Preservation of arecanut with husk

Several age-old and crude methods are followed for preserving arecanut to keep the moist chewing feel. Fresh ripe arecanut is used for chewing in Assam and Kerala. In Kerala the fresh ripe fruits are stored in water and are known as ‘neetadaka’. The nut contains mainly polyphenols, polysaccharides, fibre and fat. The husk contains easily fermentable substances such as sugars and pectins. These are easily attacked by bacteria when stored in water. The husk is loosened and the bright orange color is lost. Because of fermentation foul smell is produced which penetrates into the edible nut. In Assam fresh ripe arecanut is stored in pits. The husk gets attacked by fungus and the fat and polysaccharides from the core is eaten away by bacteria. The nut is thus rendered unsuitable for consumption.

To avoid the problems occurred during the preservation of fresh ripe arecanut in garden fresh condition, a method of preserving fresh ripe arecanut by steeping in mixed preservative solution has been developed. It consists of washing freshly harvested areca fruits in chlorinated water to remove the adhering dirt. The fruits are then blanched in boiling calcium chloride (0.2 %) solution. This treatment reduces microbial load, destroys the enzymes and preserves the firmness of the husk. The fruits are then kept immersed in a solution containing 0.1 % sodium benzoate and 0.2 % potassium matabisulphite acidified to a pH of 3.5 to 4.0 using hydrochloric acid. The fruits can be preserved in fresh ripe condition for 10-12 months. Fresh bright colour and firmness of the skin are maintained. Stored fruits will be free from foul smell without any significant changes in the constituents.

Drying of ripe nuts:

Fresh ripe areca fruits are dried in the sun by spreading in single layers for 35-40 days. The fruits are turned over at regular intervals to ensure uniform drying. To facilitate uniform drying, some times the outer skin is peeled off. Later on they are dehusked and sent to market. Whole dry nuts are known as ‘Chali’ or ‘Kottapak’. The well known grades of ‘chali’ in descending order of size are ‘moti’, ‘Srivardhan’, Jamnagar’ and ‘Jini’. Other characteristics which are valued are uniformity in size, absence of immature nuts, surface cracking, husk sticking, fungus and insect attack and good cutting feel, inside structure and taste.

Lack of attention during drying, unexpected rains and unsuitable wet drying yards contribute to onset of fungal infection and result in a poor quality final product. In Kerala and Assam harvesting season coincides with the monsoon and sun drying is difficult. The main areas producing ‘chali’ nuts are Karnataka, Kerala and Assam. Bangladesh, Malaysia and Sri Lanka also produce ‘chali’ nuts.

To facilitate drying, areca fruits are cut longitudinally into two halves and then dried in the sun. Later they are scooped out and sent to market. This half-cut form is known as ‘parcha’. It is produced mainly in Kerala and Karnataka. In Karnataka its production is concentrated in South Kanara, Sirsi and Kumta area. In Kerala its production is confined to Kasaragod, Nedumangad and Kottayam areas. Small quantities of this type are produced in Assam, Maharashtra and West Bengal. In West Bengal they are processed in parts of Cooch-Bihar and Jalpaiguri districts.

A mechanical through-flow drier is available for making ‘chali’ and ‘pacha’. Drying can be completed in about 60-70 hrs spread over 7-8 days at progressively increasing temperatures between 45-700 C. The drying schedule consists of successive 8 hr. drying period followed by 16 hr. equilibration outside the drier. The parts of the drier are a drying chamber with four perforated trays, a heat exchanger, fuel furnace and a centrifugal blower. ‘Kalipak’ can be conveniently dried using this drier. Small holders’ multipurpose dryer, using agricultural waste as fuel developed by CPCRI can be used for drying arecanut. About 150 kg of arecanut can be dried in this dryer in 100 hrs (10 days).

Storage of nuts:

Lack of proper drying yards, improper spreading and turning of nuts and exposure to unexpected rains during the drying period lead to microbial infection of the husk as well as kernel. Elimination of soil contact by the harvested nuts is beneficial in reducing nut infection since it is the prime source of infection. Harvested nuts treated with copper oxychloride showed less infection. Steeping the nuts in Bordeaux mixture followed by drying on cement floor reduced the percentage of infection significantly. Polythene lined gunny bags can be used with advantage over plain gunny bags for storing nuts. Storage of arecanut in air tight bins also minimizes the fungal infection.

