Rice starch is not as common as potato, maize (corn) or tapioca starch but it does have important functional food properties.
It is used as ingredient in various industrial and food products. Unlike other starches it has a small size which is uniformly distributed, white with a clean odour. It is especially useful in baked and dessert products.
The small granular size of the starch imparts a softer texture than other starches of other sources, relatively high water retention and low syneresis, suggesting it could be used as a fat substitute.
Extruded And Puffed Rice Properties
The variety of rice has a profound effect on the extrusion of rice products. In the early years of study of rice extrusion Roberts et al., (1951) used a commercial parboiled rice and found that short-grain varieties produced a greater expansion than the long-grained ones.
The main factor of interest is expansion ratio or volume. Rice expands very differently compared to corn (maize) and tapioca starches when cooked and extruded. Thee give an expansion ratio of 6 and 3 respectively.
Chinnaswamy and Bhattacharya (1983) found that for rice in particular the variety was more significant than perhaps with other grains and cereals where starch is the critical component. They also noticed that the starch extracted from these different rice varieties also performed almost in parallel with the rice varieties themselves which just confirms to a great extent that starch is the key component in extrusion studies.
The rice incidentally is parboiled before it is extruded.
The expansion ratio of extruded rice increases exponentially from 4 to 6 as the total amylose (%w/w) rises from 5% to between 25 and 26%. Interestingly, the expansion ratio rapidly drops back to 4 as the amylose content rises above 28%. The same effect might be observed with feedstocks from other sources.
The insoluble amylose content (%w/w) which is amylose left after hot water extraction, showed a similar pattern of behaviour to total amylose content. Here the expansion ratio rose from just below 4 to above 6 exponentially as the insoluble amylose content rose from 4% to 13% and then dropped away just as drammatically as the amylose content rose above 13% to below 4 when the insoluble amylose content was 20%w/w.
References
Antonio, A.A. and Juliano. B.O. (1973). Amylose content and puffed volume of parboiled rice. J. Food Sci. 38: pp. 915
Chinnaswamy, R. and Bhattacharya, K.R. (1983). Studies on expanded rice. Optimum processing conditions. J. Food Sci. 48(6):
Juliano, B.O., Oilate, L.U., and del Mundo, A.M. (1965). Relation of starch composition. protein content. and gelatinization temperature to cooking and eating qualities of milled rice. Food Technol. 19: pp. 1006
Roberts, R.L., Houston, D.F.. and Kester, E.B. (1951) Expanded rice product. A new use for parboiled rice. Food Technol. 5: pp. 361.
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