The stakes are high. Genuine honey is a supersaturated sugar solution produced by honeybees through the enzymatic transformation of nectar, and its value goes far beyond sweetness. Chemically, honey consists mainly of fructose at roughly 38.2 percent and glucose at about 31.3 percent, with minor amounts of sucrose, maltose, amino acids, enzymes such as diastase, glucose oxidase and invertase, organic acids like gluconic acid, minerals, vitamins, and a broad arsenal of phenolic and flavonoid compounds. That complex cocktail underpins honey’s antioxidant, antibacterial, anti-inflammatory and antiviral activities, which is why regulators classify it not merely as a sweetener but as a functional food with potential pharmacological benefits.

All of that makes honey expensive, and high prices invite adulteration. Because production is limited and global demand keeps climbing, unscrupulous producers frequently stretch their product with cheap sugar syrups, including glucose syrup, fructose syrup, invert sugar and high-fructose corn syrup. These adulterants are notoriously difficult to detect, particularly when added in moderate amounts, and their presence can significantly alter the physicochemical properties and therapeutic quality of the final product. The practice deceives consumers, undercuts honest beekeepers, and poses a persistent headache for food safety and regulatory agencies worldwide.

Existing detection methods are powerful but cumbersome. High-performance liquid chromatography, gas chromatography, isotope ratio mass spectrometry, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy have all been deployed against sugar adulteration, each with its own detection floor. Fluorescence measurements, based on the ratio of emission intensities at 365 and 425 nanometers, detect cane sugar syrup down to 15 percent. The carbon-13 to carbon-12 isotope ratio catches fructose syrup adulteration only at 27 percent. FTIR analysis in the 992 to 923 inverse centimeter range reaches 5 percent, and HPLC of rice syrup markers manages 2.5 percent. But these techniques are labor-intensive, time-consuming, and demand sophisticated instrumentation and trained personnel, making them poorly suited for routine or on-site screening.

Enter electrochemical impedance spectroscopy, or EIS. The method works by applying a small alternating voltage, in this case just 10 millivolts, across a frequency sweep from 20 hertz up to 500 kilohertz and measuring the sample’s complex impedance, the frequency-dependent opposition to current flow. That impedance reflects changes in ionic conductivity, dielectric constant and electrochemical behavior, all of which are exquisitely sensitive to composition, viscosity, ionic strength and intermolecular interactions. Because sugar syrups alter exactly those properties, the researchers hypothesized that EIS could serve as a sensitive and rapid tool for evaluating adulteration. The technique has already proven its worth in food quality control, detecting adulterants in milk, fruit juices, olive oil and wine, and it has previously been used to discriminate honey by botanical origin and to analyze potassium content.

The experimental design was elegantly straightforward. The team, led by Hamdi Ben Halima and Nicole Jaffrezic-Renault of the UTINAM Institute at Université Marie et Louis Pasteur in Besançon, together with Mustafa Kemal Sezgintürk of Çanakkale Onsekiz Mart University, purchased honeys from six botanical origins at a French supermarket: lime (Tilia europea), black locust or acacia (Robinia pseudoacacia), thyme (Thymus vulgaris), sweet chestnut (Castanea sativa), lavender (Lavandula angustifolia) and lemon citrus (Citrus × limon). Each honey was adulterated with a 99.9 percent pure saccharose syrup from beet sugar at 10, 20, 50 and 80 percent by weight, then diluted to 20 percent in deionized water to reduce viscosity. Measurements were performed with a Biologic SP-200 potentiostat in a thermostated cell at 25 degrees Celsius, using a three-electrode configuration: a saturated calomel reference electrode, a platinum plate counter-electrode and a platinum wire working electrode, all cleaned between measurements.

The raw data take the form of Nyquist plots, in which the imaginary part of the impedance is plotted against the real part, tracing a characteristic arc whose shape encodes the sample’s electrical personality. To extract meaningful numbers from those curves, the researchers fitted them to a Randles equivalent electrical circuit, a standard model comprising the electrolyte resistance, a bulk resistance term, the capacitance of the electrical double layer forming at the platinum electrode-mixture interface, and a Warburg impedance term describing diffusion effects at low frequencies. The fits were excellent, and one parameter in particular emerged as the star of the show: the bulk resistance, measured at frequencies above 15 kilohertz, which tracks the total mineral content of the honey, including potassium, the predominant cation, along with cadmium, lead, chromium, manganese, iron, nickel, copper and zinc.

That mineral link explains everything the team observed. The bulk resistance of the pure honeys followed a clear sequence, with acacia honey highest, followed by lavender, citrus, thyme, lime and chestnut, while mineral content varied in the inverse order, exactly as earlier studies had reported. The beet sugar syrup itself, essentially mineral-free, showed a bulk resistance of 181,830 ohms when diluted, so every addition of syrup dilutes the honey’s mineral load and pushes the resistance upward. Crucially, the relative change in bulk resistance varied linearly with the beet sugar percentage across the 0 to 50 percent range for all six honeys. Sensitivity was highest for lime honey, rich in minerals, and lowest for acacia, which starts out mineral-poor. Measurements repeated five times yielded relative standard deviations between 3 and 7.5 percent, and the calculated detection limit, derived from the standard expression three sigma over sensitivity, came out at just 3.3 percent saccharose syrup, with a quantification limit of 10 percent.

Set against the competition, that figure is impressive. EIS outperforms fluorescence by a factor of nearly five, beats the isotope ratio method by a wide margin, and edges past FTIR, falling short only of HPLC’s 2.5 percent threshold, a technique that requires far more expensive equipment and considerably more time per sample. The authors argue that the linear correlation between bulk resistance and syrup percentage provides a quantitative electrochemical signature of adulteration, one that can distinguish genuine honey from doctored samples with high sensitivity and reproducibility. Because the measurement is non-destructive, rapid and inexpensive, it could plausibly be implemented in quality control laboratories and even industrial production lines, and earlier work has already demonstrated a portable prototype based on a microcontroller and low-cost immersion electrodes for monitoring sugar adulteration.

The broader implications stretch beyond the honey jar. Food fraud is a multi-billion-dollar global problem, and the tools that catch it need to be fast, cheap and deployable outside specialized labs. This study shows that a technique requiring little more than a pair of platinum electrodes, a modest potentiostat and a fitting algorithm can deliver detection limits rivaling chromatography. The method’s dependence on mineral content is both its strength and its caveat: sensitivities vary with botanical origin, so calibration against each honey type matters. Still, as the authors conclude, the ease of implementation and sensitivity of EIS make it a promising approach for routine quality control in the honey industry and a potential reference point for broader applications in food fraud detection. The next time you drizzle honey on your toast, there may be a small electrical circuit standing guard between you and the counterfeiters.

Subject of Research: Detection of sugar syrup adulteration in honey using electrochemical impedance spectroscopy

Article Title: Electrochemical impedance spectroscopy for detecting honey adulteration by sugar syrup

Article References: Halima, H. B., Sezgintürk, M. K., & Jaffrezic-Renault, N. (2026). Electrochemical impedance spectroscopy for detecting honey adulteration by sugar syrup. Discover Electrochemistry, 3(1), Article 36. https://doi.org/10.1007/s44373-026-00126-1

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00126-1

Keywords: honey adulteration, electrochemical impedance spectroscopy, food fraud, sugar syrup, food safety, bulk resistance, Randles circuit, beet sugar, honey authentication, quality control, Nyquist plot, mineral content