Margarine/vegetable oil spreads are water-in-oil emulsions. The water droplets are dispersed in liquid oil, which is stabilised by solid fat. You may find vegetable oil spreads with different fat contents ranging from 10 to 90%. Depending on the fat content and whether the margarine will be used as such or as an ingredient in another food product, the level of water and the ingredients in the final product will of course slightly vary.
The seeds are harvested, then crushed to extract the oils, which are then refined. The resulting oils are identical to the table oils that are sold in supermarkets.
The vegetable oils and a bit of solid fat-that gives the "spreadable structure" to the margarine are blended together. The oils undergo a full or partial hydrogenation process to solidify them, unless solid fat has been added.
The resulting blend is subsequently mixed with water, citric acid (like in lemon juice) and possibly salt, carotenoids, vitamins and milk-powder at temperatures around 50-60°C. Lecithin (also present in egg yolk) is added to help mix the oil and water easily.
This emulsion then needs to be pasteurised at temperatures around 70 to 86°C.
The mixed spread is finally chilled while undergoing extensive and continuous stirring.
And all that is left to do is to pack the margarine and ship it to its end destination!