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Patricia B. O'Hara, "Food Chemistry in Small Bites: The Alchemist in the Kitchen" (U California Press, 2025)
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Dr. Patricia O'Hara
the New Books Network
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Melek Frat Altay
welcome to the New Books Network. My name is Melek Frat Altay and I am your host. Today we are joined by Dr. Patricia O' Hara to discuss her new book, Food Chemistry in Small Bites, published by University of California Press. Patricia o' Hara is the Amanda and Lisa Cross professor of Chemistry, Biochemistry and Biophysics at Amherst College. She is the co author of the Chemical Story of Olive Oil and has published extensively in scholarly research. Food Chemistry in Small Bites is a lively science first look at what happens to food when we cook and eat. It breaks big ideas into bite sized pieces, exploring food at the molecular level from how heat transforms ingredients to how our senses shape flavor. Using everyday examples, it explains why spicy food feels hot or why milk curdles with lemon while encouraging a hands on, experiment driven approach it is about thinking like a scientist in the kitchen and reimagining the future of what we eat in a warming world. Dr. O', Hara, what inspired you to write Food Chemistry in Small Bites?
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Dr. Patricia O'Hara
So this is actually a very interesting story, like a lot of things that have inspired me in my life. The real inspiration for getting interested in food chemistry came from the students I was teaching at the time. I was acting in a role for a brief period of time as a dean of first year students. And in that role I was offering an ice cream event where I would make liquid nitrogen ice cream in all of the first year dorms that are at Amherst College. Now, Amherst is a small liberal arts college. It wasn't that many residence halls. So as I was going around over the course of the first semester and as I was making liquid nitrogen for the 20 or 31st years that would be in that particular residence hall, there was one night when the students who were there were just so interested in how the liquid nitrogen worked and how the ice cream was created and what, what was happening as it was bubbling. And they became so enthralled that they actually stayed after for another hour exploring some of the properties of the liquid nitrogen. And it wasn't long after that that a group of three of them came to me and asked if I would be willing to sponsor a special topics course for them. And we're talking about 2010. So about 16 years ago this all happened. So a special topics course, they wanted to do molecular gastronomy and food chem. And at the time I was dean of first year students as a professor of biochemistry teaching courses in biochemistry and general chemistry. And so I replied, I said, what do I know about food chemistry? I'm not educated in that area. And these are Amherst College ambitious first year students. And they said, that's okay, we'll track down courses that are taught otherwise places and we'll get a syllabus together and we'll put the syllabus together and we'll follow it. And basically all you have to do, they said, is to supervise us. So that semester that we did, that was a spring semester, the students had done their homework, they had a great syllabus. We followed a lot of the food science classes at Harvard that are public lectures that are available and some of the material that was available freely available online. And we went through and talked a lot about different types of cooking, different types of molecular gastronomy techniques. And I became super interested in the topic almost as much as they did. And so we decided that we transform the crude syllabus that had been created by the students into, into a more formal syllabus and offered it for teaching for the next spring. And I was so surprised when that next spring and we offered the course that we called Molecular Gastronomy. We had a very large turnout of 20 or 30 students that tried to sign up for the class. And as I was teaching the class that second semester to the group of students who'd signed up, I realized that I was really able, through the cooking, to reach students curiosity about chemistry and to make them realize that students were always naturally interested in cooking because that always led to eating. And so through their interests and their curiosity about cooking and eating, I could talk to them about the underlying chemical and scientific techniques. So it turned out that the course's success meant that I could reteach it again and develop a syllabus that was more aligned with my own interests in biochemistry and chemistry, compared with other syllabi that might be more focused on the culinary aspects or more focused on the physical attributes of food. And after teaching it five or six times, realized that what I had created was a very unique course, again always received very well by the students. And so with my students encouragement, I was able to put together from the lecture notes that I had delivered and sort of finessed over the 16 years that I taught the course into the book that you see today, which is the Food Chemistry in Small Bites. So that's how the book came to be. It came about as a product of a course that I taught. And the course that I taught was inspired by a group of students who one cold night in the fall became very interested by some liquid nitrogen ice cream.
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Melek Frat Altay
Yes, I think it's a brilliant idea to walk through aspects of chemistry via food because we all have a relationship with food. So this is going to sound like a very lame question, but I want to start with the big picture. Why do we eat?
