Golden rice beta carotene disappears fast: study

Prospect as vitamin A source weakens further

Emran Hossain | Published: 00:29, Jun 27,2019 | Updated: 02:21, Jun 27,2019


After studies have confirmed that vitamin A, converted from beta carotene, is very low in genetically modified golden rice, new evidence shows that the rice is also unable to hold the biochemical for long after harvest.

Unless preserved in refrigerated condition in vacuum packaging as paddy, golden rice can lose up to 84 per cent of its beta carotene in six months, according to a new Indian government research. 

The degradation of beta carotene level gets faster with processing and is the highest in polished golden rice, said the research released two months ago in British journal Food Chemistry.

The research has noted that rice is always eaten after processing, mainly as polished, and it is in this state that it is stored, too, in Asian countries.

‘These findings are really interesting,’ observed Bangabandhu Sheikh Mujibur Rahman Agricultural University’s biotechnology professor Tofazzal Islam after going through the research at New Age’s request.

He said that so far beta carotene was generally considered a highly stable biochemical.

‘But now it is clear that beta carotene rather gets degraded rapidly,’ said Tofazzal.

High temperature and humidity also influence the degradation of beta carotene, the research revealed.

Besides, cooking can destroy up to 25 per cent of beta carotene as well, the research said. The research recommended more work on finding out how rice boiling influences beta carotene concentration.

Abdul Kader, principal investigator of the Healthier Rice Project, International Rice Research Institute, which developed golden rice, said that degradation of biochemicals in ambient air was fundamental knowledge.

‘Beta carotene degradation in golden rice is under investigation,’ he said, refusing to give any detail on his work.

The investigation Kader referred to is going on at the Bangladesh Rice Research Institute, where he also works as a principal scientific officer.

A BRRI source having knowledge of the investigation said that they found three-fourths of the beta carotene in golden rice getting degraded in eight months.

Requesting anonymity, as he was not authorised to talk about the investigation, the source said that golden rice would have to be consumed in two months of harvest to get the best result.

BRRI director general Shahjahan Kabir admitted that golden rice could not be preserved for long as it would lose its qualities with time like other rice verities.

‘We want to meet 30 to 50 per cent of the demand for vitamin A in an individual with golden rice,’ said Shahjahan.

The new findings, however, represent a setback in the  golden rice campaign promising to help fight vitamin A deficiency among the poor sections of the populations in the developing world.

Indian researchers said that the samples they had analysed contained between 7 and 22 micrograms of beta carotene per gram of golden rice depending on the variety of the rice it was inserted into and its placement in the gene.

In Bangladesh, the highest concentration of beta carotene in golden rice was found to be 10 micorgrams per gram of golden rice.

The food and health regulators in Canada, USA, Australia and New Zealand have found the beta carotene concentration in golden rice very low, refusing to accept the rice as a nutritious grain.

Now the finding about the rice not being able to contain even this low amount of beta carotene is likely to bear implications on its release in Bangladesh, expected any day.

On January 31, emerging from a meeting with the IRRI, agriculture minister Abdur Razzak told journalists that golden rice was to be commercially released soon for cultivation.

Even the Bangladesh government, with the resources at its command, is incapable of fulfilling the conditions required for retaining beta carotene in golden rice, let alone its poor population.

Less than one per cent of the 3 crore tonnes of rice consumed annually in Bangladesh is sold in packets with the rest being sold open while vacuum packaging is literally absent in the country.

The rice coming in packets are far costlier and consumed mainly by the rich and upper middle-class population.

Warehouses where the government stores its rice have no system in place to control temperature and rice is preserved there in sacks.

To prevent dampness, warehouse doors and windows are often kept open to let air and light in.

These are the conditions referred to in the Indian research as highly favourable for causing rapid beta carotene degradation in golden rice. 

The research said that the best way to retain beta carotene in golden rice was vacuum-packing the paddy at 4 degree Celsius. Still, this method would only reduce the degradation level by 54 per cent.

Beta carotene in paddy, brown rice and polished rice degraded by about 68, 72 and 79 per cent respectively even after they were air-packed and preserved at 4 degree Celsius.

If preserved at 25 degree Celsius, the rates of beta carotene degradation in paddy, brown rice and polished rice increased to about 80, 81 and 84 per cent respectively, said the research.

Bangladesh Agricultural University’s biochemistry and molecular biology professor Tofazzal Hossain likened the nature of beta carotene to that of soya bean and mustard oils susceptible to losing strength because of their participation in chemical reactions in presence of oxygen.

The chemical reaction is known as oxidation and could be set off by oxygen available in the ambient air or moisture present in the rice.

Besides oxygen and temperature, Tofazzal said, beta carotene integrity can also be compromised by light, humidity, microbial contamination or even by shaking.

‘Scientists need to work on strengthening golden rice’s anti-oxidant characteristics, increasing its capacity to hold back more beta carotene,’ said Tofazzal.

That would mean increased technological intervention and investment, which would certainly make golden rice more expensive in future, he said.

In the best-case scenario, golden rice can become an effective source of vitamin A only when it will be eaten with meals containing fat, which is required for converting beta carotene into vitamin A.

The targeted golden rice consumers, the poor in the developing world, can hardly afford fat in their diets.

Green activists have been campaigning that Asian countries are abundant in natural sources containing beta carotene. They are particularly against golden rice for scientists are yet to know the long-term health impact of genetically modified foods.

According to the Indian research, 100 grams of best quality golden rice can give 2,281 micrograms of beta carotene, which is roughly the amount found in almost all green leafy vegetables.

The lowest amount of beta carotene provided by 100 grams of green leafy vegetable was found to be 2,199 micrograms.

On the other hand, 100 grams of carrot can provide 8,300 micrograms of beta carotene.

Fruits can provide even more. 100 grams of Alphonso can provide 11,789 micrograms of beta carotene.

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