Joanne Chang: The Science of Sugar

Michael Brenner introduces the topic of phase transitions, a fundamental concept in cooking, which involves the transformation of substances between states, such as water turning into steam. Brenner emphasizes the importance of sugar water in phase transitions and its role in the lecture, highlighting the solubility of sugar and how temperature affects it. He also discusses the relationship between sugar concentration and the boiling point of sugar solutions, leading into a demonstration by Joanne Chang.

Joanne Chang expresses her excitement for learning new aspects of baking science from Brenner's introduction. She discusses her experience with baking and the various factors that affect the outcome of baked goods, such as emulsification, gluten formation, and leavening agents. Chang also shares the innovative story of Harvard students who developed a spray cake inspired by her previous lecture, touching on the impact of her teaching and the pressure to inspire further innovation.

Joanne Chang delves into the various roles sugar plays in desserts beyond adding sweetness. She explains that sugar can affect texture, stability, and even the freezing point of mixtures. Chang uses audience interaction to explore examples of desserts where sugar's function might be limited to sweetness, concluding that sugar's roles are diverse and essential in the creation of palatable desserts.

The paragraph explains how sugar affects the texture of desserts like cakes and cookies through the creaming process, which incorporates air pockets for a lighter and fluffier final product. It also discusses sugar's hygroscopic nature, which helps in preserving baked goods by retaining moisture and preventing staling. Additionally, the interaction between sugar and fruit to create sauces is highlighted, emphasizing sugar's multifunctional role in the culinary arts.

Joanne Chang educates the audience on how sugar lowers the freezing point of liquids, affecting the texture of frozen desserts like sorbets, milkshakes, and popsicles. She demonstrates this concept with different sorbet samples, showing how increasing sugar content from zero to two cups drastically changes the sorbet's consistency, from a solid, icy texture to a pourable syrup.

The role of sugar in stabilizing beaten egg foams is discussed, with examples such as French macarons, meringues, angel food cake, and buttercream. The addition of sugar to egg whites creates a syrup that protects the foam's structure, resulting in a stable, silky meringue suitable for various dessert applications. The importance of adding sugar gradually to maintain the foam's integrity is emphasized.

Joanne Chang explains how sugar tenderizes baked goods and inhibits gluten development, preventing chewiness and promoting a tender crumb in cakes. She also discusses sugar's contribution to the browning process, known as the Maillard reaction, which affects the color and flavor of baked goods. The difference in browning is illustrated by comparing a traditional sour cream coffee cake to a low-sugar version.

The various stages of sugar, from thread stage to caramelization, are detailed, along with their respective temperatures and uses in confections like iced tea, fudge, caramels, marshmallows, taffy, lollipops, and pralines. Brenner and Chang discuss the importance of controlling water content and sugar concentration to achieve desired textures in candy-making.

Joanne Chang demonstrates the process of making buttercream by combining Italian meringue with softened butter, resulting in a stable, creamy frosting for cakes. She also shows the preparation of praline by caramelizing sugar to the point where it turns golden brown and can be mixed with nuts. The importance of temperature control and the risk of crystallization in sugar work are highlighted.

The final paragraph showcases the technique of spinning sugar to create decorative strands for desserts like croquembouche. Chang explains that the process is highly dependent on temperature and humidity, making it a delicate art. She also shares tips to prevent sugar crystallization and demonstrates the proper flicking technique to create thin, long strands of spun sugar.