Insect damages by feeding on the inner central core and due to this, holes appear on the surface of the nuts. The insect damage is maximum during the rainy months when the humidity is high and minimum during winter and summer months. Arecanut beetle (Cocotrypes carpophagus Horn) is the most important storage pest of arecanut. The damage is mainly caused by adult beetles, which bore into the nuts and feed on the inner contents. The infested nuts show holes of 0.6-1.0 mm diameter. Both adults and grubs of coffee bean weevil (Araecerus fasciculatus D.) have been reported to damage stored arecanut. Infested nuts have holes 1.5-2.5 mm in diameter. Unhusked nuts with intact perianth are not infested by this insect even after one year of storage. Cigarette beetle (Lasioderma sp.) is a widely distributed storage pest infesting stored arecanuts throughout the year. Both the adult and grubs damage the nuts and make them as powder. The caterpillars of Rice moth (Corcyra cephalonica) construct galleries of silk and frass over stored nuts, remain within and feed on them.

Dehusking

A simple dehusking devise has been standardized by CPCRI., Kasargod. The out turn with this devise is 60 kg of husked nuts in the case of dry nuts and 30 kg in the case of green nuts. The cost of the devise is about Rs. 250

Kalipak

Areca fruits of 6-7 months maturity are used for making this important class of processed arecanut. The main processing centers are Karnataka and Kerala. The outer skin of the husk will be green in color and the immature nut will be soft. The processing consists of dehusking, cutting the soft nut into pieces, boiling the cut pieces with water or a thin extract from a previous boiling, ‘Kali’ coating and drying. Depending upon the number of cuts, different types representing pieces of various sizes and shapes are recognized. ‘Api’ or ‘unde’ is the type which is processed without any cutting. ‘Batlu’ or Ottavettu’ is cut transversely into two halves. ‘Choor’ is produced after several longitudinal cuttings. It is further divided into sub-groups namely ‘mukkachoor’, edachoor’, ‘pettichoor’ etc, in the descending order of thickness. Cutting the nuts both transversely and longitudinally 3 to 4 times produces ‘Podi’. ‘Erazel’ and ‘Chalakudi’ are thin slices produced by slicing the nuts transversely or longitudinally.

During the boiling operation, the same water is used for boiling 2 to 3 batches of arecanuts. The extract so obtained is concentrated to get ‘Kali’. After boiling, the pieces are coated with ‘Kali’, which imparts a good glossy appearance. In interior Karnataka the boiling and ‘kali’ coating operations are combined into single operation. The cut nuts are boiled in a thicker extract called ‘Chogaru’. ‘Lylon’ is an unboiled variety made from green arecanuts. The nuts are cut into 5 or 6 discs transversely and dried without kali coating. The nuts will be slightly more mature than those used for ‘kalipak’. Tamil Nadu and Andhra Pradesh are important consuming areas. The grades in increasing maturity and therefore decreasing grade are ‘Chittanum’. ‘Virivu’ and ‘Kora’. ‘Nayampak’ is also unboiled type and is made from immature arecanuts after cutting once transversely and drying.

Both sun drying and oven drying are practiced by ‘Kalipak’ processors. A well dried product with a dark brown colour is preferred. Other desirable qualities in ‘Kalipak’ are crisp chewing feel, glossy appearance, a well toned astringency and absence of over mature nuts.

Sagopalm nut is used for adulterating ‘Kalipak’ samples. The cut pieces have a similar cut surface and are coated with ‘kali. The chemical analysis revealed that sagopalm nuts have lower polyphenol and fat contents but have higher polysaccharides and fibre contents. Other adulterants used after ‘kali’ coating are sweet potato and tapioca and they are comparatively easier to identify.

Scented Supari:

There are many varieties of scented suparis. The processing consists of breaking the dried nuts into bits, blending with flavour mixture and packaging. Roasting of bits in oil or ghee is also practiced. Batlu adike is mainly used for making scented supari. In North India scented supari is made from ‘Chali’ nuts in addition to those made from ‘Kalipaks’. The chali supari is more popular. About 75 per cent of the marketed produce is consumed after processing either as kalipak or chali. The flavoring varies depending on the region and it is a closely guarded secret. Rose essence is used in most of the cases. Coconut grating which were used in earlier days are now avoided as they get fungal infection.

Taste characteristics of nut:

Astringency is the characteristic taste of arecanuts. Polyphenols, which are present abundantly in it, are responsible for this. Astringency is felt as a contracting and drying sensation. The astringent characteristics in arecanut decreases with maturity.

Colour development on chewing

The chewing of arecanut with betel leaf and slaked lime is very popular in India and neighboring countries. In addition to the stimulation and pleasant taste, chewing results in bright red colour of the mouth. Catechin turns brilliant red immediately after addition of alkali (pH 10) which gradually turns reddish brown on keeping for more than two hours. Similarly, the leucoanthocyanidins, which become dark red initially, turn dull brown in about two hours and pale brown on keeping over-night. The polymeric proanthocyanidins, which contain mostly leucocyanidin units also behave similarly. The colour change of all the compounds at pH 8 is basically similar though rate of change is different.