Wednesday, January 29, 2014

True cinnamon

The plant genus Cinnamomum consists of about 250 species of that are aromatic and contain flavoring substances. Some of the species supposedly show antiinflammatory, antidiabetic, and antioxidant effects which increased the use of Cinnamon in traditional medicine. Cinnamomum verum, a native of Sri Lanka, is known as the true cinnamon. It is only cultivated in Sri Lanka and India, and the dried bark is used as the famous spice for biscuits, cakes, and other sweets. Most of us know the cinnamon sticks and we can buy them for little money. However, each of those sticks requires quite a bit of work. The outer bark of the plant is scraped by hand and the inner bark is then carefully removed with a knife. The best parts are used to create an outer sheaf and the other parts are placed within. These outer sheaves are joined to each other and overlap slightly to create a standard length stick. The sticks are then rolled daily as they dry and are tied into bundles for trading and transport. Not long ago the BBC aired a 3 part series on spices - The spice trail. It is quite an eye opener as it nicely shows how much work goes into the spices we can buy for cents in our grocery stores.

As with every valuable commodity it didn't take long until authorities and researchers discovered that Cinnamomum verum is often substituted with the hard, thick, and less aromatic bark of Cinnamomum aromaticum (Chinese cinnamon). This alternative however has a more bitter and burning flavor due to a higher amount of coumarin. True cinnamon has very little coumarin. To make matter worse the dried bark of another species, Cinnamomum malabatrum, is also passed off as true cinnamon.

Any attempt to distinguish species based on the morphology of bark is futile and most cinnamon is consumed as powder. Sounds like a case for DNA Barcoding and indeed a group of Indian researchers have now developed a method that promises to help with the problem. The biggest issue for DNA-based identification of cinnamon was the the presence of proteins, polysaccharides, and phenolic compounds of the lignin pathway that act as strong inhibitors of DNA extraction. Polysaccharides and polyphenols are also known to inhibit PCR. The researchers developed a way to extract DNA from the dried bark of Cinnamomum species which reduces the concentration of all those interfering substances and tested the products by Random Amplified Polymorphic DNA (RAPD) runs that produce different banding patterns for different species - here the true cinnamon and both common adulterants. They also successfully amplified rbcL, one of the official DNA Barcode markers for plants. 

Looks like there is a good way to ensure that my next cinnamon bun actually contains only true cinnamon!

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