Tomato Pomace

When tomatoes are heated and pulped, the pulper and finisher screens pass the juice through and hold back the material that will not go: the fruit skins and the seeds, together with whatever pulp clings to them. That retained fraction is the pomace. Its make-up is not fixed — the proportion of seed to skin, and how much pulp is carried with it, depend on the cultivar processed and on how the extraction equipment is set.

Skin fraction

The fruit’s outer layer, carrying most of the pomace’s fibre and much of its residual colour.

Seed fraction

The seeds, which carry the protein and the oil in the stream and can be separated where a market for them exists.

Extraction setting

How aggressively the finisher recovers juice, which determines how much pulp stays with the pomace and therefore its composition and volume.

The established outlet is animal feed. Pomace carries fibre from the skins and protein and oil from the seeds, and it is fed either fresh to livestock near the factory or dried and incorporated into compound rations. Where volumes and economics allow, the seed can be separated and pressed for oil, which turns part of the stream into a higher-value product; and pomace is also used as a substrate for further processing or returned to land as organic matter.

• Animal feed — fed fresh near the plant, or dried for inclusion in compound rations
• Seed oil — where seed is separated and pressed at sufficient scale
• Land application and composting — returning organic matter where no feed outlet exists

Which of these actually happens is decided by distance and season more than by the composition of the pomace. A factory with livestock nearby has a same-day feed outlet; one without has to dry the stream, and drying a wet material is expensive enough that it can invert the economics of the by-product entirely.

Pomace leaves the line wet, warm, and biologically active, which makes it perishable on a timescale of hours rather than days — it ferments and spoils quickly if it is left standing. That is the central handling problem: the stream is produced continuously through a compressed processing season, at exactly the time of year when it is warmest. It is therefore moved immediately to a feed user, ensiled, or dried, and dried pomace is the form in which it travels any distance.