The presented dissertation is a study focused on the characterization of sensory quality, especially the flavour of model samples of natural cheeses. Attention is aimed to the composition and content of volatile (sensory active) substances as important markers of flavour and free/bound fatty acids as their precursors. The headspace solid phase microextraction in conjunction with gas chromatography with mass spectrometry was used to determine volatiles. For the determination of fatty acids, the lipids were isolated from the sample with a solvent mixture of diethyl ether and petroleum ether, followed by esterification using a methanolic solution of boron trifluoride as a catalyst and final analysis by gas chromatography with flame ionization detection. The experimental part was divided into two experiments; in experiment I, Moravský bochník type cheeses (45 % fat in dry matter., 60 % dry matter) were analysed, in experiment II, Edam type cheeses (45 % fat in dry matter, 50 % dry matter). Model samples of cheeses were made at Tomas Bata University in Zlín. For all samples, a classical mesophilic culture containing Lactococcus spp. and Leuconostoc spp. was used, this was always supplemented with a suitable monoculture of thermophilic bacteria; in the case of Moravský bochník cultures of Streptococcus thermophilus and Lactobacillus helveticus and in the case of Edam cheeses Lactobacillus casei and Lactobacillus plantarum. The essence of both experiments was to assess the influence of the used microbial cultures on the above-mentioned parameters, at the same time their changes during the ripening of the cheeses were monitored. The results showed that the addition of thermophilic cultures, as well as the maturation process did not affect the number of fatty acids or volatiles, but significant differences were found in their content. The content of bound fatty acids decreased during cheese ripening due to ongoing lipolytic changes while increasing the content of free fatty acids and their subsequent degradation to volatile substances, which ultimately contribute to the taste and aroma of the cheese. Ketones and acids were the most quantitatively present in all samples. During maturation, contrary to expectations, the content of identified volatiles also decreased. The addition of the thermophilic cultures didn’t have a clear effect and varied depending on the maturation phase. In the first phase, although they showed more pronounced lipolytic activity, the subsequent metabolic processes - the breakdown of free fatty acids into volatile substances, compensated for these differences. These results confirm a significant share of the basic mesophilic culture in the formation of volatile substances, in particular the flavour of cheeses.

A new method for manufacture of natural cheese was developed using 5X ultrafiltered whole milk retentate. The retentate was prefermented to pH 5.0-5.2 before curd formation to simplify the cheese making process. It was demonstrated that the process can be made commercially feasible. Ultrafiltration and diafiltration of whole milk were done so that the desired level of residual lactose was left in the retentate. Retentate was inoculated with lactic starter culture and incubated (prefermented) until all lactose was converted to lactic acid. The final pH stabilized at about 5.0-5.2; the desired pH of the cheese curd. Incubation at 25°C allowed the retentate to remain liquid during prefermentation and easily pumped through pipes. After prefermentation, retentate was passed through a mechanical curd former where rennet was injected and mixed. The retentate-rennet mixture coagulated as it traveled upward through a cylinder. The curd emerged from the curd former and was cut into cubes by a grid of knives. The curd cubes were treated for removal of moisture by cooking in liquid and evaporation under vacuum. After moisture removal, curd was drained. salted and pressed. Cheddaring and milling were unnecessary. Experiments were performed to determine proper methods for preparing retentate. Diafiltration level was significantly related to lactose concentration in retentate (p=.OOO 1) and final pH of fermented retentate (p=.OOO1). Acidified permeate and acidified, deionized water were evaluated as cooking liquids. Cheese made from curd cooked in permeate had acid defects. but curd cooked in water produced cheese with a pH similar to conventionally produced Cheddar cheese. Moisture content of all finished cheese was excessive for Cheddar cheese. Body and texture of cheese made from curd cooked in water was close to conventionally produced Cheddar cheese. Diafiltration may be used to control final pH of fermented retentate. Prefermentation of retentate prior to cheese making will simplify equipment and shorten manufacturing time. Commercial application of the process is discussed.