Nutritional and toxicological evaluation of ‘black tip’ rice

Abstract

A popular newly introduced rice variety Phalguna (RP 6-17) was found to be susceptible to the development of black colour at the tip of the grains. On parboiling the paddy, the degree of discoloration intensified and occasionally even the entire kernels were found to be discoloured. In the affected grains the breakages during milling were considerably higher than the unaffected grains. There was not much difference between the nutrient composition of the black tip and normal grains. However, contents of iron and free sugar were found to be higher in black tip grains than that in normal grains. A positive correlation between extent of discoloration of the grains and the glucosamine content was observed suggesting that this criterion could be used as an index of fungal contamination. Species of Alternaria and Curvularia were found to be more predominant in black tip raw rice than normal raw rice. Acute toxicity studies in chicks and ducklings and short-term toxicity studies in rats did not indicate ill effects.

Black Tip Discoloration in Indian Rice. Effect of Extended Milling on Milling Characteristics, Chemical Composition and Cooking Quality

“…Protein, ash, reducing, nonreducing sugars and free fatty acids increased and amylose decreased as the number of black tip discolored kernels increased. The results are in agreement with those of earlier workers (Bhat et al 1982;Duraiswamy and Marriappan 1983). Contamination of fungi might have affected the protein and ash content in the black tip kernels.…”

“…However, aflatoxin was not detected in any of the samples. Earlier reports had indicated the presence of similar mycoflora in black tip discolored paddy and rice in various regions of the country (Bhat et al 1982).…”

“…Under normal conditions the field fungi produce no visible effect on the quality of rice. However, wet weather conditions at the time of maturity of kernels promote fingal growth leading to varying degree of black tip discoloration (dePadua 1979;Bhat et al 1982). Black tip kernels are reported to be nontoxic to rats, ducklings and chicks (Bhat et al 1982).…”

“…However, wet weather conditions at the time of maturity of kernels promote fingal growth leading to varying degree of black tip discoloration (dePadua 1979;Bhat et al 1982). Black tip kernels are reported to be nontoxic to rats, ducklings and chicks (Bhat et al 1982). However, they contain hgher levels of phenol and amylase (Duraiswamy and Mariappan 1983).…”

“…This lowers the quality and creates a problem of disposal of the rice. Milling of rice to 10% degree of polish could be effective in reducing the incidence of black tip discoloration (Bhat et al 1982). However, commercially the rice in Inha is milled to 5 6 % degree of polish.…”