Recently, there has been a lot of discussion in the industry about specialty coffee as an experience rather than a product. In specialty coffee, we take a lot of care to preserve the quality of our product from seed to cup, but we have little control over the way our customers perceive this quality internally. Ultimately, how we perceive coffee with our senses is influenced by our personal biases and learned associations. Additionally, the environment, our emotions, the color of a room, and everything going on around us can also influence our sensory experience. Technically, this sensory ‘experience’ is a multi-modal perception, including taste, smell, touch, sound, and sight. Scientists and psychologists have researched these sensations individually and in combination for over one hundred years. Although I am not an expert in the field, I have taken the liberty of outlining some of the ways that our five senses interact to influence our experiences with food and beverages.
The ‘taste’ experience is actually an accumulation of multiple senses. Many now refer to this as an ‘organoleptic’, ‘multi-modal’, or ‘synesthetic’ experience. For a long time, language lacked adequate descriptors to do the relationship justice, in spite of the fact that this concept was considered by both philosophers and scientists. When neuropsychologists talk about synethesia, they are often referring to a rare and complex neurodevelopmental condition where, for example, someone sees sounds or letters as colors. Those in the food research field have co-opted this definition to mean more of a general multi-modal experience, where the stimulation of one sense causes a perception in a different sense (Auvray and Spence 2008). Perhaps ‘sensory integration’ or ‘multi-modal perception’ are better terms. For now, pick the one you like.
Due to the impossible nature of conducting an experiment where one removes all other senses from taste (although some have tried), there is still some debate over what our tongue can sense, such as our ability to taste fat and metallics (Huang and others 2006). However, we know the old ‘tongue map’ has been reduced to a myth, and that we taste sweet, salt, sour, and bitter in many places on the tongue (Huang et al. 2006). Ultimately, there is little to say about taste without bringing in other senses, so let’s get right to them.
How Other Senses Influence, and Can Be Influenced By, Taste
Smell is certainly one of the larger players in the organoleptic experience, but it is not the only one! We can smell things via two pathways, one is through the nostrils (orthonasally), and the other is up through the throat (retronasally); see figure 1, below (Bojanowski and Hummel). Either way, there is no way to close off the mouth from the nose (in real life, at least) and therefore when we talk about ‘taste’, we are really talking about the synethesia of at least smell and taste. Importantly, though, taste and smell are sent to the brain via different pathways. They converge in the orbiofrontal cortex (Stevenson and Tomiczek 2007). Located in the front of the brain behind the eyes, this cortex is known to be the center of emotions and decision-making. Besides this synethesia, we have been conditioned to ‘taste’ with both senses through associative learning, which influences all of our flavor experiences (Prescott In Press).
We often describe a smell as sweet, but sweetness is really a taste that we have grown to associate with the smell of sugary food. This specific synethesia has been studied for over fifty years. Widely used examples of this include vanilla, strawberry, and caramel. Other times, a sweet smell can be associated not directly with a sweet food, but with a related odor compound. One example is the rose, which we do not consume, but we do describe as smelling sweet. This is because roses are related to raspberries and strawberries, and the odor compounds in roses are so similar to those in the fruit that we associate it with the sweet taste of those berries (Stevenson and Tomiczek 2007). Since different cultures experience tastes based on their regional cuisine, associations can change depending on where you travel. Logically, it can be extrapolated that these taste-smell overlaps can be accumulated through associated learning. These odor associations have been found in sweet, bitter, sour, and fatty tastes as well.
Smells can also suppress tastes, such as sweetness (Stevenson and others 1999). There is evidence that certain sour smells can suppress sweetness tasted in the mouth, and vice-versa, and that ‘sweet’ smells can suppress sour flavors. This means that the enhancement or suppression of the sweetness flavor arises from a perceptual level and is not physiologically mediated. In other words, the level of sweetness is not changed physically, but our perception of its intensity can be altered by smell.
Taste can also influence smell, although not as powerfully as the other way around. Irritants and fats are some of the categories of smells that can make us taste differently (Stevenson and Tomiczek 2007). One study found a menthol smell that was reported to be more intense when a sweet taste was added to it (Davidson and others 1999). A study on the effect of sweeteners in espresso coffee found that sweetness enhanced the caramel odor, whereas the ‘roasty’ and ‘coffee-like’ flavors were reported to be suppressed (Chiralertpong and others 2008). This result may have been caused with the commonality of the odor-taste association with ‘roasty’ and sweetness (i.e. in barbeque sauce). Smell is perhaps the most common synethesia referenced within the specialty coffee industry, as we use many smells as flavor descriptors.
