Characterization of recombinant camel chymosin reveals superior properties for the coagulation of bovine and camel milk.

Enzymatic milk coagulation for cheese manufacturing involves the cleavage of the scissile bond in kappa-casein by an aspartic acid protease. Bovine chymosin is the preferred enzyme, combining a strong clotting activity with a low general proteolytic activity. In the present study, we report expression and enzymatic properties of recombinant camel chymosin expressed in Aspergillus niger. Camel chymosin was shown to have different characteristics than bovine chymosin. Camel chymosin exhibits a 70% higher clotting activity for bovine milk and has only 20% of the unspecific protease activity for bovine chymosin. This results in a sevenfold higher ratio of clotting to general proteolytic activity. The enzyme is more thermostable than bovine chymosin. Kinetic analysis showed that half-saturation is achieved with less than 50% of the substrate required for bovine chymosin and turnover rates are lower. While raw camel milk cannot be clotted with bovine chymosin, a high clotting activity was found with camel chymosin.

Diarrhoea, vomiting and the role of milk consumption: perceived and identified risk in Bamako (Mali).

OBJECTIVES: To evaluate the public health impact of milk contamination in Bamako, Mali. METHODS: A case-control study assessed the risk-factors for food-borne toxi-infections with diarrhoea and vomiting as main clinical picture. A total of 131 schoolchildren between 5 and 20 years of age were interviewed by trained interviewers in schools in Bamako. A structured questionnaire was used to record health problems, food and particularly milk consumption habits and socio-economic indicators. RESULTS: Final multivariate logistic regression analysis identified regular consumption of boiled milk [odds ratio(OR) = 4.38; 95% CI = 1.15-16.71], age between 5 and 10 years (OR vs. age group 11-15 years = 3.28; 95% CI = 1.09-9.85) and the existence of dry latrines in the household (OR = 7.65; 95% CI = 1.92-30.55) as risk factors for diarrhoea and vomiting. Other milk products and the socio-economic level of the household were not significantly associated with the outcome. Many people were unaware of the potential risks of milk consumption. CONCLUSIONS: Milk products may be a risk factor for food-borne toxi-infections. Attention has to be paid to products considered 'safe', such as boiled or pasteurized milk. The low awareness of potential risks of many people may increase the risk of milk consumption. To achieve a sustainable increase in local milk production in Africa, milk quantity and production and transformation quality should be improved simultaneously.