May we start by saying these are both excellent spices when used appropriately, however they are different and have different flavours.
For many years Sri Lankan cinnamon (Cinnamomum zeylanicum) was the only variety commonly called cinnamon.
Cassia from Indonesia and Vietnam (Cinnamomum cassia) – also known as C. burmannii, C. lourerii and C. tamala) was called Saigon Cinnamon in the USA, and Dutch Cinnamon, Baker’s Cinnamon, Bastard Cinnamon and Batavia Cinnamon in many other countries.
Sri Lankan Cinnamon
Sri Lankan, (also known as Ceylon) Cinnamon quills are 8cm lengths of tightly rolled, concentric layers of the very thin underneath layer of bark (the agissa). This has been carefully peeled off cut branches and then rolled by cinnamon peelers into metre-long quills that look like giant cigars. These long quills are then cut into the familiar short ‘sticks’. Cinnamon quills have an aromatic fragrance and can be put into stewed fresh fruit such as apples and pears, used to flavour gluwein, and curries. A centimetre broken up and put into a coffee plunger with the grounds gives it a delicately spiced flavour. Ground cinnamon quills are the best grade of cinnamon to use in delicately flavoured dishes where an overly dominant cinnamon taste is not required. Typical examples would be, when adding cinnamon to porridge, with sugar on a light sponge cake or adding to a spiced chai tea.
Notice how in cross-section a cinnamon quill is made of many layers of paper-thin bark, rolled like a small cigar. Cinnamon quills are most often seen in 3-1⁄4-inch (8 cm) lengths of many concentric layers of paper-thin bark, rolled into cylinders about 1⁄2 inch (1 cm) in diameter. Sometimes quills up to 3 feet (1 m) in length will be found, especially in cinnamon’s native Sri Lanka. The color of cinnamon is a uniform light brown to pale tan. Cinnamon quills are ground to an aromatic powder, that is a similar colour to the quills, and has a very fine dusty texture. The fragrance is sweet, perfumed, warm and pleasantly woody with no trace of bitterness or dominating pungency.
Cassia, AKA Dutch Cinnamon, Baker’s Cinnamon, Bastard Cinnamon and Batavia Cinnamon is often confused with Sri Lankan cinnamon. Cassia has a very sweet, pungent aroma and almost bitter, somewhat hot aftertaste when used to excess. This is what the majority of bakers use on cinnamon donuts, in apple strudel and in cinnamon spiced muffins. Cassia is also used extensively in the United States and at one time was referred to there as Saigon Cinnamon. Highly perfumed, cassia is delicious in sweet dishes, compotes of dried fruits, and in Chinese and Indonesian recipes. Should you find cassia too strong, one can tone it down by blending cassia 50:50 with true Sri Lankan cinnamon.
Cassia contains higher levels of coumarin than cinnamon, and should not be consumed to excess.
Harvesting cassia differs from cinnamon in that the whole tree is cut down, the bark removed and dried. For this reason, cassia is often seen in many different shapes and sizes depending on what part of the tree it was harvested from. Large ‘chips’ of bark come from the trunk and thick branches, while the smaller quills (that many people confuse with cinnamon quills) have come from the small upper branches.
Cassia bark, by contrast to cinnamon quills, is generally found in two whole forms. One is flat pieces of dark brown slivers 4–8 inches (10–20 cm) long and 1 inch (2.5 cm) wide, smooth on one surface and rough and corky on the other. The other form is as quills or scrolls. Cassia scrolls are smooth and similar in appearance to 3-1⁄4-inch (8 cm) cinnamon quills, except for the thickness of the curl of bark (about 1⁄8 inch/3 mm as opposed to paper thin) and the reddish brown color. The aroma of ground cassia (grinding releases the volatile oils and makes the smell more obvious) is highly perfumed, penetrating, sweet and lingering. The flavor has an agreeable bitterness that conveys an impression to many people of superiority over cinnamon. Cassia powder will usually appear darker and redder than cinnamon and because the texture is so fine its flowing characteristics are similar to the finest of talcum powders.
For more detailed information about cinnamon and cassia, and recipes using these wonderful spices, plus many others, refer to The Spice & Herb Bible 3rd Edition by Ian Hemphill with recipes by Kate Hemphill, published by Robert Rose Inc. Toronto, Ontario, Canada.