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Dr. Patricia O'Hara
So that very basic question is by no means the lame question and in fact motivates how much of the book starts out answering that very same question. It's not where a culinary book would start out, it's not where a book on physics would really start out. But as a lover of biochemistry and sort of interaction between molecules and the human body, I realized that if I wanted to really talk about how food was trans, how raw materials were transformed into food on a dinner plate, I really needed to get down to the basics of the molecular composition of the foods. And if I'm getting down to those molecular composition of the foods, I then want to ask myself, well, why are those particular foods consumed? Why is it that we have carbohydrates and fats and proteins, and what are those components of those, and how do they relate to the basic chemistry? So the book actually does start out addressing the need that the body has for fuel, which is the underlying answer to the question of why do we eat? We eat because our bodies need fuel to live. And the fuel that our bodies need is a fine combination of different types of molecular ingredients. And so in the early chapters of the book, I go through and explain how so much of the food comes from living materials. We're eating animal food, plants, Animals and plants. And so that I go through and unpackage down to atoms. Like, what are the atoms that compo comprise a protein, and how is that different than a carbohydrate or a fat? And each of those then can later be dealt with in the book as a what happens to these different molecular components when you add heat to them or when you do other transformations with salt, or when you do transformations with whipping or other types of culinary techniques? Once I've laid the groundwork for my students of what the molecular structures are and why those structures are important for nutrition, I then I can begin to expose students to the more tactile components of the actual laboratory that we teach in the course, which is the cooking part.
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Melek Frat Altay
And then another aspect that you cover in Food Chemistry and Small Bites is flavor and how our senses work together to create flavor. So why did humans even develop a taste of a sense of taste, um, and enjoyment of food?
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Dr. Patricia O'Hara
What a great question. It is such a fascinating answer to that question that comes from many different dimensions. And I don't know whether I'll be able to talk about all of them. And honestly, in the book, I don't have a chance to really talk about all of them. But at a basic level, your sensory system allows you to screen the foods that you're eating to make sure you're going to get the right combination of sweet and sour and umami and fat. So your sensory system, through taste, through smell, through touch, and really, honestly, through hearing and other types of senses, let your body know what it is that you're you're eating. And your taste buds and your olfactory receptors for smells can send the signals to the brain to indicate what different food group it is that you're consuming. The bitter taste buds are a unique set in which it's thought that their evolutionary history was actually to guard humans against consuming poisonous foods. So many of the bitter foods that our ancestors might have consumed, greens from the field, might have had some, might have been toxic, might have been poisonous. And so the bitter receptors that are clustered in the back of the mouth would tend to send a signal to the brain, no, don't eat this. This is a poison, a toxin. As it turns out, we grow as we age to really love many of the bitter flavors. And so certain bitter compounds are actually pleasant to our brains. So another way of thinking about this, which is really a new take on food preferences, is that we know, we've come to know more and more about how our gut microbiome exists in our bodies and that we have, we're host to many, many different types of bacteria in our guts. And it turns out that the different species of bacteria that we have, the different populations, have their own food preferences. And so there might be one microbiome ingredient that really prefers a sugar based diet, whereas another one might prefer a different type of diet based on maybe more complex carbohydrates or maybe fats. And so there is communication, always chemical communication, between the gut microbiome and our brain that might signal an appetite. I'd really like something salty. I'd really like something sweet. And so we've come to appreciate more and more that every individual's unique microbiome can actually play a part in directing us to different foods. So to summarize, I think, from those just two perspectives, so that there are nutritional needs, that our body directs us through the sensory systems to the types of foods that will satisfy those nutritional needs. And then we have that newer take on our appetite, which includes the microbiome that's in our body and it's directing our food consumption. And if I might just take as an example, when women are pregnant, it's often the case that their taste preferences really change, that they really can't stand something that they loved before or they really crave something. And so again, our bodies know that there's a certain food group that might be necessary for the growth of a fetus. And so your body is directed against things like coffee or alcohol and towards things like something that might be considered carbohydrate or protein based food.
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Melek Frat Altay
Dr. O', Hara, you also talk about the different ways in which we transform food. Actually, some of them I never even heard of before reading your book, to be honest. Could you talk to us a little bit about the science behind how we transform food?
