By Lee Su Ying and Dr. Khor Sook Mei
When we buy food, we often rely on what we can see. Fresh fish with bright eyes, vibrant vegetables, or a clear bottle of fruit juice all give us confidence that what we are about to eat is safe. Yet some of the greatest food safety risks cannot be detected by sight, smell, or taste. Toxic heavy metals such as lead and cadmium are invisible contaminants that may already be present long before food reaches our plates.
These contaminants can enter the food chain through polluted soil, contaminated water, industrial activities, and environmental changes. As they accumulate in crops and aquatic organisms, they eventually make their way into foods that we consume every day. Long-term exposure to these heavy metals has been associated with serious health problems affecting the nervous system, kidneys, liver, cardiovascular system, and other vital organs. Because these contaminants are invisible, regular monitoring becomes one of the most important safeguards for public health.
Fortunately, laboratory methods for detecting heavy metals already exist and are highly accurate. However, they also present practical challenges. Many require sophisticated instruments, specialised laboratories, trained personnel, and lengthy analysis procedures. While these methods remain essential for confirmatory testing, they are less suited for routine screening across today’s increasingly complex food supply chain.
This challenge inspired our research. We asked a simple question: can we develop a sensor that provides faster and reliable detection of toxic heavy metals without sacrificing accuracy?
The answer is not simply to make a faster sensor. The greater challenge lies in the food itself.
Many existing sensors perform very well under controlled laboratory conditions using simple test solutions. Unfortunately, real food is rarely that simple. Fish contains proteins and fats. Fruit juice contains natural sugars and organic acids. Tea contains a wide range of naturally occurring compounds. These substances can interfere with the sensing process, making it difficult for the sensor to distinguish the harmful metals from everything else present in the sample. As a result, a sensor that performs well in clean laboratory solutions may not necessarily perform equally well when analysing actual food.
This is one of the reasons why developing practical food sensors has remained such a challenge. Detecting heavy metals is no longer the main difficulty. Detecting them accurately in complex food samples, while maintaining speed, sensitivity and reliability, is where the real scientific challenge lies.
To address this challenge, we developed an electrochemical sensor that combines several advanced materials, each performing a different role. One selectively captures lead and cadmium ions, another provides a rapid electrical pathway, while a third amplifies the sensing signal. Together, they allow the sensor to detect extremely small amounts of both metals simultaneously, even in complex food samples.
More importantly, we evaluated the sensor using actual food products rather than relying solely on laboratory solutions. Fish, black tea and orange juice were selected as representative food samples because each presents different analytical challenges. Our results demonstrated that the sensor was able to accurately detect lead and cadmium with performance comparable to established laboratory methods.
For consumers, the technical details are less important than what this achievement could mean in practice. Faster screening tools have the potential to support food manufacturers, quality control laboratories, and regulatory agencies by identifying contaminated products earlier in the supply chain. Instead of waiting for lengthy laboratory analyses before every decision can be made, rapid screening methods can help prioritise samples that require further investigation while allowing routine monitoring to become more efficient.
Earlier detection also creates wider benefits beyond individual food products. It can reduce the likelihood of contaminated food reaching consumers, strengthen public confidence in food safety systems, minimise unnecessary food waste, and help identify sources of environmental pollution before they become more widespread. At the same time, industries can improve quality assurance while maintaining confidence in the safety of their products.
Our research does not suggest replacing conventional laboratory analysis. Comprehensive laboratory testing will continue to play an essential role in regulatory enforcement and detailed food safety investigations. Rather, we see rapid sensing technologies as an important first line of defence. By combining quick screening with confirmatory laboratory analysis, food safety monitoring can become both more responsive and more efficient.
Food safety is often judged by what we can observe, but the greatest threats are sometimes the ones we cannot detect ourselves. As food production and supply chains become increasingly complex, developing practical tools for earlier detection will become even more important. We believe advances in sensing technologies can help ensure that invisible contaminants remain exactly that: detected before they ever become a danger to public health.
The authors are from the Department of Chemistry, Faculty of Science, Universiti Malaya.
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