At the farm
After harvesting, the leaves are removed from the plant and the roots are carefully washed to remove soil. Leaf scales and long roots are trimmed off. The branches (fingers) of the main rhizomes (bulbs) are separated. Bulbs and fingers are heaped separately covered in leaves and remain for a day for sweating. Some bulbs are kept for planning following year.
Before drying, the rhizomes are cooked in boiling water to be soften. It is called curing. Curing gelatinizes starch in a rhizome and makes more uniform drying. At the best timing for curing 2-3 days after harvesting, rhizomes are cooked in boiling water during 45 min on average, different from size, thickness, age, and variety of the rhizome. Rhizomes can be boiled until froth appears at the surface and the typical turmeric aroma is released.
The rhizomes are sliced before drying to reduce drying time and improve the quality of the final product. The rhizomes are sliced by machine. To minimize contamination, mold growth, and fermentation, the cured rhizomes are dried as soon as possible. The rhizomes are dried until the final moisture to reach to 5-10%. Optimally dried rhizome sounds clear and metallic when snapped by fingers. Clean and sanitary drying is important for hygiene of the final product, thus, Yesang Food monitors carefully the drying process particularly.
Dried rhizomes are polished to remove the rough surface. It can be done by hand or by shaking the rhizomes in a gunny bag filled with stones. Drum with abrasive metallic mesh lining can be used for polishing, too. After polishing a plain sifter and air screen separator can help remove small materials like dead insects, excreta, and extraneous matter, while a rotary knife cutter, screen separator and de-stoner will help remove residual insects and other extraneous matter.
At the grinding mill
Grinding is a process involving cutting and crushing the rhizomes into small particles, then sifting it through a series of screens of different mesh size to get powder with the desired fineness. For higher quality of turmeric power, the grinding temperature should be kept as low as possible. Our grinding unit controls temperature for keeping the volatile taste and aroma compounds and curcumin content. After grinding, the powder is sieved through different mesh screens until a uniform and fine powder is obtained.
Regardless of careful management, it is possible to be contaminated by any particles or adulterants until the grinding process. Yesang Food adopted two patented unit from South Korea to completely filter out contaminants: 1) Sorting apparatus of foreign substances, and 2) Magnetic sorting apparatus.
The sorting apparatus of foreign substances filters any type of adulterants including but not limited to metallic substances, small papers, string, vinyl, hair, and small stones. It separates substances larger than 0.5mm at the first stage, and removes impurities smaller than 0.5mm.
In addition to the sorting unit, Yesang Food installed magnetic separator to filter completely the metallic substances. The magnetic sorting machine doubles the magnetism and orts out metallic substances effectively.
Turmeric powder is packed in a 20kg air-tightened paper bag inner coated with polyethylene. To maintain the quality, the bags are stored away from light and in dry storage.