Effect of two yeast strains and fermentation time on metabolomics and flavoromics of Nam Hom (aromatic) coconut (<i>Cocos nucifera</i> L.) cider

The fermentation process of 'Nam Hom' coconut cider was investigated using two yeast strains: K1-V1116 and EC-1118. During the fermentation period, the Brix and reducing sugar levels exhibited a persistent decline, while the alcohol content continued to escalate. Additionally, a slight decrease in pH indicated a progressive increase in acidity. The fermentation time was divided into three main stages: Pre-Fermentation, In-Process, and Final-Product. Both yeast strains exhibited similar tendencies in metabolite conversion, with elevated levels of sugars such as glucose, sucrose, and fructose observed during the early stages of fermentation. Flavoromics analysis identified a range of volatile compounds, including esters, alcohols, volatile acids, and phenols. Notably, acetate esters and ethyl esters were identified as contributors to the fruity aroma of the cider. Correlation analysis revealed strong associations between sugars and esters/ethanol, amino acids, and free fatty acids (FFAs)/flavor compounds, and fatty acid methyl esters (FAME), with sugars/esters. These findings provide valuable insights for controlling fermentation conditions and factors to produce coconut cider with distinctive aromas and increased levels of bioactive components.