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Dr. Patricia O'Hara
Sure. I think the most fundamental way that we transform food we inherited from our caveman ancestors. Which was basically through fire. So by taking some material that we would sometimes have considered eating raw, but then if we add a heat to it, we can make it more palatable. We can make a very tough steak become stewed, if you will, and easier to consume. And we can often blend flavors together by processing them over a fire. In the book, one of the things that I. I do talk at first just about some of the mechanical transformations of just slicing and dicing and what you are doing to foods, if you're prepping them that way, where you're disrupting cell walls and ingredients from that were once intracellular are exposed to the air. And therefore you get things like browning of an apple. And as material that was in the apple gets oxidized. So the secondary analysis of how food is transformed as we cook it gets back to that. What are the components of the food, and then how each of those components can be transformed by heat. To take a first example, a process of heating. And we learned that if you take something like a protein, which is a polymer of an amino acid, a small group that defines the identity of proteins, or small amino acids, they're linked together in a complex structure that folds on itself. And when heat is added to that, to this really fundamentally polymer of amino acids, what happens is the intricate folding of the protein is destabilized by the heat, and the protein unfolds and then is no longer soluble. So that makes it more digestible. It changes the flavors. And other types of additional reactions can happen as some of the food is converted to new molecules with the addition of heat. And I think a perfect example of that is just cooking an egg. If you think about cracking open an egg, it's a viscous white with a more viscous yolk. And then as you add heat to it, you unfold the proteins of the egg white first of all, and you get the egg white that's no longer transparent as those proteins are unfolded. And then they don't. Light can't pass through the egg white anymore. And then in the egg yolk, you have different proteins, and again, the heat will transform them, and they have different temperatures at which transformation. So you can get an egg where the yolk is runny and the white is set. And so that's an example of how heat can transform proteins. It's also true that one can think about making caramel and taking sugars and transforming them into ingredients that have very, very delicious flavors and fragrances. And heat can go too far. You can burn your caramel quite easily. And that's another example of how heat can transform sugars. We have a very famous, in the culinary world reaction called the Maillard reaction. And the Maillard reaction is a reaction between amino acids and sugars. And in the presence of heat, the Maillard reaction does generate a whole host of very delicious flavors and fragrances that are very highly pleasurable to humans. So that's an example of how heat can transform foods. And I could also go on to describe how other processes like pressure or acid can, can transform foods as well. At the basis of all of those is an understanding, understanding of the basic makeup of the food and then how that perturbation, how the heat or the acid is going to cause changes in the molecular structure of those foods. So as I'm talking about making eggs or hard boiling eggs, or making ceviche with acid and fish, I can talk about both the food, which is super interesting to everybody, and then also the underlying molecular structure and the reactions between the heat and those molecular structures or the acid and that molecular structure. So I get a chance to really capture the student's interest with the food and then explain or answer their underlying questions by bringing in the chemistry.
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Melek Frat Altay
Food waste is a growing concern. How is it linked to climate change, in your opinion? And what are the promising ways to make food production or consumption more sustainable?
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Dr. Patricia O'Hara
Such an important question. I'm really glad that you ask that. And I'll have to say that the answers that I will give are not opinions that I have, but research that I've done based on very incredibly smart people who've done research about this. And while I don't have all of the figures exactly in my head, a very large, I think it's like 40% of the food in the United States ends up going to food waste. And when I say food waste, what I'm saying is that food that could have been consumed, but it ends up in landfills or just incinerated. So the origin of. So first I'll talk about the origin of the food waste, and then I'll connect it to the greenhouse gas issues. So the food waste has many different facets. It's not only things that are happening in our kitchens and in our dining halls, but it's also when you're in the fields and the farmer is harvesting a crop, and the crop then is analyzed for quality, and the farmer knows that, for instance, though it's completely nutritionally adequate, consumers are not going to purchase a pear that has a blemish or a carrot with a strange shape or a potato that looks Unlike other potatoes. And so they sort through and they grade their different products and then they may end up disposing of a large quantity of their harvest just because it doesn't meet the cosmetic requirements of the market. And it's a challenge, but not impossible for us to discover ways to bypass that consumer bias for pretty vegetables. One very famous example are baby carrots. The farmer who first thought about the creation of baby carrots, they are not baby carrots. They are carrots that were not originally, they were carrots that were just of second class quality because of an aberration in the shape. Maybe it was bent or maybe it had two, two legs that came out of it rather than one, but they are perfectly good. And so he just discovered or thought, well, what if I just took those and shaved them down and packaged them as baby carrots? So these were carrots that otherwise might have gone to animal feed or you know, God forbid, maybe even gone into a, an incinerator or landfill. So that was one brilliant way of transforming a very large amount of food waste into an edible product that today