagen that is used in Jell-O comes from hooves, bones, connective tissue found on cows, horses and pigs. Along with collagen, Jell-O consists of water, food coloring, sugar, and artificial flavors. Collagen is found in all living animals. This protein is what gives body parts strength, flexibility, and protection. There are five major categories of collagen that range from the fibers in your eyes to the structure of placentas. To harvest the collagen needed for gelatin the Jell-O Corporation turns to natural sources found in cows, horses, and pigs. The animals' body part's which were previously mention are ground up to expose the proteins within. After they are ground up the bio matter is then treated with a strong acid or base, which breaks down the cellular structures of the collagen to release the proteins from connective tissue. After the proteins become separated from the tissues the bio-mass is then discarded. Then, the mixture created from the released proteins (collagen proteins, which are the basis of Jell-O) and the strong acid or base is then boiled.

(From General Chemistry Online)
Pineapple contains a plant enzyme called bromelain that breaks down proteins. Bromelain is used in many meat tenderizers for this purpose (and that's why cooking ham with pineapple makes it tender). JellO packages warn you not to put pineapple chunks into the gelatin. Jello is a protein mesh with trapped pockets of liquid; the bromelain cuts the protein chains and keeps the gelatin from jelling properly. Why do pineapples produce an enzyme that tenderizes meat? It's a defense mechanism. The sap of the pineapple plant contains much higher concentrations of bromelain and can cause severe pain if eaten.

Other uses for bromelain:

(From Wikipedia)
Bromelain can be used in a vast array of medical conditions. It was first introduced in this area in 1957, and works by blocking some proinflammatory metabolites that accelerate and worsen the inflammatory process. It is an anti-inflammatory agent, and so can be used for sports injury, trauma, arthritis, and other kinds of swelling. Its main uses are treatment of athletic injuries, digestive problems, phlebitis, sinusitis, and aiding healing after surgery.

Chalk and Vinegar

A big piece of sidewalk chalk sitting in a glass of vinegar, not really doing much of anything.

Lesson: Carbon dioxide is heavier than air
What Happened: CO2 collected in a glass can be poured out so that it extinguishes a candle

Last week a friend who used to teach chemistry at a local community college brought her son over for the afternoon. I had bought some Diet Coke and Mentos for the kids to try outside. My friend's son let my boys take his turn, while he played the role of "brave photojournalist."

I also got my friend to try a demonstration I read about in Uncle Tungsten, and which is mentioned in passing in Joy of Chemistry as an example of the effects of acid rain. It involves dissolving a piece of chalk in a glass of vinegar. My friend and I tried Crayola brand blackboard chalk from Wal-Mart but did not get much of a reaction. Old sidewalk chalk, much thicker and softer, worked a little bit. But for the second half of the demonstration, we had to resort to baking soda.

In Uncle Tungsten, Oliver Sacks describes watching his mother "pour" off the carbon dioxide accumulating in the glass over a candle, which goes out. That's the part of the demonstration I was interested in seeing. A small amount of baking soda and vinegar -- not enough to bubble out of the glass -- did indeed produce enough CO2 to recreate Sacks' childhood memory.

In addition to proving that carbon dioxide is heavier than air, we also demonstrated that even middle-aged moms like to mess around with concoctions. Sometimes more than their kids.

NOTE: Chalk is made of calcium carbonate, a base, the same stuff in limestone and marble. Vinegar is acetic acid. The reason our chalk didn't react very much with the vinegar was that it contained other substances. A little Googling revealed Prang Hygieia, 95% calcium carbonate, as the brand of choice for this demonstration. If I get ahold of some I will give it another go.