Acidification, Presumptive Microbial Dynamics, and Illustrative Dose–response Modelling in Two Tepache Fermentations: An Exploratory Two-Vessel Case Comparison

Abstract

Acidification is widely associated with microbial control during spontaneous fermentation, but its relation to culture-dependent indicators is affected by microbial identity, matrix composition and process conditions. This exploratory case comparison followed one Traditional tepache preparation containing cinnamon, cloves and star anise and one Modified preparation containing Hibiscus sabdariffa, Xylopia aethiopica, Monodora myristica, Piper guineense and African lemon. Each formulation was prepared in a single vessel and sampled at 0, 24, 48 and 72 h; duplicate laboratory determinations were analytical rather than independent fermentation replicates. Measured pH and operational chemical assays were described alongside presumptive culture-group counts. Conditional Beta-Poisson scenarios and primary kinetic fits were examined only as mathematical illustrations. At 72 h, pH was 2.875 in the Traditional vessel and 2.775 in the Modified vessel. The corresponding titrimetric outputs labelled lactic acid were 13.050 and 18.675 g/L, respectively, but species-specific acid identity was not established. In the Modified vessel, presumptive thermotolerant coliform-like counts changed from 5.150 log10 CFU/mL at 0 h to 4.300 at 24 h and 5.400 at 48 h, followed by a negative enrichment result at 72 h. In the Traditional vessel, enrichment was negative from 24 h onward. Salmonella-like colonies were observed initially without confirmatory identification. Monotonic microbial models could not represent the Modified vessel's count reversal, and short-term extrapolation did not reproduce its 48-h scenario output. In these two particular preparations, declining pH did not consistently parallel culturable coliform-like counts. Neither formulation effects nor product safety can be established without independent fermentations, species-selective chemical measurements and confirmatory microbiological testing.