Tobacco

The leaves used for tobacco concrete and tobacco absolute come exclusively from the Oriental and cigar types. Nicotiana tabacum is an annual plant that grows 1 to 3 metres high and is native to tropical and subtropical America. Nicotine makes up 90 to 95% of the pyridine alkaloids of the plant, with nornicotine and anatabine at roughly 2.5% each. The main polyphenols of the leaf are rutin and chlorogenic acid.

From leaf to aroma

After harvest the leaf is cured, then aged to improve its flavour. During curing and aging the carotenoids of the leaf are slowly oxidised and degraded. This gives the leaf a sweet hay, tea, rose oil or fruity aromatic flavour. Four methods of curing are common: air curing, fire curing, flue curing and sun curing. Air-cured tobacco dries for six to eight weeks in a well-ventilated barn, sheltered from wind and sun. In fire curing, smoke from a low-burning fire on the barn floor permeates the leaves, which gives them a distinctive smoky aroma and flavour. Fire curing takes three to ten weeks and gives a tobacco low in sugar and high in nicotine. Flue-cured tobacco is kept in an enclosed barn heated by flues of hot air, without direct exposure to smoke, and the process takes about a week. Virginia tobacco that has been flue-cured is also called bright tobacco, because flue curing turns its leaves gold, orange or yellow. Sun-cured tobacco dries uncovered in the sun and is used in Greece, Turkey and other Mediterranean countries to produce oriental tobacco. Cured tobacco is tied into hands or made into bales, which are aged for one to three years to improve flavour and reduce bitterness. Cigarette blends generally use three major types of tobacco: Oriental (also known as aromatic, Turkish or Greek tobacco), flue-cured (Virginia bright) and Burley (light air-cured).

Aroma compounds

Megastigmatrienone is the key flavour compound in tobacco. It is a cyclohexenone and a carotenoid-derived aromatic compound. As Tabanone, it is manufactured as a perfume ingredient. Solanone is an unsaturated ketone with the formula C₁₃H₂₂O that is used as a fragrance. Solanone was discovered in 1967 and occurs naturally in tobacco leaves. Because extracting the natural product is expensive, solanone is now mostly manufactured synthetically. Solanone is also found in blackcurrant buds. Dihydroactinidiolide, a volatile terpene with the formula C₁₁H₁₆O₂, occurs naturally in tobacco. It has a sweet, tea-like odour and is used as a fragrance. The odour of β-damascone is described as tobacco, rose, apple, tea and fruity. In the essential oils of Bulgarian Virginia, Burley and Oriental tobaccos, the main carotenoid degradation products include α-ionone, dihydro-β-ionone and β-damascenone. Ionone and its derivatives were not identified in the concrete and resinoid made from Bulgarian tobaccos. They were not identified in the commercial-grade absolute either, apart from 3-oxo-α-ionol and 3-oxo-7,8-dihydro-α-ionol.

Flower concretes

Concretes can also be extracted from the flowers of Nicotiana tabacum. The flower concrete of Oriental-type tobacco yielded 3.2% and that of Virginia-type tobacco 5.2%. The Oriental-type flower concrete has a very strong green odour with fresh undertones, reminiscent of freshly cut hay. The Virginia-type flower concrete has a very strong green odour with slight floral and honey-like undertones.