November 1, 2003
The marketplace is rife with meal-replacement products, energy bars and sports drinks. Consumers are turning to quick nutritional fixes to support on-the-run lifestyles and becoming more conscious of the healing value of specific food compounds. They also expect more from the old standbys. Nutritionally speaking, cereals, teas and other staples should be, as Emeril Lagasse would say, "kicked up a notch." At the same time, foods should contain less calories and more fiber. Some consumers look for low-fat products, others want low carbohydrates, while still others shy away from excessive protein.
As companies strive to satisfy an informed and diverse market, food technologists face new challenges in creating products that meet consumer demands and taste good. This is where flavor-masking comes into play: Like Mary Poppins' "spoonful of sugar," taming the often-unpleasant tastes of healthful add-ins helps the medicine go down.
The science of taste
Flavor is a complex of three system responses: gustation (taste), olfaction (smell) and somatosensation. Gustation is the act of taste. Chemicals in food and beverages provoke specific responses from taste buds - sugars, which are carbohydrates, taste sweet, while acids taste sour. Simply put, the brain perceives taste when food touches taste buds on the tongue and inside the mouth. Sweet, salty, bitter and sour make up the four taste sensations everyone recognizes. A fifth savory attribute, umami, is typified by a specific reaction to the taste of glutamate.
Olfaction, or smell, is virtually linked to taste in our perceptions, so much so that when a strawberry flavor is combined with a sweetener, people rate the sweetness level higher than they would if tasting the same level of the sweetener alone.
Somatosensation is a broad category that includes touch, pressure, warmth, coolness, pain, kinesthesia, itch and tickle. Stimuli can include the irritation of capsaicin, physical temperature, the cooling affect of menthol and texture. Texture may be an auditory or a visual response: for example, a thin or thick crunch.
All of these systems can interact with each other at different levels. Intensity and reactions to pleasantness and unpleasantness contribute to flavor perception, which is an individual reaction based on age, gender, experience, the environment and learned associations. To create a pleasant-tasting product, the food scientist or flavor chemist must weigh not only these factors, but also the interactions of the combined ingredients. Flavor is truly the sum of the whole: Reductions or increases in any one ingredient can change the entire flavor system by altering the perception of other flavor notes. This is key when flavoring functional foods and supplements.
The importance of balance
The appearance of unexpected flavors has challenged most developers who attempt to reduce fat or sweetness in a tried and true formulation. "Fat is one of the best masking agents," notes Cozy Helm, vice president, R&D, Wixon Fontarome, St. Francis, WI. "It also can accentuate some flavors, but it covers up a lot of things. When you pull fat out of a product, you start tasting other things that you never even knew were there."
Adding healthful, functional ingredients often upsets the mix by introducing stray notes. Soy protein tends to give foods a "beany" flavor, certain botanicals can impart grassiness, and minerals can be bitter or metallic. Simply adding a stronger flavor to overpower the offender isn't the answer, any more than using drums to cover a discordant string player is. The addition of sweeteners, starches or fats can certainly help suppress off-notes, just as the addition of acid can sharpen focus of other flavors. But product designers can mask unpleasant flavors by modifying the perception of the other notes.
To achieve this, Wixon Fontarome has developed a line of masking agents formulated to suppress certain flavors, such as green notes, bitterness and astringency. However, Mariano Gascon, flavor lab director, cautions there are few simple fixes: "We normally recommend the use of a combination of masking agents. We have masking agents to cover soy notes, but they can have a problem with excessive sweetness or sourness." When this occurs, the company recommends adding another masking agent.
Most of the flavoring problems that Gascon has tackled involve a combination of different issues, rather than one particular descriptor. "There is no one magical ingredient to fix it all," he says. "Taste is a delicate balance. Once you modify one of the perceptions, the other perceptions may change. There is a lot of fine-tuning between the flavor chemist and the food developer. Most of the time, the product requires a little adjustment. The developer may have to decrease the sugar or increase acidity."
