Dromedary milk lactic acid fermentation: microbiological and rheological characteristics

The ability of dromedary skim milk to form an acid curd during a lactic acid starter fermentation was investigated. The activity of the starter in dromedary milk was characterized by a longer lag phase ( approximately 5 vs. approximately 1 h) and by an earlier decline phase. This suggests the presence of inhibiting factors. The maximum buffering capacity of dromedary milk as well as its minimum apparent viscosity were obtained at lower pH values. Similarly, its elastic modulus appeared later (pH 5.7 vs. 6.3). Because these rheological and biochemical events took place at lower pH values, dromedary skim milk seems to present a higher physical stability toward the increase of acidity. Determination of the rheological and microscopic characteristics of the dromedary milk coagulum (pH 4.4) did not reveal curd formation but indicated a fragile and heterogeneous structure. This coagulum, which is very different from that of cows' milk, seems to be made up of dispersed casein flakes.