The baked products for which cassava flour is the basic ingredient are known commercially as tapiocas or tapioca fancies. In Malaysia and some other areas these products are commonly known in the industry as sago products. The term probably originated with the Chinese production of sago-palm starch products. The manufacture of tapioca fancies is a logical follow-up of the production of the flour itself in the countries of origin. Separation of the processing of the flour and of the derivatives would be illogical. Many medium-size and larger factories are also equipped for the manufacture of such baked products as flakes, seeds, pearls, and grist.

These products are made from partly gelatinized cassava starch obtained by heat treatment of the moist flour in shallow pans. When heated, the wet granules gelatinize, burst, and stick together. The mass is stirred to prevent scorching. They are manufactured in the form of irregular lumps called flakes or of perfectly round beads 16 mm in diameter known as seeds and pearls. The grist is a finer-grained product obtained by milling gelatinized lumps, and siftings and dust are residual products of the manufacture of seeds and pearls.

Preparation of wet flour

The raw material for baked products is the flour scooped up from sedimentation tanks or tables after the supernatant, or excess water, has been drained and the “yellow” flour scraped off. Clearly the use of moist starch, an intermediate stage in the processing of the Dour, is economically advantageous.

Only very white first-quality flour can be used in the manufacture. To obtain this, sulfurous acid is often added in the first sedimentation. This chemical should, however, be washed out as completely as possible by a second sedimentation in clean water; any traces of the acid left in the flour tend to spoil the quality of the end product. It is strongly advised not to use active chlorine preparations in this case, as they influence the agglomeration of the starch into pearls and other forms in an unfavourable way.

The cake of moist flour, containing about 45 percent water, is broken up by a small mill, spades or pressing it through frames strung with steel wire spaced about 10-20 cm apart, after which the lumps are rubbed through a screen of about 20 mesh/inch to produce a coarse-grained moist flour.

At this stage the flour is ready only for gelatinization and the production of flakes; to prepare pearls and seeds, the small aggregates of moist starch should be subjected to a process of building up and consolidation. which gives them the size and cohesive strength desired for the further treatment. The operation is known by the Indonesian name as the gangsor method. A portion of the moist starch is put into a long cylindrical bag of twill cloth which is held at each end by one man. Together. with a rhythmical strong jerking movement, they throw the mass of starch lumps from one end of the hag to the other. After a few minutes of this treatment the irregular lumps have grown into beads of varying size and have gained in firmness. Another portion of the moist flour is added and the gangsoring is continued. the operation being repeated until the heads have grown more or less to the desired size. Depending on the skill of the worker. the size of the starch balls is fairly uniform. Curiously enough, the knack of gangsoring is achieved only by a fraction of all workers, so the operation should be classified as skilled labour.

In Malaysia the flour is fed into open, cylindrical rotating pans about 0.9 m in diameter and 1.2 m deep. During rotation the starch grains are forced to adhere together in the form of small particles or beads. The resulting product depends on the speed and the length of time of rotation.

After gangsoring, beads of the right size are sorted out by screening between plates with circular holes corresponding to the required dimensions.

Gelatinization

In gelatinizing, starch undergoes a radical alteration in molecular arrangement, with a concomitant change in properties. From a practically insoluble product of semicrystalline structure it becomes an amorphous substance, miscible with water in any proportions at sufficiently high temperatures, giving viscous solutions which after cooling set to a semisolid elastic mass: a jelly, or gel.

This process may be brought about by the action of chemicals or by heating in an aqueous medium; only the latter case is of interest here. The onset of gelatinization is characterized by a loss of granular, structure which also promotes swelling; both processes can easily be followed under a microscope. With cassava starch, gelatinization sets in at about 60°C, and the process is completed at about 80°C. The point of gelatinization depends to a certain extent on granule size, the smaller granules being more resistant to swelling.

In the manufacture of baked products, the treatment is kept at a moderate temperature so as to cause gelatinization only in the surface layer of the lumps of moist starch. The product obtained therefore consists of agglomerations of practically raw starch enclosed by a thin layer of the tough and coherent gelatinized form.

For flakes, gelatinization is performed in shallow pans about 60-90 cm in diameter and 20-25 cm deep, having the profile of spherical segments, which are placed in holes on a brick oven and heated on a moderate fire. In order to prevent burning the starch, and perhaps also as an aid in achieving an end product of the desired lustre, the pans are wiped beforehand with a towel soaked in an edible oil or fat. Shorea (tenkawang fat) or Bassia (illipe fat), having properties approaching those of cocoa butter, seem to be preferable for the purpose, but groundout oil is used as well. Furthermore, it is necessary to rake the mass continuously with large forks, both to prevent burning and to ensure uniform gelatinization. From time to time a sample of the flakes is tested for toughness until proper consistency is attained.

The hand-baking process can also be applied in the manufacture of pearls and seeds, but rather irregularly shaped beads are obtained, inferior in colour and in other qualities.

Better mechanical methods for obtaining a first-rate product have long been known. In one of these, gelatinization is performed with the direct application of steam. The starch beads are poured onto plates in a rather thick layer, the plates forming a conveyor belt which is slowly drawn through a tunnel charged with steam. In this way, uniform gelatinization is ensured.

A device widely used in Indonesia (Java), which combines the advantages of several other methods, consists of a hollow cylinder revolving on rollers and driven by motor via a suitable transmission, all resting on a foundation which at the same time serves as a hearth with fire-holes. Flanges on the rollers hold the revolving drum, which is inclined at an angle of about 10°. The raw beads are poured into a gutter at the higher end of the drum at such a rate that they spread into a single layer by the time they reach the hotter parts of the inner surface of the drum. The width of this flow of beads need not exceed 15 cm if the drum has a diameter of 80 cm and revolves at 8-10 rotations per minute. A suitable length for the drum is 4 m. In rolling down, each bead covers the same long, screw-shaped path across the inner drum surface, and in the hotter regions a gradual gelatinization sets in, the rotation of the drum preventing overheating. By the rolling movement, moreover, the surface of each bead is uniformly gelatinized and at the same time becomes perfectly spherical in form.

Drying

The gelatinization process in the hand-worked flakes changes the moisture content of the product by no more than a few percent, and the same applies to the steam-treated pearls and seeds. In the drum described above, drying sets in parallel with the gelatinization and may be promoted by ventilating the drum, but the removal of water here is also incomplete.

Thus, in general, a final drying after gelatinization is necessary in order to bring down the moisture content to the desired level of about 12 percent. Drying in this case is best accomplished in chamber driers of the circulating type. For instance, in a chamber drier for pearls and seeds the initial temperature should not exceed 40″C lest further gelatinization and bursting of the beads set in. Toward the end of the treatment the temperature may be raised to 60-70ºC. With efficient exhausters, drying may be completed in 1 1/2-2 hours. Normally, from 16 tons of moist starch, 10 tons of the dried product are obtained.

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Source: FAO.org