Durian Ripeness Indicator from the Sugar in Its Stem – Chemistry Knowhow from Chula

A Chula lecturer from the Faculty of Science has analyzed sugar and amino acid content in durian stems to indicate the age of the fruits before harvesting them to help growers identify the right products for distribution and export, and aims to develop a sensor to detect ripeness in all varieties of durians.

“Durian”, the king of fruits from Thailand, the number-one export that’s dominating the world’s market with its taste, smell, and unique texture is beloved among Thai and foreign connoisseurs. With its massive export value, growers need to carefully harvest the durians just at the right age to ensure their great taste to be sold both domestically and internationally.

But one of the major problems for growers is how to make sure that the durians are just right and ready for harvest because premature harvests will affect the taste, quality, and price. Therefore, Assoc. Prof. Dr. Thanit Praneenararat, Department of Chemistry, Faculty of Science, Chulalongkorn University, has come up with a way to help growers to accurately assess the ripening age of durians before harvesting.

“In the past, most of the chemistry research focused on analyzing the chemical composition of durian fruit that had been cut from the tree to determine their ripeness, but this research aims to assess the age of durian from its stem, which still receives little attention,” said Assoc. Prof. Dr. Thanit.

Generally, the most common method used by growers to determine the age of durian is to count the days after the durian blossoms bloom until the day the fruit is ready for harvest.

“This method has some practical limitations. Although the age of harvest is well known, for example, Monthong durian has an optimal maturity of about 120 days, but the fruits on the same branch may not mature at the same time. So, counting days requires a lot of attention and follow-up,” explained Assoc. Prof. Dr. Thanit.

Another method that has been practiced based on long traditional wisdom is to taste the liquid at the base of the stem of the durian fruit.

“If it tastes sweet, that means that the durian is at the right age and ready for harvest. But the accuracy of this method also depends on the experience and expertise of each grower.”

The traditional wisdom of durian growers in tasting the liquid of the durian stem sparked an interest in Assoc. Prof. Dr. Thanit to use the knowledge in chemistry to analyze the age of durian from the stem without cutting the fruit from the tree.

For the research, Assoc. Prof. Dr. Thanit used three groups of Monthong durian from the orchards in Rayong province: 13-weeks old, 15-weeks old, and 17-weeks old, respectively. Each durian fruit is from a different tree to ensure more accurate research results. The research aimed to study the chemical composition of the liquid in the durian stem if it could be an indicator of the optimal durian age for harvest.

“We found that the liquid in durian stem contains sugar compounds that correspond to the sweetness from tasting, but chemical analysis showed that when the durians began to ripen, the amount of sucrose drastically increased while glucose and fructose decreased. Moreover, it was found that certain amino acids significantly increased as the durian aged,” Assoc. Prof. Dr. Thanit revealed the research findings which were published in Scientific Reports, an international journal affiliated with Nature.

“This research is the first step towards developing a method that will help growers assess the age of uncut durian, which can reduce economic losses from premature harvest,” Assoc. Prof. Dr. Thanit emphasized the importance of the research. He also detailed the plans to increase the number of durian samples for analysis, expand the research to include other durian varieties besides Monthong, and produce portable paper-based sensors to detect the substances discovered in this research, which will provide growers with an alternative that’s easier to use, and less prone to human error.

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