The Engineer

Discarded jackfruit seeds are being saved from landfill and used to make lactic acid in a process developed by scientists from Nanyang Technological University, Singapore.

In 2022, approximately 1.5 million metric tons of lactic acid were manufactured worldwide. It is added to dairy products for a tangy taste, controls acidity in jams and canned fruits, and extends the shelf life of packaged meat. In baking, lactic acid conditions dough for better texture and volume. Additionally, lactic acid helps in emulsification of dressings and sauces and maintains vibrant colours in fruits and vegetables.NTU said its method requires fewer chemicals and processes, produces negligible amounts of by-products, and reduces food waste by using unwanted jackfruit seeds. Current industrial methods to produce lactic acid typically involve fermenting raw materials such as sugarcane, corn starch and beetroot sugar, which have become more expensive due to the increasing scarcity of farmland, natural disasters, and rising inflation.

Industrial methods also result in large amounts of by-products, such as gypsum, which release greenhouse gasses when not disposed of properly.

Jackfruits are increasingly popular in diets worldwide, with their flesh, which resembles meat in taste and texture, being made into meat substitutes. However, its seeds, which make up nearly a fifth of the fruit’s total weight, are discarded in landfills.

Professor William Chen, director of NTU’s Food Science and Technology (FST) programme, who led the project, said: “Upcycling these products to cultivate lactic acid, an indispensable component for nearly all the food we eat, is an opportunity for enhancing processing efficiency in the food supply chain, while addressing two main pressure points for the food industry – rising costs of production and waste management.”

To produce lactic acid from jackfruit seeds, the NTU scientists first washed the seeds before adding sodium hydroxide at room temperature. This is a common process to remove skins from fruits and vegetables for canning, before freeze-drying the seeds and blending them into a powder. They then added lactiplantibacillus plantarum, a bacterium commonly found in probiotics, to the jackfruit seed powder. It takes about two days to break it down into sugars and lactic acid, the latter of which is later extracted during a filtration process.

Prof Chen said: “We are confident that our technique could become a powerful tool for manufacturing companies to produce lactic acid. On one hand, it already uses several common production techniques that are already in use in food processing facilities, such as freeze-drying, starch filtration, and the extraction of lactic acid. On the other hand, the feedstock of our lactic acid is a ubiquitous unwanted product – jackfruit seeds. It has a much lower cost than current feedstocks, corn and beetroot starch, and the usage of a waste product would reflect well on corporations as they strive towards sustainability goals. A necessary difficulty, however, would be getting the jackfruit seeds to the lactic acid producers, but that could be easily addressed by making some adjustments in the food supply chain.”

The NTU team will be working on optimising their lactic acid production method to further improve its yield and quality. The researchers also plan to scale up their production process through collaborations with food and beverage partners. The team’s findings have been published in Journal of Functional Foods.