Remembrance of foods past

When you sit down to a meal, how do you decide how much to eat? Perhaps it seems a ridiculous question. Most of us would answer that it depends simply on how hungry we are. That is, we eat less when we are relatively full and more when our stomachs are empty. But there is increasing evidence that physiological hunger is only one of many influences on how much we consume. Some recent research suggests, for example, that meal size depends not just on how full your stomach is, but also on your recall of what you have recently eaten.

There are some very dramatic examples of just how important memory can be in determining how much we eat. These come from studies of individuals whose ability to remember recent events has been abolished by brain damage. In one such study, two brain damaged men ate three consecutive lunches, each separated by as little as 30 minutes, because they had no recall of previously having eaten [1]. But what of the rest of us? Surely we can all recall – more or less – what we had in our last meal, and it is obvious that we recall more recent meals better than those from days earlier. So what actual impact does this have in how much we eat now?

Sometimes, eating is very memorable. For most of us, restaurant experiences – particularly at the high-end of dining – are not an everyday experience, and we want to savour and recall a chef’s ability or creativity. As a result, we pay attention to what we experience because this is crucial to the formation of memories. In contrast, everyday meals are very often anything but memorable. This is not because of their quality, but rather due to the lack of attention that we pay to the food while eating in our usual environment. We eat while watching TV, or reading, or texting.  But we now know that attending elsewhere, instead of on the food we are eating, has a number of important consequences.

The phenomenon of mindless eating is familiar to most of us. When distracted by our favourite TV program, we will munch through whatever is at hand – popcorn and confectionary, for example – without any real awareness of how much or how fast we are eating. Such distraction can lead to overconsumption, relative to those times when we are more conscious of eating. In particular, according to one recent study [2], this can be a problem for regular dieters, sometimes referred to as restrained eaters. Here, groups of restrained and unrestrained eaters were allowed to eat sweets (candies) while watching a TV program containing either food-related or food-unrelated material. The content of the program was relevant only for the restrained eaters who ate more calories while watching the food-related TV program. This, incidentally, is a clear example of the fact that restrained eaters are vulnerable to environmental cues that remind them of food.

But such distraction continues to have an effect even after we have eaten. If we do not recall, through distraction, what we have eaten, then at a subsequent meal we will eat more. Female university students were provided with a variety of sweet and savoury snack foods and drinks, with half watching a TV program at the same time [3]. Those students who had watched TV while snacking ate more of a lunch that was later provided than did their less preoccupied colleagues. Nor did it depend, in this case, on the nature of the TV program since a later study explicitly varied the content between humorous, sad or boring (lawn bowls!). Because the researchers had also asked their student participants to estimate how much of the snack foods they had consumed, they were able to explain these results by showing that those watching TV were less accurate in remembering how much of the snack foods they had eaten – indicating that their attention was on the TV program, rather than the food they were consuming.

In a more direct attempt to determine if paying attention to what you eat enhances memory and influences later consumption, another group of researchers asked their students to focus on the sensory properties – the tastes, textures, and odours - of a simple lunch of sandwiches and crisps as they ate, as compared to other groups eating the same meal who either read a newspaper article about food or did nothing [4]. In this case, a selection of sweet biscuits was available to consume in another session two hours later. Those who had earlier paid attention to their lunch ate fewer biscuits than the other students. Moreover, as in the previous study, this group also indicated that their memory of what they had eaten at lunch was much more vivid.

So clearly memory for what we have eaten is crucial in modulating what we will eat. Why? One obvious explanation is that if we recall how much we have eaten, we consciously limit what we subsequently eat to maintain some sort of overall daily calorie intake. While this is plausible, some sort of calorie calculation does not tell the whole story. Examining the response of the student groups in this last study to the different biscuits though suggests another possibility. The two most highly liked biscuits (both chocolate covered) were eaten far more than the plainer, less liked biscuit …. but only by the groups not asked specifically to focus on the food’s sensory properties. If those who were somewhat inattentive to their earlier lunch were highly responsive to the different degrees of palatability of the biscuits, why wasn’t the food focus group?

