Inhibitory effects of garlic and rosemary powders on microbial proliferation and shelf-life extension of teff injera

Injera, a fermented flatbread produced from teff ( Eragrostis tef ), is highly susceptible to microbial spoilage during ambient storage, resulting in substantial postharvest losses in Ethiopia and other Horn of Africa countries. This study investigated the effects of garlic ( Allium sativum ) and rosemary ( Rosmarinus officinalis ) powders (1% and 2%, w/w) on the physicochemical properties, microbial stability, and sensory quality of teff injera during storage at 25 ± 2 °C and 65 ± 5% relative humidity for five days. Moisture content, water activity (a w ), total aerobic count, and yeast and mold populations were evaluated at regular intervals. Sensory evaluation was conducted using a seven-point hedonic scale with 50 semi-trained panelists following informed consent procedures. Both plant powders retarded microbial growth and delayed quality deterioration compared with the untreated control. Among the treatments, 2% (w/w) rosemary powder exhibited the greatest preservative effect, maintaining aw values around or below 0.92 and reducing yeast and mold populations by approximately 1.0 log10 CFU g−1 relative to the control during storage. during storage. Although 2% garlic powder also suppressed microbial proliferation, its strong characteristic flavor resulted in lower scores for taste and aroma attributes. Injera treated with 2% rosemary powder retained acceptable sensory characteristics throughout the five-day storage period. The observed preservative effects are consistent with the antimicrobial properties previously reported for rosemary and garlic; however, the bioactive constituents responsible were not characterized in the present study. Under the conditions investigated, rosemary powder at 2% improved the microbial stability and sensory acceptability of teff injera, maintaining acceptable quality throughout the five-day observation period. Since some treatments remained acceptable at day 5, the maximum shelf life was not fully established, and longer storage studies are warranted. These findings indicate that rosemary powder may serve as an inexpensive and locally available natural preservative for extending the shelf life of traditional fermented foods.