Exposing Fake Honey Using Carbon-13

Scientific Concepts and Discoveries

Honey Adulteration

Some dishonest producers dilute honey with cheaper sugars such as beet syrup, corn syrup, rice syrup, or cane sugar.

Prevalence

A European Commission report found that 46% of honeys imported into Europe were adulterated.

Photosynthesis Types and Carbon Isotopes

• Plants use different photosynthesis pathways: C3 and C4.
• C3 plants (e.g., wildflowers, clovers, trees) produce sugars with lower carbon-13 content.
• C4 plants (e.g., corn, sugarcane) produce sugars with higher carbon-13 content.

Stable Isotope Analysis

• By measuring the ratio of carbon-13 to carbon-12 in honey, adulteration can be detected.
• Genuine honey (from C3 plants) shows a characteristic lower carbon-13 ratio.
• Adulterants from C4 plants (corn syrup, cane sugar) show higher carbon-13 ratios.

Combustion and Mass Spectrometry

• Honey samples are combusted to produce CO₂.
• Gas chromatography separates the gases.
• Mass spectrometry measures carbon isotope ratios.

Other Testing Methods Attempted

• Crystallization test: Corn syrup interferes with honey crystallization, but this test was inconclusive.
• Brix test: Measures sugar concentration via refractometry; results were inconclusive due to overlapping values.
• Fluorescence under black light: Honey fluoresces due to flavonoids and amino acids, but all samples fluoresced, making this test inconclusive.

Enzymatic Activity and Physical Signs

• Natural honey contains glucose oxidase, which produces bubbles (oxygen release) when honey sits open.
• Suspected adulterated honey lacked these bubbles.

Sensory Testing

• Blind taste tests distinguished genuine honey from adulterated samples.
• Adulterated samples tasted more like caramel syrup than honey.

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Methodology for Detecting Honey Adulteration

1. Sample Collection

• Purchased 20 honey samples from various sources including specialty stores, discount stores, and farmers’ markets.
• Additional 5 samples purchased and adulterated by a collaborator (George), with some intentionally mixed with corn syrup as controls.

2. Initial Home Tests

• Crystallization test (refrigeration, freezing, microwaving, adding sucrose/fructose) — inconclusive.
• Brix test using a refractometer to measure sugar concentration — inconclusive.
• Fluorescence under black light — inconclusive.

3. Stable Isotope Analysis

• Samples weighed and combusted to convert organic material to CO₂.
• Gas chromatography separates CO₂.
• Mass spectrometry measures carbon-13 to carbon-12 ratios.
• Isotope ratios compared to known values for C3 (honey) and C4 (corn syrup, cane sugar) plants.

4. Result Interpretation

• Genuine honey samples showed carbon-13 ratios around -25 to -27‰.
• Corn syrup and cane sugar showed ratios around -11‰.
• One commercial honey sample showed a ratio around -14.5‰, suspiciously close to corn syrup.
• Two samples from George showed intermediate values, suggesting partial adulteration.

5. Additional Observations

• Physical signs (bubble formation) and sensory taste tests supported isotope analysis findings.

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Researchers and Sources Featured

• Jennifer Cotton (CSU Northridge) — provided stable isotope analysis lab access and expertise.
• George — collaborator who purchased and adulterated honey samples.
• European Commission report on honey adulteration.
• Podcast “Criminal” — source of inspiration for stable isotope analysis methodology in fraud detection.