Machine-hulled and auto-dried describe different steps in making hulled sesame. Machine-hulled refers to how the seed coat is taken off, by mechanical rubbing after soaking. Auto-dried refers to how the wet seed is dried afterwards, in closed mechanical dryers rather than in the open sun.
In practice, Indian sellers use these terms loosely. Some quote machine-hulled as a basic grade that may be sun or partly sun dried, and auto-dried as a fully mechanised line. Always ask for the full process flow.
How hulled sesame is made
- Cleaning: natural seed is cleaned and often sortex sorted.
- Soaking: seed is soaked in water so the hull softens.
- Hulling: the soaked seed is rubbed mechanically to loosen and remove the hull.
- Separation: hulls are washed away or separated by density.
- Drying: the wet seed is dried, either in mechanical dryers or on open floors in the sun.
- Final cleaning: colour sorting removes unhulled and discoloured seeds before packing.
Machine hulling versus chemical hulling
Some hulling processes use a chemical such as caustic soda to loosen the hull, followed by washing. Mechanical hulling relies on soaking and friction. Many buyers prefer mechanical hulling to avoid any chemical residue or effect on flavour. If you have a preference, write it into the spec and ask the plant to confirm it in writing.
Hulling quality also shows in the finished seed. Look for an even white colour, few seeds with hull left on and few broken seeds. Set a limit for each in your spec.
Why the drying method matters
Wet hulled seed is a good place for microbes to grow. Sun drying on open floors exposes it to dust, birds, insects and animals, and drying can be slow and uneven. That increases the risk of Salmonella, high plate counts and foreign matter. Closed mechanical drying is faster, more even and easier to keep clean.
Auto-dried seed is therefore usually preferred by food manufacturers in the EU, UK and US. It is not a guarantee. A dirty dryer, poor water quality or bad handling after drying can still cause problems. The controls are covered in why Salmonella is a concern in sesame.
Questions to ask the supplier
- Is hulling mechanical or chemical?
- Is drying fully mechanical, or is any stage done in the sun?
- What is the source and testing of the soaking and washing water?
- Is there a steam sterilisation or pasteurisation step, or will you need one?
- Can you see the line running and the recent Salmonella results?
How we help
We visit hulling plants in Gujarat to see how they hull, wash and dry, and we write the agreed process into your spec. Samples go to an NABL-accredited lab for microbiology and residues. To find an auto-dried line you can rely on, ask for a free sourcing review.