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Introduction to Flavors

What is a Flavor?

Flavors are the sensory impressions of food or other substances and are determined mainly by the chemical senses of taste (gustation), smell (olfaction) and trigeminal nerve impact. By creating a unique combination of flavoring compounds which affect these senses, the overall flavor impact of a food or other substance can be altered. This is where the combined art and science of flavor creation comes into play.

How Does Taste Work?

Taste is that sensation produced when stimuli are taken into the mouth and react with the receptors of the taste buds. Simply put, it is a chemical reaction between stimuli (food) and receptors (taste buds). Taste receptors in humans and other mammals are located on the tongue and soft palate.

Distributed over the tongue are numerous small, fingerlike projections called papillae. These are the home of the taste buds. The papillae at the back of the tongue are each surrounded by a trench into which a watery fluid (saliva) is secreted by the surrounding glands. The papillae on the front of the tongue have their taste buds on top rather than in trenches. Since there is no mechanism here for collection, this may possibly be why we feel more salivating activity at the back of our mouths.

Within each taste bud are 50-150 single taste receptor cells (TRCs) arranged like the segments of an orange. The TRCs have small microvilli about 4 microns (a micron is a thousandth of a millimeter) in length and 0.2 microns in diameter which are presumed to be the excitable portions of the taste receptor. This is where it all happens! And it is a very tiny area for a sensation noticed so strongly. The average taste bud lives only about 10 days, and adults have about 9,000 of them.

Although taste is simpler than smell in the number of qualities sensed, there are more nerves associated with taste than for smell. The trigeminal sensory nerve cables for taste also contain touch, temperature, and pain fibers in addition to taste fibers. These are considered factors in a flavor’s character, like the heat/pain of red chili or the cooling sensation of menthol.

What Are the Basic Tastes?

Individual tastes (along with aroma and sensation) make up flavors. Five basic tastes have been identified, although much debate has surrounded the acceptance of the fifth, which has only recently been widely recognized:

Sweet
Salty
Sour
Bitter
Umami (Japanese implying “deliciousness”)

It was previously believed that separate taste buds/receptors existed for each of the basic tastes. However, recent data has shown that responses to the five basic tastes can be obtained in all areas of the tongue. Previous evidence to the contrary may be explained by the fact that certain regions of the tongue are simply more responsive to certain tastes than others.

Figure 3 - The Five Basic Tastes

(A) Classic View of the Tongue ‘Map’

This is the traditional view of the tongue map, showing the four basic tastes defined in the late 1990s.

(B) Modern View of Taste Receptor Distribution

Recent molecular and functional data have revealed that, contrary to popular belief, there is no tongue 'map’. Responsiveness to the five basic tastes-bitter, sour, sweet, salty and umami-is present in all areas of the tongue.

What Does Smell Have To Do With It?

While only five basic tastes can be detected, it is possible for thousands of aromas to be identified. It turns out that much of the individual character of a food’s flavor comes from its aroma. To illustrate this fact, try tasting an unknown beverage with your nose held closed and see how well you do! The number of successful responses in this type of exercise is extremely poor.

Airborne odorants are sensed by the olfactory epithelium, a mucous membrane, which is located in the roof of the nasal cavity. The odor molecules are sensed by tiny hair-like cilia which cover the epithelium. The actual physiological mechanism is not well understood. But, being able to detect thousands of aromas makes the human nose an instrument that’s 10 to 100 times more sensitive than a gas chromatograph. (A trained perfumer can detect a minimum of 200 individual and distinct aromas!)

Flavor Naming Regulations

Flavor manufacturers commonly designate flavors as being ‘Natural’, ‘Natural and Artificial’ (N&A), or ‘Artificial’. Other common designations include ‘Natural Type’ and ‘Natural With Other Natural Flavors’ (WONF). The U.S. Food and Drug Administration and the European Union both have strict definitions for what constitutes as natural or artificial flavorings, but below are more generalized definitions:

Natural Flavors

Natural — Contains only natural flavoring ingredients from the named source and non-flavoring ingredients. All flavor ingredients fit the FDA definition of “natural flavoring” and the flavor contains essence or juice derived from only the named source (i.e. orange, strawberry, etc.).
Natural WONF — Contains natural flavoring ingredients from the named source and other natural flavoring ingredients. All flavor ingredients fit the FDA definition of “natural flavoring” and the flavor contains essence or juice derived from the named source (i.e. orange, strawberry, etc.) along with natural botanicals or essential oils from other natural sources.
Natural Type — Contains natural flavoring ingredients, but does not contain the named flavor. All flavor ingredients fit the FDA definition of “natural flavoring” but the flavor does not contain essence or juice derived from the named source (i.e. orange, strawberry, etc.).
All Natural — Contains natural flavoring ingredients and naturally-derived non-flavoring ingredients. Not currently defined by the FDA.
TDNS — Contains ingredients which are 'Totally Derived from the Named Source'.

Artificial Flavors

Natural & Artificial — Contains a mixture of natural flavoring ingredients from the named source and flavoring ingredients derived from artificial/synthetic sources and/or processes.
Artificial — Contains flavoring ingredients derived from only artificial/synthetic sources and/or processes which simulate the named source.
Non-Characterizing Artificial — Contains one or more artificial flavoring ingredients that do not simulate, resemble or reinforce the named source.

Flavor Delivery Systems

Flavors can be created in several physical forms, with the desired form depending on the application in which it is being used. The physical form and flavor delivery system are both critical to ensuring the end consumer experiences the flavor impact intended by the manufacturer.

Liquid

Water Soluble — Soluble in water in at least the amount necessary to impart sufficient flavor. Solvents used include but are not limited to water, propylene glycol, ehtyl alcohol, triacetin, glycerin and polysorbates.
Oil Soluble — Souble in vegetable oil, usually in all proportions. Solvents used include but are not limited to vegetable oils, benzyl alcohol, ethyl myristate, polysorbates and d-limonene.

Powder

Spray Dried —Most common form of powdered flavor encapsulation.
Specialty Encapsulation —Proprietary technology is used to create specialty encapsulates that deliver the desired amount of flavor at the desired time in food and other applications.

The Science of Flavor Creation

Flavors are created by specialized flavor companies (often called 'flavor houses') that invest a significant amount of time and money into proprietary technologies and flavor research and development. Flavor chemists ('flavorists') are specially trained by individual flavor houses to combine natural and artificial flavoring compounds in unique ways to produce commercial compounded flavors. Flavorists rely on the sciences of chemistry, biochemistry, organic chemistry, molecular biology and biotechnology to develop their flavors, but the process is also a highly creative one similar to that of an artist.

The development of new flavor technology encompasses both volatile and non-volatile components as well as the delivery of these compositions in a form which preserves their integrity until they are released in the mouth of the end consumer. The interactions of these components with each other and the target food and beverage ingredients which make up the total product formulation must be taken into consideration by the flavorist in order to create high performing, top quality flavors.

Generally speaking, the science of flavor creation is composed of three integral parts: ingredient discovery, flavor design and delivery and sensory evaluation.

Ingredient Discovery

Ongoing ingredient discovery is essential to flavor creation. Flavor houses must invest research and development (R&D) dollars into programs directed at novel ingredient exploration and analysis in order to continually expand their flavor creation 'toolbox' of raw material ingredients. Givaudan Flavors Corp., the largest flavor house in the world, is the industry leader in R&D investment and uses their innovative TasteTrek program to stay on the leading edge of ingredient discovery.

Flavor Design and Delivery

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Sensory Evaluation