Emerging Culinary Perspectives on Flavor Research

American Chemical Society’s Agriculture and Food Division Flavor Research Workshop in Boston brings together academics and food industry leaders to share insights on flavor science and its applications.

Chef Francisco Migoya and Dr. Chris Loss (The CIA) gave a talk on flavor development and innovation in the kitchen and the role of multi-modal interactions between the senses in traditional and avant-garde cuisine. The chef-scientist team provided workshop attendees with a guided tasting that included miso-nori bon bons, curiously colored macarons, French toast and bacon candy bar, vanilla scented milk, and tongue tingling Sichuan spices. The article below summarizes their talk and tasting exercises, and provides highlights from other presentations at the two day workshop.

Dr. Loss and Chef Migoya present at the ACS Agriculture and Food Division's pre-conference workshop on flavor research.

Introduction

Understanding flavor is integral to the career of a chef. Developing flavors is what motivates every chef to spend long days and nights in the kitchen, and it’s what draws customers back to their restaurants again and again. The flavors of new ingredients and emerging global cuisines challenges and inspires chefs to be innovative and incorporate new items onto their menus. Memories of flavor guide production and help maintain consistency in the kitchen. Emotional connections to flavor permeate every eating experience creating psychological context for enjoyment (or disappointment.) The flavor of foods might also help inform us of nutritional quality¹, defects in food and beverages^{2, 3}, and cultural identity of food⁴. One might consider that flavor is the primary driver of the $3 trillion worldwide food industry.

Flavor is inherent in our ingredients and is modulated and developed through culinary techniques. The simple act of slicing a piece of fruit, sauteing a piece of meat, or caramelizing sugar on top of a crema Catalan, produces a complex array of biochemicals, varied textures, and colors that inform our perception of flavor, the topic of a two day flavor science workshop in Boston.

Despite flavor’s biological and financial importance, and the fact that we experience it multiple times throughout the day, it is an elusive and complex sensory experience to understand. Increased understanding of the science of flavor perception and application of flavor science can provide an advantage to chefs and restaurateurs striving to capture the consumer’s food dollar in an increasingly competitive market place.

The American Chemical Society's Agriculture and Food Division held a pre-conference workshop in Boston (August 20-21) that brought together a cross-discplinary group of scientists and food industry professionals to share the latest research and insights on flavor. The workshop focused primarily on the chemical senses (which includes olfaction, gustation, and chemsethesis) and touched on the physical senses (which include audition, vision, and touch). Presenters included neurobiologists, biochemists, psychophysicists, sensory scientists, food scientists, and chefs. Physiological, biochemical, and psychological aspects of flavor science and applications in the food industry were explored. The workshop attendees included flavor chemists, sensory scientists, product developers, and food technologists from leading companies in the food industry, from around the world.

A culinary sense of flavor science

Chef Francisco Migoya and Dr. Chris Loss represented The CIA at the workshop, and gave a presentation titled, "Emerging Culinary Perspectives on Flavor." Their talk focused on chemical and physical flavor development in the kitchen and multi-modal interactions between the senses. They provided historical context⁵ for the emergence of "experimental cookery", an overview of tools and new ingredients in the modern kitchen, and a tasting of confections and spices that illustrated aspects of multimodal experiences in flavor perception.

Tasting tray illustrating aspects of the multimodality of flavor. (a) Macrons varying in color only (overall texture and "flavors" were the same); (b) Miso-nori bon bons balanced and unbalanced; (c) milk scented with vanilla and plain; (d) Sichuan button and red and green huajiao; (e) cinnamon-vapor scented, French toast, maple syrup, and Bacon praline chocolate bar.

To illustrate the interactions between color and perceived flavor⁶, Chef Migoya prepared 3 identically "flavored" apricot macarons that differed only in their color. The flavoring and textures were identical. Workshop students were asked to taste each of the macarons and note their flavors. Some students pointed out that the lighter samples were less intense in flavor, but that it was difficult to identify the flavor. Some thought the whiter macarons were creamier. Other students thought that each of the macarons had entirely different flavor systems. Interestingly, one person perceived the macarons to have increasing intensity of cheese flavor. So flavor perception is colored by color. Research chefs striving to translate authentic cuisine profiles for the retail or multi-unit market should keep this in mind and work with ingredient suppliers and co-packers who can help provide ingredients or process strategies that will help retain colors conveying intended flavor.

Chef Migoya presented two chocolate bon bons for a lesson in flavor balance. One bon bon was carefully balanced in flavor between sweetness of the sugar, bitterness of chocolate, umami of miso, and saltiness using a small piece of nori. The nori also provided texture contrast⁷ for balance, lending crispness to the center of the smooth chocolate bon bon. The second bon bon was purposefully unbalanced, and did not contain the nori, resulting in a flavor profile perceived as too sweet. In general, the workshop participants liked the flavor of the balanced bon bon better than the unbalanced. Chef Migoya used the comparison to explain how pastry chefs balance tastes, colors, and textures in the kitchen to create highly liked flavor profiles.

