Refined Soybean Oil — Frequently Asked Questions

Because its high polyunsaturate content makes it a semi-drying oil. Linoleic acid carries two double bonds and alpha-linolenic three, and those double bonds react with atmospheric oxygen to crosslink the resin, which is how an alkyd coating dries. An oil low in polyunsaturates would not cure. The same reactivity that limits its shelf life as a food oil is the basis of its value in coatings.

As a plasticiser and heat stabiliser in PVC. Reacting the double bonds with a peracid converts them to epoxide groups, and those epoxides scavenge hydrogen chloride released as PVC degrades under heat, slowing the degradation. It also plasticises the polymer, so it performs two functions at once, and it is bio-based, which suits non-phthalate positioning.

Because crude soybean oil is unusually rich in phospholipids, which form gums that foul equipment, poison hydrogenation and hydrotreating catalysts and cause haze. Degumming removes them, and the recovered material is sold separately as lecithin, so the step both purifies the oil and produces a saleable co-product.

Less stable than monounsaturated oils. Around half its fatty acids are linoleic acid with two double bonds, plus 7 to 8 percent alpha-linolenic with three, and each double bond is an oxidation site. It develops a characteristic grassy or painty reversion flavour, and antioxidant addition, nitrogen blanketing and cool dark storage all extend its life.