The objective of the thesis is to analyze the composition of raw milk of goats milked in Lithuania: the content and quality of fat, protein and lactose according to the somatic cell count in milk.
Tasks of the thesis: 1. Determine the fat, protein and lactose content as well as SCC in the milk of controlled goats.
2. Determine the average indicators of quality and content according to SCC in milk for the milk of controlled goats in the 2008-2010 period.
3. Analyzis changes in milk contents and SCC at different years.
4. Isolate correlations between milk content and quality indicators.
Goat milk is a valuable foodstuff, from which butter, kephir, curds, cheeses and other products can be produced. Digestibility of goat milk and its product is the highest – 94-98%. Especially popular are fermented cheeses from goat milk, which are appreciated in many countries as delicatessens.
Work on the thesis was executed in several stages. During the first stage of study, the 2008-2010 data on goat control milkings from the VĮ „Pieno Tyrimai“ database.
In the second stage of the work, a statistical analysis of the data was performed. It was carried out with the us of the „R“ statistics package (http://www.r-project.org/). Among the things calculated were arithmetic averages of attributes ( ), their margins of error (± ) as well as dispersal characteristics – the mean square deviations (SD) and coefficients of variation (Cv). Correlation analysis was performed. The statistical reliability of the arithmetic averages of attributes (P) was evaluated.
With the goal to determine the most frequent values of fat, protein and lactose content and SCC in goat milk, the data was divided into 12 classes. Values were ordered from minimal to maximal.
A correlation analysis of the components of goat milk was performed.
After having divided the goat milk fat content data (img 2), it was determined that the most prevalent class of goat milk fat content was 2,78-3,40% at 21,99% of total samples, and that 19,88% of goat milk samples had fat content of 3,40-4,02%.
After the study we established that the most prevalent class of goat milk protein content was 2,71-3.14%, at 25,60% of the total, and that 65,33% of milk sample protein content was in the 2,71-4,00 range. The results of the study showed that the dominant lactose content was in the 4,41-4,64% range, with these samples of goat milk being at 26,71%.
The results of the studies show that the majority of samples (35,65%) have an SCC in the 21-436 thous./ml. range. A lower percentage (17,60%) of the samples have an SCC in the 436–851 thous./ml. range. It has to be noted that a whole of 10,10% of samples had an SCC of 4582–5000 thous./ml.
The largest mean square deviation is in regards to the somatic cell count in milk. Lactose content variation was the lowest of the milk indicators analyzed (7,90%), whereas protein content of milk displayed a phenotypical variation of 22,64% in separate cases, and the variation of milk fat content was 33,04%. SCC in milk displayed an especially high phenotypical variation, at 107,95%. Comparing the 2008, 2009 and 2010 goat milk study data we have established that milk had the highest fat content in 2010, or statistically reliably 0,2% (P<0,001) greater than in 2008 and 0,12 (P>0,05) greater than in 2009. The highest proteint content in milk was registered in 2008 (3,63 ± 0,025%), and this indicator became lower each following year. In 2009 it dropped at a statistically reliable 0,21%(P<0,001), and 2010, in comparsing with 2008, goat milk protein content was lower at a 0,24% (P<0,001). Lactose content in goat milk was highest in 2010, or 0,02% higher than in 2009 (P>0,05) and 0,04% higher than in 2008 (P>0,05).
SCC was lowest in 2008, whereas in 2009 it was 1568,15 thous./ml or 15,22% higher. In 2010 this indicator was 1448,9 thous./ml or 6,46% higher than in 2008.
Having analyzed the relationships between the different attributes studied, it was determined that the mean statistically reliable correlation was between the goat milk fat percentage and milk protein percentage, r=0,433 (P<0,01). An average positive reliable correlation was established between fat content in goat milk and the SCC in milk. As the somatic cell count in goat milk increases, the lactose content in milk reliably decreases. A mean negative correlation r=-0,399 (P<0,05) was established between these two indicators.
Raktažodžiai: goat, milk, fat content, protein content, SCC