Helm adds, "Any time you start covering up a flavor, then you're going to start seeing other flavors come through disproportionately to what they were before you started masking flavors." She stresses that skilled flavor chemists know how each flavor component will act, and, because they will approach a problem differently than a food technologist, it's like having other professionals on the R&D team. Besides making formulation recommendations, the flavor chemist may be able to combine flavor modifiers into one ingredient for a specific customer.
The need to work with a flavor house is emphasized by another consideration - ensuring that the flavor does not complex or react with the functional ingredient, rendering it inactive - according to Brian Grainger, director, flavor creation, International Flavors and Fragrances, Inc. (IFF), Dayton, NJ. Creating a masking agent is best left to the flavor developer because, as he notes, "It is the creativity of the masking combination that is unique, as often the individual flavor ingredients have limited masking capability, but in combination, have synergy, thus enhanced masking capability."
There is a distinction between masking agents and flavors, emphasizes Paulette Kerner, marketing and advertising manager, Virginia Dare, Brooklyn, NY: "If somebody wants a raspberry flavor for their nutritional bar, we would need to identify the raspberry flavor and then also look at their fortifiers and bases to see which masking agent is best for their particular product. That way, we can give the greatest number of options and a broader selection of choice. It's best to work with the base first and mask and try to get the base flavor of the product to as neutral as possible, and then add flavor. You don't flavor the product and then try to mask the whole works." She also cautions against adding too much flavor: Not only is it expensive, but the flavor might get to a threshold where it becomes undesirable.
Virginia Dare is introducing a new line of proprietary flavor systems, which are said to be more intense and offer longer flavor shelf life in the product. Kerner says the company has begun to develop the line specifically for flavor-masking applications in fortified and functional foods.
Flavor with function
Masking flavors needn't stop at simply suppressing the tastes of unpalatable nutrients - they can complement them functionally, as well. Philip Katz, president, Shuster Laboratories, Inc., Canton, MA, believes that as the functional-food market grows, the industry is paying attention to the technology behind the ingredients themselves. Flavor developers are starting to work with some functional ingredients, such as soluble fiber and calcium, incorporating them into masking flavor systems. Although these functional flavor ingredients can be costly, they can also be very effective.
Microencapsulation can also solve off-flavor problems. Coating nutrients with a protective covering drastically reduces strong odors and bitter tastes, so products require less masking. It also improves mouthfeel and prevents reactivity. The added stability and neutralized flavor add value to these ingredients, which might otherwise be considered more costly. Harry Bille, sales and marketing coordinator, Wright Nutrition, Inc., Crowley, LA, notes that the added stability reduces overages, making it much easier to achieve RDI values.
The company has a line of microencapsulated nutrients that have been used in applications from bars to viscous beverages to some high-temperature applications. "We've used them in a number of different applications to hide and mask flavor, especially in anything bitter, vitamin C being the most notable of all the vitamins that you would probably want to microencapsulate," Bille notes. "It has a bitter taste and is the most susceptible to outside factors."
Selectively incorporating vitamins and minerals into a custom blend delivers the best results. "Everything we do is a custom blend," Bille explains. "Depending on the application, we'll mix the level of nutrients required for the RDI target levels. We'll evaluate a premix that a customer has." But rather than encapsulating an entire blend of nutrients, the company will target nutrients that pose flavor and stability problems, and then incorporate the microencapsulated ingredients into those blends to maximize the potency of the premix without creating an off-flavor in the final product.
Tricks of the trade
Developers at the bench can try some useful tricks to help mask off-notes. Katz recommends selecting flavors that are compatible with the off-flavor being developed. For example, a dark chocolate, which tends to give a bitter aftertaste, can help complement a bitter note better than a milk chocolate, which is not bitter.
A recent project at Shuster involved developing a high-protein pudding. "We had to stay away from vanilla because it just was not compatible with some of the flavor attributes being contributed by the active ingredients," Katz explains. "The approach was to go on a chocolate base and run modifications off that chocolate base. We had a regular chocolate, a mocha, a chocolate raspberry, and a chocolate orange. We really put some culinary input into the technology for very technical reasons. You want to turn the negative into the positive."
