Claudia Niimi
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Why Does Food Taste Strange?
Understanding flavour changes through aroma chemistry and sensory science.
A small and unexpected change in flavour can have significant consequences. Consumer complaints, quality deviations, reduced shelf life, and costly investigations often begin with a simple observation: something tastes different.
Perhaps a product suddenly tastes slightly bitter, metallic, stale, or develops an unfamiliar aroma. The change may be subtle, yet enough to affect consumers' perception and acceptance. Understanding why flavour changes occur is therefore an important part of ensuring product quality, consistency, and consumer satisfaction.
Flavour is more than taste
When we eat, our brain processes information from several sensory systems simultaneously. Taste receptors detect sweet, sour, salty, bitter, and umami (savory), while our sense of smell perceives thousands of volatile aroma compounds released from food.
What we experience as flavour is the result of a complex interaction between taste, aroma, texture, mouthfeel, and even previous experiences and expectations. Chemical sensations such as the fizziness of carbonated beverages or the burn of chili also contribute to the overall sensory experience.
Our sensory systems are remarkably sensitive. Even a small change in coffee storage conditions, for example, can shift its aromas from fresh and roasted to stale or cardboard-like. Similarly, subtle changes in milk aroma often provide the first indication of quality deterioration, long before visible signs appear.
What causes flavour changes?
Whether it is coffee, baked goods, dairy products or plant-based foods, hundreds and sometimes thousands of compounds contribute to the flavour consumers perceive. Many of these compounds continuously undergo chemical changes throughout processing, storage, and distribution.
Factors such as oxygen, heat, light, moisture, and microorganisms can all influence these processes. Lipid oxidation may generate undesirable rancid notes in oils, nuts, and other fat-containing products. Thermal processing can create desirable roasted, nutty, and caramelised aromas through reactions such as Maillard reactions. Fermentation can transform flavour profiles entirely, creating both desirable characteristics, such as those found in sourdough bread, or undesirable off-flavours when microbial spoilage occurs.
When the balance between aroma compounds changes, the sensory properties of the product may change as well. A flavour deviation is therefore rarely just a sensory issue. It often signals changes in the raw materials, processing conditions, packaging systems, transportation, or storage environments.
For food manufacturers, identifying the root cause requires tools that can connect what consumers perceive with what is occurring chemically within the product.
Aroma chemistry – understanding the molecules
Aroma chemistry provides powerful tools for investigating which compounds are present in a product and how they change over time. Techniques such as GC-MS/O (Gas Chromatography-Mass Spectrometry-Olfactometry) combine chemical analysis with human sensory assessment. This makes it possible not only to identify compounds present in a product but also to determine which compounds contribute most strongly to the perceived aroma.
By comparing a product with an appropriate reference sample, researchers can identify, quantify and characterise compounds responsible for off-flavours or unexpected sensory characteristics. This helps explain why two seemingly similar products can be perceived as different in terms of sensory qualities.
One of the most fascinating aspects of aroma science is the extraordinary sensitivity of the human nose. Some aroma compounds can be detected at extremely low concentrations, meaning that even minor chemical changes may significantly affect flavour perception.
Sensory science – understanding the human experience
Chemical analysis alone cannot explain how a product is experienced by consumers. This is where sensory science plays a crucial role.
Through structured sensory evaluations, trained assessors or consumer panels can systematically evaluate flavour, aroma, texture, appearance, and aftertaste. Rather than simply describing a product as "different" or "strange", sensory analysis allows specific characteristics to be identified and measured.
Attributes such as metallic notes, earthy character, citrus-like aromas, floral nuances, astringency, or mouldy off-notes help create a detailed sensory profile. The more precisely a sensory change can be described, the easier it becomes to investigate its origin and significance.
Combining sensory science and aroma chemistry
The greatest value often comes from combining aroma chemistry and sensory science. While analytical instruments measure the compounds present in a food product, while sensory evaluations reveal how the product is perceived; combining these with chemical analyses helps to identify which substances are responsible for that perception.
Together, these approaches provide a powerful framework for investigating flavour changes and understanding why they occur. By connecting sensory observations with analytical data, it becomes possible to move beyond identifying that a problem exists and instead understand the mechanisms behind it.
In one recent case, researchers spent several years investigating reports of milk developing an unexpected blueberry-like flavour. By combining sensory evaluation with advanced analytical techniques, researchers were ultimately able to identify the underlying cause, illustrating both the complexity of flavour chemistry and the value of a multidisciplinary approach.
Read more in the following article "Fem års forskning löste gåtan om mjölkens blåbärssmak" published by SLU:
The value of understanding flavour changes
Understanding flavour changes creates value throughout the food value chain. By revealing the chemistry behind these changes, the food industry can troubleshoot more effectively, accelerate innovation and product development, optimise formulations, reduce food waste, and strengthen quality control. This knowledge also helps improve product quality, consistency, and shelf life.
For manufacturers, understanding when and why flavour changes occur makes it possible to identify potential quality issues earlier and take preventive action before products reach consumers. For product developers, the knowledge provides valuable insights for creating products with better sensory performance and greater potential for consumer acceptance.
Here is an example of a project where aroma chemistry and sensory science are applied to tackle off flavour challenges in legume proteins.
Every flavour change has a cause
Understanding the cause of a change in flavour is often the key to improving product quality, solving manufacturing challenges, and developing foods that meet consumer expectations.
As consumer expectations for quality, consistency, and sensory experiences continue to rise, the ability to understand and manage flavour becomes increasingly important.
By combining sensory science and aroma chemistry, flavour changes can be traced back to their molecular causes, enabling better decisions, more effective problem-solving, and continued innovation throughout the food value chain.
