Changes in physicochemical properties, microbiological quality and safety status of pasteurized traditional sorghum “mpedli” beer supplemented with bitter leaf (Vernonia amygdalina) aqueous extract during a month-storage at room temperature

Abstract

“Mpedli” is a popular white sorghum beer in the Far-North of Cameroon, but its main disadvantages are variable quality and short shelf life. Therefore, this study was conducted to determine the effect of aqueous extract from bitter leaf and pasteurization on the quality and safety of “mpedli”. The beer was brewed in the laboratory using a modified in-house procedure with addition of 10% aqueous extract of V. amygdalina leaves (VMB samples) combined to the pasteurization at 63 °C/30 min (PVMB samples). At room temperature, the physicochemical and microbial parameters were monitored for a month. PVMB samples showed the highest values of soluble solids (10.9 - 9°Brix) and alcohol content (5.06 - 5.93%), while VBM aliquots had the most relevant values of dissolved solids (1245.7–1795 ppm) and conductivity (2492–3623 μS/cm). Microbial counts of all the samples increased up to the 18th day for total plate and mesophilic spore-forming bacteria, and the lowest loads were recorded in PVMB and VMB samples. Total coliforms were found under permissive limit for VMB (0–2.6log10) and PVMB (0–2.55log10) samples. Through the storage of mpedli beer, VMB showed the lowest unsafety score (16.2), followed by PVMB (18) and control (322), suggesting that VMB recorded the most secure samples. According to the findings, the treated "mpedli" (VMB and PVMB) were safe to consume after being stored for up to 6 days, whereas the control untreated "mpedli" was unsafe and spoiled after 1 day of storage at room temperature.