Biochemical and Microbiological Characteristics of Raw Milk and Curdled Milk Originated from the Central Region of Burkina Faso

Abstract

Milk and dairy products play an important role in human nutrition in Burkina Faso as in several developing countries. This study aimed to describe the curdled milk process in the Central region of Burkina Faso through a monitoring of the production and to study the biochemical and microbiological characteristics of raw milk and curdled milk. Microbiological and biochemical characteristics of the products were determined using standard methods. Biodiversity of lactic acid bacteria in curdled milk was determined using (GTG) 5-PCR and 16S rRNA gene sequencing. Processing of curdled milk takes place in calabashes or plastic containers, without heat treatment of raw milk. The fermentation is spontaneous and lasts for 24 - 48 h at ambient temperature. Biochemical analysis showed a low mean pH of curdled milk (4.34 ± 0.10) compared to that of raw milk (6.47 ± 0.02). Dry matter (DM), protein and lipid contents were respectively 7.85%; 16.96 g/L DM and 37.11 g/L DM for raw milk while those of curdled milk were 15.85%; 20.85 g/L DM and 27.03 g/L DM. An increase from 0.22 to 0.37 g/L DM of phosphorus and from 1.10 to 2.46 of calcium was observed with the fermentation. However, iron and zinc contents obtained were 0.55 mg/L DM and 1.97 mg/L DM for raw milk and 0.27 mg/L and 1.6 mg/L for curdled milk, respectively. Microbiological analyzes indicated a high number of aerobic mesophilic bacteria for raw milk (1.9. 107 UFC/mL) as for curdled milk (3.9. 108 UFC/mL). In addition, Enterobacteriaceae counts from raw milk and curdled milk were higher than the acceptable limit of 102 CFU/mL for dairy products. Lactobacillus fermentum, Enterococcus durans/feacium, Lactococcus lactis, Lactobacillus helveticus and Enterococcus feacalis were the predominant species identified in the curdled milk.