Samir Kalit

Proteolysis of Livanjski cheese during ripening

Livanjski cheese belongs to the group of hard cheeses which is traditionally produced in Livno (Bosnia and Herzegovina). Proteolytic changes during the ripening of Livanjski cheese have not been investigated extensively. The aim of this paper was to determine its proteolytic changes during the different stages of ripening. Five Livanjski cheeses (from raw cow’s or a mixture of sheep’s and cow’s milk) were observed during the ripening to evaluate its typical proteolytic profile. An electophoretic profile of Livanjski cheese was determined by Urea-polyacrylamide gel electrophoresis (urea-PAGE) and a densitometric evaluation of the urea-PAGE gels was performed using a densitometer. The water-soluble nitrogen fraction in the total nitrogen (WSN %TN) and the 12%-TCA-soluble nitrogen fraction in the total nitrogen (TCA-SN %TN) of the cheese were determined using the Kjeldahl method. Degradation of αs1-casein by chymosin caused a significant decrease (P < 0.05) of relative content of this protein in Livanjski cheese at the sixth week point of ripening. Due to the activity of chymosin on αs1-casein, αs1-I-casein and αs1-II-casein developed, which caused a significant increase (P < 0.05) of Index alpha. The relative ratio of β-casein significantly decreased (P < 0.05) during ripening leading to a significant accumulation (P < 0.05) of degraded product (sum γ1-casein, γ2-casein and γ3-casein). These proteolytic changes caused a significant increase (P < 0.05) of Index betta. Accumulation of medium, small peptides and amino acids caused a significant (P < 0.05) increase of the relative content of WSN %TN and TCA-SN %TN. In general, proteolysis of Livanjski cheese during ripening was moderate probably due to the low moisture content and low water activity, although it was produced from raw milk. Taking into account that the ratio β-casein : αs1-casein at the end of ripening was 1.46, it could be concluded that degradation of αs1-casein could be the indicator of the maturity of Livanjski cheese. Due to that Livanjski cheese could be classified as “α-type of ripening” cheese.

Microbiological changes throughout ripening of Keş cheese

Microbiological changes in Kes cheese, traditional Turkish raw cow’s milk cheese made without the addition of starter culture, were studied during 90 days of ripening. Physico-chemical parameters, pH, salt content and water activity (aw), as important parameters for microbial growth, were also determined. Lactic acid bacteria were predominant microbial group. The time of ripening significantly influenced the count of total aerobic mesophilic bacteria, psychrophilic bacteria, mould (P<0.05), Lactobacillus spp. and Lactococcus spp. (P<0.01) which increased during ripening. E. coli and coagulase-positive staphylococci were not detected. The counts of Enterococcus spp. (P<0.05), Staphylococcus- Micrococcus spp., Enterobactericeae and coliform bacteria decreased throughout ripening of Kes cheese, which was connected to the physico-chemical parameters. Water activity significantly decreased (P<0.05), while the salt content increased (P<0.01) during ripening of Kes cheese. The obtained results will contribute to the establishment of the microbiological quality standards for Kes cheese and give necessary information for formation of autochthonous starter culture, which will help to understand ripening process of sour dried cheeses and improve the traditional farmhouse cheese production.

The impact of changes in the milk payment system and season on the hygienic quality of milk

The aims of this paper were to investigate the impact of changes in the milk payment system and the season on the hygienic quality of raw milk. The bulk cow’s milk samples were collected throughout the whole area of Bosnia and Herzegovina over the period of four years (2010-2013), from farms that deliver milk to the dairy industry. The total bacterial count (TBC) was analysed in 52,999 milk samples and the somatic cell count (SCC) in 53,363 milk samples. The results of the research showed that the proportion of bulk milk with the SCC < 300,000 mL-1 significantly increased in the observed period, as well as the proportion of farms that produce milk of EU quality (P < 0.05). The season had a significant effect (P < 0.05) on the SCC; in April the proportion of bulk milk with SCC < 300,000 mL-1 was significantly higher (P < 0.05). A significant increase (P < 0.05) in the proportion of milk with the TBC < 200,000 cfu∙mL -1 was perceived, as well as the proportion of farms which deliver that type of milk (P < 0.05). A Significant lower (P < 0.05) proportion of milk in the summer period with TBC < 200,000 cfu∙mL-1 was determined. It can be concluded that consistent appliance of regulations which determine the quality of milk, leads to the improvement of the hygienic quality of redeemed milk, as illustrated by the case of Bosnia and Herzegovina. This kind of milk payment system is important for both, the higher economic benefit of farms and the dairy processing industry.