Summary of "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.
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.
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.
Category
Science and Nature
