Maroon 5’s sugar anthem rang loud and clear in the Harvard Science Center on Monday night for the third event in this semester’s Harvard Science and Cooking lecture series. This week’s topic: “The Science of Sugar.”
When speaker Joanne Chang from Flour Bakery mentioned her book “Cooking with Less Sugar,” many audience members may have expected the evening to focus on sugar and health science. But Chang had a different (and more fun) evening in mind.
Chang anticipated that making desserts sweet with less sugar would be the major challenge for her new book. But it turns out that sugar is a common dessert ingredient for many other reasons. To put this in perspective, she asked the audience to name desserts that only use sugar to add sweetness. Her list included chocolate, whipped cream on top of fruit, and yogurt, and the audience contributed cheesecake and gelatin too.
That’s only about five desserts. Most dessert recipes, namely cakes, cookies, and pastries need sugar for more than just adding sweetness. Specifically, there are seven chemical reactions that sugar is used for in during the baking process.
- Sugar and butter can be creamed together with a wooden spoon or mixer to make cakes and cookies light and fluffy. Butter fat is dense, and mixing it with sugar provides aeration. When a cake is baked in an oven, these pockets remain filled with air. This is essentially what a farmer does when he uses a hoe to plow the land and loosen the soil. To emphasize, Chang showed a picture of a cake baked with the full amount and half the amount of sugar. The cake with half sugar was shorter and denser (and probably less tasty) than the regular cake.
- Sugar is hygroscopic. “Sugar actually attracts water from the air,” Chang explained. “And whatever liquid is in the pastry already, sugar holds on to so it doesn’t evaporate.” Thus, more sugar means a moister pastry. She said her half-sugar coffee cake won’t stay fresh for more than one day because of this.
- Sugar lowers the freezing point of frozen desserts. Chang showed a video from an experiment with scoops of grapefruit sorbet containing between zero to two cups of sugar. No sugar makes the sorbet resemble a ball of ice more than a delectable treat, whereas two cups of sugar turns it into sorbet soup. One cup of sugar was just right.
- Sugar stabilizes beaten egg foams, something necessary for a good, sturdy lemon meringue pie. Egg whites are made of protein molecules and water. In a whisk, the protein molecules are stretched out like rubber bands and capture the surrounding air, and without any sugar these protein strands are very unstable and immediately want to collapse again. But when you add about the same amount of egg and sugar, the sugar and water will mix to form a syrup that holds up the air bubbles around the proteins. “Whenever you pack something that is very delicate you add all those packing peanuts, and that’s essentially what this is,” Chang explained as she demonstrated making meringue with and without sugar. Without sugar the protein and water separate, creating a runny an unappetizing goop.
- Sugar is responsible for the classic brown color in cookies and other baked goods. Amino acids and sugars react together in the Maillard reaction to create the colors and flavors that cookie connoisseurs know and love. Chang laughed while she said this use of sugar was especially tricky to get around in her new book. “When we were taking the pictures for the Baking with Less Sugar book the photographer thought everything looked too pale, and he wanted me to put it back in the oven, or Photoshop it to make it look better. But we wanted to keep it realistic for the book.”
- Sugar tenderizes and inhibits gluten development in flour. Gluten development is important when making bread because it will create big holes and a chewy texture. Good for a big loaf of bread maybe, but as Chang said, “if you are eating a cake the last thing you want is something chewy and tough.”
- Finally, sugar makes pastries crispy. “In the new book, one of the things I tried to make was a low-sugar, sugar cookie,” Chang said. And even the lowly sugar cookie was difficult to make with less sugar. It involved extra efforts in dehydrating cookies overnight to give them a crispy snap.
After explaining these seven uses for sugar in baking, sugar cookies with a heaping piles of buttercream from Chang’s bakery were administered to all guests as a treat for making it through a voluntary science lecture.
Later on when asked what inspired her write a book about baking with less sugar she replied, “It wasn’t actually for health reasons. It does use less sugar period, but there is a whole chapter on honey. The cover photo is a carrot cake made from apple juice. And your body doesn’t know the difference between white sugar and honey, but things like honey have more taste, and I wanted to use things like maple and honey to add more taste. One chapter is using white sugar, but just less white sugar.”
But how much sugar is enough?
“If I think it tastes good it probably needs a little more sugar, but we have a whole team that tries everything,” she said.
Harvard Science and Cooking Lecture Series, Speaker Joanne Change on “The Science of Sugar.” 7:00 PM in the Harvard Science Center Lecture Hall on Monday, September 21, 2015