Fermentation dynamics of water kefir in coconut and coconut–pineapple substrates: an evaluation of carbon source effects

Abstrak

Water kefir is a promising non-dairy probiotic beverage, yet its microbial dynamics in coconut water and coconut–pineapple substrates remain insufficiently explored. This single-run study evaluated microbial growth using three carbon sources (glucose, sucrose, and commercial sugar). Fermentation was carried out with 5% (w/v) water kefir grains and 5% sugar at 25–28 °C for 72 h, with sampling every 24 h. Optical density (OD₆₀₀) ranged from 0.13 to 0.83, generally increasing during the first 48 h and declining thereafter, while pH remained acidic (3.65–3.93). Plate counts on MRS agar were too numerous to count during the first 48 h, followed by enumerable counts at 72 h. Coconut–pineapple substrates showed higher culturable lactic acid bacteria counts (~10⁸–10⁹ CFU/mL), whereas coconut-only substrates were lower (~10⁷ CFU/mL or below detection). Pineapple-containing and sucrose-based treatments were associated with higher activity. Because the study was a single run without replication, results are presented descriptively as observed trends and should be regarded as preliminary. Fermentation up to 48 h supported microbial growth, whereas extended fermentation reduced culturability under MRS-based enumeration. These observations highlight the roles of fermentation time and substrate composition, providing a basis for future replicated studies.