Turmeric : Processing of turmeric

Turmeric processing technology
Botanical name of turmeric is curcutha longa L. It is an important spice which is used for yellow colour and special flavour. Rhizomes of turmeric are often found in violet yellow colour. Central rhizomes are like tubers and small rhizomes like fingers coming out from the central one. It contains 1.8 to 5.4% curcumin due to this it has yellow colour. Some amount of starch and 2.5 to 7.2% oil is also obtained. It is used in the form of spices for colouration and flavour. In this very form it is used in medicine and cosmetic goods manufacturing. There are two types of turmeric produced in central India. One has solid and dark colour and the other long, soft and light colour.

Processing of turmeric by traditional method

In India, at various places different methods and equipments are used, but basic method is mentioned below in a process flow sheet.

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Washing

At first rhizomes are separated after digging out from the soil and these are washed, so that particles of soil, spray residues and unuseful particles attached with the rhizomes are removed. For this rhizomes are kept soaked in water throughout the night. Later on rhizomes are taken out and water is sprayed. This process can be achieved by soaking and spraying equipment. Spraying is done at low pressure and wide angle jet or with high pressure jet. At the time of washing rhizomes are divided in two parts. First part from middle is called mother rhizomes. The second part of it which is long and thin is called Doctor Rhizome. Mother rhizome is kept for seed while Doctor rhizomes are further processed and sold.

Boiling/Blanching/Cooking:

The next step of processing is boiling or blanching. Traditionally boiling is done in metal or mud pots alongwith ¾ water. Top of the pots are covered with a lid or dry leaves. Boiling process is continued till foams and white foams start coming out. These come out with a special quality of flavour. Rhizomes are tested by pressing with fingers. If rhizomes are soft and inner colour has become yellow instead of red then this process is said to be complete.

By using developed method of boiling or blanching both colour and quality are improved. Time taken is less. In the developed method bulbs are treated with 0.1% Soda (Sodium Carbonate, Sodium bicarbonate or Ammonium Carbonate) and water solution. The time required for this process is 30 minutes to 6 hours. Boiler is used in the developed method which is metal kettle open from the top. Soda solution is filled in it and it is heated from the bottom by electric heater or fuel oil. Perforated frame loaded with turmeric tubers or bulbs are sunk here. Water from all sides of perforations enters inside making turmeric tubers soft. After 30 or 40 minutes bulbs/tubers are taken up and tested alongwith the frame.

Drying

Cooked rhizomes are cooled first and spread slowly in the yard for drying. It takes at least 10 to 15 days for drying in the sun. Tubers are brought up and down in the middle of drying so that all are dried well. Mother rhizome takes comparatively more time while Doctor rhizome dries up quickly. Therefore these are dried separately also. After drying these become hard and solid. Completely dried turmeric holds 6% moisture content.

PolishingDried rhizomes are rubbed against ground or below the foot to take out the hard layer over them and small roots are removed. By this process colour of turmeric becomes bright or shining. Later on removed roots, light garbage and thin layerings are cleaned.

Machine is also used for polishing. For this a drum having 0.9m diameter and 0.6m length is used. It is kept horizontally on a shaft and operated by a handle. Average capacity of this machine comes to 32kg per batch. Dry turmeric 32kg approx.is filled and polishing is done at least for 7 minutes. During this period water is also sprinkled which causes improvement in the colour of turmeric.

Colouring

Exporting turmeric is given special colour by mixing yellow so that powder and processed materials can give better look and quality. Cleaning is done by two methods. One is dry colouring and the other wet colouring. In the first process dry powder of yellow colour is sprayed on boiled turmeric and rightly mixed. Powder is known as middle crome. In the wet colouring process its solution is prepared in water which is sprayed on rhizomes and mechanically mixed. After colouring is complete for one week these are dried. Later on these rhizomes are kept in sacks and closed for exporting.

Grinding or Powder making

Traditionally dried and polished turmeric are cut into pieces and beaten in mortar and pestle. After this is milled or ground with hand operated chakki. Hammer mill is also used for grinding. Powder should be so fine that it passes through 300 micron sieve and nothing is left over the sieve.