An alternative hypothesis is that the influence that memory exerts on subsequent intake is really concerned with the memory of the pleasure of eating, rather than the calories consumed.  This is consistent with the fact that, much of the time, we are driven to eat by hedonic (that is, pleasure-based) hunger rather than any real need to replace nutrients.

The influence of “memory for pleasure” might explain some interesting cross-cultural differences in eating. Much has been made of the “French Paradox”, also known as the “how come the French don’t get fat even though their food is delicious and rich” puzzle.  The French, it turns out, are far more focused on food pleasure than say diners in the USA [5] whose concerns are less about pleasure and more about the food’s health consequences. It is this focus on pleasure that underlies the satisfaction shown by French diners with smaller portions and the lack of a need to search for food pleasures – snacks - between meals.

So, from a weight control point of view, the message is simple. Distracting yourself from food pleasures – either via TV or via eating unpalatable food – is likely to leave you searching for the pleasure you have missed or can’t recall.

                                                                                                                       

1.  Rozin, P., et al., (1998) What causes humans to begin and end a meal? A role for memory for what has been eaten, as evidenced by a study of mulitple meal eating in amnesic patients. Psychological Science, 9, 392-396.

2.  Shimizu, M. and B. Wansink (2011) Watching food-related television increases caloric intake in restrained eaters. Appetite, 57, 661-664.

3.  Mittal, D., et al., (2010) Snacking While Watching TV Impairs Food Recall and Promotes Food Intake on a Later TV Free Test Meal. Applied Cognitive Psychology, 25, 871–877.

4.  Higgs, S. and J.E. Donohoe (2011) Focusing on food during lunch enhances lunch memory and decreases later snack intake. Appetite, 57, 202-206.

5.  Rozin, P. (1999) Food is fundamental, fun, frigtening, and far-reaching. Social Research, 66, 9-30.

The mathematics of flavour

We travel to enjoy new experiences and in particular the cuisines of other cultures. No two cuisines are exactly alike, even when the countries have a similar ethnic heritage. Some differences are obvious – eating lamb rather than beef or rice rather than bread, for example. Even when a cuisine’s ingredients are familiar, we can be bemused by the flavour combinations that the locals take for granted. In Japan, a very popular snack combines pretzels and chocolate; in the USA, pumpkin can be found inside sweet pies, and in parts of both Scotland and New Zealand, chocolate bars are sometimes covered in batter and deep-fried. But sometimes the animal and plant species consumed are totally foreign, presenting a challenge for all but the most adventurous. Exactly what is it that defines a cuisine and distinguishes one cuisine from another?

In the early 1980s, Elizabeth Rozin published “The Flavour Principle Cookbook” [1] in which the characteristic dishes of different cuisines were described in terms of unique combinations of specific ingredients used across a variety of foods within a culture. For example, a characteristic combination of ingredients in Japanese cooking is soy sauce, mirin (sweet rice wine) and dashi (a stock made from flakes of the bonito fish). While Korea is geographically close to Japan, its flavour principles are very different, with the intense flavours of garlic, chilli, sesame and soy dominating many dishes. In Moroccan cooking, cinnamon, cumin, tumeric, ginger, paprika, coriander, saffron, anise, cardamom and other spices are combined into Ras El Hanout, a universal blend that renders the chicken, beef or lamb that it flavours characteristically Moroccan. 

