Fighting against adulteration of watermelon

Md Amjad Hossain talks to a Dhaka University research team that finds a method to detect the added colour at watermelon


For the last few years, news of mixing chemicals in fruits has become a national issue. The first ever incident of using chemical in fruits, came in few years back while several national dailies reported that harmful chemical substances as calcium carbide was used in mango and these illicit activities were carried out by a few dishonest businessmen.

Later the issue gained momentum four years back with another accusation against the businessmen of using formalin and other harmful chemical substances in fruits. The latest addition to the list is injecting colour into watermelons to make the inside of the watermelon more radiant and attractive.

A team of Dhaka University’s Chemistry Department, however, learning the issue of using colour in watermelon, came up with an idea by which people now can be able to detect whether any sort of colour was used in the watermelons they just bought from the market.

The primary idea came to the Chairperson of Chemistry Department, Nilufar  Nahar, after reading reports in different dailies that a few people died and some children also fell sick after eating watermelons.

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Talking to New Age Xtra, she shared that another thing worked behind the idea and that was a YouTube video which went viral. ‘The video depicted a new level of dishonesty-where traders were injecting artificial dye with syringes inside the watermelon’ she says.

She also shared that the colour was ‘red-40’, a form of red colour that is harmful for human body.

A year back in 2016, she along with her two students- Tanhaul Islam and Ahasan Habib Khandakar, started to conduct a research by which they have invented a process of detecting the added colour in watermelon.  Talking to New Age Xtra, Tanhaul Islam said that anybody can detect the added colour in watermelon at home by following the method they have formulated.

For their research, at first they had collected two varieties of watermelon- deep green and light green with white stripes from Natore and Rajshahi. Then they conducted the test on the juice-extracted from the watermelons by using coconut oil. Sharing the full process Tanhaul says that at first they took the juice from the collected watermelons and then put them into different test tubes. Some of them had added colour and some had the plain juice.

After that the same amount of coconut oil was added into the test tubes. Later, after shaking the liquid for few seconds the test tubes were placed randomly for five minutes. Interestingly at their test, they found that the lower level of liquids with added colour in the test tubes were turned into red or pinkish tone, while the colour of liquid was transparent as water in the case of real juice, says Tanhaul.

Explaining the matter, Nilufar shares that as the real juice has lycopene- a pigment that gives tomatoes, watermelon and pink grapefruit their red color, dissolves with oil and the colour remains transparent. ‘Meanwhile the colour added to the juice cannot be dissolved with the oil, therefore, the colour turns into red’ she says.

In terms of doing the test at home, Ahasan Habib says that instead of test tube one can use a transparent glass. The mix of watermelon juice and coconut oil needs to be poured into that glass and then the liquid needs to be shook. ‘If the colour of lower level of the liquid turns red or pink then we have to understand that the watermelon was added with colour’ he says.

Talking about the test Habib says that although they have started the plan for their research last year, the test got its final shape in this year. This year they have collected 40 watermelon samples from markets or producers to taste the added colour, but it was a good news that none of their samples was found positive to added colour, he claims. He also says that his two teachers, professor Mohammad Shoeb and lecturer Kamrul Hasan also helped in the research.