To keep curry and coriander leaves green, they must be dried quickly at a moderate temperature, out of direct sun, and then packed so that light, air and moisture cannot reach them. Most colour loss happens either during slow or hot drying or during storage afterwards.
You cannot fix brown leaves after drying. So the controls belong at the processor, and your spec should make them clear.
Why the leaves lose colour
The green comes from chlorophyll. It breaks down with heat, light, acidity and time, and it turns olive or brown when leaves stay wet too long. Coriander leaves are thin and delicate, so they lose colour and aroma faster than many herbs. Curry leaves are tougher but also darken when dried badly.
Controls at the drying stage
- Process leaves soon after harvest, before they wilt or heat up in sacks.
- Wash and drain well, so drying starts without standing water.
- Dry in shade or in mechanical dryers with controlled temperature and good air flow.
- Spread leaves thinly and evenly so no wet pockets remain.
- Avoid direct sun drying, which bleaches the colour.
- Some processors blanch briefly before drying to protect colour. Ask whether it is done and agree it in writing, as it changes flavour and texture.
- Cool the dried leaf before packing to avoid condensation.
Controls after drying
Our guide on how dried herbs should be packed covers liners and pack types in more detail.
- Keep moisture low. Set a maximum in the spec and test it on arrival.
- Pack in bags with a moisture barrier liner, heat sealed or tightly closed.
- Use opaque packing or cartons so light does not reach the product.
- Store in a cool, dry warehouse, off the floor and away from sunlit areas.
- Ship in a container with dry bags if the route is long or humid.
- Use stock in date order. Colour fades steadily over the shelf life.
What to watch for
Be wary of leaf that looks unusually bright compared with other samples. Added colour is a known form of adulteration in some herbs and spices. If in doubt, ask a lab to check for synthetic colours. See detecting starch or colour adulteration.
Also check microbiology. Leaves dried at moderate heat can carry high counts, and many buyers require steam sterilisation, which itself can dull colour slightly. Agree the colour standard for sterilised product with a sample.
Curry leaves and coriander differ
Curry leaves are thicker and hold their shape, so they are usually sold whole or broken. Coriander leaves are fine and fragile, and they lose aroma quickly, so many buyers accept a rubbed or flaked form. Coriander leaf is also sensitive to over drying, which leaves it brittle and dusty.
Because of these differences, agree separate colour and size standards for each product rather than using one herb spec for both.
How Creston & Co helps
We see how the leaves are dried and stored during the audit, compare lot samples against your approved colour, and check packing before the container is loaded. Begin with a free sourcing review.