An improved alkali reaction test for rice quality.

An improved 9-point scoring scale for the alkali reaction test for rice (Little, Hilder &
Dawson, 1958) has been devised by studying the successive stages of degradation of
rice kernels of individual varieties by increasing concentrations of alkali. Each variety
was just attacked by a certain concentration of potassium hydroxide and was essentially
fully degraded by a 0-7-0-8% higher concentration of the alkali. Nine distinct stages
could be distinguished in this degradation process based on the amount of residual
chalky substance in the degraded kernel, the diameter of the collar, and the consistency
of the collar. A concentration of 1.4% KOH was found to give the maximum
spread of the scores among different varieties. The test could be conducted in ordinary
Petri dishes and at room temperature for 18-24 hr.
Different rice varieties exhibited three types of reaction. Reaction type A was
characterized by progressive cracking and corrosion; type B by progressive grilling
and cottony transformation; and type C by opening and splitting with gradual dense
cottony transformation of the kernel when treated with successively higher concentrations
of KOH. The implication of this reaction type on the quality characteristics of
a variety is not known, but most indicas gave reaction of type A, and japonicas type C.