Hulling is a value-adding step that costs stability, and the trade-off is rarely priced explicitly.
The seed coat does two things. It is a physical barrier that slows oxygen diffusion into the oil-rich kernel, and it concentrates natural antioxidant compounds – tocopherols and phenolics – that scavenge the free radicals which propagate oxidation. Removing it removes both defences at once.
Surface area compounds the problem. A hulled kernel exposes more of itself to air than a whole seed, and a chopped or milled kernel exposes far more again. Practical shelf life falls steeply across that sequence.
Composition decides how much this matters. Highly unsaturated oils oxidise faster than saturated ones, which is why hemp and flax – both dominated by polyunsaturated fatty acids – run the fastest oxidation clock in the category, ahead of hulled sunflower and well ahead of tree nuts.
The controls are the same in every case and they are conditions rather than specifications: an oxygen barrier packaging with vacuum or nitrogen flushing, a temperature ceiling in transport and storage, and the shortest practical interval between hulling and use. Chilled storage roughly multiplies practical shelf life on high-fat kernels.
Measurement should always pair peroxide value by ISO 3960 with free fatty acids by ISO 660. Peroxide value alone misleads, because peroxides decompose and an old kernel can read low. And because oxidation is driven by conditions after despatch, the measurement point named in the contract decides whether the buyer has a claim at all.