Greener Industry - Vanillin

Vanilla Pods

The rapid-growing, climbing orchid vanilla planifolia produces pods of seeds, similar to bean pods. In its native Mexican environment pollination is by the tiny melipone bee, but for commercial production outside Mexico hand-pollination is necessary. The fresh pods do not smell of vanilla as the vanillin is tied up as the glucoside.
diagram: vanallin glucoside

Hot water immersion is used to stop photosynthesis, and the beans are sun-dried and "sweated" by rolling up in straw mats at night. This curing process results in enzyme hydrolysis, releasing vanillin, and the pods become shrivelled and brown. Some of these are exported at this stage for sale in shops.

The time between pollination and harvest can be as long as nine months, and curing may take a further six months. This is why natural vanilla is so expensive to produce.

The pods may be used directly, or vanilla extract can be produced. "Natural" vanilla extract must conform to a precise specification. Click here to find out more about vanilla extract.

Synthetic Methods

The first method, dating from the late 19th century, used oil of cloves, the main component of which is eugenol. Although the feedstock was renewable, significant quantities of synthetic chemicals were used during manufacture, including acid, sodium hydroxide and nitrobenzene. It involved production and re-crystallisation of pure eugenol, followed by conversion to vanillin with further washing and crystallisation. This method is no longer in use.

Vanillin may be produced from lignin, a component in waste material from the wood pulp industry. The sulphite process, which makes paper from wood or straw, generates waste that contains a mixture of useful materials. Sugars are present and can be fermented to produce alcohols, and the remaining solution can then be processed to make vanillin. Although using a waste product, the process was not very "green" as every 1kg of vanillin also produced over 150kg of waste to be disposed of. For more information on the lignin route, click here

Manufacture from petrochemical feedstock via catechol and guaiacol is now the most common route for synthetic vanillin. The volume and type of waste produced is much more manageable by this route, even though the feedstock is non-renewable. Catechol can, however, be made from glucose and so the option remains for the process to be based on renewable feedstock. For more detail on these processes, click here

The manufacture of vanillin from agricultural waste is now a real possibility. Research has shown that it can be made from ferulic acid, present in this waste. The conversion can also be achieved using fungi or bacteria rather than conventional chemical reagents. This inevitably means working at much lower temperatures and pressures than many conventional production processes, saving in energy at this stage. Click here to find out more.