Tactile sensations in the mouth cannot be separated from taste. The structure of a food or beverage can influence the release of volatile compounds in your mouth, therefore these compounds can find their way up to your nose retronasally (Bojanowski and Hummel 2012). To address this, a body of research has been conducted on viscosity and how this influences perceived flavor. Most work has found that as food hardness increases, perceived flavor intensity decreases (Tournier and others 2009). Some think that the texture alone influences how volatiles are released, which is of course influenced by our ‘mastication’ (chewing) patterns (Wilson and Brown 1997). Others have evidence that only perception is influenced by the textural properties of whatever is in our mouths and the volatile aromas remain unchanged (Weel and others 2002; Hollowood and others 2002). One such study investigated if food texture changed the release of flavor compounds into the mouth and therefore nose space (Weel et al. 2002). They found that texture was not responsible for this (using a variety of protein gels with different viscosities), and hypothesized that instead, a psychophysical mechanism was at play that changed the way study participants perceived flavor intensity. In other words, even though the chemical flavor or aroma of the food wasn’t influenced by the texture of the food (in this case) study participants still had different multi-modal sensory experiences based on the texture alone. This has also been shown with sweetness perception, in which the less viscous the solution, the less sweetness was perceived, despite the fact that the chemical composition of air in the mouth remained constant (Hollowood et al. 2002).
The method of food or beverage delivery to the mouth can also influence the perception of flavor. Since this is a complex external influence, it will not be addressed here, other than to say that different metals in cutlery have been shown to alter perceived bitterness, saltiness, metallic sensation, and pleasantness (Piqueras-Fiszman and others 2012). In one study, specific tastes were related to different specific spoon metals, making broad conclusions difficult. You can imagine that since cutlery is placed physically on your tongue, it can be more directly relevant to taste than say, the shape of a bowl and its influence on volatile release and therefore aroma perception. Overall, it’s probably a good idea to consider any product delivery method, and we often do, but also to know that the texture and viscosity of your coffee drink can change the physical and psychophysical perception of its sweetness and other multi-modal flavors.
A lot of how we see influences taste through expectation based on our own learned associations (Small In Press). We can all be influenced by how a meal is presented (Zellner and others 2011), but it turns out that the way sight influences our perception of food and beverages is much more complicated. Presentation can affect both how much we expect to like the food and our actual sensory experience with it, although not all studies about this link have found a positive correlation between the two. Since we can never get away from our learned experiences and history with food, the relationship between expectation and actually liking food can always be influenced by our past based on what we see in front of us.
That being said, we have learned that the color of food and drink makes them ‘taste’ a certain way. For example, a study that investigated the impact of color on refreshment level in different beverages found that almost always clear (water ‘colored’) liquids were rated the most refreshing (Zellner and Durlach 2003; Zellner and Durlach 2002). Other studies have shown that adding a red coloring to a sugar solution will increase the perceived sweetness of the liquid. Why? Think of the above example of ‘sweet’ smelling items, which are often red, such as strawberries, raspberries, apples, and other related plants. In the coffee industry, we often use descriptors like ‘red fruit’ when cupping. We only understand what this means because of experiences in which we have actually tasted red fruits. If your neighbor at the cupping table has no learned associations with red fruit, this reference would be lost. However, in a study where participants were allowed to describe what constitutes a ‘refreshing’ food or beverage, color was only reported by 24% of participants, far after factors such as temperature, sweetness, smoothness, juiciness, and wetness.
What tends to happen when these theories about color and taste are tested is that food-specific color preconceptions start to appear. Clear liquids were consistently rated as most refreshing due to the fact that we ‘know’ and ‘have known’ water for a long time. Another example, light brown was found to be more ‘refreshing’ than darker brown (Guinard and others 1998). This was because people who drink beer already have a certain notion of light versus dark beer. On top of this, if a food or beverage is the ‘wrong’ color, people tend to say that it is less refreshing than the ‘properly’ colored version (Zellner and Durlach 2003). It is easy to understand that people want ‘properly’ colored beverages, and think that the beverages are off if they are not the ‘right’ color. Essentially, we have all been biologically conditioned this way. Brown is the color of rotten fruits and vegetables, and this association is difficult to unlearn.
