Spent coffee grounds (SCG) represent a significant source of waste generated from coffee consumption worldwide. Annually, approximately 6 million metric tons of waste are produced from preparing coffee beverages and making instant coffee. To address this environmental concern, scientists have been exploring ways to convert SCG into value-added products for various applications, ranging from industrial materials to biofuels. In a pioneering effort, a team of researchers led by Associate Professor Liu Shao Quan from the NUS Department of Food Science and Technology under the Faculty of Science has ventured into the creation of an alcoholic beverage from fermented SCG. This innovative approach offers a sustainable solution to manage the increasing amount of coffee waste while exploring new flavors and potential health benefits.
Traditionally, alcoholic beverages are made using Saccharomyces yeasts. However, Assoc Prof Liu and his team took a different approach by exploring non-Saccharomyces yeasts to impart novel flavors and other characteristics to the SCG-derived alcoholic beverage. In a study published in the journal LWT in 2021, they used two types of yeasts supplemented with yeast extracts for the fermentation process. This combination resulted in a complex flavor palette, enhancing the overall sensory experience of the beverage. By broadening the range of yeasts used, the team opened up possibilities for diverse and unique flavor profiles.
Building upon their previous study, the NUS team further investigated the use of lactic acid bacteria in combination with yeast for fermentation. By introducing a lactic acid bacterium (Lactiplantibacillus plantarum) alongside a yeast strain (Lachancea thermotolerans), the researchers aimed to enhance the smell and taste of the SCG-derived alcoholic beverage. The fermented SCG hydrolysates produced through this method exhibited higher contents of compounds associated with pleasant aroma and taste compared to using yeast alone. This promising result was published in the journal Foods in March 2023.
In their latest study, published in the journal Food Research International, the research team went a step further to conduct a detailed metabolomic analysis of the SCG-derived alcoholic beverage. Using advanced analytical techniques, such as liquid chromatography quadrupole time of flight mass spectrometry (LCQTOF-MS), the researchers obtained a comprehensive profile of the chemical contents present in the fermented SCG. This approach provided valuable insights into the bioactive compounds found in the beverage and their potential health benefits.
The metabolomic analysis revealed that the fermentation of SCG hydrolysates with a combination of yeast and bacteria led to an increase in bioactive compounds associated with various health benefits. These compounds encompassed anticancer, anti-inflammatory, and antimicrobial activities. The discovery of these health-promoting compounds indicates the potential of the SCG-derived alcoholic beverage not only as a novel and sustainable alternative but also as a source of bioactive substances that could contribute positively to human health.
Through their research, the team developed multiple prototypes of the alcoholic beverages derived from SCG, each with its own distinct flavor profile. Some prototypes retained the coffee flavor, appealing to coffee enthusiasts, while others achieved a pleasant flavor without an overpowering coffee taste. Importantly, all the prototypes retained compounds known to confer health benefits, such as alkaloids and phenolic acids. This diversity in flavor and health-promoting compounds offers consumers a range of options to suit their preferences and nutritional needs.
The transformation of spent coffee grounds into alcoholic beverages presents a creative and sustainable solution to mitigate coffee waste. The utilization of non-Saccharomyces yeasts and lactic acid bacteria during fermentation contributes to the development of unique flavors and improved aroma and taste. Furthermore, the comprehensive analysis of bioactive compounds underscores the potential health benefits associated with consuming the SCG-derived alcoholic beverage. As the research progresses, it opens up exciting possibilities for the utilization of coffee waste in the production of value-added products while promoting environmental sustainability and enhancing our drinking experience.