Effects of Pasteurization and High-Pressure Processing of Camel and Bovine Cheese Quality, and Proteolysis Contribution to Camel Cheese Softness

Abstract

The effects of high-pressure processing (HPP) compared to thermal treatments on the quality of camel vs. bovine cheeses were studied. The study showed that camel milk has a lower microbial load compared to bovine milk, which is maintained during 7 days' storage of the processed milk. The effect of three HPP treatments (350, 450, and 550 MPa for 5 min at 4°C) and two pasteurization treatments (65°C for 30 min and 75°C for 30 s) on the quality of soft unripened camel and bovine milk cheeses were accessed. The cheeses were evaluated for pH, yield, proximate composition, textural and rheological properties, microstructure, and protein profile by SDS-PAGE electrophoresis. The effects of the treatments on cheese's hardness were different between the camel and bovine cheeses; while heat treatment at 65°C for 30 min gave the hardest bovine milk cheese (1,253 ± 20), HPP treatment at 350 MPa for 5 min gave the highest value for camel milk cheese (519 ± 5) (p < 0.05). The hardness of the cheeses was associated with low yield and moisture content. SDS-PAGE electrophoresis revealed that extensive proteolysis might have contributed to the softness of camel cheeses compared to bovine and suggested the involvement of some residual enzyme activities.

The Texture of Camel Milk Cheese: Effects of Milk Composition, Coagulants, and Processing Conditions

“…κ-casein is considered the primary factor responsible for coagulation of milk ( 17 , 58 , 80 – 82 ). However, the high level of β-casein in CM seems to also play an important role in this effect ( 11 , 61 , 76 ) in agreement to what has been described for BM ( 82 ). β-Casein possesses higher hydrophobicity than the other milk proteins and has more chaperone-like activities leading to suppression of protein aggregation ( 83 ).…”

“…SDS-PAGE electrophoresis shows clear differences in the protein and peptide profiles of CM and BM cheeses and whey ( Figure 2 ). The CM cheeses show several low molecular weight bands suggesting that excessive proteolysis of caseins has occurred in these cheeses ( 61 , 76 ). Endogenous enzymes such as plasmin in CM ( 94 – 96 ) might be responsible for the hydrolysis of caseins, especially β-casein.…”

“…Milk pasteurization is vital to assure CM cheese's safety ( 98 ). However, high pasteurization temperature could affect the quality of cheese, such as yield and texture ( 61 , 99 , 100 ). High temperatures are known to enhance the formation of κ-casein complexes through disulfide bonds between whey proteins and casein micelles, which may hinder casein coagulation ( 101 ).…”

“…Studies have shown that the coagulation properties (coagulation time, rate of curd firming) as well as the yield) improved after HPP treatment of camel milk ( 61 ). This is also the case for bovine milk ( 105 , 106 ) and caprine milk ( 107 ).…”

“…This is also the case for bovine milk ( 105 , 106 ) and caprine milk ( 107 ). HPP treatment at 200–400 MPa has been reported to enhance CM coagulation and coagulum strength ( 61 , 108 ) but HPP treatment at 600 and 800 MPa inhibited clotting ( 108 ). Due to its ability to inactivate gram-positive and gram-negative bacteria at room temperature, high-pressure processing (HPP) is used in the food industry as a preservation technique ( 109 ).…”