Exploring fruit-enhanced traditional Ethiopian fermented milk (Ergo): Effects on microbial dynamics, physicochemical characteristics, and sensory properties during spontaneous fermentation

Spontaneously fermented dairy products are an invaluable heritage in food fermentation practices and offer a valuable model for understanding aspects related to microbial ecology and agrogeography. This study investigated for the first time Ergo, a traditional Ethiopian fermented milk produced in two distinct geographical areas, as a fermentation case study by evaluating the effects of mango (Mangifera indica), papaya (Carica papaya), and avocado (Persea americana) juice supplementation (0–25%, v/v) on its physicochemical traits, microbial quality, sensory acceptance, and lactic acid bacteria (LAB) diversity. Fruit addition increased carbohydrate content, titratable acidity, viscosity, and total solids, while reducing pH, protein, fat, and ash (P < 0.05). Control Ergo showed the highest LAB counts, whereas fruit-supplemented samples exhibited higher counts of total aerobic mesophilic bacteria, yeasts and molds, and coliforms. Rep-PCR genotyping and 16S rRNA gene sequencing revealed that fermentation was dominated by Limosilactobacillus fermentum (28.6%) and Enterococcus songbeiensis (12.4%), with species distribution influenced by sampling area and fermentation time. Sensory analysis identified 15% mango supplementation of Ergo as optimal for consumer acceptance. Overall, this work provides novel insights into how fruit supplementation modulates spontaneous Ergo fermentation and the functional contributions of indigenous LAB. The dominance and diversity of key LAB strains underscore their potential to develop tailored starter cultures to support the standardization and improve the safety of traditional fermented dairy products at larger scales.