Few aroma chemicals serve two markets as different as D-limonene (CAS 5989-27-5). To a flavourist it is the citrus top note recovered from orange peel. To a formulator of industrial cleaners it is a readily biodegradable solvent that replaced chlorinated hydrocarbons in a range of degreasing applications. Same molecule, entirely different specifications and buying behaviour.

Where it comes from

D-limonene is the dominant terpene in citrus peel oil and is recovered as a co-product of juice processing and of orange oil folding. Folding concentrates the oxygenated flavour compounds by removing terpenes, and the terpene fraction removed is largely limonene. That relationship is worth understanding, because the availability and price of one moves with demand for the other.

As a flavour and fragrance material

Here the requirement is sensory. Buyers want a clean citrus character without the oxidised, turpentine-like off-notes that limonene develops on exposure to air and light. Peroxide value and storage handling matter, and material is normally specified alongside orange oil 5 fold or 10 fold depending on how much flavour concentration is wanted.

As a solvent

In cleaning and degreasing the sensory question largely disappears and is replaced by solvency performance, biodegradability and regulatory acceptability. D-limonene is attractive precisely because it is derived from a renewable co-product stream and breaks down readily, which lets a formulator make a credible bio-based claim without sacrificing performance on grease and adhesive residues.

Practical buying notes

State which market you are in — the grade conversation changes completely.
Ask about peroxide value and recommended storage if the application is sensory.
Expect price to move with the citrus crop and with juice processing volumes, not with aroma chemical demand alone.
For flavour work, consider whether folded orange oil is a better fit than isolated limonene.

Specifying it properly

As with any material sold into two markets, the risk is receiving a grade optimised for the other one. Naming the CAS number and the intended application in the enquiry removes that ambiguity before it becomes a rejected delivery.