What strategies for food taste modification?
Formulating new food is challenging. One of those challenges to face, especially when it comes to functional foods and nutraceuticals, is taste. To some extent, you can taste that it is good for you. Broccoli sprouts and drinks are rich in glucosinolates, a bitter-spicy tasting compound. Yet, it can help prevent some forms of cancers. Strong antioxidants from the chemical group of polyphenols are in wine, tea, or cocoa. Their bitter and astringent taste limits their penetration in the market. This is especially relevant when extracting functional elements from a plant and enriching other food. On one side, there is an effort to increase the consumption of functional foods. Those have health-promoting factors that could benefit the population. On the other side, the additions required affect the sensory profile of the finished product. It is difficult to avoid unpleasant new flavor characteristics. When it comes to healthy functional foods, making formulations that are both effective and palatable is a must to ensure its adoption. Yet, the bitter taste seems unavoidable as it can be inherent to the compound itself. Strategies need to be taken to hide the undesired taste or to make it more appealing. For this purpose, there are 3 routes:
Balance the different taste and optimize the taste-taste interaction
Change the perception by modifying product texture or influence cognitive perception
Masking the taste by interfering with the substance ability to interact with the taste receptors
During this article, we will develop each of those strategies along with application examples.
Taste-taste interaction
As humans, we are capable of identifying five tastes: sweet, sour, bitter, salty, and umami. Millions of molecules have an associated taste. Despite this diversity, there is a limited number of taste receptor types. Many compounds can stimulate each of them but still lead to the same chemical pathway. The signal is carried the same way by the brain which understands it as the same taste. This process is thus independent of the initial stimuli. When it is not single taste information that needs processing but two or more, how does the brain react? What does the final mixed information look like? It may sound sophisticated but questions on taste interactions do not have to be. They actually can justify frequent ingredient association choices. Why would you blend the sweetness of a sugar cube with the bitterness of coffee? Is the sourness of lemon a good match with your refreshing summer wheat beer? Those associations, when put together, do give something separated than tasting both one after the other. Indeed, when it comes to understanding taste, interaction between different ones plays an important part. One taste can enhance the perception of another, or the other way around, suppress its intensity. The intensity of the change is also concentration-dependent. The effect can be barely noticeable at one concentration and become very significant at another one. A look at the following graph can help to give a better understanding.
The typical taste intensity response toward a change in concentration follows this shape in 3 phases. First, an initial phase once the threshold for perception is reached. Then, it is followed by an exponential increase where a change in concentration is of great consequences for taste intensity. Finally, we are getting to a saturation phase where taste receptors on the tongue are not able to treat more information. Through the example of this graph, the addition of a substance A leads to a decrease in the taste intensity of the initial sapid substance. The addition of substance B, however, gives an increase in intensity, and enhancement of the taste.
This impact on the perception of the taste intensity isn’t the same all along with the possible concentrations. Moreover, the interaction between two or more tastes can happen at three different levels. This complexifies even the understanding and prediction of this phenomenon.
Chemical interactions can result in the bonding between different substances and the formation of new ones. The newly formed element will likely not taste the same as the two originals. Its intensity can be changed or even making it tasteless
Oral physiological interaction can occur when a single compound has two actions. On one side it stimulates some taste buds and at the same time blocks others. This action happens in the mouth, at the cellular level, and not at the brain level.
Cognitive interaction. Prediction or modelization of those interactions in a model system is much more difficult. In this case, the perception of several tastes occurs simultaneously in the mouth. Once the signals received by the brain, the taste stimuli are mixed and the final perceived intensity can differ from their sum. When synergy happens, this means that the taste of the mixture is more intense than the addition of taste intensities of its components. The other way around is a mixture suppression.
To be able to exploit taste interaction and apply them in formulations, the easiest option is to look at what is already known. But, with all the combinations that can exist, the part of the unknown is much more important. Exploratory blends, new associations, and collection of associated information are likely the best bet to hit a precise taste target. You then need to use analytical devices, like the electronic tongue, or work with tasters to guide you through the taste optimization process.
A few examples of interactions between different tastes
There are many examples of situations where taste-taste interaction occurs. Knowing them is the first element of knowledge that you can leverage to improve taste, optimize costs, reduce the number, or the quantities of certain ingredients and additives.
Sweetness
High-intensity sweeteners are sugar replacers that are much sweeter than sugar and add very limited or no calories to the foods. The most used are acesulfame potassium, sucralose, aspartame, and saccharin. They are used in most “light” or “zero” sodas and many other applications. When mixing several high intensity sweeteners, there is a synergy with an increased sweetness. For example, when associating aspartame and acesulfame potassium (or Ace-K), a synergy occurs. It is as well the case between aspartame and saccharin (at low concentration).
Besides, the sweetness is generally suppressive of the four other tastes. This is especially true at high concentrations. The sweetness has a strong ability to suppress bitterness and sourness. This explains why a sweetened coffee doesn’t feel as bitter as a black unsweetened one.
Umami
Various additives are taste enhancers for a savory taste. Those are commonly found in instant noodle soups as umami taste is most present in Asian cuisine. There is a synergy observed between monosodium glutamate (MSG) and the sodium salts of disodium inosinate and guanylate which are all known for their umami taste.
As an illustration, this part of the ingredient list for an instant noodle soup, chicken flavor: Soup Base Ingredients: Salt, Chicken Fat, Monosodium Glutamate, Hydrolyzed Corn, Wheat and Soy Protein, Powdered Cooked Chicken, Sugar, Dehydrated Vegetables (Onion, Garlic, Chive), Dehydrated Soy Sauce (Wheat, Soybeans, Salt, Maltodextrin), Autolyzed Yeast Extract, Spices, Caramel Color, Natural And Artificial Flavors, Silicon Dioxide (Anti-Caking Agent), Lactose, Turmeric, Disodium Inosinate, Disodium Guanylate. [1]
Results differ depending on the molecule used but umami taste also generally suppresses bitterness and enhances saltiness, especially at high concentrations.
