Inspired by how milk soothes the burn of chili peppers, scientists designed a casein-infused gel that senses heat levels in seconds, offering a safe, high-tech way to measure spice without singeing taste buds.
Research: A Soft and Flexible Artificial Tongue for Pungency Perception. Image Credit: BrittanyD / Shutterstock
The appearance of a hot sauce or pepper doesn't reveal whether it's mild or likely to scorch someone's taste buds. Researchers have developed an artificial tongue to detect spiciness rapidly. Inspired by milk's casein proteins, which bind to capsaicin and relieve the burn of spicy foods, the researchers incorporated milk powder into a gel sensor. The prototype, reported in ACS Sensors, detected capsaicin and pungent-flavored compounds (such as those responsible for garlic's pungency) in various foods.
"Our flexible artificial tongue holds tremendous potential in spicy sensation estimation for portable taste-monitoring devices, movable humanoid robots, or patients with sensory impairments like ageusia, for example," says Weijun Deng, the study's lead author.
Challenges in Measuring Spicy Compounds
Currently, measuring flavor compounds in foods requires the use of taste testers and complex laboratory methods. As an alternative, scientists are developing artificial tongues that can measure tastes, including sweet and umami, among others. However, capsaicin in chili peppers, piperine in black pepper, and allicin in garlic produce stinging, tingling, or burning sensations that are hard to replicate and measure with synthetic materials. Jing Hu and colleagues noted that the heat of peppers, for example, can be neutralized when their capsaicin is bound by casein proteins in milk. The team aimed to create an artificial tongue by incorporating casein into an electrochemical gel material and measuring spiciness through an electrical current change that occurs when casein binds to capsaicin.
Designing a Casein-Based Gel Sensor
The researchers created a tongue-shaped film by combining acrylic acid, choline chloride, and skim milk powder, and then they exposed the solution to UV light. The resulting flexible and opaque gel conducted an electrical current. Ten seconds after the researchers added capsaicin to the film, the current decreased, indicating its potential as an artificial, spice-detecting tongue. Initial tests showed that the milk-containing material responded to capsaicin concentrations ranging from below the level of human detection to levels perceived as painful (known as the oral pain threshold). Additionally, the material detected other pungent-flavored compounds commonly found in hot sauce ingredients, including ginger, black pepper, horseradish, garlic, and onion.
Testing Spiciness Levels in Peppers and Hot Sauces
As a proof of concept, the researchers tested eight pepper types and eight spicy foods (including several hot sauces) on the artificial tongue. They measured the spiciness by changes in electrical current. A panel of taste testers rated the spiciness of the same items. Results from the artificial tongue and the tasting panel matched well. Therefore, the researchers suggest that the casein-containing artificial tongue could be used to quickly assess a food's spiciness level, without compromising one's taste buds.
Adding Intelligence to Taste Detection
While the current prototype relies on electrochemical changes to measure spiciness, future versions could integrate artificial intelligence and machine learning to interpret complex flavor profiles more accurately. By training models on large datasets of sensor outputs and human taste responses, such systems could learn to distinguish subtle combinations of pungent compounds, predict perceived heat levels, and even adapt to regional or individual taste preferences. This would transform the artificial tongue from a passive sensor into an intelligent flavor analysis tool, paving the way for applications in smart food monitoring, culinary robotics, and assistive technologies for individuals with impaired taste perception.
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