d-Limonene is the major component of the oil extracted from the citrus rind during the citrus juicing process. When the fruit is juiced, the oil is pressed out of the rind, then separated from the juice and distilled to recover certain flavor and fragrance compounds.
After the juicing process, the peels are conveyed to a steam extractor. When the steam is condensed, a layer of oil floats on the surface of the condensed water. This removes the bulk of the oil from the peel.
Food grade d-Limonene is extracted through the juicing process and Technical grade d-Limonene is removed through the peel steam extraction process. The chart below shows the citrus oil manufacturing process and the specific oils that come from each part of the process.