Together with her husband Paul Rozin, a noted researcher in the psychology of food, Elizabeth Rozin pointed out that these combinations of different ingredients provide a characteristic flavour that unites foods within a culture, and identifies them as originating from that culture [2]. Such a characteristic and preferred combination of flavourings may also assist in ensuring that a culture can be flexible in the range of foods that it consumes, thus maintaining dietary variety and an adequate intake of nutrients. A problem with incorporating new foods into diets lies in our tendency to reject those foods that are unfamiliar, a phenomenon known as food neophobia. Since food neophobia is largely based on fear of a food tasting unpleasant, using a familiar combination of flavours is a way to address this problem. This explains how whole cultures can successfully incorporate new foods, if circumstances suddenly change. If your staple meat is chicken, which you fry with vegetable oil, garlic, chilli and lemongrass, becoming vegetarian is not the only option if chicken is unavailable for any reason. The flavour principle – that is, frying in this particular combination of spices – allows a newly chickenless culture to start to consider other sources of animal protein without worrying if it will be rejected [3].

Our understanding of flavour principles has been largely anecdotal, gleaned as much from the information provided by chefs and books of recipes as anything else. In particular, there has been little understanding of the underlying principles that distinguish cultures on the basis of enjoying particular flavour combination and avoiding others? So, are ethnic flavour combinations merely the result of availability of particular ingredients or is there something more fundamental underlying flavour choices? 

It is often assumed – without any real evidence - that ingredients with similar flavours are more likely to be combined because of their compatibility than ingredients with contrasting flavours. Now, for the first time, quantitative research has addressed this question. Yong-Yeol Ahn of the USA’s Northeastern University, together with colleagues from Harvard, Indiana (USA) and Cambridge (UK) universities, recently published the results of a study [4] in which a rather complex mathematical method was used to explore the links between a set of 381 ingredients used is a variety of the world’s cuisines and the more than a thousand chemical compounds that give these ingredients their characteristic flavour. The basis of their analysis was the fact that many ingredients share one or more such compounds and so the number of shared compounds can be used as a measure of the similarity of different ingredients to one another. For example, the chemical compound 4-methylpenanoic acid contributes to the flavour of both tomatoes and Parmesan cheese.

The researchers asked if different cuisines were more or less likely in recipes to use ingredients that are linked strongly within this network of flavour similarities. To answer this question, they used databases containing more than 50,000 recipes representing a range of the world’s cuisines including those from North America, Western and Southern Europe, Latin America, and East Asia.

They found that cuisines from North America and Western Europe cuisines show a strong tendency towards recipes using ingredients that share flavour compounds. In contrast, both East Asian and Southern European cuisines are characterised by recipes with ingredients using distinctly different flavour compounds. Latin American cuisine tended to fall into the middle ground. This finding seems very consistent with ideas from both Japanese and Chinese cuisines in which the balance of distinctly different flavour qualities is emphasised. 

Digging into this unusually rich data set further, the researchers were able to discover that cultural differences in this “shared compound effect” did not involve the majority of ingredients used by the different cuisines. Rather, each cuisine was dominated by a small set of key ingredients that were very frequently used. They noted, for example, that around 75% of all North American recipes contained 13 key ingredients, with this list dominated by dairy products, eggs and wheat. East Asian cuisines on the other hand rely heavily on plant derivatives such as soy sauce, sesame oil, and rice and ginger. An important consequence of this study was therefore to provide empirical support for the Rozins’ “flavour principles”. 

Because of the ways in which Ahn and colleagues studied the inter-relationships of ingredient combinations across cultures, they were also able to investigate the similarity of flavour principles between different cultures. While we can all do this on an anecdotal basis – we know that German and Dutch dishes are more similar than German and Turkish dishes, for example – their data analysis provides a more scientific basis on which to make such judgments. Hence, they found, as expected, that North American and Western European cuisines were closely related, but also observed that in terms of signature ingredient combinations, Southern European cuisine is much closer to Latin American than it is to Western European cuisine.

Another intriguing finding from these data was to do with the complexity of different cuisines. Bookshops these days are filled with cookbooks containing supposedly authentic national, regional and sub-regional cuisines from all over the world. These give the impression both that many “authentic” dishes require sometimes dozens of different ingredients, and also that there are large cultural differences in cuisine complexity. We do not think it is surprising that French recipes tend to have many ingredients, more than a typical Brazilian recipe, for example.  But the final word on this comes from the flavour study. In their analysis of the huge number of recipes, they noted variation in the number of ingredients per recipe but in fact it is typically only a handful of “authentic” ingredients that distinguish a stew from a cassoulet or a curry.