consists for a very large fraction of the carrots that are consumed, or so called baby carrots. And so that's one small facet of the food waste problem. Another facet is that when foods are packaged and then put on the shelf, sometimes they have, they're either not treated well in shipping, or it might be a fruit that ripens too quickly or ripens not quickly enough. And so they're wasted because the food rots as they're ripening too quickly or consumers don't buy them and the retail spaces have to throw them away because they just never ripen. So you have that issue of ripeness as well. Another factor in that's quite prevalent in the US Markets is that consumers don't understand food labels. So the food that they purchase might have a best buy date and a consumer might think that means you can't consume it after that date is over and so throw away the food. So food mislabeling of food is, is particularly bad in the United States and it's much, much better regulated in, for example, the European Union has about a quarter of the problem of consumer misidentification of foods that have spoiled by poor labeling. And in the United States, a consistent food labeling regulation has just never passed the U.S. you know, at the, at the federal level, states might have their own regulations about food labeling, but then as you go from state to state, you'll have different regulations and it gets confusing. So accurate food labeling is another way, and having consumers educated about that, that you could reduce food waste. And then another aspect, one we all can control, is just what we do with our food at home, in our kitchens, when it does, in fact, spoil to the point where we can't consume it any longer, what do we do with that food? Most of it in the United States is just put in the trash and then put into a landfill. But if we can learn and embrace and encourage composting, then those degraded foods can be turned into rich nutrients that could get returned to the soil. So I'm a big proponent of home composting, and my nieces and nephews, of which I have many, have all received as Christmas gifts, home composters from me. And it's just a really responsible thing to do. And it's just so much better than putting it in a trash and then putting it into a landfill or an incinerator. So that's an answer to the part of your question about what is food waste and how does it. Where does it come from? And then the second part of your question, which is about how does it contribute to greenhouse gas emissions? So much of the food that is in landfills will end up producing carbon dioxide and contributing that to the air. In addition, if we have poor farming practices, then you're also going to have fuel that might be used more than it needs to be if it's not a good, efficient farm practice. So we have greenhouse gas emissions going from the landfills, greenhouse gas emissions going from the process of agricultural farming. And it's also true that we sometimes are not wise in our choice of where we're going to farm or how we're going to farm. So those kinds of levels, the protections that we have with certain sort of ecosystems that might have helped us prevent greenhouse gas commissions, you might, you know, you know, take down forests to set something up, and then you lose the purification of the air by the. By the forest. So, once again, there's many, many factors that have gone into that. And I think it's a question that is, how can I say this? I received a lot of curiosity and a little bit of skepticism about my including a chapter on food waste in a book on food chemistry. Chemistry. And I felt that with the chapters that preceded that last chapter in my book, students had all the tools they needed to think about that question of food waste in an intelligent way and realize that there were solutions to these questions of greenhouse gas emissions and global warming that were in their own hands, that there was not only things that scientists are doing and interesting new crops that are being created by things like genetic mutations that happen through things like CRISPR gene editing, but also through the choice of what foods that they consume. Going to a plant based diet is so much less greenhouse gas producing than going to a meat based diet. And so not only by sort of following the advances from the scientific community, but also by making day to day choices about what foods you select and how you're going to deal with the trash of food that's created. That students will have that power. They'll be empowered to be able to make those choices after having finished up with the book.
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Melek Frat Altay
Final Question what do you hope readers take away from Food Chemistry in Small Bites?
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Dr. Patricia O'Hara
So I hope students take away the knowledge, the sort of realization that chemistry is not an abstract science that has nothing to do with them, but rather in fact that it underlies everything that they're experiencing in their daily lives and in particular, as illustrated in this text, by the foods that they're preparing that they're cooking. We do go through in the text the more modern techniques of sous vide cooking and making foams and espumaz and all of those being understood at the molecular level, and that these are not things that are so beyond a novice student's capacity. You don't have to be a graduate student in chemistry to understand the basic idea of how acid denatures the proteins in a shrimp so that students will feel mastery and empowerment because they've had things explained to them at a basic level and kept their curiosity engaged long enough so that they can get the explanations that they need to really understand what's going on. So I hope when students come away from the course, they'll say, wow, I really learned a lot of chemistry along the way and I also learned how to make a really fantastic scrambled egg.
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Melek Frat Altay
Thank you for listening to this episode where we explored food Chemistry in Small Bites with its author, Dr. Patricia O'. Hara. I hope you enjoyed the discussion and encourage you to dive deeper into this compelling work on how food transforms through chemistry. Thanks for tuning in.
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Dr. Patricia O'Hara
Keep exploring. Foreign.
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