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< prev - next > Food processing Herbs and spices KnO 100321_Turmeric Processing (Printable PDF)
Turmeric (Curcuma domestica) is an erect perennial plant
grown as an annual crop for its rhizome (underground
rootlike stem bearing roots and shoots). It belongs to the
same family as ginger (Zingiberaceae) and grows in the
same hot and humid tropical climate. The rhizome is a
deep bright yellow colour and similar form to the ginger
but slightly smaller. The plant originated in the Indian
sub-continent and today India is the worlds leading
producer and consumer of turmeric. It is also produced in
China, Taiwan, Bangladesh, Indonesia, Sri Lanka,
Australia, Africa, Peru and the West Indies. Turmeric
plays an important role in Indian culture- it is an essential
ingredient of curry, used in religious festivals, as a
cosmetic, a cloth dye and in many traditional health
remedies. The spice is sometimes referred to as ‘Indian
Figure 1: Fresh turmeric.
Photo: Practical Action / Neil Noble
Turmeric production
The Turmeric plant is propagated by planting pieces of the previous season’s rhizome, which
grows to form plants of about 0.9 metres tall. The plant has long stemmed leaves and pale
yellow flowers and requires a loamy soil. It grows in a wide range of climatic conditions, but
does require rainfall of between 1000 and 2000mm a year. It can grow in locations that are up
to 1220m above sea level.
Turmeric is harvested when the plants are between 7 and 10 months of age, when the stems and
leaves start to dry out and die back. The whole plant is removed from the ground, taking care
not to cut or bruise the rhizomes.
The leaves are removed from the plant and the roots carefully washed to remove soil. Any leaf
scales and long roots are trimmed off. The side (lateral) branches (which are known as the
fingers) of the rhizomes are removed from the main central bulb (known as the mother). The
mothers and fingers are heaped separately, covered in leaves and left to sweat for one day. The
‘mothers’ are the preferred material for planting the following year.
Before drying, the turmeric rhizomes have to be cured. This involves boiling the roots to soften
them and remove the raw odour. After curing, the starch is gelatinised, which reduces the drying
time required, and the colour is uniformly distributed throughout the rhizome.
The specifications for curing turmeric vary from different places. The Indian Institute of Spice
Research and the Agricultural Research Centre recommend boiling in plain water for 45 minutes
until froth appears at the surface and the typical turmeric aroma is released. Using this method,
the colour will deteriorate if the rhizomes are boiled for too long. However, if not boiled for long
enough, the rhizome will be brittle. The optimum stage is reached when the rhizomes are soft to
touch or can be pierced by a blunt piece of wood.
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