Processing and value added products


Processing
    Processing
    • The quality of cured turmeric is assessed on the basis of several factors, such as the curcumin content, the organoleptic character, the general appearance, size and physical form of the rhizome.
    • The method of curing turmeric consists of boiling or steaming the prepared fresh rhizomes in water, drying in the sun and finally peeling or polishing.
    The following steps are involved in the processing.
    Cleaning
    • The harvested rhizomes are cleaned of other extraneous matter adhering to them and the roots are removed. Only the good fingers separated from the rhizomes are used for curing.
    Boiling
    • The process is aimed at destroying the vitality of the fresh rhizomes and to obviate the raw odour, to reduce the drying time, to gelatinise the starch and give a more uniformly coloured product.
    • The fingers and mother rhizomes are separated and cured separately, since the mother rhizomes take a little longer time to cook. The boiling is done in galvanized iron vats or pans or other containers of a suitable size. A pan of 1 m length, 0.62 m breadth and 0.48 m depth is found to be suitable.
    • The cleaned fingers (approximately 50 kg) are placed in a trough, which is 0.9 m x 0.55 m x 0.4 m in size and made of GI sheets with an extended parallel handle. This perforated trough in which the fingers are placed is then immersed in the pan.
    • An alkaline solution prepared by dissolving 100 g sodium bicarbonate (NaHCO3) or sodium carbonate (Na2CO3) in 100 ml of water is poured into the trough so as to immerse the turmeric fingers. The whole mass is boiled till the fingers become soft. This can be
    • tested by piercing it with a wooden needle. If the needle passes through the rhizome without much resistance, the softness is confirmed. Usually the boiling is continued for 45 to 60 minutes until frothing occurs and white fumes appear emitting a characteristic turmeric odour.
    • The cooked fingers are taken out of the pan by lifting the trough and draining the solution into the pan. The alkalinity of the boiling water helps the development of an orange-yellow tinge to the core of the turmeric. The drained solution in the pan can also be used for cooking another lot of turmeric along with the fresh solution prepared for the purpose.
    • Usually, the cooking of turmeric should be done within 2 or 3 days after harvesting. The colour and aroma of the final product depends greatly on the stage at which the boiling is stopped. Therefore, only skilled persons should be employed for this job. Both delayed cooking and over-cooking will spoil the quality of the final product.
    Drying
    • The cooked fingers are sun-dried by spreading them out on a bamboo mat or on the drying floor for 5-7 days until the moisture reduces to 8-10%, which is fit for storage and sale.
    • The sun-drying of sliced turmeric in particular gives a slight surface bleaching effect on the colour.
    • During the night-hours, the material should be heaped and covered over to protect it from dew.
    • It takes 10-15 days for the rhizomes to become thoroughly dry, when they become quite hard and brittle, and break (with the fingers) with a metallic sound.
    Polishing
    • This operation is done in order to smoothen the rough and hard outer surface of the boiled and dried turmeric.
    • It also improves the colour of the product from a dirty-brown to a bright-yellow.
    • There are two types of polishing; they are Hand polishing, and Machine polishing.
    Hand polishing
    • This method is simple and involves rubbing the turmeric fingers wrapped in several folds of gunny cloth on a hard surface with the hands or by trampling them under the feet or shaking the rhizomes mixed with stones in a long narrow gunny bag or in a bamboo basket.
    • The improved method is through the use of a hand-operated barrel or drum mounted on a central axis, the sides of which are made of expanded metal mesh.
    • When the drum filled with turmeric is rotated, the abrasion of the surface against the mesh as well as by mutual rubbing against each other will polish them effectively.
    Machine polishing
    • The machine used for polishing consists of a hexagonal wooden drum, mounted on a central axis and rotated by power.
    • These power-driven drums are gaining popularity because a higher degree of polishing (smoothness) can be attained by this method.
    • The capacity of these drums is also high compared to the hand-operated ones and, hence, the output is also higher.
    Colouring
    • The colour of turmeric always attracts buyers.
    • Thus, giving the required colour externally to the rhizome is an important step in the processing of turmeric.
    • For this, the boiled, dried and half-polished fingers are placed in a basket, which is shaken continuously in a prepared emulsion.
    • They are later sun-dried.
    • The colour emulsion comprises of alum (0.04 kg), turmeric powder (2 kg), castor seed (0.14 g) or sodium bisulphate (30 g) and concentrated HC1 (30 m1).
    Grading (Indian standards)
    Turmeric is included in the list of spices which must have an Agmark' grading before they can be exported from India. Three grades of finger turmeric, two of bulb turmeric and one grade of powdered turmeric are specified, as follows:
    1. Finger turmeric, other than the Alleppey variety is sub-graded into 'Special' Good' and 'Fair'.
    2. Alleppey finger turmeric is sub-graded into 'Good' and 'Fair'.
    3. Rajapore finger turmeric is sub-graded into 'Special'. 'Good' and 'Fair'.
    • The maximum limit for extraneous matter in the prime sub-grades of the above grades of whole turmeric is 1.0%.
    • In the case of Alleppey finger turmeric, which is exported to the United States, the content of extraneous matter according to the specifications of the American Spice
    • Trade Association is usually less then 0.5%. In the case of the turmeric powder, the characteristics are more exacting.
    • The maximum percentage limits are specified for moisture, total ash, acid insoluble ash and starch.
    • The ASIA (1) and FDA (2) chemical and physical specification of turmeric are as follows: (1) Whole dead insects by count 3; mammalian excreta (mg/lb) 5; other excreta (mg/lb) 5; mould (% by weight) 3; insect defiled (% by weight) 2.5 (2) volatile oiV curcumin (% min) 5; moisture (% max) 10; ash (% max) 8; acid insoluble ash (% max) 1.0, average bulk index (mg/100 g) N/A.
    Value-added products
    The value-added products of turmeric are
    • Curcuminoids,
    • Dehydrated turmeric powder,
    • Oil and
    • Oleoresin.

Last modified: Sunday, 11 March 2012, 6:23 AM