Tvarogs, known in Poland as ‘white cheese’, are highly popular products among consumers. The objective of the study was to determine the degree of retention of protein and selected minerals in tvarogs produced from the milk of cows raised on traditional farms, in relation to a breed (Holstein-Friesian and Simmental), production season (spring/summer and autumn/winter) and the starter cultures used (homo- and heterofermentative). Samples of bulk milk were collected from cows (three each from each breed from the spring/summer and autumn/winter seasons). Tvarogs were produced from milk according to a traditional technology, using two types of starter cultures, i.e. homofermentative (culture 1) and a mixture of homo- and heterofermentative cultures (culture 2). Basic chemical composition and contents of K, Ca, Na, Mg and Zn were determined in the milk, whey and tvarogs. The content of protein and minerals was used to calculate the degree of retention of these nutrients in the experimental tvarogs. The yield and quality of tvarogs is integrally linked to the quality of the milk used to produce them. Higher tvarog yield was obtained using milk from Simmental cows in the summer, which can be linked to higher protein content in this milk. The dry matter of tvarogs produced from the milk of Holstein-Friesians contained significantly more fat and less protein. It should be noted that no significant differences were found in the degree of protein retention from the raw material to the products, while a higher retention index was obtained during the summer season. Higher content of minerals was noted in the milk obtained from the Simmental cows in the spring/summer and in the tvarogs produced from it. However, very low retention indices were found for these minerals. It should be emphasised that both the production season and the cultures used significantly determined the degree of retention. Higher retention indices were obtained in the spring/summer season using culture 1.

23.3.2018