This week marked a major turning point in the course. Prior to this week, the focus has been on the chemistry that takes place in the context of cooking. Many of the chemical reactions we have seen can be summed up into a few basic principles. It has seemed as though “protein matrix” or “maillard” has served as a formidable answer to almost any chemical question that has arose in our experiments.
However, our reading this week delved much deeper into the chemistry in the kitchen and how that manifests itself into a science of its own. This field deemed “Molecular Gastronomy” studies the molecular chemistry of food and cooking. The reading was “Molecular Gastronomy, a Scientific Look at Cooking” by the INRA Team of Molecular Gastronomy. I found this article very interesting as it sought to explain why Molecular Gastronomy was created and how it can be classified as a science.
Of particular interest to me was their description of mathematical modeling techniques such as Complex Disperse Systems (CDS) that aid molecular gastronomists in objectively describing complex physical changes among an array of compounds in a dish being studied. The reading was much more in the style of what is typically seen in a chemistry journal as opposed to Harold McGee, and Shirley O’Corriher which are our normal texts. I would venture to guess that it provided those of us yearning for more traditional-type chemistry “more than enough to chew on”.
What is the nature of color in our food? What chemicals define color and what are their characteristics? These are just some of the questions that formed a basis for this week’s in class experiment. In order to gain insight into the chemical properties of some of the colors in the food we encounter everyday, we created an experiment that would test the effectiveness of polar vs. nonpolar solvents in extracting color and also, what effect pH has on color.
In order to test these properties, several common foods with a wide range of colors were tested. Check them out below!
Foods Tested: Beets, Cabbage, Radishes, Purple Fingerling Potatoes, Red Peppers, Blueberries, Raspberries, Cilantro, and Carrots
Each food was mashed to a pulp with a mortar and pestle. The pulpy mixture was then divided into two parts in two separate containers. To one container was added boiling water, and to the other was added boiling oil. Each container was then analyzed to determine which solvent effectively extracted the color from the pulp. It was determined that all the foods tested had their color(s) extracted by the water, and not the oil as seen below!
In chemistry, like molecules will often stay together. Oil is a non-polar molecule while water is polar. Polar refers to a molecule that has an uneven distribution of electronic charge. Polar molecules tend to stick together due positive/negative attractions while they repel nonpolar solvents. The fact that the colors mixed with water but not oil gave us a good indication that the molecules that provided the foods we tested with their color must also be polar.
Next, each colored mixture in the water solvent was poured into a separate glass. To each glass was first added acid (vinegar) and any color changes were noted. Then, to each glass was added base (basking powder) and the glasses were reexamined for color change. The observed changes in color suggested that the color molecules absorbed and reflected different wavelengths depending on the relative pH of the mixture.