Jasmina Havranek

Dynamics of Bacterial Communities during the Ripening Process of Different Croatian Cheese Types Derived from Raw Ewe's Milk Cheeses

Microbial communities play an important role in cheese ripening and determine the flavor and taste of different cheese types to a large extent. However, under adverse conditions human pathogens may colonize cheese samples during ripening and may thus cause severe outbreaks of diarrhoea and other diseases. Therefore in the present study we investigated the bacterial community structure of three raw ewes milk cheese types, which are produced without the application of starter cultures during ripening from two production sites based on fingerprinting in combination with next generation sequencing of 16S rRNA gene amplicons. Overall a surprisingly high diversity was found in the analyzed samples and overall up to 213 OTU97 could be assigned. 20 of the major OTUs were present in all samples and include mostly lactic acid bacteria (LAB), mainly Lactococcus, and Enterococcus species. Abundance and diversity of these genera differed to a large extent between the 3 investigated cheese types and in response to the ripening process. Also a large number of non LAB genera could be identified based on phylogenetic alignments including mainly Enterobacteriaceae and Staphylococcacae. Some species belonging to these two families could be clearly assigned to species which are known as potential human pathogens like Staphylococcus saprophyticus or Salmonella spp. However, during cheese ripening their abundance was reduced. The bacterial genera, namely Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium, Brevibacterium, Corynebacterium, Clostridium, Staphylococcus, Thermoanerobacterium, E. coli, Hafnia, Pseudomonas, Janthinobacterium, Petrotoga, Kosmotoga, Megasphaera, Macrococcus, Mannheimia, Aerococcus, Vagococcus, Weissella and Pediococcus were identified at a relative low level and only in selected samples. Overall the microbial composition of the used milk and the management of the production units determined the bacterial community composition for all cheese types to a large extend, also at the late time points of cheese ripening.

Free amino acid profile during ripening of ewe's milk cheese from the Croatian island Krk

The aim of this study was to determine a content of FAAs and their ratio in Krk cheese during its ripening. FAA content was determined by RP-HPLC of cheese aque-ous/ethanol extracts after FAAs were transformed into their 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate derivatives. Their concentration increased during ripen-ing, reaching the value of up to 5 % in cheese dry matter. Dominating FAAs were Glu>Leu>Val>Asp>Phe>Ser>Pro, and higher content of nonessential vs essential AAs was revealed. Krk cheese has, in relation to other cheeses, higher values for Glu/Leu, Glu/Phe, Glu/Pro and smaller values for Leu/Asp, Val/Asp, Phe/Asp ratios, while other ratios are comparable to those of other hard ovine cheeses.

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.