Plant sterols and stanols: the sterol profile is the specification

Two phytosterol powders at 95% total sterols can have quite different compositions, and in the markets where sterols are regulated as a novel food, composition is what the authorisation is written against.

Where sterols come from

Commercial phytosterols come mainly from two feedstocks: tall oil, a by-product of wood pulp processing, and vegetable oil deodoriser distillate, usually soy or rapeseed. The feedstock determines the sterol profile and also determines what you can say about the material — a soy-derived sterol carries an allergen consideration that a tall oil sterol does not, and a wood-derived one is not a food-crop material at all.

Sterols and stanols

Stanols are the saturated form, produced by hydrogenating sterols. They behave similarly in most applications but are analytically distinct and are regulated separately in several jurisdictions. A specification should state the sterol-to-stanol split rather than reporting a combined figure.

Esterified or free

Free sterols are crystalline, high-melting and essentially insoluble in both fat and water, which makes them difficult to incorporate into anything. Esterifying with fatty acids produces a fat-soluble material used in spreads and dairy. The ester is heavier per unit of sterol, so a 100% sterol ester contains roughly 60% actual sterol — another case where the headline percentage needs converting before quotes are comparable.

What to put on the specification

• Total sterols by GC, with the individual profile: beta-sitosterol, campesterol, stigmasterol and the rest, each as a percentage.
• Sterol to stanol ratio.
• Free or esterified, and for esters the sterol equivalent content.
• Feedstock and origin, with an allergen statement for vegetable-oil-derived material.
• Particle size for free sterol powders, which drives dispersibility more than anything else on the sheet.
• Residual solvents and peroxide value, the latter for esters in particular.

Check the regulatory position before the price

Phytosterols are authorised novel foods in the EU with conditions attached, including specified compositional criteria and mandatory labelling on finished products. Other markets treat them differently again. Confirm that the specific material and its intended use fall inside the authorisation in your destination market before you get as far as negotiating a price — the compositional detail is what that determination turns on.