Chocolate contains nicotine update…
Dark secrets: Alkaloids in chocolate, including nicotine
Caffeine is a well-known component of coffee and tea but many people are unaware that chocolate also contains substantial amounts of caffeine, possible because the regulatory authorities do not require it to be listed on nutrition labels.
It is a natural constituent of the coffee bean at about 0.1-0.7%, so finds its way into chocolate products. Dark chocolate contains more caffeine than milk chocolate due to the higher proportion of cocoa solids that go into the product.
The presence of other natural alkaloids in chocolate like nicotine and myosmine, a minor tobacco alkaloid, is more uncertain, with conflicting reports. Myosmine has been found in foodstuffs like peanuts, milk and cocoa while nicotine has been discovered in many foods such as peppers, potatoes and tomatoes, which are all members of the family Solanaceae, as is the tobacco plant.
Nicotine has also been detected recently in spices, fresh herbs and herbal infusions, prompting the EU Food Safety Authority to raise its maximum residue level in these foods to values between 0.03 and 4.0 mg/kg food.
Pressed by concerns over the potential toxicological effects of these three alkaloids over the long term, especially in pregnant women and children, a team of scientists in Germany has been examining them in chocolate, to try and establish some baseline measurements.
Christoph Miller, Florian Vetter, Elmar Richter and Franz Brache from Ludwig-Maximilians University, Munich, located several published HPLC methods but decided on a GC/MS approach, which they described in Journal of Food Science.
Processed chocolate
Chocolate is a complex matrix but the researchers developed a simple procedure for isolating the target compounds. Melted portions were mixed with hydrochloric acid and centrifuged, before the aqueous layer was mixed with sodium hydroxide solution followed by solid potassium carbonate for phase transfer.
The alkaloids in the alkaline solution were extracted from the headspace volume by solid-phase microextraction then the fibre was removed and inserted into the inlet of the gas chromatograph. It was heated to desorb the three compounds which were separated on the column for electron ionisation and multiple reaction monitoring.
Nicotine eluted in the first time segment, between 6.5 and 7.5 minutes, followed by myosmine between 7.5-9.0 minutes and caffeine at 9.0-12.0 minutes. The absolute concentrations were determined by comparing the peak intensities of the monitored fragmentation reactions with those of the corresponding trideuterated standards, which were added to the melted chocolate at the start of the extraction procedure.
Caffeine and nicotine but no myosmine
The detection limits were 216, 0.00011 and 0.00012 mg/kg for caffeine, myosmine and nicotine, respectively and the recoveries and other analytical data were all acceptable.
Following the tests to check the method and determine the analytical parameters, the method was used to examine 30 different types of chocolate from 5 manufacturers with cocoa contents from 30-99%.
Myosmine was not found in any of the samples but both caffeine and nicotine were present in every chocolate tested. This was particularly surprising for nicotine given the doubts about its presence at all. Its concentration ranged from 0.00023-0.00159 mg/kg with a mean value of 0.000645 mg/kg. There was a weak correlation between the amount of cocoa in the chocolate and the level of nicotine.
In contrast, the levels of caffeine were far higher at 420-2780 mg//kg with a mean of 1640 mg/kg. They correlated strongly with increasing levels of cocoa and were in broad agreement with reported concentrations from other studies.
A full interpretation of the results will require consideration of factors involved in the manufacturing process, as well as the type and origin of the cocoa beans, which was not possible since the researchers only had access to the information on the chocolate labels. A wider approach should also be taken to check more types of chocolate to see if nicotine is present in them all.
Originally written By Steve Down