Dr. Loss described the concept of flavor balance in traditional Sichuan cuisine which has been explored by Chef Shirley Cheng in her research project on the on the culinary function and sensory properties of Huajiao. "Ping ha" is the Sichuan term for balance of flavor, and there are over 23 compound flavor principles that Sichuan chefs use to create that balance in their cuisine⁸. One of the more fundamental compound flavors is "Ma la" which combines numbing (Ma) from the Sichuan peppercorn known as huajiao, and heat (la), provided by the chili peppers prevalent in so many Sichuan dishes. The huajiao also provides strong aromas of citrus, tea, pine, and wood, that contributes to the overall flavors of many Sichuan dishes such as spicy chicken, scallions and cashews, and Ma la duck (below). Samples of red (huajiao) and green (tengjiao) peppercorns were tasted with caution by the workshop attendees, as they have a strong chemisthetic numbing effect.

Traditional Sichuan dishes incorporating the "Ma la" compound flavor principle. Left, spicy chicken, scallions and cashews, and right, Ma la duck. Heat (la) is generated by the capsaicin in the chilis and is balanced by a numbing effect (Ma) of the huajiao (generated by the chemical sanshool).

Dr. Loss drew some examples from Migoya’s blog, The Quenelle to illustrate the sensory phenomenon of "visual incongruity"⁹, which is often encountered in the restaurants of avant garde chefs. This occurs when the appearance of the food you consume does not jibe with the anticipated or the actual dining experience. There are 2 types of visual incongruity: visual novelty and hidden novelty. Visual novelty is when you are served a food and it does not look like something you intend to eat, but you engage with it anyway, and find it to be a memorable and pleasurable experience. Chef Migoya’s gin and tonic spheres, terrarium cake, and chocolate dome bar, were examples given in the presentation. Hidden novelty is when you are served a food that looks like one thing, but in fact tastes like something else. A classic example is the chocolate truffle, which was originally intended to look like an earthy subterranean fungi, but when bitten into, it reveals a silky smooth chocolate flavor.

Examples of "visual novelty" in avant-garde cuisine. Left, gin and tonic spheres; center, terrarium cake; right chocolate dome "bar". From Thequenelle

Chef Migoya created a candy bar to illustrate the sensory phenomenon of "hidden novelty" and to demonstrate that aromas can facilitate an enjoyable first experience with a novel flavor profile. The bar appeared to be a typical candy bar, but under the chocolate it contained the components of breakfast: French toast, maple syrup, and bacon. Chef Migoya used a volcano vaporizer to extract volatile compounds from cinnamon and infused the aromatic vapor into the headspace in the candy bar packaging. Upon opening the package the cinnamon volatiles were released, and wafted a familiar aroma to the consumer, providing "flavor context" for the novel bar.

HIGHLIGHTS FROM OTHER PRESENTATIONS AT THE TWO DAY WORKSHOP

Seminal research in flavor science: connecting food to perception through neurobiology

Dr. Terry Acree (Cornell), who co-organized the workshop, provided an historical perspective on seminal research in the field of flavor science. He emphasized that flavor research involves both psychology and biochemistry, and that work in the field of neurobiology¹⁰ has provided a critical connection between the two allowing for new advances in understanding flavor perception. Dr. Acree emphasized that flavor involves two processes, sensation and perception. He pointed out that "the uinification of sensory impressions…does not occur at the level of sensation, but rather at the level of perception"¹¹. In other words, flavor is a concept created in the brain.

Somewhat surprising, the brain is not a "multi-tasker", and when it comes to flavor perception, we have limits of how much information we can process. Terry pointed out that the current science indicates that people can only detect 3, or at most 4 flavor chemicals in mixtures at one time. He cited a quote from the gastronomical literature to reinforce this principle, which was by M.F.K. Fisher describing the smell of Dijon gingerbread: "It’s flat strange odor, honey, cow dung, clove, something unnamable but unmistakable, blew over the town (from Two Birds Without a Branch). Perhaps this will provide some consolation when you are sniffing and sipping wine at dinner and trying to draw out its elusory aromas and flavors perceived by the brain.

Mapping out the future for menu design and flavor perception

Michael Nestrud ('04) described cutting edge research on menu development techniques involving "graph theory", and how it can be used to optimize liking of multiple flavor combinations. This approach is novel because it looks at "connections between items to predict [appropriate] combinations" as apposed to looking at specific flavor attributes of ingredients and their measurements, as is traditionally done.

