By no means does good food equate with food that is good for us, however. Although most of us know something about preparing and enjoying food, few of us, including chemists, know much about food chemistry, which deals with what we eat, what we need to eat, and what we enjoy eating. This is a complicated subject as it deals with many disciplines including chemistry, physics, biology, analysis, and even psychology. Chemistry is arguably the most important of these. A good place to begin one’s exploration of food chemistry is T. P. Coultate’s Food: The Chemistry of Its Components, a popular book now in its fourth edition.

The book begins with an extensive discussion of the major constituents of food: sugars and their polymers, lipids, and amino acids and their polymers. One discovers what the compounds are, what foods contain them, and what happens to them on handling, processing, preparation, and storage. A good knowledge of organic chemistry is assumed here and elsewhere in the book. This is followed by fascinating chapters on colors and flavors, the “ingredients” that do so much to make food enjoyable.

Color vision is a fascinating subject in itself and no less so when associated with food. It was surprising to learn how few organic structures are responsible for the large variety of colors in food. What is responsible for this diversity is the variety of molecules that are covalently attached to these chromophores. Interestingly, colors from one food source can be used to enhance the color of other foods. Caramel, which is derived from sugars by heating, can be used to enhance the “brownness” of food products. Synthetic colors may also be used to enhance the colors of food, but their use is often strictly limited by law.

Flavor chemistry is also fascinating because it involves a complex interaction between a limited number of tastes and a seemingly endless number of aromas. What is of import in the book, of course, are the chemistry and chemicals that are responsible for these often pleasant physiological responses. Even today the causes of these sensations are poorly understood. Monosodium glutamate (MSG), an amino acid derivative, and inosine monophosphate (IMP), of a completely different structural type, are both flavor enhancers found in food. When used together they show an effect neither one alone remotely possesses. Manufacturers often take advantage of this: IMP is added to foods rich in MSG, and vice versa.

Coultate continues with a discussion of vitamins, organic compounds essential to human life but not synthesized biochemically by humans. These compounds do not enhance the enjoyment of eating but are required to maintain good health. One discovers what these compounds are, the foods that contain them, and the roles they play biochemically. I was surprised to learn that cobalt-containing vitamin B₁₂, cobalamin, is only made by microorganisms, but can be found in eggs, milk, meat, and liver. It makes one wonder where vegans get this essential nutrient. I won’t tell; you’ll have to read the book to find out.

The author next tackles preservation. Before the advent of refrigeration food spoilage was unavoidable. Microorganisms ravaged meats and vegetables, and still do. Probably by serendipity people discovered ways to preserve food, that is, to prevent microbial growth. Interestingly, flavors were often enhanced in doing so. Smoked meats come to mind. What chemicals are responsible for the smoky flavor? You’ll learn that here. Being an oenophile I also learned why sulfites are added to wine musts: they don’t inhibit the growth of desirable yeasts, but they do suppress undesirable ones as well as bacteria through very specific biochemical reactions. Sulfites are also added to finished and bottled products to suppress secondary fermentation.

In foods there may, of course, be chemicals that are not desirable to consume. These are covered in the next chapter, Undesirables. It is the food chemist’s job to find out what they are, where they are found, and hopefully to keep them out of food. The undesirable compounds include toxins produced by microbial agents, chemicals derived from agricultural practices, metals, packaging residues, and environmental pollutants such as PCBs, a class of chlorinated compounds on which I have carried out research. Not all undesirables come from commercial enterprises, however. Grilling meat, probably done in most backyards in the U.S., is a source of high levels of often highly carcinogenic polycyclic aromatic hydrocarbons.

The book concludes with chapters on minerals, the bulk and trace elements (roughly 24 in number) required for a healthy life, and water. Of all the topics covered in the book, the one on water was, initially, the most surprising to me. It shouldn’t have been. Most foods, even dried fruits, honey, and flour, contain water. Some foods aren’t palatable unless hydrated: pasta, for example. Not surprisingly, the structures of liquid water and ice and how they interact with food components are described in detail. I was particularly intrigued with the physical and analytical chemistry of water in food. Such concepts and practices as water activity, sorbtion isotherm, and water quantitation are widely used by the food industry to understand and control their products.

What can I say about the book overall? The writing is clear and concise and the coverage is comprehensive. There is a wealth of tables and adequately drawn structures. The book is devoid of color, which is not a drawback in my opinion since it keeps the final product modestly priced. For a book in its fourth edition there were a surprisingly large number of typographical errors, about one every two or three pages. This is fortunately a relatively minor distraction from what is otherwise a well-written, authoritative book.

How would one use the book? It is clearly a good place for anyone to learn the basics of food chemistry. It could also easily be used as a textbook in food chemistry although there are no problems. It might be used to supplement courses in biochemistry, nutrition, and organic chemistry. I will use it as a source of interesting and often unusual chemistry to enliven and enrich the organic chemistry courses I teach. I learned, for example, what raspberry ketone is, how one can use an isotope effect to distinguish the natural sources of sugar, what food is responsible for the sulfur that tarnishes silver, and so much more.

Enjoy the book!