Morsi El Soda

Influence of the fat content of Cheddar cheese on retention and localization of starters

Abstract Microbiological counts of fat-free, 50% reduced-fat and full-fat Cheddar cheeses were obtained to determine the population of starter bacteria in the different cheeses. Microbiological counts and observations on the cheese curd by transmission electron microscopy indicated that bacterial populations in the curd were directly related to the fat content of cheese. Electron microscopy examinations of cheeses ripened for less than one month showed that cells were either directly in contact with the fat globule membrane or located at the casein-fat interface. However, a higher number of bacterial cells appeared to be in close contact with the fat globule membrane. After one and two months of ripening, the number of ghost cells increased and bacteria seemed to be embedded in the milk fat globule membrane or directly in contact with the inside of fat globules.

Accelerated Maturation of Cheese

Abstract The methods used to reduce the maturation time of cheese have traditionally included the use of enzymes, like β-galactosidase, proteinases, peptidases and lipases. These approaches have shown that addition of free enzyme led to uncontrolled biochemical reactions. Consequently, during recent years, new approaches have been attempted to accelerate the maturation process. The addition of liposome-entrapped enzymes and physically or genetically modified lactic acid bacteria to cheese seem to provide a definite advantage. This article reviews some of the developments in the area of accelerated cheese maturation. Attention is also given to non-conventional cheese as well as to cheese made from milk other than cows milk.

Peptidase activities in debittering and nondebittering strains of lactobacilli

Abstract Three Lactobacillus casei strains, which were isolated earlier from Cheddar cheese and which exhibited debittering and nondebittering effects during cheese ripening, were analysed for their peptide hydrolase systems. All strains exhibited an active aminopeptidase, a dipeptidase, a tripeptidase, a dipeptidyl aminopeptidase and a carboxypeptidase. The most significant difference between debittering and nondebittering strains was observed at the specific activity level of the aminopeptidase. The stability of the aminopeptidase in cheese was also investigated, and it was seen that this enzyme remained active for at least 2 months before its activity began to decrease.