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1.      Rozin, E., Ethnic Cuisine: The Flavor-Principle Cookbook.1983, Brattleboro: The Stephen Greene Press.

2.      Rozin, E. and P. Rozin, Culinary themes and variations. Natural History, 1981. 90(2): p. 6-14.

3.      A more detailed account of flavour principles and food neophobia can be found in Taste Matters. Why we like the foods we do. 2012, London: Reaktion Books.

4.      Ahn, Y.-Y., et al., Flavor network and the principles of food pairing Science Reports, 2011. 1(196): p. 1-7.

Paring wine and food pairing

At the Parisian restaurant Il Vino [http://www.ilvinobyenricobernardo.com/], the house philosophy is that a poulet de Bresse roti avec girolles is a nice piece of fowl with mushrooms, but a bottle of ’95 Domaine de Romanee Conti is something worth a detour. In contrast with most everywhere else, Il Vino asks you to choose your wine from their extensive cellars, allowing the chef to sauté, flambé, or simply fry-up some nice morsels to match it (or more likely, them – who’d choose only one wine?).

I mention this not because Il Vino is likely to be at the vanguard of changing attitudes to wine and food hierarchies – although, perhaps it might – but because their approach to wine does make us consider how and why we match foods and wines. In fact, why does this question even arise? Certainly, wine and food writers all seem to think it important. Unfortunately, such writing sometimes comes across as an idiot’s guide to what you are supposed to do with the wine: a cool-climate Chardonnay is the perfect accompaniment to langoustines in a beurre noisette sauce; the Riesling’s ideal with chilled Andalusian gazpacho. I suppose that it is possible that you’ll be caught in the dilemma of being given a nice bottle of Shiraz-Cabernet-Malbec. How to drink it?! Rustle up a supper of venison sausages with roast beetroot - problem solved!

Isn’t this all perfectly fine? After all, we do tend to feel that some wines go with some foods, and that other matches are less appealing, or perhaps seem less appropriate. But it all sounds a bit like homeopathy: white wines go with white meat, reds with red meat, sweet wines with sweet foods, and so on. Is there any rational basis for these pairings? The usual thinking is that whites – whether wine or meat – are delicate, shy, wallflower flavours. Red, however, is the colour of strength – lets face it, it’s the colour of blood. A white meat doesn’t stand a chance against the sort of wine that’s willing to spill blood at the slightest provocation! And as for a poor semillon caught in the same paddock as a rare steak ….. I’ll stop there for fear of frightening the children.

The prevailing wisdom on wine and food matching appears to rely on two assumptions about how tastes and flavours interact with one another. The first of these is that strong flavours overwhelm weaker ones, an issue of contrasting strengths. The second assumption concerns the ways in which qualities are meant to interact. One the one hand, similar tastes – sour plus sour, or sweet plus sweet – are thought to accentuate one another, while dissimilar tastes counteract each other. Thus, a sour food will build upon the acidity in a wine; but an acidic wine will cut through the sweetness of a dessert.

Let’s deal with these each of these assumptions in turn. Firstly, its important to remember that eating and drinking occur over time – we eat something, then have a sip of wine, then another bite and so on. The one thing that we can reliably predict about our senses of taste and smell (and indeed other senses) is that repeatedly experiencing the same quality over a short time will reduce its intensity. Hence, the second sip of a sweet drink is always less sweet, the effect of a process known as adaptation. Interspersing different flavours and tastes, as well as the passage of time, acts to reduce adaptation and maintain flavour intensity.

