Review of Flavor by Bob Holmes

Flavor: The Science of Our Most Neglected Sense by Bob Holmes starts with an ode to flavor in the Introduction to the book, and he takes us on a voyage through the science of what makes food delicious or not. At the outset, the author clarifies that flavor is not a single sense but rather the combination of taste and aroma. He does not stop there, however, as he explains that flavor is much more than these two senses. In this context it leaves us wondering just what the “most neglected sense” is, but that point is merely a quibble over a very interesting and informative book.

Scroll down to the bottom of the post for my holiday gift recommendations

Both senses of taste and aroma are covered in some depth in the early chapters bringing in some of the recent, exciting research in both areas. It is clear that there have been some interesting developments in taste research since I stopped teaching my course on Flavor Chemistry and Evaluation only four years ago. Contrary to many books published about food recently, Holmes comes to the defense of the much-maligned MSG (monosodium glutamate). He explains its importance in the least-understood taste, umami, and indicates that the case against the ingredient is weak. We are also treated to a nice overview of the chemistry of aroma, which is much more complex than most of us can appreciate. The author introduces us to an elegant study by David Laing who found that few panelists could identify more than three distinct flavor-impact compounds such as those of almond, cloves, orange and spearmint.1 Unfortunately, he misinterprets the implications of the study suggesting that wine connoisseurs are unable to detect more than a few distinct flavor notes. In addition to the role of taste and aroma in flavor we learn about feeling factors and how they contribute to the overall perception of food quality.

From the contribution of different senses to perception of flavor, the book moves into how the brain interprets flavor. This series of chapters were my least favorite ones, perhaps because they strayed from the food-science perspective prominent in the rest of the book. I found the comments in this section to be highly speculative based on limited data. For example, in a paragraph using the word ‘might’ five times and ‘may be’ once, Holmes concludes that artificial sweeteners lead to overconsumption of high-calorie sweet foods. His descriptions of food cravings represent a minority point of view that conflicts with the more predominating views described in Food and Addiction and Mindless Eating. The author also proclaims, without any reference, that in the world “overnutrition now kills more people each year than undernutrition.” I find such a statement to be a gross oversimplification as overnutrition is not listed on any death certificate, although it can be a contributing factor to many, modern, chronic diseases. Fortunately, these chapters do not get in the way of an invigorating reading experience.


For me the most exciting chapters were on flavor chemistry and sensory evaluation. Holmes points out that natural, whole foods contain many more chemicals than are found in highly processed foods. He uses the example of a flavorist presenting an apple-flavored candy and an apple to people and asking them which one contains more chemicals. Invariably the response is the candy (26 chemicals) when the answer is the apple (at least 2500). So much for “chemically laden” processed foods versus pristine fresh fruits and vegetables. We learn about the complexity isolating and identifying individual aromatic compounds and the way flavorists and developers put together natural and synthetic compounds to provide the flavor impact of a novel food product. In the thick of discussing flavor compounds, the author stumbles into the answer to the question he raised with respect to David Laing’s research and the complexity of wine flavor as described above. Laing was working with individual compounds while flavor notes are usually the result of the melding of multiple compounds within a food or beverage.

Although the author seems to favor food chemists, he delves into the art of sensory evaluation as well from both descriptive analytical and consumer acceptability perspectives. We learn about how the flavor of a particular product can be broken down into specific descriptors and why it is so necessary to have the evaluators speaking the same language when discussing a specific food item. Holmes appears to be particularly intrigued with Hedonic testing and determining which sample is best. He does describe, however, the importance of digging deeper into flavor description than just declaring a winner. In this journey we are also introduced to such concepts as

    • effects of added flavors on healthiness of a product,
    • molecular gastronomy,
    • culinary aspects of flavor and flavor pairings, and
    • Maillard browning and its potential dangers.

My favorite chapter, however, involves a search for the perfect tomato and strawberry flavors. The book provides an explanation on the development of flavors in fresh strawberries and tomatoes. A major challenge facing fresh fruits that is not a problem with processed products is that fresh flavor is delicate, changing from day-to-day. Strawberries are ‘nonclimacteric’ fruits, which means that ripening and flavor development cease once they are picked. Unfortunately, strawberry flavor degrades rapidly after harvest. Developing an artificial strawberry flavor is an intricate task as variety, degree of ripeness when picked, and loss of flavor after harvest all make a big difference in our perception of its flavor. Tomatoes, are ‘climacteric’ fruits (botanically speaking as the bearer of seeds) and ripening can proceed after harvest, although not necessarily as fully as when left on the vine.

Like Mackay Jenkins in Food Fight and me on my personal journey, Bob Holmes visits the lab of Harry Klee, the molecular biologist at the University of Florida who looks to unlock the secret of tomato-flavor perfection. I am convinced that if anyone will be successful in this endeavor, it will be Dr. Klee. Should he find the key to capturing full-flavored tomatoes, the challenge will still be finding ways to get it to the supermarket with its flavor intact. Calgene introduced the McGregor tomato that came close to perfection, but I understand that less than 20% of the tomatoes they grew, measured up to the McGregor standard. They could not get the other 80% into the existing supply chain. The makers of Zip-Lock bags had a proprietary packaging system to slow down ripening during distribution. I never had the opportunity to taste any of their tomatoes, but I understand that the flavor was close to home-grown. The problem this company had was getting them into the supermarket. Calgene and Zip-Lock were working decades before Whole Foods Market and today’s home-delivery services. Perhaps, Klee’s perfect tomato could make it in today’s market.

In summary, Flavor is a great book when it comes to explaining flavor chemistry and sensory evaluation in very understandable language. Anyone who has walked away from a conversation trying to explain why chemicals in foods are not to be feared but actually make food flavorful and nutritious might want to buy and give this book to friends and family. I was not as impressed with aspects of food and the brain as Holmes wanders too much into “what if” land for my tastes. These passages are not enough to shy away from the book, however. I am pleased to recommend the book particularly for anyone not directly involved in flavor or sensory research wishing to know more about the topic. For the rest of the month of December, I will be following up on different aspects of food flavor.

Holiday gift ideas

It will come as no surprise to followers of this blog that I am an avid reader, averaging about a book a week read cover-to-cover. My award for the best food book I have read this year must be shared by two books. One of those books, Flavor, which is reviewed above, was selected because it best depicts food science as it is practiced. Cuisine & Empire, a very different type of book, provides insight into the role of processed food in history. It is much more than that as it gives us a clearer picture of how processed food has been a part of the historical record since the beginning of civilization. Rachel Laudan also demonstrates why we currently live in the golden age of food, for good or for ill, where most of the population has access to a varied and plentiful diet. Cuisine & Empire will challenge long-held assumptions about food by consumers, chefs and even food scientists.


For a more technical book, particularly for anyone who has taken a food chemistry class, I direct them to the Maillard Reaction Reconsiderd. Written by a food chemist, this book challenges the benefits of Maillard browning and points out potential dangers of these products. 

Finally, if you like the blog and have not read In Defense of Processed Food, my book might make a gift for someone you know who fails to understand why it is not a good idea to completely avoid processed food.

Anyone wishing to purchase any of these books can click on the image of the book cover for ordering information.


1 Laing, D.G. and G.W. Francis, 1989. The capacity of humans to identify odors in mixtures. Physiology & Behavior 46:809-814.

Next week: Food Flavor 101


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