A common approach is to incorporate the flavor profile of the offending ingredient as part of the basic flavor - for example, designing a non-bitter grapefruit flavor to combine with a bitter nutraceutical. "Often a mixed-citrus or citrus-punch flavor can bridge the gap between consumer acceptability and compatibility with the bitter-tasting ingredient," Grainger notes.
Katz agrees. "If it's very acid and drying in its characteristics, you want to go with a citrus/citric-acid-type flavor to complement what would be a negative characteristic."
To reduce bitterness, Russell Keast, research associate, Monell Chemical Senses Center, Philadelphia, suggests adding salt. "In something as basic as sodium chloride, ordinary table salt, the sodium can actually inhibit bitterness at the receptor site by interfering with the signal being transferred up to the brain," he says. "Before we perceive the bitterness, the sodium is starting to inhibit it. If you've got a food product that has bitterness to it and you add a sodium salt to that, you'll be knocking the bitterness down, depending on the initial level, maybe around 50%."
Keast also suggests adding sucrose or a sweetener, which invokes a phenomenon called mixture suppression, where tastes in a mixture are weaker than the individual components. Mixture suppression occurs at the cognitive area of the brain, rather than at the oral receptors. This two-prong approach inhibits bitterness both in the oral periphery and in the brain.
Sometimes, a product is too sweet, but the levels of sugars can't be reduced because of the functionality they provide. Adding acid, bitterness or salt can reduce the perception of sweetness, as can simply changing the sugars used. Lactose is much less sweet than other sugars and can actually suppress the sweetness of other sugars when used in combination. Lactisole, a lactose derivative recognized for its sweetness-inhibition properties, is added to some sugar-based sweeteners marketed for low-sweetness applications.
When process or preservative issues require the use of salt, reducing the salty flavor requires a similar sleight of hand to reduce the perception without reducing the percentage. One way to do this is to choose a sodium compound with a larger anion than chloride, such as sodium gluconate, which blocks the sodium from going through tight junctions between taste cells, thereby reducing the perception of saltiness.
Sourness isn't quite so simple, because of the way that the tongue perceives acidity. A stronger acid, such as hydrochloric acid, will be perceived as less acidic than citric acid, even if both are at the same pH level. The tongue responds more to titratible acidity, the measure of total acidity, than it does to pH or to the dissociated hydrogen ions. Changing the acid used is one way to change the perception of acidity. Adding a sweetener will reduce sourness through mixture suppression, just as the addition of a sweetener decreases bitterness.
Still another way to mask off-flavors is by using hydrocolloids. Some starch and gum systems coat the mouth and prevent the taste buds from touching the offending flavor. After the negative flavors have been swallowed, the coating disappears and a pleasant aftertaste can emerge.
Enrobing with a confectionery coating seals and protects the product, which is an especially good trick for prolonging shelf life and preventing age-related off-flavors. It also has textural benefits, providing a mouth coating that helps improve flavor. While coatings on a bar are very pleasing to the consumer, they are a boon to developers because of their impact on flavor and stability issues.
Finally, when considering flavor masking, think about nutrient stability. Katz notes that this should be a key factor when incorporating oil-based nutrients, such as omega-3 fatty acids, because they can develop rancidity and other oxidative reactions can occur. The challenge is in anticipating off-flavors that may develop down the road.
Room for optimism
As marketing departments seek the next wonder product, the demands on food technologists can seem daunting. Fortunately, our industry is continually evolving, and ingredients and technologies are improving. We need only look at the meal-replacement bars of 4 or 5 years ago to see how far we've come: Even the best had short shelf lives and flavors that deteriorated unpleasantly within 6 months. Because of improvements in protein technology and the industry's understanding of flavor masking, today, that same product is much more flavor-stable. The rows of meal-replacement products at the grocery store serve as testimony of the industry's ability to adapt, develop new technology and mask off-flavors.
Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached at [email protected].
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