Final Thoughts

It seems appropriate to finish this book with the equivalent of a dessert or aperitif, to send the reader off with a sense of satisfaction, satiation, and hopefully pleasure. I thought about polishing my crystal ball and trying to project into what food might look like in the future but, as the Nobel Prize-winning Danish physicist Niels Bohr once said, prediction is very difficult, especially when it is about the future. Futuristic predictions are of course notoriously unreliable, as can be seen by the fact that we should all surely have our personalized jet-packs by now. Interestingly, one theme that may have come through in this book is that the future of food, at least for the next few decades, is, to adapt a quote by the writer William Gibson, probably here already, but just not equally distributed. The progress of food science has happened sporadically and unevenly, as when Bert Hite showed that high pressures could preserve food a century before anyone figured out how to make that work in a practical sense, and when NASA was introducing innovations in food safety and packaging for space travel that years later have become common practice in our restaurant kitchens and on our supermarket shelves. The story of food science in the last century has been about taking all that we knew about the art, provenance, and processing of food in the prescientific era and underpinning anecdote with fact and understanding. I think that this great era of scientific study of food has answered the main questions, such that we understand broadly why most of the things we have observed since mankind emerged and started to eat things happen, and moreover how to control these to our greatest advantage. Many scientific phenomena relating to food are well described, in textbooks, websites, and a huge body of scientific papers, while of course leaving plenty of interesting questions and challenges for future generations of food scientists to explore.

The Rising Power of Yeast

In the last chapter, yeast was mentioned a few times as one of the generally less-problematic microbial denizens of food systems, and in fact the roles of yeast in the production of two of our most common and popular food categories, alcoholic beverages and bakery products such as bread, are so critical that it is worth dedicating a whole chapter just to the consideration of the science of these products. The ability of yeast to grow in a wide range of raw materials and convert sugars to alcohol, carbon dioxide, and other interesting products is the basis for production of products such as wine and beer, as well as higher-alcohol-level spirits, and is a process that has been exploited for the purposes of human pleasure for thousands of years. The origins of alcoholic fermentations, like those of many food products, are somewhat murky, but it is thought that honey or fruit may have been the original basis for the fermentation of such products, and that wine arose because of accidental adventitious spoilage of grapes and their juice that turned out to have, well, interesting consequences. The Greeks and Romans had wine-making down to an art, and it features frequently in their art; it also makes many appearances in the Bible (including a nonscientifically verifiable production protocol based apparently solely on water). The main reason alcoholic fermentation became of interest was as a way to prevent bacteria or other undesirable microorganisms from growing in juice by allowing a different kind of microorganism to get there first, use up the goodies, and produce products that made conditions highly unsuitable for colonization by later invaders. We routinely associate the word “intoxicated” with a formal description of the result of overconsumption of the outputs of such fermentation, but the heart of that word is “toxic,” which reminds us that alcohol is a poison. It just happens to be one that humans can tolerate only up to certain levels, beyond which poisoning and death can readily occur, but at lower levels has a range of effects that need not be described here.

Consistency and Change

Proteins are, in my view, the most impressive molecules in food. They influence the texture, crunch, chew, flow, color, flavor, and nutritional quality of food. Not only that, but they can radically change their properties and how they behave depending on the environment and, critically for food, in response to processes like heating. Even when broken down into smaller components they are important, for example giving cheese many of its critical flavor notes. Indeed, I would argue that perhaps the most fundamental phenomenon we encounter in cooking or processing food is the denaturation of proteins, as will be explained shortly. Beyond food, the value of proteins and their properties is widespread across biology. Many of the most significant molecules in our body and that of any living organism (including plants and animals) are proteins. These include those that make hair and skin what they are, as well as the hemoglobin that transports oxygen around the body in our blood. Proteins are built from amino acids, a family of 20 closely related small molecules, which all have in chemical terms the same two ends (chemically speaking, an amino end and an acidic end, hence the name) but differ in the middle. This bit in the middle varies from amino acid to amino acid, from simple (a hydrogen atom in the case of glycine, the simplest amino acid) to much more complex structures. Amino acids can link up very neatly, as the amino end of one can form a bond (called a peptide bond) with the acid end of another, and so forth, so that chains of amino acids are formed that, when big enough (more than a few dozen amino acids), we call proteins. Our bodies produce thousands of proteins for different functions, and the instructions for which amino acids combine to make which proteins are essentially what the genetic code encrypted in our DNA specifies. We hear a lot about our genes encoding the secrets of life, but what that code spells is basically P-R-O-T-E-I-N. Yes, these are very important molecules!

