Influence of mixed microbial starter cultures and fermentation duration on the quality and shelf life of Ethiopian Injera

• Defined LAB and yeast starters improved injera quality and shelf life • Mixed cultures reduced fermentation time to 30 hours • Sensory scores favored L. plantarum – S. cerevisiae at 30 hours • Microbial loads varied significantly with culture and time • First use of molecularly identified strains in injera fermentation Traditional fermentation of Ethiopian injera using natural mixed starter cultures (ersho) often results in prolonged fermentation times and inconsistent product quality. This study isolated and molecularly characterized dominant lactic acid bacteria (LAB) and yeast species involved in teff dough fermentation and applied them in controlled fermentations. Four mixed culture combinations, Limosilactobacillus fermentum–Saccharomyces cerevisiae, L. fermentum–Pichia kudriavzevii, Lactiplantibacillus plantarum–S. cerevisiae, and L. plantarum–P. kudriavzevii, were prepared in equal volumes (1:1 ratio) and inoculated into teff dough at a rate of 5% (v/w, flour basis). Fermentation was conducted for 18, 30, and 42 hours using a completely randomized design (5 × 3 = 39 treatments) in triplicate. Significant differences (p ≤ 0.05) were observed among treatments in pH (ranging from 3.40 to 3.85), titratable acidity, texture, and sensory attributes. Aerobic plate counts ranged from 2.07 to 3.96 log CFU/g, while yeast and mold counts reached 6.04 log CFU/g by the fifth day of storage. The optimal sensory acceptability (score: 4.45) was observed for injera fermented with L. plantarum–S. cerevisiae for 30 hours. Although sensory quality remained acceptable for up to five days, microbial safety standards were only met for three days, indicating a safe shelf life of three days under the tested storage conditions. This study demonstrates the potential of using controlled mixed starter cultures to enhance injera quality, reduce fermentation time, and improve product consistency. The findings have broader implications for food safety, industrial-scale production, and improving shelf life in traditional fermented products.