"Salad of Hawaiian Hearts of Peach Palm - Sugar Snap Peas, Red Radish 'lamelles' and mint 'Aigre-Doux'", a dish served at The French Laundry that Nestrud used as an example to help illustrate the fundamentals of graph theory and application in menu design. Image provided by M. Nestrud.

Nestrud’s approach involves presenting a list of pairs of food combinations to a group of panelists, who are asked to respond yes or no to the question, "Are these two components appropriate to combine on a pizza?" (for example). He applies highly sophisticated statistics to determine which combinations will work best. "Graphically," Nestrud's data can be represented by three components: nodes (the colored dots in the image) which represent components in a group of flavors; edges (the black lines) which represent strong associations between two items; and a "clique" which represents a strong association between 3 components. This is a new and potentially powerful approach to gaining insight into the complexity of consumer flavor preferences. Michael described potential applications of this method in the bake and serve pizza business to help design highly liked combinations of toppings. This approach is also being considered by the armed forces as a way to optimize "Meals Ready to Eat" menus for combat troops. In the current market place where we are continuously encountering new ingredients and flavors from around the world, Nestrud’s approach might help product developers minimize the financial risk associated with introducing new flavor combinations.

Flavor perception involves interactions between taste and aroma, and their release over time.

Dr. Andy Taylor (University of Notingham and Flavometrix Ltd.) covered topics of taste-aroma integration and flavor release. He explained that the difficulty of correlating flavor composition and perception is in part due to the fact that flavors are released from food while we are chewing them. These temporal changes in flavor make it difficult to model. Perhaps working with chefs and culinary professionals, who have an empirical understand of the dynamic temporal effects of flavor during a meal, can help advance understanding on this topic.

Dr. Taylor described a test conducted with Chef Heston Blumenthal of the Fat Duck on flavor release. Blumenthal demonstrated how Dr. Taylor's equipment combines highly accurate chemical analysis with consumer’s perceptions of flavor. The perceived intensity of flavor it turns out, can be greater than the amount of aromas released (i.e. detected in our exhalations).

Taylor’s lab has also worked to better understand aroma release in low fat food systems. For example, flavor is released at a faster rate in 1% milk as compared to full fat milks, due to the affinity of flavor compounds (especially volatile aroma compounds) for the lipid (or fat) portion of the milk. The more fat, the more dilute the flavor, because the aroma compounds preferentially solubilize in the lipids. Water does hold valuable basic tastants such as salts, sugars, acids etc., but fewer aroma compounds, which are integral to overall flavor perception. This is an interesting and important physiochemical property of food for chefs to be aware of, because the general wisdom is to add milk fat (in the form of butter) to augment the flavor. However it is possible that the aromas of a dish might be muted or delayed in delivery due to the additional butter, which has been demonstrated in classical culinary sauces¹². Taylor did point out that the rate of flavor release is dependent upon the food composition.

Multi-sensory nature of flavor and interactions that occur during a meal

The workshop included Jeannine Delwiche, Ph.D.from Firminich who focused on the multi-sensory nature of flavor and interactions between the senses. She described the science underlying a variety of sensory interactions including how color impacts taste and aroma intensity, how the tingle of carbonation can suppress odor intensity, and how viscosity can depress taste and smell, amongst others.

Dr. Delwiche also explained "adaptation", "mixture suppression", and "release from suppression", common sensory phenomenon experienced throughout the course of a meal. Adaptation is the perceived decrease in the perception of basic tastes or a flavor that occurs due to repeated exposure to that flavor. Consider tapas, and how small bites of these composed flavors allow for a greater variety of fresh flavors to be presented.

Adaptation. The perceived flavor intensity of a food is diminished with increasing exposure to that food.

Mixture suppression is the perception that tastes or aromas in combination are less intense than when perceived individually. If you add sugar to a cup of strong French roast coffee, the bitterness will be muted. This is not due to any chemical change to the bitter compounds present, but reflects how the brain processes information about food flavors. Flavor perception is a "top down" process, which means that it occurs in the brain and not on the tongue or in the nose -what sensory scientists refer to as the "periphery". Jeannine also refers to flavor as an "emergent property" of food, to emphasize that it is a concept created in the brain, and not entirely inherent in the chemical composition of the food being sampled.

Mixture suppression. When tastes are mixed together they are perceived to be less intense than when sampled individually.

Dr. Delwiche described release from suppression,which is a temporal sensory phenomenon that occurs while we eat. In other words the sequence in which we eat foods impacts our perceived intensity of flavor in those foods. She illustrated this with 3 lemonade samples: one that was regular strength (control), one that had been spiked with citric acid (overly tart), and one that had been spiked with sugar. By tasting in sequence the workshop attendees were able to experience adaptation and release from suppression. When the control lemonade sample was tasted after adaptation to the excessively sour sample, it was perceived to be overly sweet. In the parlance of the chef, "the balance was off." Again, the composition of the control sample was unchanged, but how the flavor profile was processed and interpreted by the brain was different.

