Old rice is not good for health

May 8, 2008
By Syed Akbar
Hyderabad, May 7: Old rice cooks well but it may cause severe health problems
including poisoning if it is not washed properly.
Old rice is infested by fungus that release aflatoxins, which are ranked
among the most carcinogenic substances known to science. A study conducted by the
city-based Directorate of Rice Research revealed that most of the rice
available in farmer fields, godowns and consumer markets is infested by a type of
fungus known as Aspergillus. The worst is the rice which is 36 months old or more.
As part of the study, senior DRR scientists CS Reddy and K Muralidharan
collected as many as 900 rice samples covering 250 varieties in 20 States
across the country. The collection was from areas exposed to rain/flood or stored in
storage bins or from the whole sale/retail market places.
The team isolated aflatoxin-producing mycoflora, Aspergillus species. "Aspergillus contamination was detected in most of the seed samples. A. flavus, A. niger, A. ochraceus and A. parasiticus were identified from these samples. In general, the Aspergillus contamination was more in the seed samples collected from the crop/seed exposed to rain followed by seed stored for long periods," they pointed out.
Around 60 to 84 per cent of the rice samples collected were found positive to
Aflatoxin B1. Of the samples collected from different sources, 93 per cent
of the seed which was exposed to rain was found positive followed by the samples
stored for more than 3 years (77 to 79 per cent) and the samples collected
from consumer markets (75 per cent). Of these, 21 seed samples recorded 32.8 to
308 ìg aflatoxin B1/ kg rice, which is above the permissible limit.
The DRR team attributed the growth of fungus on rice to the crop being
exposed to frequent and heavy rainfall and floods, particularly just before
harvest. Often harvested sheaves remain wet and grains become prone to invasion by fungi. Such grains with moisture content higher than the desired levels enter the
storage system.
"As a result, invasion by both, field and storage fungi take place. In general, fungal invasion leads to discoloration, loss in viability and quality of the grains. Aflatoxin contamination of agricultural commodities including rice is a serious food safety issue besides being a significant economic concern," the DRR study warned.
The team recorded infection of Aspergillus species in rice grains in surface-
sterilised seed, kernel, hull and kernel powder. The scanning electron microscopic examination showed the presence of Aspergillus species, particularly A. parasiticus in kernel, starch, endosperm and embryo. The discoloured kernel revealed the presence of tubular, long, turgid and ramified fungal hyphae both in vegetative or reproductive stage and had disintegrated starch.
"Consumption of these discoloured rice grains is a definite risk to health," the DRR study said adding that use of certain biological agents and plant extracts like clove, garlic, neem and turmeric will prevent the fungal growth on rice or drastically reduce its effect.