Secondly, does a weak taste or flavour appear even weaker following a stronger one? Quite probably, if they are of a similar quality (e.g., sweet and sweet; vanilla and vanilla) and adaptation takes place. Often, though, the effect may be more apparent than real. Certainly, intense qualities are more likely to hold your attention and be remembered than weaker ones. In all likelihood, though, paying attention to what’s in your mouth is likely to maintain the strength of any taste or flavour.

Thirdly, when we are dealing with tastes, the most common interaction seen with different qualities is a process known as mixture suppression. You’ll realise that you are already intimately familiar with this principle when I invoke (and I apologise in advance for this) the voice of Julie Andrews chirping that “a spoonful of sugar helps the medicine go down, the medicine go …….”. Horrible, but true. Sweet tastes reduce the bitterness of medicine or anything else. In fact, all taste qualities – sweet, salty, bitter, sour – suppress one another to varying degrees.

So, what do all of these interactions mean for our food and wine matches? Does the acidity of a wine “cut through” the sweetness of the dish, or does it render the dish sweeter by making you less sensitive to acidity in the food? Now, this is not what most people want to hear from a scientist, but …… who knows? Taken together with adaptation, the fact that tastes suppress one another means that it has suddenly started to get quite complex to predict what we are going to experience. Having a sip of a sweet wine prior to tucking in to your mousse au chocolate is likely to make the pudding less sweet, not more – because you have just adapted yourself to sweetness, making subsequent sweet tastes less intense. But, in addition, the mouthful of sweet mousse will accentuate the sourness of a wine because you have adapted to the sweetness that, in the wine, was suppressing its sourness, but is no longer.

We can consider how these effects may build and multiply ad nauseam, but it is neither a great way to endear yourself to your dining companions nor does it add to eating enjoyment. But it does mean that it becomes very difficult to provide some underlying principles of why some foods and wines might go together particularly well. Moreover, there is yet another factor we must consider. It is not enough to know the science of processes like adaptation and mixture suppression. To understand how we perceive the complex mixtures of tastes and flavours that are foods and wines, we also need an in-depth understanding of the impact of our expectations and beliefs derived from prior experiences with foods and wines.

Those aspects of perception that occur more in the mind than the nose and mouth are frequently shown to be immense influences. In one study [1], wine enthusiasts were asked to sniff white wines with all visual cues hidden, and to describe the aroma characteristics of the wine. When led to believe that they were sniffing a red wine, the words used matched those of red wines – blackcurrant, cherry, chocolate, and so on. Since these research participants were neither clueless nor, we assume, wanting to deliberately embarrass themselves, this outcome indicates a powerful influence of expectations over what we experience.

None of this means that we have been deluding ourselves when we thought that shiraz and red meat were a great combination, or that there’s something fishy about our choice of Sauternes with foie gras. But it probably does mean that such combinations, far from being based on some elemental principle, are – like food and wine preferences generally – part of our eating culture, a heritage of combinations that work because circumstances originally dictated their use. We expected those combinations to work and our expectations became reality over time. So, go ahead, drink whatever you like with whatever you eat. If it isn’t a success, you can always spit out your food.

1. Morrot, G., F. Brochet, and D. Dubourdieu (2001) The color of odors. Brain & Language, 79, 309-320.

Tastes Like Home

What would you rather eat – sautéed duck breast with a chestnut foam nestling on forest mushrooms enlivened with herbs de Provence or some roast chicken with vegetables? It rather depends, doesn’t it? Are you in the mood for a big night out or a quiet night in? We recognize that either of these dishes could be terrific in the right circumstances. So how does the humble roast chicken compete with the clearly more gastronomically adventurous dish? The answer is that sometimes we simply feel like comfort food, food that is not only familiar but also part of our childhood, our culture and that reminds us of ‘home’.

Even haute cuisine chefs recognize the power of simple, familiar food. Chef Alain Ducasse, weighed down as he is by multiple Michelin stars, produces at his flagship Paris restaurant a main course of Bresse chicken and spring vegetables. It is a very good (and – it goes without saying – expensive) chicken, but simple nonetheless. The anointed head of the new British food movement, Fergus Henderson, knows too that the dish of Middlewhite (pork) and peas served at his St John restaurant in London is memorable not just for being delicious but for the resemblance it bears to home cooking.

