Rice starch: Rice starch granules are quite small and are embedded in a protein matrix.
To separate them from protein, broken rice is steeped for 24 hours in 5 times its weights of 0.3 per cent caustic soda.
The caustic soda treated granules are washed, dried and ground into flour. The flour is then mixed with about ten times its weight of caustic soda solution.
This removes gluten. After 24 hours, the starch that settles down is removed, washed and dried. Rice starch is used in puddings, ice-creams and custard powder. It forms a tender opaque gel.
Bran includes several sublayers within the pericarp and the aleurone layer. Breakage of the white rice kernel during milling also results in small fragments of the endosperm becoming part of the bran fraction. These broken fragments are primarily starch and normally contain 10-12 per cent of bran.
If the bran is subjected to a short term high temperature after milling, the lipase activity is destroyed and stabilized bran of edible grade is produced.
Bran produced from parboiled rice is already stable and does not require any further stabilization treatment.
Stabilized or parboiled food grade rice bran is normally finely granulated light tan in colour and it has bland flavour and can be used in preparation like bread, snacks, cookies, and biscuits. In addition rice bran is a very rich source of dietary fibre so it is an effective stool bulking agent.
Parched rice products:
About 4-5 per cent of total supplies of rice in India is converted into rice products-parched rice, parched paddy and rice flakes.
Parboiled rice is soaked in salt water to increase the moisture to about 20 per cent. Parched rice is prepared by throwing rice in sand heated to a high temperature in iron or earthen pan.
On stirring rice begins to crackle and swell. Then the contents of the pan are removed and sieved to separate the parched rice from sand.
Parboiled rice is used in making parched rice. Parched rice is a crisp product with a greyish to brilliant white colour and is sold either salted or unsalted. It is eaten as such or mixed with buttermilk and then consumed.
Parched paddy or puffed rice:
Sun ripe paddy is filled in earthen jars and is moistened with hot water. After 2-3 minutes, the water is decanted and the jars are then kept in an inverted position for 8-10 hours.
The paddy is exposed to sun for a short time and then parched in hot sand 190-210°C for 40-45 sec.
During parching, the grains swell and burst into soft white product. The parched grains are sieved to remove sand and winnowed to separate the husk.
Flaked rice is made from parboiled rice. Paddy is soaked in water for 2-3 days to soften the kernel followed by boiling water for a few minutes and the water is drained off.
The paddy is heated in a shallow earthen vessel or iron pan till the husks break open. It is pounded by an iron pestle or use iron roller which flattens the kernel and removes the husk.
The husk is separated by winnowing. Flaked rice is thin and papery and of white colour.
Advantages of parched rice products:
(i) Easily digestible and hence good for children and old people.
(ii) Readily available to eat due to faster cooking.
(iii) It adds variety in the diet.
(iv) Since iron pans are used, iron content is increased.
(v) Improves flavour and texture.
Basmati rice has its origin in the foot-hills of the Himalayas. When cooked, it is nonsticky and soft.
Basmati grain quality components are intermediate amylose content, intermediate gel consistency, and gelatinization temperature.
Kernel elongation without significant increase in breadth and possess pleasant aroma which are ideal for making pulav.
Aromatic rice varieties contain acetyl 1-1 pyrroline as the major aroma principle while cooking. These are characteristic of the rice variety.
Non-aromatic rice varieties can be flavoured by adding one or two fresh leaves of Pandanus latifolius while cooking as they contain 2-acetyl 1-1 pyrrole.
Freshly harvested rice cooks to a sticky lumpy mass, swells but a little and yields a thick gruel; these drawbacks tend to disappear as the rice is stored for a few months.
The ageing process is characterized by an initial increase followed by steady decrease in the power of hydration.
This is due to a slow but steady decrease in the solubility of amylose, starch and protein and in the physical loss of solids during cooking, a slow but steady increase in the gelatinization temperature a decrease in the intrinsic viscosity of the starch and in the settling rate of a rice-flour suspension, an initial increase followed by a steady decrease in paste viscosity and a steady increase in the hardness and decrease in stickiness of cooked rice.
These results suggest that the rice grain or its constituents become more organised or reinforced as they age.
The cell walls are disrupted earlier in new rice during cooking. The ageing process is hastened by high total insoluble amylose content, by a high storage temperature, by exposure to light and by milling and vice versa.
Changes in fat and fatty acid composition also occur. The rice lipids are liable to oxidation and/or hydrolysis during storage and thereby contribute to the flavour characteristics of aged rice.
Total saturated fatty acids increase steadily and unsaturated fatty acids decrease during storage.