Citrus Peel

Citrus extraction is designed to take the juice out of the fruit while leaving the peel structure as intact as possible, because peel oils ruin juice. What remains after extraction is the whole rest of the fruit: the coloured outer flavedo carrying the oil glands, the white albedo beneath it, the segment membranes, and the seeds. It comes off the line wet, acidic, and continuous, for as long as the plant runs.

Wet peel is a problem for the same reasons apple pomace is: heavy, quick to ferment, impossible to stockpile. The standard route is to treat the wet residue with lime, which breaks down the pectin and releases bound water so the material can be pressed, then to press it and dry the pressed cake and pellet it. The result — dried citrus pulp pellets — is a stable, dense, shippable feed commodity that travels internationally, and it is the transformation that made the residue worth handling.

The liquid pressed out is not discarded either: it is concentrated into citrus molasses, itself a feed ingredient and a fermentation substrate. Drying is energy-intensive, and the economics of pelleting swing with fuel prices and with how far the nearest livestock market sits from the plant.

Dried citrus pulp pellets are a well-established energy and fibre feed for ruminants, valued for a digestible fibre that behaves differently from cereal starch, and traded across borders as a feed commodity. Pectin extraction takes citrus peel — along with apple pomace — as its principal raw material, and citrus peel is the source of much of the world's commercial pectin. Peel oil, recovered from the flavedo during or after extraction, is a valuable flavour and fragrance material and also a solvent and cleaning agent.

• Feed — dried citrus pulp pellets for ruminants, the largest outlet by volume
• Feed — citrus molasses from the pressed liquid
• Industrial — pectin extraction, with citrus peel a principal raw material
• Industrial — citrus peel oil for flavour, fragrance, and solvent use
• Food — candied peel and fibre ingredients from selected material

Because the peel is the fruit's outer surface, it concentrates whatever was applied to or deposited on the fruit, which makes the incoming fruit's treatment history directly relevant to the by-product's suitability for feed and food use. Feed use and permitted materials are governed by the feed regulations of the jurisdiction concerned.