A recent study led by Kriskamol Na Jom from Kasetsart University has unveiled the intricate processes involved in the fermentation of Nam Hom coconut cider, highlighting how different yeast strains can significantly influence the beverage’s aroma, flavor, and bioactive properties. Published on March 17, 2025, in the journal Beverage Plant Research, the research provides valuable insights that could enhance the commercial viability of this tropical drink.
Coconut water, derived from the Cocos nucifera L., is celebrated for its natural sweetness and rich nutrient profile, but faces challenges due to its short shelf life. Fermentation offers an innovative solution, transforming this perishable product into a low-alcohol cider with appealing sensory characteristics. The study meticulously tracked the physicochemical changes during fermentation and utilized large-scale metabolomics and flavoromics data to understand the conversion of sugars into alcohol and aromatic compounds.
Yeast selection is crucial in the fermentation process, akin to its role in wine and apple cider production. Different yeast strains yield varying flavor profiles: some enhance fruity and floral notes through ester production, while others maintain a cleaner taste that emphasizes the coconut’s natural characteristics. Despite the growing popularity of coconut-based fermented beverages, the precise chemical transformations occurring during fermentation have remained largely unexplored.
The study employed a comprehensive approach, combining physicochemical monitoring with an untargeted metabolomics and flavoromics strategy. Two commercial yeasts, K1-V1116 and EC-1118, were used to inoculate the coconut cider. Through multivariate statistics, the researchers identified three distinct fermentation stages: pre-fermentation, in-process, and final product. Principal component analysis accounted for 83.76% of the total variance, while a thorough profiling detected 152 metabolite peaks, of which 64 were identified, alongside 16 volatile flavor compounds.
Throughout fermentation, the basic kinetics revealed similar trends for both yeast strains. The Brix and reducing sugars declined steadily, while the pH decreased slightly, indicating increased acidity. Alcohol content significantly rose to approximately 7–8%, aligning with typical cider parameters, and no traces of lactic acid bacterial contamination were found.
As the fermentation progressed, distinct changes in metabolomics were observed. Initial samples contained high levels of sugars such as sucrose, glucose, and fructose. Mid-fermentation samples (2–14 days) showed increased primary amino compounds indicative of yeast activity, while final products were characterized by fruity volatiles, particularly esters like ethyl octanoate and ethyl 9-decanoate. The study demonstrated that sugars were progressively converted into ethanol and other metabolites, with glycerol levels rising as a normal byproduct of yeast activity.
Amino acids, including leucine and isoleucine, increased in both yeast strains, aligning with metabolic processes involving pyruvate and acetyl-CoA cycling. The lipid analysis revealed decreasing levels of fatty acid methyl esters but an increase in free fatty acids, particularly lauric and stearic acids, with higher concentrations observed in K1-V1116 fermentations.
Flavor analysis confirmed that esters served as the primary aroma contributors. Notably, the EC-1118 strain produced a more pronounced fruity profile due to a higher abundance of ethyl esters. Correlation networks illustrated strong positive associations between sugars, ethanol, and esters, as well as between amino acids and flavor compounds, underscoring the interconnected metabolic pathways that can be optimized to refine coconut cider’s aroma and bioactive composition.
The findings provide practical guidance for producers of coconut cider. Both yeast strains proved effective, yet each offered unique advantages. K1-V1116 was found to enhance aroma and ester production, while EC-1118 facilitated clean fermentations with more pronounced fruity characteristics. By judiciously selecting yeast and managing fermentation duration, producers can customize flavor profiles, ranging from dry and clean to fruity and aromatic, while preserving beneficial bioactive compounds.
This research not only advances understanding of coconut cider fermentation but also opens avenues for developing value-added coconut beverages. The study was conducted under the project titled “Utilization of health in driving value addition along the food industry chain from rice, palm oil, and coconut” at the Center for Agricultural Biotechnology, Kasetsart University.
