Different Methods for Sensory Testing of Foods

Every food product you pick up from a store shelf has been evaluated not just in a chemistry lab but also by human senses. Sensory testing is the scientific practice of using sight, smell, taste, touch, and hearing to assess the quality and acceptability of food. These tests give food manufacturers objective data about how their products are perceived – and whether consumers will actually enjoy them. Broadly, sensory test methods fall into two categories: analytical tests (conducted by trained panelists to measure specific product attributes) and affective tests (conducted by everyday consumers to gauge personal liking and preference). Understanding these methods is essential for anyone involved in food quality testing, product development, or quality control.

The two main categories of sensory test methods 🔗

Sensory test methods are grouped based on the type of question they answer. Analytical tests are product-focused. They aim to objectively measure whether differences exist between samples or to describe the nature and intensity of specific sensory attributes. These tests rely on trained or screened panelists who act as calibrated “instruments.” Affective tests, on the other hand, are consumer-focused. They measure how much people like or prefer a product. Here, the panelists are untrained individuals who represent the target consumer population. Together, these two categories cover both the technical and market-facing sides of food evaluation.

Analytical tests: measuring sensory attributes objectively 🔗

Analytical tests are performed under controlled laboratory conditions to maximise the accuracy of results. The panelists used for these tests undergo screening or training so that their responses are consistent and reliable. Within analytical testing, there are three main sub-categories: sensitivity (threshold) tests, discrimination (difference) tests, and descriptive tests. Each type serves a distinct purpose in food quality evaluation.

Sensitivity tests (threshold tests) 🔗

Sensitivity tests – also known as threshold tests – measure the lowest concentration at which a person can detect or recognise a sensory stimulus. These tests are fundamental to understanding human sensory capabilities and are widely used in flavour research and quality control. According to research published on ScienceDirect, there are several types of sensory thresholds relevant to food science:

Absolute (detection) threshold is the lowest concentration of a substance that can be perceived as different from a blank or water sample. The panelist may sense “something is there” but cannot yet identify what it is. Recognition threshold is the concentration at which the panelist can both detect and correctly identify the stimulus – for example, recognising that a solution tastes salty. Difference threshold (also called the just noticeable difference or JND) is the smallest change in concentration that a person can reliably detect. Terminal threshold is the concentration above which no further increase in perceived intensity occurs.

To measure these thresholds, panelists are typically presented with a series of samples in ascending concentration using a forced-choice procedure. For instance, a common method involves a two-alternative forced-choice (2-AFC) staircase procedure, where the panelist must choose which of two samples contains the stimulus. The concentration is adjusted up or down based on correct or incorrect answers until a reliable threshold value is determined.

Threshold tests are particularly useful in scenarios like determining the minimum detectable level of an off-flavour compound in a beverage, establishing how much salt can be reduced in a product before consumers notice, or screening panelists for their sensitivity before including them in a trained panel.

Discrimination tests (difference tests) 🔗

Discrimination tests determine whether a detectable sensory difference exists between two or more products. These are among the most commonly used analytical methods in the food industry, especially for quality control and ingredient substitution decisions. The three principal discrimination tests are the triangle test, duo-trio test, and paired comparison test.

Triangle test: This is one of the most widely used difference tests in sensory science. Panelists receive three coded samples – two identical and one different – and must identify the odd sample. As explained by the Food Safety Institute, samples are presented in randomised orders (such as AAB, ABA, BAA, BBA, BAB, and ABB) to prevent positional bias. The chance of guessing correctly is only 33.3%, which makes the test statistically efficient – fewer panelists are needed compared to two-sample tests. However, evaluating three samples can cause sensory fatigue, particularly with strongly flavoured products.

Duo-trio test: In this test, the panelist first receives a reference sample and then two coded samples, one of which matches the reference. The task is to identify which coded sample is the same as the reference. This method is simpler for panelists because they directly compare each sample against a known reference, reducing memory load. There are two formats: constant-reference mode (the same product is always the reference) and balanced-reference mode (both products take turns being the reference across sessions). The duo-trio test is especially useful when testing the effect of ingredient changes or packaging modifications on product perception.

Paired comparison test: Here, panelists receive two samples and are asked which one has more of a specific attribute – for example, “Which sample is sweeter?” or “Which sample has a stronger aroma?” Unlike the triangle and duo-trio tests, paired comparison provides directional information about the difference. It is also the simplest test to administer and causes the least sensory fatigue since only two samples are evaluated. However, it can only compare two products at a time and does not indicate the magnitude of the difference.

Descriptive tests 🔗

Descriptive tests go beyond simply detecting differences. They identify and quantify the specific sensory characteristics of a product – such as the intensity of sweetness, the crunchiness of a cracker, or the fruity aroma of a juice. These tests require highly trained panels of typically 8-12 people who have been calibrated to use standardised vocabulary and intensity scales consistently.

Several well-known descriptive analysis methods exist. Quantitative Descriptive Analysis (QDA) involves panelists independently rating the intensity of pre-defined attributes on a line scale. Spectrum Descriptive Analysis uses larger panels (up to 15 participants) and more refined intensity scales, sometimes up to 150 points, for a detailed product profile. Flavour Profile Method was one of the earliest descriptive techniques where a small panel discusses and reaches consensus on the flavour attributes and their intensities in a product.

The data from descriptive tests can be plotted as sensory maps or spider diagrams that visually represent the sensory profile of a product. According to a study published in npj Science of Food, these maps allow manufacturers to compare competitive products or track how a product’s sensory profile changes over shelf life. Descriptive analysis is considered the most detailed and informative of all analytical sensory methods.