On the Origin of the Spices (and Other Foodstuffs)

The beginning of the story of food is what is termed food production. This might sound logically like the process of making food, such as a chef or food company might, but this term is rather generally used in food science to refer to the so-called primary production of food, from growth of crops to harvesting of fish and minding and milking of cows. Primary production is, for example, what farmers do, producing the food that is brought to the farm-gate, from where the processors take over. So the food chain runs, according to your preference for a snappy soundbite, from grass to glass (for milk), farm to fork, slurry to curry, or (taking the food chain to its logical conclusion, and including the role of the human gut charmingly but appropriately in the chain) from farm to flush. But where do these raw materials that are yielded by primary production actually come from? It is often said that all things found on earth can be divided into categories of animal, vegetable, and mineral. To these could perhaps be added two more categories, microbial and synthetic (man-made). Within these five groups can essentially be placed everything we know as food, so using this classification to consider where our food comes from seems like a good starting point for this book. Perhaps the simplest group to start with is minerals, which might intuitively seem an unlikely source of foodstuffs (do we eat metal or rock?), until we consider where salt comes from and how much of it we add to our food (in other words, probably too much). Our bodies, however, absolutely need for us to consume certain metals and other chemical elements to survive, beyond the sodium and chloride we get from salt, and so many extracted minerals find their way from deposits in the earth into food products. This is particularly important where their biological effects are a desirable outcome (such as in carefully formulated nutritional products). In addition, products such as milk contain minerals like calcium, magnesium, zinc, and more, because the infant or calf needs them to thrive.

Packaging of Food

History and fiction provide many examples of barriers being constructed to keep undesirable enemies away, containing a few points at which crossing from one side to the other is carefully controlled, whether it be Hadrian’s Wall, the Berlin Wall, or a 300-mile-long, 700-foot-tall ice wall. This is also the basic principle of food packaging: keep the food and its quality in, and keep all things that can impair that quality, or threaten consumer safety, out. Food packaging has many functions: Contain the product in a physical sense in a single mass and place. Protect the product from physical damage. Protect the product from chemical damage by controlling the access of gases, moisture, or light to the product inside, and also perhaps protect the product from sudden changes in temperature. Present the product to consumers in defined portion sizes. Provide convenience (for example, in how consumers can carry, open. or use and perhaps reuse the package). Provide surfaces on which information (marketing and practical) can be provided to consumers. Be compatible with whatever processes a consumer will subject it to, such as freezing or microwaving, if that is part of the function of the package and intended handling of the product. “Be the least evil” in terms of impact on the environment and our planet. The most common materials used for food today are cardboard, plastic, metal, and glass, while other materials occasionally used in food packaging include wood and ceramics. To achieve the properties just mentioned, though, most food packages today are complex composites of several materials, frequently bonded together in a way that is invisible to the naked eye. Such arrangements are necessitated by the fact that no one material usually has exactly the right properties needed, so such composites (called laminates where layers are glued together, as of paper, foil, and plastic, for example) are used to give a combination of strengths that overcomes any individual component’s disadvantages, like physical weakness, sensitivity to water or fat, or transparency.

From Sweetness to Structure

When we refer to food as containing “sugar,” we tend to picture white crystals we buy in bags or pour from sachets into our coffee, but to a food scientist sugar is not a single thing, but a type of thing. While, most commonly, when we say sugar we refer to sucrose, in reality there are many sugars that can be found in (or added to) food. They all have in common the chemical characteristic that they are carbohydrates, which means, as the name suggests, that they are based on carbon and water (giving hydrated carbon), and indeed the three core elements found in all sugars are carbon, hydrogen, and oxygen. One of the simplest sugars, molecularly speaking, is glucose, in which there are 6 carbon atoms, 6 oxygen atoms and 12 hydrogen atoms (so it is like 6 carbons plus 6 water molecules, as each water molecule has two hydrogens to one oxygen). These are arranged, not in a long chain, as in the proteins we discussed in the previous chapter, but rather in a ring structure (not technically round, but more like a hexagon might appear if you gave it a good twist). Glucose is the main sugar found in biology, being found in our bodies and also produced by plants by photosynthesis. Another simple sugar is fructose, found widely in fruit and honey, which has an even simpler structure, a pentagon structure, but again has 6 carbon atoms bound together with 6 oxygens and 12 hydrogens, while a rarer one (at least in its unbound state) is galactose, again with the same number of the core atoms but arranged in yet another slightly different state. Here is a wonderful example of the significance of chemistry for food, where the exact same number of atoms of the same three elements can naturally be found in (at least) three different arrangements, which reflect subtly different molecular shapes but yet give compounds that differ greatly in their sweetness, solubility, reaction with other components in food, and many other properties.

The Kitchen and the Lab

To this point, my focus has been largely on the transformations and processes that convert raw materials and ingredients into packaged final food products, while considering the relationships between such a scale and what happens in the kitchen. I believe that food science is food science whether it happens on a 10-tonne scale in a factory or in a kitchen at home or in a restaurant. It is just a matter of scale. But is this really a defensible proposition? As pointed out several times already, all food products consist of a set of raw materials and ingredients, which we submit to a process or series of processes and then place in a package in which it should remain safe and suitable for consumption for a defined period of time. What about a meal? Ingredients and raw materials, check, just taken from a larder, fridge, or freezer. Processes? Check, just maybe a different set and scale, as will be discussed. Package and storage? No, but one could say the plate, room, atmosphere, and a million other elements of presentation of a dish at home or in a restaurant are the package. Likewise, being able to maintain a shelf life may not be a priority, but it is usually regarded as a good thing when safety for the eater is guaranteed, while we often hope that those leftovers we put in the fridge or bring home in our doggy bags will retain some form of safe edibility for at least a while. Food science is science above all else, whatever scale it happens on. In the kitchen, our raw materials, animal or vegetable in particular, are products of biology, while the reactions that take place on plate or during cooking (or other processing steps) are driven by chemistry, and physics determines what happens when we heat, cool, mix, or all the other things we do. Like I said in the Introduction to this book, even the humblest kitchen is a highly scientific environment, and every meal is an experiment.

