Sensory analysis is the measurement of consumer responses to sensory stimuli. It is used in grading, consumer preferences, quality assurance, shelf life testing, product development and research. The food industry probably has the greatest number of sensory analysts ranging from specialist wine, beer, and tea tasters to researchers investigating how consumers perceive flavors and textures. Sensory analysts also work in the cosmetics, toiletries and household care products industries.
To understand why sensory evaluation is so important, it is vital to understand the role taste and smell play in the consumers’ perception of a product. Taste (flavor) and smell (odor) can evoke complex psychological and physiological reactions. “Flavor is a sensory perception that results from a combination of: olfactory sensations elicited by volatile substances in the nasal and the retronasal cavity; gustatory sensations of soluble substances on the taste buds; and feelings such as heat, pungency, or cooling, elicited by the trigeminal nerve.” Unlike odors, tastes do not fuse or blend to form new qualities; rather, they combine to keep their identities. Essentially, flavors are sensory perceptions that result from a combination of smell and taste. The contribution of taste to flavor is actually very small. When smell is impaired, flavor impulses can no longer be detected. It has been well recognized that flavor is of dominant importance to food acceptance or rejection. Flavors that generate pleasant or unpleasant associations can directly influence the acceptability of a product.
The two most important factors for obtaining successful sensory evaluation results are panelist selection and test types. Panelist selection is key to obtaining useful sensory results. Although both in-house and outside panelists can be used, each has advantages and disadvantages. Purpose of the tests and the current stage of product development must be considered. For initial screening, many companies use their own employees. To avoid biased results, product developers and those close to the project are disqualified as panelists. An initial screening by in-house panelists can help identify attribute and acceptability differences. Such panelists are useful for evaluating ingredient substitutions or changes in processing or packaging. Advantages of utilizing in-house consumer testing include its low cost and quick results. In addition, more samples can be evaluated at one time, and panelists are already familiar with the product being tested. In-house screening usually involves from 30 to 50 panelists per test session.
Outside consumer testing is best when a product is targeted to specific demographic groups such as age, gender, income, ethnicity or geographic area. Unbiased consumers are the ultimate test panelists for decisions related to product launch. However, outside consumer testing does have its disadvantages. It is more costly, and fewer samples may be presented at one time. There is also a greater chance for panelists to misunderstand test procedures. For an outside test session, a minimum of 50 to 500 panelists from three or four different cities are generally recommended.
The type of test is another important consideration that strongly influences test results. Tests can either be qualitative or quantitative. Qualitative tests include focus group testing and feasibility studies. In focus groups, panelists evaluate prototypes in small round table discussion groups. For feasibility studies, consumers evaluate and comment on the test samples. Quantitative tests include in home tests where consumers are asked to rate or evaluate finished products. Two main questions are asked: Which product do you prefer, and how much do you like the products? One advantage of in-home use tests is that they shed light on how products are used in everyday real-life situations. The sensory analyst is able to ask more questions of the consumer and repeat consumption information is obtained. However, these tests are time consuming and the return rate is generally low.
Sensory evaluation can link consumers to product development and production.
Sensory science is generally recognized as being divided into three fields of specialization–perception, sensory analytical testing, and affective testing. The latter two are related to the psychology and behavior of humans. One method of analytical testing where descriptive terms are used to describe and evaluate the sensory properties of a product is “Descriptive Analysis.” This normally involves judges who are rigorously trained to describe attributes and sensory properties of products in chosen terms.
Quantitative Flavor Profiling by Givaudan-Roure is one the most modern techniques of descriptive analysis. It focuses on the quantification of the sensory properties related to flavor in a particular product. Sensory scales are anchored with physical references representing the low and high intensity extremes. References are any chemical, spice, ingredient, or ingredient product that can be used to characterize and identify a certain property or product.
If “taste” is the primary factor in whether we find a food acceptable or not, then understanding how we perceive taste is critical in the development of successful products. No sensory response is instant – time is an important variable. Time intensity (TI) testing is used to monitor the intensity of sensory characteristics such as sweetness, bitterness, saltiness and textural characteristics over time. The use of TI testing is particularly relevant in today’s market, which features a new generation of low-fat and low sugar food products. Product developers must recognize the importance of evaluating key sensory characteristics of established traditional food products if “light” equivalents are to be formulated to minimally affect characteristics and thus, consumer acceptability. Sweetness is an important contributor to our liking of many foods. However, sweetness perception is itself dependent on a number of parameters, including choice of sweeteners and their concentrations, temperature and product viscosity, as well as an evaluator’s “oral conditions.” This makes sensory evaluation in finished products complex. TI testing has proved exceptionally useful when investigating the sensory attributes of intense sweeteners. Investigation of bitterness, a flavor defect associated with some of the intense sweeteners, is also important if an aftertaste is to be avoided. TI testing with trained taste panels offers advantages over conventional sensory profiling where it may be assumed that only maximum intensity is recorded. TI testing, however, is time-consuming and costly. It is imperative to make the most of the data generated.
Sensory research is often used together with market research in product development. Sensory methodology, particularly the use of sensory profiling, is a valuable product development tool. A sensory methodology must be chosen to answer each different specific question. Most problems encountered in sensory evaluation are related to determining differences among samples. For example, a flavor based on natural vanilla extracts may show variation in chemical-composition depending on the source of the raw materials. A simple yes or no answer by the panelist that there is a difference may be enough to reject the flavor, but the difference could be too small for the average consumer to discern. Asking the right question of the right people is the only way to obtain correct information.
The sensory technique of flavor profiling may be chosen to further identify and describe differences among or between samples. Profiling is the measurement of the intensity of each of a number of well-defined flavor profiles that can be described through sensory panels or characteristics for each flavor sample evaluated. If the sensory data can be correlated to chemical data, corrective action can be suggested to restore the flavor balance desired.
Many natural flavors are produced by technological processes such as heating or extrusion, and slight differences in these process parameters may result in noticeable flavor differences. Sensory analysis can be used to optimize the flavor production by correlating flavor-profiling data with processing parameters. A trained sensory panel may be able to recognize and evaluate the intensity of as many as 30 specific flavor notes–or descriptors–commonly found in various food products. Texture profiling can also be carried out using an appropriate list of descriptors. Such sensory evaluations have become very important in the introduction of low-fat foods in today’s competitive marketplace. Addition of fat replacers may alleviate some texture problems, but the release of flavor is seriously affected by the lack of fat. Knowing there is a distinctive difference between low-fat and full-fat foods, based on sensory evaluation, is one thing, but knowing what to do to the fat-free products to make them resemble the standard product is something else. Sensory analysis can reveal several trends that show where improvements are needed. This example is only one of the applications of sensory research to product development, but it demonstrates how correlations can be made between ingredients and perceptual effects.
Flavors play a key role in the development and acceptance of foods, and the application of sensory evaluation techniques to determine the extent that consumers derive pleasure from the products they consume is a goal of food processors. Yet, even though most products are evaluated for consumer acceptance, nine out of ten new products entering the marketplace will fail. This makes the practice of sensory evaluation a constantly changing and expanding market. Food processors that know how to effectively utilize data obtained from sensory testing have a better chance of making the one new product that succeeds theirs.
Brandt, L.A., Sensory Analysis Hones Good Taste. Prepared Foods 98: 71-74.
During, A., Sensory Perception’s Role in Product Development. Food Processing 92:14-17.
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