Affective tests: understanding consumer response 🔗

While analytical tests tell you what a product is like in technical sensory terms, affective tests tell you whether consumers actually enjoy it. These tests are conducted by untrained panelists – typically 50 to 150 or more – who represent the target consumer group. Affective tests do not require any special training because they measure personal, subjective responses. There are two main types: acceptance (hedonic) tests and preference tests.

Acceptance tests (hedonic tests) 🔗

Acceptance tests measure the degree of liking or disliking for a product. The most common tool is the 9-point hedonic scale, which ranges from “dislike extremely” to “like extremely.” Consumers rate their overall impression of a product or specific attributes (such as flavour, texture, or appearance) on this scale. The result is a clear numerical indication of consumer acceptability.

According to Lab Manager, hedonic scaling is the most common affective method used in food and beverage research. It provides straightforward data that can be statistically analysed to determine whether a product meets acceptable liking thresholds. For example, a food company launching a new yoghurt flavour might ask 100 consumers to rate the product on a 9-point scale. An average score above 6 (“like slightly”) is typically considered a positive result, though benchmarks vary by product category.

Beyond the 9-point scale, other formats include the 7-point scale, facial hedonic scales (often used with children, where smiley and frowning faces replace text labels), and just-about-right (JAR) scales that ask whether an attribute is “too little,” “just about right,” or “too much.”

Preference tests 🔗

Preference tests ask consumers to choose which product they prefer from a set of options. Unlike acceptance tests that measure the degree of liking, preference tests focus on relative choice.

Paired preference test: Consumers are given two products and simply asked which one they prefer. This is the most straightforward preference method and is easy for participants to understand. It does not tell you how much one product is preferred over the other – only which one is chosen. A minimum of 50 to 100 consumers is typically required for statistically meaningful results.

Ranking test: Consumers receive three or more samples and rank them in order of preference – from most preferred to least preferred. This method provides a clear hierarchy of preference across multiple products. However, as noted in research published on PMC, ranking does not reveal the magnitude of the difference in liking between products. Two products ranked next to each other may be almost equally liked or vastly different in acceptability.

Preference tests are particularly valuable during the early stages of product development when a company needs to narrow down several prototypes to the most promising candidates. They are also used in competitive benchmarking – comparing a new product against established brands in the market.

Testing environments and practical considerations 🔗

The setting in which sensory tests are conducted has a significant impact on the quality of results. Analytical tests are almost always conducted in controlled sensory booths – small, partitioned stations with standardised lighting, temperature, and ventilation – to eliminate external variables that could influence perception. Samples are coded with random three-digit numbers, and the order of presentation is randomised to reduce bias.

For affective tests, two common environments are used. Central Location Testing (CLT) brings consumers to a designated facility like a sensory lab or rented hall. This allows for rigorous data collection and follow-up questions. Home Use Tests (HUTs) send products to consumers’ homes, providing data about how a product is perceived in its natural consumption setting – over multiple uses, with typical preparation methods, and alongside everyday meals.

Regardless of the test type, certain best practices apply universally. Panelists should rinse their palate with water or eat plain crackers between samples. The number of samples per session should be limited to avoid sensory fatigue – generally no more than five or six sets. And all panelists should be screened for allergies to the test products before participation.

Newer rapid sensory methods 🔗

In recent years, the food industry has adopted several rapid sensory methods that complement traditional approaches. These methods are faster, more flexible, and sometimes can be used with semi-trained or even untrained panelists.

Check-All-That-Apply (CATA) is a consumer-friendly method where panelists select all applicable attributes from a provided list to describe a product. It is widely used for identifying which sensory characteristics drive consumer liking. Temporal Dominance of Sensations (TDS) captures how the dominant sensory perception changes over time during consumption – useful for understanding flavour evolution in products like chewing gum or wine. Flash Profiling asks panelists to rank products on self-generated attributes, producing quick comparative profiles without the lengthy training required for traditional descriptive analysis.

A review published in PMC notes that these newer techniques, while evolving rapidly, have not yet fully replaced traditional methods. Instead, they are most effective when used alongside established analytical and affective tests to provide a more complete picture of a product’s sensory characteristics and market potential.

Why combining both approaches matters 🔗

No single sensory test can answer every question about a food product. Analytical tests reveal what a product’s sensory profile looks like in precise, measurable terms – but they do not predict whether consumers will buy it. Affective tests reveal whether consumers like a product – but they do not explain why. The most effective sensory evaluation programmes combine both approaches.

For instance, a manufacturer reformulating a biscuit to reduce sugar might first use a triangle test to check whether the change is even detectable. If it is, a descriptive analysis identifies exactly which attributes have changed (perhaps sweetness decreased and dryness increased). Finally, a hedonic test with consumers determines whether the new version is still acceptable. This layered approach gives the manufacturer a complete understanding – from technical formulation to market readiness.

What do you think? How might the growing demand for healthier, reduced-sugar, and reduced-salt foods push the food industry to rely even more on sensory testing methods? And in your experience, do you think trained panel evaluations or consumer preference tests play a bigger role in shaping the products you see on supermarket shelves?

References

1. https://en.wikipedia.org/wiki/Sensory_analysis
2. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sensory-evaluation
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC8560331/
4. https://foodsafety.institute/food-fundamentals-chemistry/difference-tests-sensory-variations-food-products/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC8834440/
6. https://www.nature.com/articles/s41538-018-0019-3
7. https://www.labmanager.com/sensory-evaluation-methods-in-food-and-beverage-research-34289
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC7922510/
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC8001375/