This study examines the fermentation dynamics of natural yeast of filtered and unfiltered palmyra (Borassus flabellifer L.) sap under different storage conditions. The vacuum filtration was employed using a 0.45 μm nylon membrane filter. The temperature and relative humidity were 5 ± 2°C and 55% for chill conditions and 37 ± 2°C and 40% for ambient conditions, respectively. The filter chill (FC) condition retains the biochemicals properties of the sap without significant changes during the storage period, with an ethanol concentration of 2.78% (v/v) and an optical density (OD) yeast count ranging from 8.08 \(\:\times\:\) 102 to 1.74 \(\:\times\:\) 105 CFU/mL. The unfilter chill (UFC), filter ambient (FA) and unfilter ambient (UFA) conditions had ethanol concentrations of 3.68%, 5.60% and 9.45% (v/v), respectively, with corresponding yeast counts of 3.46 \(\:\times\:\) 106, 2.45 \(\:\times\:\) 106, and 5.98 \(\:\times\:\) 106 CFU/mL. The Luedeking-Piret model was concluded that ethanol concentration was a growth associated process, showing the strong model fitting with R2 > 0.90 across all the treatment conditions. Furthermore, FTIR confirmed the biochemical changes, peaks at 3310, 1630 and 1048 cm–1 reveal the biochemical transformation in palmyra sap during storage. FC showed the minimal yeast growth and retention of all phenolics component and antioxidants activity which provide the optimal preservation for non-alcoholic palmyra sap. These findings highlight the stabilisation of molecular integrity and the preservation of sap quality, which highly depends on treatment and storage conditions. These findings show that yeast transforms the biochemical components and leading to sap degradation.
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