Defining starter culture performance in finger millet fermentation: growth kinetics, acidification, and quality attributes of sprouted and non-sprouted beverages

Spontaneous finger millet fermentations yield complex flavours but suffer from inconsistent safety and quality. Defined starter cultures can improve control, yet strain-specific performance in African cereal systems remains underexplored. This study evaluated the growth kinetics and effects of lactic acid bacteria ( Lacticaseibacillus casei, Limosilactobacillus fermentum, Lactiplantibacillus plantarum, Lactococcus lactis, and Pediococcus pentosaceus ) in sprouted and non-sprouted finger millet substrates. All strains showed sigmoidal turbidity responses (maximum OD₆₀₀ 0.164-0.207; μ̂ max 0.00068-0.00386 h⁻¹; λ̂ −9.42 to 0.82 h), reduced pH from 4.91-5.33 to 3.04-3.73, and increased titratable acidity to 0.53-0.94%. Sprouting effects were strain-dependent: L. plantarum in sprouted substrate showed comparatively fastest growth (0.0023 h⁻¹), a short apparent lag phase (-3.40 h), and acidification (pH 3.14; TTA 0.94%), whereas P. pentosaceus in non-sprouted substrate exhibited the highest apparent growth rate (0.00386 h⁻¹). Sprouting increased protein from 1.42-2.02% to 4.03-5.54%, with some sprouted treatments exceeding commercial mageu (4.61%), and enhanced phosphorus and sulphur; the highest calcium was observed in sprouted P. pentosaceus (26.19%). Sprouted P. pentosaceus produced the highest total phenolic content and FRAP, while sprouted L. casei showed the highest DPPH, ABTS, and flavonoid content. Texture changes were strain-dependent, with the secondary force peak showing the greatest variation (Cohen's d = 3.21 for L. casei ). Principal component analysis revealed clear substrate-associated separation, suggesting the potential for more targeted fermentation strategies rather than purely empirical processing.