Saltiness
The table salt or sodium chloride (NaCl) is the salt we all know and use. Its overconsumption remains a strong preoccupation for health authorities. One of the main alternatives currently available is potassium chloride (KCl). Yet, its bitter-metallic aftertaste makes it much less palatable. The mixture of NaCl and KCl, at low concentration, enhances salty taste. This relation is concentration-dependent. At higher concentrations, the synergy is lost, and a suppressive effect can occur.
Sourness
The sourness has a suppressive effect on bitterness. The other way around, bitterness can be neutral, suppress or enhance sourness depending on the concentration of both compounds. When sour and sweet are both mixed at high concentrations, they suppress each other.
Bitterness
Bitterness intensity decreases with a salty taste. It is also enhancing sourness and has an inconsistent effect on sweetness. The bitter taste is often undesirable. Strategies to hide bitterness can be done by taking advantage of its interaction with other tastes, especially sweetness, saltiness, and umami. Yet, other routes are available to alter tastes by playing on other components of the formulation than the taste active fraction.
Other routes for taste modification
Texture
Changing texture can change taste perception. This is especially true in beverages and other aqueous solutions, where most of the experimental work that has been done. Some additives can modify the texture of a drink and make it more viscous or more jelly-like. A wide number of those texturing agents exist. Some of them have been tried, such as cellulose, carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), xanthan, or gelatin over a range of viscosities. The increase in viscosity (making the preparation less liquid) can decrease the bitterness of quinine or caffeine by up to 60%. This is likely true for other ingredients where the application has simply not been done yet. The beverage being denser, it is less likely that the bitter molecule will reach the appropriate taste buds. Reducing interactions is also reducing taste perception. This may be a particularly interesting strategy for functional beverages. Some texturing agents are natural fibers. By using them, you can ensure the delivery of a health beneficial substance in the drink without compromising too much on nutrition and still play on the drink palatability.
Odorant
Our brain has always been exposed to certain associations of odors and tastes. Those repeated exposures led to the conditioning of your brain. You do not expect something with a strawberry flavor to be salty or bitter? For all, the strawberry flavor goes with sweetness and not umami or bitter. This link is not only a belief. Some odors, due to the strength of the cognitive association, can enhance the taste perception. Strawberry and vanilla flavors increase the perception of sweetness. Studies on coffee and chocolate aromas have demonstrated that they enhance bitterness. While exploiting this type of approach seems a promising strategy, it will only work if the cognitive association exists. To ensure the effectiveness of the formulation for everyone, you will need to hypothesize on their previous food experiences. Those can be greatly influenced by individual and cultural factors and tricking the mind might not be so simple.
Development of taste-masked formulation
The addition of an ingredient to a formulation can prevent the undesired taste of another one to be perceived. This process is called taste-making. There are several ways this phenomenon can occur. In all of them, the poorly tasting compound won’t be able to liaise with the taste receptors. The masking interaction can occur on the taste receptor itself. In this case, the masking molecule would adsorb on the receptor and block the access for others. Sugar-based masking techniques exploit this property. Taste blockers can also decrease taste through complexation or encapsulation of tastants.
The following figure presents the different possible masking mechanisms
Bitterness is the taste that is the most targeted by taste-masking approaches. It has indeed the strongest effect on food acceptability. Cyclodextrins are cyclic oligosaccharides with a donut-like structure which can catch the bitterant in their center. The connection with the bitterness receptor is thus not possible. Other bitter blockers can be used. Some examples are riboflavin-binding protein (found in the chicken eggs), Flavanones (such as the ones found in Yerba Santa plant extract), phosphatidic Acid, β-Lactoglobulin, neodiosmin (a citrus fruit extract), magnesium sulfate, zinc salts, and fatty acids. It requires work and efforts to carefully match bitter blockers to the bitter-tasting substance needed in the product. Especially as the action mechanism is not always understood.
The use of the electronic tongue can be an effective solution. It can measure the taste change without knowing the underlying mechanism. Indeed, the electronic tongue, such as the TS-5000Z commercialized by Insent is an analytical device to evaluate tastes. Many academic publications applied this equipment for bitterness masking of pharmaceuticals. The e-tongue has proven to be a great support for taste masking formulation. It can test a range of possible masking excipients in various concentrations and combinations. The taste profile of existing formulations can also be done. The comparison of formulations can help reverse-engineering what are the efficient compound associations. Of course, it required confirmation with human sensory panels, mostly because of individual and cognitive factors. Yet, a large part of the taste-related work can be realized only based on objective taste analysis provided by the electronic tongue.
For more information and to better understand how the electronic tongue can support taste modification of food and beverages, I suggest you go through the following post …. Or feel free to contact us.
Florian Woisel
Sources
[1] : https://www.amazon.com/Maruchan-Ramen-Roast-Chicken-Pack/dp/B003OB4C60
And
Gaudette, N. J., & Pickering, G. J. (2013). Modifying bitterness in functional food systems. Critical reviews in food science and nutrition, 53(5), 464-481.
Toko, K. (Ed.). (2013). Biochemical sensors: mimicking gustatory and olfactory senses. CRC Press.
Woertz, K., Tissen, C., Kleinebudde, P., & Breitkreutz, J. (2011). Taste sensing systems (electronic tongues) for pharmaceutical applications. International journal of pharmaceutics, 417(1-2), 256-271.