Microbial diversity, safety and biotechnological potential of traditional African fermented milk products: protocol for a systematic review with quantitative descriptive synthesis

This systematic review aims to provide a comprehensive synthesis of the microbiological diversity, safety profile and biotechnological potential of traditional African fermented milk products (TFMs). A systematic literature search was conducted in PubMed and ScienceDirect, covering the period January 1990 to December 2020, using Boolean operators combining terms related to fermented milk, lactic acid bacteria (LAB), Africa and individual African countries. From an initial corpus of 458 articles, 73 peer-reviewed studies were retained following a two-stage screening process based on predefined PICOS inclusion and exclusion criteria. The retained studies cover 19 TFMs from 15 African countries. Three quantitative descriptive pooled analyses were performed on the compiled data: (i) pooled estimates of microbiological contamination levels (total plate count, coliform counts, fungal load and Staphylococcus aureus counts) expressed as mean ± SD with 95% confidence intervals and compared against ANZFA international safety thresholds; (ii) LAB species diversity assessed using the Shannon diversity index (H') and Pielou evenness index (J') calculated from species citation frequencies across included studies; and (iii) comparison of microbiological contamination levels between spontaneously fermented and back-slopping products using the Mann-Whitney U test. Heterogeneity was assessed using the coefficient of variation and sensitivity analyses were conducted. Methodological quality of all 73 included studies was assessed using the JBI checklist for prevalence data. Expected outcomes include a quantitative characterization of microbiological safety deficiencies across African TFMs, a bibliometric assessment of LAB species richness, and a structured framework for the valorization of indigenous African LAB strains as region-specific starter cultures and probiotics for sustainable dairy industry development across the African continent. This review is being submitted for publication in Frontiers in Food Science and Technology (Manuscript ID: 1847264).