Formulation, fabrication et caractérisation de fromages frais aux laits de dromadaire et de chèvre.

Abstract

This study aims to improve the coagulation of camel milk for the production of fresh cheese by using goat's milk and various rennet substitutes. First, we studied the raw materials used, including the raw composition of camel and goat milk and the characteristics of camel rennet, goat rennet and chicken pepsin. Then, we studied the optimization of flocculation and coagulation parameters mainly pH and temperature with milk alone and camelgoat milk mixed with different formulations using response surface methodology (RSM). The optimum points obtained will be used for the manufacture of fresh cheese with enzymatic coagulation and with mixed coagulation by adding mesophilic lactic bacteria. The chemical and mineral analysis of camel milk and goat milk showed the specificity of the composition of camel milk in comparison with cow milk mainly in terms of protein, fat and total solids, lactose and even in chloride, sodium and copper. On the other hand, the characterization of the enzymatic extracts of camel rennet, goat rennet and chicken pepsin revealed variable protein contents and coagulant activities and good coagulant strength, respectively 1/4166.67, 1/2531.64, 1/6153.85. The optimization of the flocculation and coagulation time made it possible to highlight the specific optimum points according to the enzymatic extract used, the type of milk and the formulation tested. It appears that each enzyme acts differently on the coagulation of milk depending on the pH and the temperature, and even when we are under the same conditions, each enzyme gives a specific coagulum. Overall, the pH ranges from 5 to 6.7 and the temperature from 30°C to 42°C. At the level of the manufacture of fresh cheese, twelve formulations were produced and characterized, according to the proportions of camel and goat milk (75/25, 50/50, 25/75) and the type of enzyme. The best cheese yields of enzymatically coagulated fresh cheeses are those of camel rennet cheese with 19.3±0.9% of the FD25, goat rennet cheese with 13.45±0.5% of the FC25, chicken pepsin cheese with 16.65± 1.0% of FP25 and microbial coagulating agent cheese with 18.3±0.4% of FM50. Most of the cheeses obtained can be classified according to the food codex as soft and semi-fat. In rheological terms, the cheeses produced are quite firm. Cheese gel with camel rennet behaves like a dilating coagulum while those produced with chicken pepsin behave like a pseudoplastic coagulum. Whereas, cheeses produced with goat rennet and microbial coagulant behave as a dilating and pseudoplastic coagulum. This clearly shows the effect of the type of enzyme on the coagulation of the camel-goat milk mixture. In addition, electron microscope observations showed the specificity of each coagulum according to the enzymatic extract tested and according to the proportion of goat milk added to camel milk. The difference is noted in the number and diameter of the pores and the appearance of their compactness. Moreover, the statistical analysis of the amino acid concentration results revealed a significant difference (P<0.05) between most of the different formulations with the dominance in the cheeses of histidine. Finally, the best enzymatically coagulated cheeses according to sensory tests are the FD50, FC75, FP50 and FM25 formulations with an overall acceptability score on a score of 15 from 7.85±2.34 (FM25) to 10.05±3.81 (FC75). Finally, the physico-chemical characterization of the best four mixed coagulation formulations (FD50B, FC75B, FP50B and FM25B) gave cheeses with a total solids content of 25.66±0.5% to 43.55±1.2% and Fat/TS of 30.47±2.7 to 49.85±0.16 with a significant difference (P <0.05) for all parameters analyzed. From a sensory point of view, it should be noted that the addition of ferment has clearly resulted in more characteristic and more appreciated cheeses. The results obtained tend and converge towards the possibility of using camel rennet, goat rennet and chicken pepsin in cheese processing based on camel milk mixed with goat milk, taking into account the specific optimum points for each enzyme and each formulation.