Squashing, Filtering, and Other Ways We Process Food

As I have discussed throughout this book, mankind has relied on heating to preserve and make safe our food for a very long time, even long before the science of how and why this works was understood. However, clearly using heat to process However, clearly using heat to process food is a rather blunt tool, sometimes as subtle in its effects as hitting it with a club or bat. Just as it kills bacteria, molds, and other microorganisms, it inflicts collateral damage on the sensory and nutritional quality of the food. The greater the level of kill, and hence stability and safety conferred, the greater damage to the “fresh-like” characteristics of the food has usually been caused. A question could then be posed as to whether, instead of applying such a crude and damaging (although undoubtedly effective) treatment, we could treat food with more of a surgical-scalpel or laser-focused treatment, which zoomed in on and very specifically destroyed the target microorganisms while leaving the surrounding food as little changed as possible. This is the target of so-called minimal (sometimes called invisible) processing, and today there are a range of technologies that have promise for achieving this goal. Indeed, because of the desirability of such an outcome, this has been thus one of the most active areas of research on food processing in recent years. We have encountered the importance of pressure several times already in this book, usually in how its manipulation can affect properties of water such as boiling. Pressure has another important application in food processing, though, in that it can replace heat as the physical force we apply to achieve desirable change in food. In food processing circles, high-pressure (HP) processing is often referred to as a novel processing technology, but in fact it has been around for quite a long time. Remarkably, around the same time that Pasteur was explaining how heat works in terms of preserving food, on the other side of the Atlantic an American scientist called Bert Hite at the West Virginia Agriculture Station was doing experiments on his own homemade pressure-generating apparatus.

For My Next Trick

Compared with some of the processes we have discussed so far, like heating or cooling, drying is one we might think less of in a kitchen context and consider to be more a large-scale industrial process. However, when we look around a kitchen we find a lot of products of such activity, in terms of containers of powders like salt, sugar, spices, milk powder, soups, flavorings, flour, and much more, as illustrated in Figure 12.1. These have enormous advantages of long life, not needing to be kept in the fridge, taking up relatively little space, and providing a neat and concentrated source of whatever flavor or other character we wish to add to a dish. The key consideration is that whichever powder we use will behave in a convenient way when we come to use it, dissolving in water or other meal bases easily and reliably. We also routinely remove water from food in the kitchen, perhaps not by having a mini—spray dryer on the counter (at least not in most kitchens), but by removing a lid from a pot to allow some water to be driven off in the form of steam. We also essentially remove water from food more subtly, for example, by adding sugar to a jam recipe, which does not remove the water as such, but rather renders it less available for undesirable things like supporting microbial growth, thereby achieving many of the stabilizing and preservative benefits of actual drying without the drying. Removing water from food greatly improves the stability of food products and, by inhibiting the actions of microorganisms, increases its safety. As a result, drying of food, wholly or partially, has been practiced for centuries as a way to make food more stable. Not only does removing water from food add major hurdles in terms of stability and safety, but it adds an enormous bonus feature of convenience. To illustrate this clearly, I always think of what life would be like if we had to buy all our coffee in liquid form, and no dried (or highly concentrated pod) versions existed.

Heating and Cooling of Food

As we have seen, heating of food is one of the oldest and most powerful ways of making food safe and stable, whether cooking a burger on a barbecue or pasteurizing juice, but is also a potentially highly damaging thing to do to many food products. So, it makes sense that a key principle of processing food is to understand how to control the flow of heat as precisely as possible. In Chapter 8, I introduced how we can maximize the efficient transfer of heat into and out of food in a kitchen in simple systems, like pots on stoves. In practice, in large-scale processes, to transfer heat efficiently from hot to cold, and in this way keep the lords of thermodynamics happy while minimizing damage to the food being heated, we need to use clever pieces of equipment, called heat exchangers (reflecting the fact that, just as the cold part of the system gets hotter, so the hot part gets colder in the deal; fair exchange is no robbery). To visualize a heat exchanger, imagine a simple metal tube, through which a cold liquid is flowing from one end to the other. Now surround that tube with a larger one, through which a hot liquid flows (as shown in Figure 11.1). The wall of the inner tube is exposed to cold on the inside and hot on the outside, and this temperature gradient is the pump that transfers heat across that wall, in nature’s obsessive quest for equality in all things temperature-y. So, now we have two tubes laid horizontally in concentric neatness, say with a hot and a cold liquid flowing in from the left-hand side; as they exit at the right-hand side, the outer hot liquid will be colder, and the inner liquid will have gained the lost heat and thus become hotter. If the tubes were sufficiently long, then both would come out at exactly the same temperature.