What about the color of things around us, in our environment? There has been some work on this topic that suggests that ambient lighting can influence our sensory experience with a food or beverage. However, it may be impossible to know how much of this is the way certain colors complement the particular food or beverage that is presented, versus how it affects our emotions (Chen and Dalton 2005). Most research agrees that this effect is context-dependent, meaning it is limited to certain beverage-color combinations (Oberfeld and others 2009). Generally, red and orange are associated with sweet tastes and yellow is associated with sour tastes. Also, blue has been associated with thirst quenching properties (Gueguen 2003). In a study on wine, white wine was deemed more pleasing in taste and more valuable in blue or red environments (Oberfeld et al. 2009). Why? Perhaps because blue and yellow are complementary colors, or perhaps the red light made the wine taste sweeter. There are still many questions in this realm of sensory research.
To apply this color research to other foods and beverages (such as coffee), the question should probably be asked, “What is the goal of this sensory experience?” It seems as though each individual food needs to be addressed separately due to the nature of our learned associations and preconceptions about what edible products ‘should’ look like. What is the flavor ‘goal’ of specialty coffee? Let’s not dye the coffee red to suggest sweetness (since that would look ‘off’ anyway), but consider aiding customers in learning what ‘proper’ espresso crema, milk foam, or extracted coffee looks like.
Since our brains are wired to combine information from all sensory modalities, we must not forget that sounds can also be associated with, or influence, flavors. Some of the most interesting research on this topic has linked certain tastes to musical pitches, and that those pitches are capable of influencing flavor perception (Crisinel and others 2012; Crisinel and Spence 2010). One study even went so far as to link specific types of instruments with flavors. Specifically, sweet or sour tastes were linked to high notes, whereas bitter and umami tastes were matched to low notes. Instruments such as piano or strings were linked to sweet and pleasant flavors, whereas bitter and sour tastes were associated with intensity and brass or woodwind instruments (Crisinel and Spence 2010). Follow up by the same research group found that ‘soundtracks’ designed to fit bitter or sweet tastes had the ability to influence the perceived sweetness of food (Crisinel et al. 2012). Other evidence is split as to whether background noise enhances or reduces flavor perception, but it likely depends on the type of food being consumed, the specific taste of interest, as well as the nature and pitch of the background noise (Woods and others 2011; Christensen and Vickers 1981; Spence and Shankar 2010).
Food and beverages can also make sounds inside the mouth, or while being masticated by the teeth. As you can probably imagine, we have grown to associate certain sounds with certain foods. Like the other senses, these learned food associations with sound can influence our perception of flavor, despite the fact that this has not been demonstrated universally in all studies (Christensen and Vickers 1981). Biologically, it is good for us to recognize certain sounds associated with ripeness or freshness in order to avoid spoiled foods. Think of the sound a crisp apple makes when you bite into it, versus when you bite into a soft spot. There is evidence to support that changing the sound of a food can alter our perception of it without any corresponding change in texture (Guest and others 2002). In a study on potato chips, it was found that perception of crispness and staleness were altered by varying the loudness or pitch of the ‘crunching’ noise (Zampini and Spence 2004). When the sound of crunching was amplified, participants rated the chips as both crispier and fresher. There must be something comforting in a food making an appropriate sound when you take a bite or sip. Of course, the mystery of the synethesia or pitch and taste is an intriguing area of research. Likely, we will have to wait for the secrets of the brain to be unlocked before we can fully understand this topic.
Other Interesting Taste Influencers
More on Context
When we rate a food or beverage, our hedonic rating of it is based on the context in which it is presented. Ultimately, if we are already familiar with a product or what we perceive to be a similar product, then our expectations are based on this knowledge. A study by Zellner (2007) tested this ‘categorization theory’ with coffee. In this study, participants were asked to rate ‘good’ and ‘less good’ coffee (using ‘canned’ coffee and ‘gourmet’ coffee). They found that people who categorized all coffee as ‘coffee’ found ‘gourmet’ coffee hedonically better than ‘ordinary, canned’ coffee. However, researchers also noticed that the people who thought of these beverages in different categories tended to rate both beverages hedonically pleasing. The same sort of outcome has been found in studies on beer. This result brings up interesting questions as to the type of marketing currently applied to specialty coffee. Do you consider types of coffee different categories of beverage?
