Oil Content

Solvent extraction is the reference method: a solvent dissolves the lipid fraction out of a ground sample, the solvent is removed, and the residue is weighed to give the extracted oil as a share of the original sample mass. This is accurate but slow, destructive, and unsuited to testing every truckload arriving at a crushing plant. Nuclear magnetic resonance and near-infrared spectroscopy are the routine alternatives, both non-destructive and fast, and both calibrated against solvent-extraction values so their readings can be trusted only within the range and matrix they were calibrated on.

As with protein, the result is only meaningful with its moisture basis attached. A lot dried further after testing, or tested at a different moisture than the buyer’s specification assumes, will not report the same oil percentage even though nothing about its actual oil content has changed — the arithmetic basis, not the seed, has shifted.

In most oilseeds, oil content and protein content move in opposite directions across varieties and growing conditions: a lot bred or grown toward higher oil tends to carry somewhat lower protein, and vice versa. This is not a strict rule for every sample, but it is consistent enough that crushers and feed buyers weight the two differently depending on what they intend to do with the meal versus the oil, and breeding programmes make deliberate trade-offs between the two traits.

A lot with a high oil percentage can still yield oil that performs poorly or degrades quickly. What determines the oil’s fitness for food, feed, or industrial use is its fatty acid composition, its free fatty acid level (a marker of hydrolytic breakdown), and its oxidative state — none of which the oil content figure addresses at all. Two lots at the same oil content can require entirely different downstream handling depending on these separate properties.