Descriptions:
Benzoin Siam Gum is a balsamic resin from Styrax tonkinensis (Pierre) Craib ex Hartwitch tree, which belongs to the Styracaceae family. It is collected directly from the tree, cleaned and sorted into three grades according to size. The production is entirely manual, from tapping to packaging. It is variously referred to as Siam benzoin gum, Siam benzoin and Benzoin Vietnam or in a generic way as “benzoin gum”. Vietnam & Laos are considered as the major producer of Benzoin tonkinensis, if not the only two at present.
Benzoin tonkinensis is commercialized after it has been cleaned and sorted into three grades, according to its size: grade 1- large tears; grade 2 – medium tears; grade 3 – small tears and powder.
The production is distributed in the following way: 30% Grade 1, 30% Grade 2, and 40% Grade 3. The various grades do not present any significant variation of the chemical composition, but are the result of the cleaning process. They can have only an impact on the colour of the product during the storage at ambient temperature (from beige to brown colour).
The product presents a strong vanilla smell, is insoluble in water and soluble in ethanol.
Ready processed for export, Benzoin tonkinensis appears as pieces which are opaque, grainy, ovoid, flattened (almonds), from few to 30 mm, white-yellow.
After storage at ambient temperature, Benzoin tonkinensis can slightly melt and appears as agglomerated brown-red mass. Its colour turns reddish outside due to air exposure, but stays white- yellow inside.
Besides Benzoin tonkinensis, another type of benzoin is produced, Benzoin sumatranus, obtained from two other Styrax species, Styrax benzoin Dryander and Styrax paralleloneurum Perkins. These two resins differ in their botanical source, geographical origin and chemical composition. The term “benzoin gum” can include one or the other of the two sources or their mixtures.
In Siam benzoin the main constituents are benzoic acid and its esters (such as coniferyl benzoate and benzyl benzoate), while in Sumatra benzoin the major constituents are cinnamic acid and its esters (such as coniferyl cinnamate and cinnamyl cinnamate). Vanillin is present in both types of benzoin resins and gives rise to its familiar vanilla odour (most readily detected in the Siam type).
Chemical characterization:
The product can be described as white-yellow to reddish splits of flattened almond-like grains with a strong vanilla smell. The resin is composed mainly by benzoic acid (15-45 %) and coniferyl benzoate (15-60%), with lesser amounts of vanillin (<5%), benzyl benzoate (<2%), 2-hydroxy-1- phenylethanone and 1-(4-hydroxy-3-methoxyphenyl)-2-propanone.