Optimizing the Extraction Process
Preserving Nutritional Compounds
Expanding the Applications
Food waste is a significant global issue, with millions of tons of food and vegetables being discarded each year. Leafy vegetables such as kale and lettuce often undergo a commercial practice where farmers cut off outer leaves to ensure perfectly sized and visually appealing vegetables for sale. This practice results in the disposal of large quantities of perfectly edible leaves, contributing to food waste. In Singapore alone, approximately 817,000 tons of food waste were generated in 2021, nearly half of which consisted of fruit and vegetables.
In response to this pressing issue, scientists from Nanyang Technological University (NTU) in Singapore have developed an innovative technique to convert kale waste into valuable components for health and personal care products. This groundbreaking method not only reduces food waste but also minimizes emissions associated with the extraction process.
Traditionally, extracting phytochemicals from kale requires energy-intensive processes involving high pressures and temperatures, which contribute to CO2 emissions. Additionally, these industrial extraction methods target only a single type of phytochemical at a time. Seeking a more sustainable and efficient solution, the NTU researchers turned to naturally-derived natural deep eutectic solvents (NADES). These non-toxic liquids, composed of plant-based compounds such as amino acids, sugars, and vegetable oil by-products, have been used in separation technology in the food and pharmaceutical industries.
Although NADES have been extensively studied, their ability to extract various classes of bioactive compounds from vegetable waste remains largely unknown. The NTU research team focused on bioactive compounds in kale and experimented with different NADES to observe their interaction with the molecules in kale waste. Through meticulous testing, the researchers identified the optimal NADES solvent that could effectively extract the desired bioactive compounds from kale, including polyphenols, carotenoids, and chlorophylls.
Unlike conventional methods that require heating or pre-treatment of kale waste such as freeze-drying, the NTU method does not necessitate these additional steps. By eliminating the need for heating, the costs of the extraction process are significantly reduced. The research team is confident that their environmentally-friendly technique is scalable and cost-effective for industrial adoption.
Lead author Professor Hu Xiao highlights the advantages of the method, stating, “The use of non-toxic and naturally derived solvents in our method makes it a food-safe technique. At the same time, our method preserves the potency of the extracted active ingredients, making it highly attractive for industry adoption. The extracted nutrients can potentially be used for applications in personal care products, cosmetics, food supplements, and herbal extracts.”
The waste-to-resource approach developed by the NTU research team effectively addresses both the issue of food waste and the reduction of emissions. This aligns with the principles of a circular economy outlined in the United Nations Paris Agreement, promoting zero waste. NTU’s five-year strategic plan, known as NTU 2025, emphasizes leveraging innovative research to mitigate human impact on the environment.
Unlike established industrial methods that involve harmful chemicals like methanol, the NTU method utilizes naturally derived NADES, which are non-toxic and environmentally friendly. The researchers begin by blending the kale waste into a paste or freeze-drying and grinding it into a powder form. They then mix the processed kale with the specially formulated NADES solvent and stir it mechanically at room temperature. The mixture is subsequently filtered to extract the beneficial compounds. This entire low-energy process is not only fast and completed within 30 minutes but also preserves the temperature-sensitive bioactive nutritional compounds, preventing degradation.
Lab experiments conducted by the NTU team demonstrated the superiority of their approach compared to conventional methods using methanol. Their technique delivered an extract that was 2.2 times richer in polyphenols, which are highly beneficial bioactive compounds. Furthermore, the bioactive phytochemicals remained stable even after storage, displaying excellent shelf-life.
Dr. Lee Sze Ying, the first author of the study, emphasizes the uniqueness of their approach, stating, “Our extraction approach is unique because it allows for the simultaneous recovery and separation of multiple valuable compounds from the vegetable waste in a single process without using heat.” Manufacturers can directly add the polyphenol-rich extract to their cosmetic products without further processing, reducing production time.
Co-author Dr. Liang Yen Nan explains that their method manipulates the chemical nature of NADES to maximize the extraction efficiency of bioactive compounds found in kale. This approach can easily be adapted for other types of vegetable and fruit wastes, making it a versatile and scalable solution for industry use. The research team has already filed a patent in Singapore for their innovative technique and plans to explore the extraction of beneficial compounds from other fruits, vegetables, and medicinal plants in the future.
The groundbreaking technique developed by scientists from NTU offers a sustainable and efficient solution to convert kale waste into valuable components for health and personal care products. By utilizing naturally derived solvents and eliminating energy-intensive processes, this method reduces food waste and emissions while preserving the potency of bioactive compounds found in kale. With further research and development, this approach has the potential to transform waste management practices and contribute to the development of a circular economy.
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