UDC 636.2.034:591.146:637.12.04/.07
doi: 10.15389/agrobiology.2014.4.99eng
STUDY OF THE SYNTHESIS OF MILK MAIN INGREDIENTS AS COMPONENTS OF A POLYDISPERSE SYSTEM
V.V. Tsyupko
Institute of Animal, Academy of Agrarian Sciences of Ukraine,
3, vul. 7-I Gvardeiskoi armii, p.d. KuIynychi, Kharkiv Region, Kharkiv Province, 62404 Ukraine,
e-mail valentiniaa@gmail.com
Received August 8, 2013
Milk can be regarded as a colloidal system (hydrocolloid), consisting of the dispersed medium, and the dispersed phase. Dispersed medium is formed by the lactose at its constant concentration in the solution. Proteins in a wide range of concentrations make a dispersed phase in milk. Milk fat presents in the dispersed medium to form an emulsion. Proceeding from the fact that the synthesis of the milk ingredients occurs in various enzyme systems, the content and relation of elements of a polydisperse system can be regarded as the indicators of activity of these systems. Based on the analysis of a large number of milk samples (n = 6338) from Holshtine black mottled cows, we found an inverse relationship between the amount of milk and protein and fat yield. Lactose content differed slightly in cows with the different level of milk yield at the different stages of lactation. Particularly, both on winter and summer diets, a positive correlation of the milk yield and the lactose content was found (r = 0.27, p < 0.01, and r = 0.28, p < 0.01, respectively), while the negative correlations were observed between the protein and lactose content, and also between the fat and lactose content. It confirms the role of lactose as a factor influencing the milk yield regardless of protein and fat synthesis. By the end of lactation if compared to its beginning, the fat, protein and lactose content reached 108.9, 109.2 and 97.3 %, respectively, and their yields were 84.1, 83.6 and 75.3 %, respectively. So the fat and protein content increased, but their output decreased due to milk yield depression, whereas small changes were observed in the lactose percentage, and a decrease of lactose output resulted only from the milk yield decline. Decrease of milk yield at damping lactation occurs due to decrease of the lactose production. In cows with the highest milk production the level of lactose was 5 % more (р > 0.05) if compared to low-yielding ones, while the fat, protein and lactose output was 360 %, 403 % and 491 % higher, respectively. Close lactose percent was also observed in the cisternal and alveolar portions of milk yield. It is concluded that the constituent components of milk are synthesized independently from each other, and the milk yield is determined by an amount of the synthesized lactose which provides a relatively constant dispersed media, enough to stabilize the dispersed phase.
Keywords: milk yield, colloid system, milk, fat, protein, lactose.
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