Tack­ling a thorny is­sue

See­ing rot­ten Thai duri­ans be­ing sold in China’s su­per­mar­kets pushed an up­set pro­fes­sor to cre­ate a spe­cial coat­ing to keep the ‘king of fruits’ fresh longer for ex­port. By Yuthana Prai­wan

Bangkok Post - - COMPANIES -

What’s worse t han the pun­gent smell of durian, var­i­ously com­pared by Western­ers to sewage, old gym socks or, at best, rot­ting cheese? The even more pu­trid odour of de­cay­ing duri­ans.

It was such an un­for­tu­nate en­counter in China that per­suaded As­soc Prof Vo­raphat Luck­a­nat­in­vong to do re­search on pro­long­ing the shelf life of the fruit, keep­ing it fresh from har­vest right up to the time it gets to the cus­tomer.

As­soc Prof Vo­raphat of Tham­masat Univer­sity’s Science and Tech­nol­ogy Fac­ulty was on a work stint in the Chi­nese cities of Shang­hai and Guangzhou when he was hit by the mal­odor­ous stink of the “king of fruits” dis­played on the shelves.

Some of the duri­ans were de­com­pos­ing with the over­ripe flesh ooz­ing out of the cracked hard, thorny shells, giv­ing al­to­gether a rather dis­taste­ful sight and smell pre­sen­ta­tion of a fruit that is muchloved in the re­gion. In some gro­cery shops, the duri­ans were just care­lessly dumped in plas­tic bags.

Be­ing Thai and there­fore know­ing how good the qual­ity of the fruit from his coun­try is, As­soc Prof Vo­raphat felt des­per­ate and trou­bled by the de­cay­ing duri­ans on the shelves and even wor­ried about the fu­ture of Thai­land’s fruit ex­ports. He thought the Chi­nese were will­ing to buy the rot­ten, low-qual­ity duri­ans af­ter hav­ing eaten the fruit dur­ing vis­its to Thai­land, as duri­ans can­not be grown in China.

Putting the bad smell aside, the Chi­nese buy­ers might not have re­alised that the ran­cid flesh of the durian could be con­tam­i­nated with bac­te­ria and mould, says As­soc Prof Vo­raphat, 48. This could cause se­ri­ous ill­ness when eaten, which would fur­ther de­stroy the rep­u­ta­tion of Thai duri­ans, he says.

Duri­ans must be han­dled prop­erly to re­tain its taste as well as its clean­li­ness, says the pro­fes­sor.

“Han­dling duri­ans care­lessly like that could also de­stroy the fu­ture of thou­sands of Thai durian grow­ers, as well as ad­versely af­fect mil­lions of other fruit grow­ers in the coun­try,” As­soc Prof Vo­raphat says.

Thai­land pro­duces about 600,000 tonnes of duri­ans a year and gen­er­ates more than 10 bil­lion baht of ex­port value each year. The mas­sive trade value means the coun­try has a well-thoughtout and clear-cut strat­egy to pro­duce high-qual­ity duri­ans, plus strong mar­ket­ing cam­paigns to pro­mote the fruit along with other fruits from Thai­land that are much in de­mand.

Of the to­tal pro­duc­tion, some 380,000 tonnes of duri­ans are for ex­port and the rest for do­mes­tic con­sump­tion. Ma­jor ex­port mar­kets for Thai duri­ans are China, Hong Kong, Tai­wan, the US and Canada.

Nor­mally it takes about two weeks for ex­ported duri­ans to reach China af­ter leav­ing port in Thai­land, and then an­other week be­fore they reach the su­per­mar­kets or gro­cers.

That was the ques­tion that As­soc Prof Vo­raphat needed to find the an­swer for: how do you ex­tend the life­span of fresh durian, which nor­mally starts to ripen within a week af­ter be­ing har­vested?

Ear­lier this year, af­ter spend­ing a year on re­search, the pro­fes­sor fi­nally found what he was look­ing for: a spe­cial way to pre­vent the fruit from go­ing bad so fast. The process is called “ac­tive coat­ing”, which can make durian stay fresh for twice as long as the nor­mal time.

What’s more, the ac­tive coat­ing tech­nique helps not only to ex­tend the fresh­ness of the durian, but it also con­tains the smell of the ripen­ing fruit.

Prak­a­sit Chum­cheun, a stu­dent do­ing a bach­e­lor’s de­gree at Tham­masat who helped with the re­search, says the ac­tive coat­ing is made when sugar-cane fi­bre — the waste that comes out of the sug­ar­crush­ing process — is blended with ac­tive car­bon. This process gen­er­ates a new type of fi­bre that when ap­plied to the durian shell will make it stronger and pre­vent it ripen­ing too fast.

“The ac­tive car­bon has a good prop­erty to ab­sorb strong, odor­ous smell when durian starts to ma­ture, while the sugar-cane fi­bre helps strengthen its shell so it doesn’t split so eas­ily, even when it has al­ready ripened,” Mr Prak­a­sit says.

The cost of coat­ing the durian with the blended fi­bre is about two baht per fruit. The ex­pense will be off­set by the higher com­mer­cial value of the coated duri­ans, since they can now stay fresh for longer, al­low­ing them to reach a wider mar­ket, Mr Prak­a­sit says.

Thai­land has been do­ing re­search on tech­niques to ex­tend the life of durian for years. Sev­eral have been found, in­clud­ing wax with methyl cy cl op rope ne, but they have all turned out to be im­prac­ti­cal.

The ac­tive coat­ing process, how­ever, is easy to use and more prac­ti­cal, ac­cord­ing to durian grow­ers and ex­porters, who have re­sponded well to the new tech­nique. The ac­tive coat­ing is ex­pected to be com­mer­cialised soon.

Hav­ing suc­ceeded with pre­serv­ing the fresh­ness of the durian for longer, As­soc Prof Vo­raphat is now work­ing on the proper pack­ag­ing. The fruit, with its sharp spikes, needs to be care­fully packed for the safety of sell­ers and buy­ers, he says.

“I think we should fig­ure out the new pack­age for duri­ans that are for ex­port, not like the plas­tic bags used by the Chi­nese su­per­mar­kets,” he says. “We have the rep­u­ta­tion of the king of fruits to pro­tect.”

As­soc Prof Vo­raphat says bet­ter de­sign for Thai duri­ans could help lift the im­age of the fruit and may even turn it into a high-end prod­uct that is worth it for the cus­tomer to present as a spe­cial gift to other peo­ple.

“There are many, many mil­lion­aires in China,” he says. “So, bet­ter care and bet­ter pack­ag­ing should help the Thai durian be­ing bought by peo­ple who can af­ford to buy it in good con­di­tion.”

Ap­pro­pri­ate pack­ag­ing would also help ex­pand durian mar­ket­ing chan­nels be­cause bet­ter pack­ag­ing means the fruit could be de­liv­ered via e-com­merce, he says.

As­soc Prof Vo­raphat Luck­a­nat­in­vong hopes that his method for keep­ing duri­ans from rot­ting too quickly will help Thai grow­ers.

As­soc Prof Vo­raphat has been able to ex­tend the use­ful life of durian, cre­at­ing greater mar­ket­ing op­por­tu­ni­ties.

Im­prop­erly stored, ripened durian flesh can, quite lit­er­ally, cause a big stink, es­pe­cially if it breaks out of the shell.

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