Free THAT’S THE WAY THE COOKIE CRUMBLES by Dr. Joe Schwarcz

can result in food poisoning severe enough to make the most ardent backyard barbecuer leap for broccoli. Actually, eating broccoli along with barbecued food is a great idea. It contains sulphoraphane, one of the most potent anticarcinogens we’ve discovered so far. I wouldn’t barbecue it, though.

Agitate for Ice Cream
    Nancy Johnson of Philadelphia had a problem. She loved ice cream. But she found that making it was a struggle. She’d often spend up to an hour shaking the metal pot containing her mixture of cream and sugar before the stuff would freeze. And all that time she had to keep the pot immersed in a bath of ice and salt. There had to be a better way. So, in 1843, Nancy dreamed up the ice cream maker. She placed a metal can filled with ingredients in a wooden bucket and packed it with layers of ice and salt. Then she attached a hand crank to a brace positioned across the top of the bucket and ingeniously connected it to a paddle that would churn the mix as it froze. Thanks to Nancy, anyone could now make ice cream at home.
    The concept of making ice cream is simple enough. Take some cream, add sugar and flavor, and freeze the mixture. Pure water freezes at zero degrees Celsius, but by dissolving any substance in water we lower its freezing point. So the ice cream mix, with all of its dissolved sugar, requires a temperature lower than zero to solidify. Now picture what happens if we place this mix in a container and then immerse it in a bucket packed with ice. The original temperature of the ice is well below zero (just check the temperature in your freezer), but the surfaces that are in contact with the air will quickly warm up to zero degrees and begin to melt. The water from the melted ice will also be at zero degrees, and this mixture of ice and water will remain at that temperature as long as any ice is present. But at zero degrees, the ice cream mix will not freeze. However, if we sprinkle salt on the ice, we create a different scenario. As before, the surface of the ice warms up and melts. The water dissolves the salt, and soon the pieces of ice are swimming in salt water. Since this liquid has a lower freezing point than pure water, the ice will lower its temperature until the new freezing point is reached. In other words, the ice cream container is now surrounded by salt water, which is at a temperature well below zero. The mix freezes.
    But just freezing the mix won’t give you ice cream. It will yield a dense, solid mass filled with ice crystals. Hardly mouth-watering stuff. If you want good taste, you must agitate. Shaking or mixing the ingredients during the freezing process is the key to making good ice cream. This accomplishes two things. First, it minimizes the size of the ice crystals that form; second, it blends air into the ice cream. The smaller the ice crystals, the smoother the ice cream. But it is the pockets of air blended into the product, known as the “overrun,” that give it its prized foamy consistency. Nancy Johnson’s hand-cranked device minimized crystal formation and incorporated air admirably. Indeed, ice cream manufacture today still uses the same principle.
    Human ingenuity does come to the fore when ice cream makers are unavailable. During World War II, American airmen stationed in Britain and pining for ice cream discovered that the gunner’s compartment in a bomber had just the right temperature and vibration level for making the sweet treat. They would put the ingredients into a can before a mission, stow it in the gunner’s compartment, and then look forward to returning to base with a batch of freshly made ice cream.
    The method of simultaneous mixing and freezing solves the main problems of ice cream manufacture, but it does introduce a complication. Cream essentially consists of tiny fat globules suspended in water. These globules do not coalesce, because each is surrounded by a protein membrane that attracts water, and the water keeps the globules apart. Stirring