As to our day-to-day food and beverage choices, recent research has found a link between the food we eat over a 24-hour period and our subsequent food preferences (Griffioen-Roose and others 2012). More specifically, if we eat a relatively savory or sweet diet, then the next day we crave the opposite taste category. The authors of the study explain this phenomenon by reminding us that biologically, humans need a diet based on carbohydrates and protein. Generally, savory diets are more protein based, and sugary diets are more carbohydrate based. Over time, our bodies learn to associate these energy sources with certain tastes, and with that, our bodies can learn to crave whatever our metabolism needs (Booth 1985). So congratulate yourself for having what the experts call ‘nutritional wisdom’ the next time you are in the buffet line.
In the long-term, regional cultural preferences play a big role in overall food and beverage preference (Einstein and Hornstein 1970). One of the first studies to investigate this found that despite ethnicity, people living within the same country would show similar odor-preference. In addition, they found that different regions of the world showed different preferences to odors (Pangborn and others 1988). This likely stems from regional cuisine and learned preferences. As far as coffee goes, a cross-cultural study found that Americans did not like coffee as much as people from Spain (Zellner and others 1999). That same study found that American women craved chocolate significantly more than Spanish women, suggesting that this craving is not a universal physiological one, but a cultural influence. It is likely that these examples depend on the cultures compared as well as the differences in regional flora and fauna (i.e. what is available to eat). However, we cannot assume that these relationships can be transferred to coffee unless it is specifically included in a study, as with Zellner et. al. We can all probably think of examples of regional coffee preferences, but more research needs to be conducted in this area to speak definitively on the topic.
Since the 1960’s, we have been aware that temperature sensations can cause tastes of their own. However, in the past decade a suite of new research has revitalized the concept and reported more specifics on the topic. In 1964, the journal Science published an article detailing how warm and cold stimuli could produce taste sensations on the tongue (von Békésy 1964). More recently, a study from the Yale School of Medicine found that a majority of people tested reported a sweet taste when their tongue was warmed and a salty or sour taste when it was cooled (Cruz and Green 2000). These ‘tastes’ were generally described as weak, but they were the first recent records of this phenomenon. They also found that in some people, warming the tip of the tongue up from 20 to 40 °C caused an increase in perceived intensity of the sweetness taste. With sour and salty tastes, they found when the tip of the tongue was cooled from 35 to 5 °C, subjects experienced a significant loss of perceived intensity of these flavors on the tongue (Cruz and Green 2000).
Physically, temperature can also affect the way a food or beverage releases aromatic compounds, thus altering our olfactory perception of the item. Chemically, heating anything speeds the movement of (and therefore the reactions between) molecules. This can lead to an increased rate of volatile formation. If there are more smelly molecules floating around, we are likely to pick up more of them in our nose and perceive the sense as more intense or profound. Also, the effects of heat on viscosity can play into this, as we have learned (above) that the more viscous (i.e. less solid) a food or beverage is, the more intense flavor perception can be.
As far as consumer perception of temperature goes, one study found that this category was one of the key descriptors of what they considered to be ‘refreshing’ (Zellner and Durlach 2002). Specifically, 28% of study participants described hot food and beverages as refreshing, which may seem odd considering that most of us would perhaps think that cold food or beverages are refreshing. Actually, 78% of study participants did. However, is it unreasonable to consider a hot cup of coffee refreshing? The coffee industry might have a biased opinion in this matter.
As we transform specialty coffee to an experience, efforts to retain quality from seed to cup are as important as ever, but it may be advantageous to remember that coffee is internally perceived, based on complex individual sets of expectations, learned associations, and integrated multi-modal senses. The multi-modal sensory experience is obviously a complex topic, and all areas of research are not covered in this article. There is still much to be investigated on the cognitive role in sensory synethesia, but there is already much to be learned from an industry perspective. Perhaps this multi-modal experience is the reason why coffee has a following all over the world, and this beverage spread across the globe because it was an experience, one that used all of the senses and made strong learned associations with comfort, mental acuity (or at least alertness), and sweetness. Let’s take a quiet moment to thank sugar for the role it has played in those associations. Practically every paper noted here mentioned the strong preference towards perceived sweetness. Some good advice for the specialty coffee industry might be to try to make drinking coffee as complex and beautiful an experience as possible; remember the importance of learned associations in consumer expectation and sensory experience, and use that to re-shape the way the world drinks coffee. Perhaps we can teach the world to appreciate our efforts in new ways.
Emma Sage is the new SCAA Coffee Science Manager. Before moving into the coffee industry, she completed degrees in ecology and botany, and dabbled in the wine industry. She is excited to learn all there is to know about the science of coffee (and more importantly, to share it with you).
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