Sameh Awad

Rep-PCR characterization and biochemical selection of lactic acid bacteria isolated from the Delta area of Egypt

Samples of raw milk and traditional dairy products were collected from different rural areas in the Delta region. 170 isolates from these products were identified using repetitive genomic element-PCR (Rep-PCR) fingerprinting. The identified isolates were tested for efficiency of biomass production and separation, acidifying activity, autolytic and aminopeptidase properties, antagonistic activities and exopolysaccharide production. The obtained results revealed that the Lactobacillus delbrueckii subsp. lactis, Lactobacillus fermentum, Enterococcus faecium Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus paracasei subsp. paracasei, Lactobacillus plantarum and Lactococcus lactis subsp. lactis were the predominant species in Egyptian dairy products. Two percent of Lactococcus, 10% of Lactobacillus and 1% of Enterococcus isolates showed fast acidifying activity. Aminopeptidase and autolytic properties were generally higher for most Lactobacillus strains when compared to other strains. Among these species, lactobacillus paracasei subsp. paracasei was the highest in Aminopeptidase activity and autolytic properties. Antagonistic activity was detected in 40% of Lactococcus, 70% of Lactobacillus and 50% of Enterococcus isolates. Some isolates produced exopolysaccharides in milk and dairy products.

Influence of microfiltration and adjunct culture on quality of Domiati cheese

The effects of microfiltration and pasteurization processes on proteolysis, lipolysis, and flavor development in Domiati cheese during 2 mo of pickling were studied. Cultures of starter lactic acid bacteria isolated from Egyptian dairy products were evaluated in experimental Domiati cheese for flavor development capabilities. In the first trial, raw skim milk was microfiltered and then the protein:fat ratio was standardized using pasteurized cream. Pasteurized milk with same protein:fat ratio was also used in the second trial. The chemical composition of cheeses seemed to be affected by milk treatment-microfiltration or pasteurization-rather than by the culture types. The moisture content was higher and the pH was lower in pasteurized milk cheeses than in microfiltered milk cheeses at d 1 of manufacture. Chemical composition of experimental cheeses was within the legal limits for Domiati cheese in Egypt. Proteolysis and lipolysis during cheese pickling were lower in microfiltered milk cheeses compared with pasteurized milk cheeses. Highly significant variations in free amino acids, free fatty acids, and sensory evaluation were found among the cultures used in Domiati cheesemaking. The cheese made using adjunct culture containing Lactobacillus delbrueckii ssp. lactis, Lactobacillus paracasei ssp. paracasei, Lactobacillus casei, Lactobacillus plantarum, and Enterococcus faecium received high scores in flavor acceptability. Cheeses made from microfiltered milk received a higher score in body and texture compared with cheeses made from pasteurized milk.

Cheese | Accelerated Cheese Ripening

Ripening of cheese is a slow and expensive process not fully predictable or controllable. The development of an efficient way to reduce aging time would allow significant savings to the cheese industry. The dairy researchers tried to reduce the maturation time and costs by applying some methods to accelerate the cheese ripening without altering the characteristic flavor of the final product. Methods have been described during the last 50 years to achieve this goal. The aim of the present article is not to provide an exhaustive review of the literature on accelerated ripening but rather to discuss the different technologies available and to evaluate the most promising ones.

Antioxidant activity of milk protein hydrolysate in alloxan-induced diabetic rats

We investigated the effects of milk protein concentrate (MPC) and milk protein concentrate hydrolysate (MPCH) as antioxidant agents in rats. Six groups of healthy (non-diabetic) and type-II diabetic rats were used: (1) healthy rats (control), (2) alloxan-induced rats (diabetic control group), (3) healthy rats treated orally with MPC, (4) diabetic rats treated orally with MPC, (5) healthy rats treated orally with MPCH, and (6) diabetic rats treated orally with MPCH. We concluded that treatment with MPC or MPCH reduced the level of thiobarbituric acid reactive substances in healthy and diabetic rats. Treatment with MPC or MPCH improved activities of antioxidant enzymes (catalase, superoxide dismutase, reduced glutathione, glutathione-S-transferase, and glutathione peroxidase) in healthy and diabetic rats. From the present data, we concluded that both MPC and MPCH contain potent antioxidants and could improve the health of rats or other animals with diabetes mellitus.

CHEESE | Role of Specific Groups of Bacteria

Propionibacterium freudenreichii is a Gram-positive, nonmotile bacterium that plays an important role in Swiss-type cheeses. Propionibacterium freudenreichii contribute to the nutty and sweet flavors of the cheese, and the carbon dioxide by-product is responsible for forming the eyes in Swiss-type cheeses. Propionibacterium freudenreichii also is classified as a probiotic culture to enhance human health. Brevibacterium linens is a major surface microorganism that is present in the smear of surface-ripened cheeses.

Cheese | Cheeses Matured in Brine

Brined cheeses originated in the area known today as the Middle East and around the Mediterranean shores some 8000 years ago. Cheeses matured in brine share the characteristic of being preserved in brine and in most cases without the need for refrigeration. This method of cheese storage has a determinable effect on biochemical, textural, and structural changes that occur in these cheeses and lead to the development of their characteristic flavor and texture. Most of the brined cheeses are produced in family enterprises or in small artisanal units. The increased demand for cheeses matured in brine has created the need for standardized techniques for their manufacture. Therefore, Feta cheese, for example, is manufactured nowadays by traditional, standardized traditional, and fully mechanized techniques.