Release from suppression. Workshop attendees were asked to taste sample A, a well balanced lemonade and to note its flavor. Then they tasted sample B which was lemonade containing an excessive amount of citric acid (very sour!). They then went back and tasted sample A and perceived it to be much sweeter than during the previous tasting. The sweetness was released from its intended suppression (balance) with the sourness of the lemon.

You have likely observed release from suppression in the dining setting, when tasting a well balanced wine after a few bites of a salad dressed with vinaigrette. The wine will seem sweeter after the salad because your "palate" has adapted to the sourness of the vinegar in the dressing. The sweetness in the wine that is normally suppressed is "released" from its intended balanced intensity.

Other topics of interest covered at the workshop:

"Mechanisms Underlying Chemesthesis" was the title of a talk presented by Bruce Bryant of Monell Chemical Senses Center in Philadelphia. He covered the perception of tactile or physical sensations in the mouth (and on skin in general) caused by chemicals such as capsaicin (the "heat" perceived when eating chili peppers), spilanshool (the "numbing" or "buzzing" perceived when eating hujiao A.K.A. Sichuan peppercorns), and methol (the "cooling" casued by alcohol).

"The Neurobiology of Olfaction" was covered by Stuart Firestein of Columbia University. Firestein described advances in understanding olfaction permitted by techniques in molecular genetics. He noted that approximately 2% of the human genome is dedicated to generating olfactory receptors. He also pointed out that the "shortest pathway to the brain" is through two neuronal synapses in the olfactory system.

Johan Lundstrum (Monell Chemical Senses Center in Philadelphia) gave a talk titled "Integration of the Senses: Multimodal Processing in the Human Brain" His work suggests that faster and more accurate detection of a stimuli occurs when two senses work in concert. More research is needed to better understand if 3 senses combined are better than 2, in this respect. Dr. Lundstrum referred to "flavor" as a "supramodal sense" that transcends the existing modalities. Also of interest, the scientific literature suggest that when it comes to sensitivity, the stimulus is less important than the number of senses stimulated. So a glass of water at room temperature will be less engaging to a customer than a glass of cold water with ice that clinks in the glass, and that contains a twist of lemon.

Gavin Sacks (Cornell) covered the flavor chemistry of wine making and described how grapes largely contain the chemical precursors for aroma compounds (not the aroma compounds themselves) and act as "bioreactors" for flavor. He noted that although there is complex flavor chemistry represented in a bottle of wine, there is still an important aspect of serendipity and artistry in the business of wine making.

Bill Cain (U.C. San Diego) emphasized the importance of considering flavor as a "concept" and human construct that must be observed from psychological perspectives as well as biochemical and physiological. He emphasized that integral to understanding flavor is understanding and measuring attention to flavor. He also described "sensory ageing" and how older cohorts have been able to correctly identify spices better than younger cohorts. His hypothesis being that older people have worked with foods from scratch more than younger people, and are more familiar with those ingredients.

Jane Leleand, Ph.D. (Kraft Foods), who co-organized the workshop, covered the basic tastes and molecular screening techniques used in taste research. She described how companies are using molecular methods to probe samples from the environment (fruits, herbs, etc.) for taste active compounds that might have application in the food industry.

A convivial context for exchanging ideas

The workshop included time scheduled for attendees and speakers to discuss the topics presented, in an informal setting, over wine, cheese, and crutdite. This opportunity to ask questions and exchange ideas between industry professionals and academics was a highlight of the workshop.

Many thanks to Kathryn Deibler, Jane Lealand, and Terry Acree, who organized and coordinated this workshop, which is offered through the American Chemical Society's Agriculture and Food Division every few years.

References:

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2. Fromm, H., Boor, K, (2004) Characterization of pasteurized fluid milk shelf-life attributes. Journal of Food Science, 69(8):M207-M214.

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4. Rozin, E. (2005) Culinary themes and variations. In C. Korsmeyer (Ed.), The Taste Culture Reader, Experiencing Food and Dink (pp 34-41). NY Berg

5. For more detailed reading on the history and origin of "molecular gastronomy" visit Harold McGee's Curious Cook site at http://www.curiouscook.com/cook/erice.php

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8. Zhang, F. (1983) Encyclopedia of Sichuan Cuisine. 1st Ed. Chongqing People's Publishing, Chongqing.

9. Schifferstein, H.N.J., Spence, C. (2009) Multisensory product experience. In Schifferstein, H.N.J.and Hekkert, P. (Eds), Product Experience. Oxford, Elsevier.

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12. Rapp, E. et al. (2007) The sensory effect of butter in culinary sauces. Journal of Food Service, 18: 31-42.