In a North American context, the prototypical comfort food is chicken soup. Researchers Jordan Troisi and Shira Gabriel from the State University of New York, Buffalo recently set out to examine where the comfort in this particular comfort food comes from[i]. Their starting point is previous research, unconnected to foods, showing that feelings of loneliness are often offset by social surrogates, including favorite television programs and the lives of celebrities. They suggest that some foods act in much the same way. Why? Because they are foods that have most often been eaten in the company of those with whom we have important relationships, including parents, siblings and partners. They argue that the feelings of psychological comfort that were experienced at the time of eating such foods becomes ‘encoded’ with those foods.

This idea makes sense and is also consistent with how we typically develop likes and dislikes for food. In the latter case, food flavour become associated with their metabolic consequences – provision of calories or other important nutrients – and this association is expressed in future in terms of liking. This form of associative learning can also be seen when a novel flavour is paired with something that is already liked – a sweet taste, a convivial environment or a famous actor or sports personality.

How did Trosi and Gabriel make their case? First they divided the 111 university student participants according to whether or not they considered chicken noodle soup to be a comfort food or not. Next, in each approximately equal group of students they were asked to undertake a word completion task. This involved asking the participants to complete word fragments, some of which could be made into whole words that were associated with relationships (e.g., welcome, like, include) and other fragments into different sorts of words unrelated to relationships. At the same time the students either consumed the soup or not.

The researchers were interested in how many words fragments were completed as relationship-related words. As they hypothesized, the number of relationship words completed was highest when the soup was eaten ….. but only for those who considered chicken noodle soup a comfort food. The interpretation by the authors was that the soup activated those relationship-related words because of past experiences of the soup in the context of their own important relationships.

One other characteristic of comfort food, according to these researchers, is that because it evokes associations with positive relationships, it may actually counteract feelings of loneliness. To test this notion, in a second experiment, another group of university students were divided via a standardized “Attachment Scale” according to whether their relationship style was generally ‘secure’ or ‘insecure’ – that is, those whose experience of relationships is generally positive or not, respectively. Half of each of these groups was then asked to write about a fight they had had in the past with someone who was close to them. The other half wrote about something completely neutral. Next, the participants were asked to write about their experience with either a comfort food or a novel food. Finally, all participants filled out a standardized “Loneliness Scale”.

Consistent with their predictions, the authors found that “securely attached participants who wrote about a fight with a close other experienced less loneliness if they were given the opportunity to write about their comfort food than if they wrote about a new food” (p. 750). In other words, the comfort food offset the feelings of loneliness that were evoked by writing about a relationship-threatening fight.

This research gives us some important insights into the motivations behind seeking out comfort foods. Such foods not only evoke pleasant associations, they can clearly act as surrogates in the absence of loved ones. The idea of comfort food is therefore not just merely a way of referring to home cooking – rather it is food that literally provides comfort.

While this may sound very positive, the authors raise the possibility that such effects may also underlie instances of increased eating that sometimes – and in some people – accompanies negative emotions such as loneliness, sadness and anxiety. Such ‘emotional eating’ is considered to be a risk for obesity in susceptible individuals.

We can also see some opportunities following from this research to further explore how foods may be attached to other emotions or experiences. Could we through suitable associations tailor foods or beverages to make us feel energetic or optimistic or sophisticated? Certainly, the idea that foods can influence our emotions in quite specific ways suggests a world of possibilities in intelligently utilizing the various elements – sensory, image, packaging – that have an impact on our food choices to increase positive emotions.

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[i] Troisi, J.D. and S. Gabriel, Chicken soup really is good for the soul: "Comfort food" fulfills the need to belong. Psychological Science, 2011. 22(6): p. 747-753.