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The composition of sheep milk and its production per lactation are influenced by a large number of factors; however, the most important factors are breed, nutrition, health of the animals, environment and the number and stage of lactation. The effect of the stage of lactation on milk composition in different sheep breeds was studied by Jelínek et al. (1990), Maria and Gabina (1993) ABSTRACT:The evaluation of the effect of the stage of lactation on milk composition, its properties and the quality of rennet curdling was carried out over the period of three successive years using milk samples (n = 162) obtained from a total of 27 ewes of the East Friesian (EF) breed, reared on a small sheep farm in Juřinka in the region of Wallachia. The stage of lactation had a highly significant effect on the contents of all milk components. However, only the contents of total solids (TS), solids non-fat (SNF), fat (F), protein (P) and casein (CN) gradually increased with the advancement of lactation. The stage of lactation also had a highly significant effect both on all the properties of milk and the rennet curdling quality (RCQ). All phenotypic correlations between the particular contents of TS, SNF, F, P, CN and urea nitrogen (UN) were positive and high (P ≤ 0.001). On the other hand, all phenotypic correlations between milk yield and particular contents of TS, SNF, F, P, CN and UN were negative and high (P ≤ 0.001). The majority of phenotypic correlations between rennet clotting time (RCT) and the other particular parameters was insignificant. However, the phenotypic correlations between lactose (L) and RCT and between pH and RCT were positive and high (P ≤ 0.001) whereas the phenotypic correlation between titratable acidity (TA) and RCT was negative and high (P ≤ 0.001). The majority of phenotypic correlations between the rennet curdling quality (RCQ) and the other particular parameters was insignificant. Nevertheless, the phenotypic correlations between pH and RCQ and between RCT and RCQ were positive and high (P ≤ 0.001) whereas the phenotypic correlation between TA and RCQ was negative and high (P ≤ 0.001).

J�������� R., Š������ K. (2003): Analysis of cow milk by near-infrared spectroscopy. Czech J. Food Sci., 21: 123-128.In this work, the major components (total solids, fat, protein, casein, urea nitrogen, lactose, and somatic cells) were determined in cow milk by near-infrared spectroscopy. Fifty calibration samples of milk were analysed by reference methods and by FT NIR spectroscopy in reflectance mode at wavelengths ranging from 4000 to 10 000 cm -1 with 100 scan. Each sample was analysed three times and the average spectrum was used for calibration. Partial least squares (PLS) regression was used to develop calibration models for the milk components examined. Determined were the highest correlation coefficients for total solids (0.928), fat (0.961), protein (0.985), casein (0.932), urea nitrogen (0.906), lactose (0.931), and somatic cells (0.872). The constructed calibration models were validated by full cross validation. The results of this study indicated that NIR spectroscopy is applicable for a rapid analysis of milk composition.

ABSTRACT:The objective of this paper was to determine basic components of pork and beef (fat, protein, water content) using FT NIR spectroscopy. The samples were analysed on an FT NIR Nicolet Antaris device in a reflectance regimen. Reference results from classical analyses were used for the calibration of the device. Calibration models were created using PLS algorithm (method of partial least squares) and verified by cross-validation. High correlation coefficients (R) of calibration were calculated (fat 0.998; protein 0.976; water 0.994), and subsequently of validation as well (fat 0.997; protein 0.970; water 0.993) and very low standard deviations of the calibration and validation (SEC, SEP). No statistically significant differences between the reference and predicted values of determination were detected in Z-test. According to the published results, the NIRS method has a high potential to replace an expensive and time demanding chemical analysis of meat composition.

ABSTRACT:Our study deals with a possibility of determining true protein and casein in cow's, ewe's and goat's milk and in ewe's colostrums by FT NIR spectroscopy. Samples of milk were analysed by FT NIR in the reflectance mode with the transflectance cuvette. The NIRS results were compared with reference data and no significant differences between them were found (P = 0.05). Results of this study indicate that FT NIR spectroscopy can be used for a rapid analysis of protein and casein in cow's, ewe's and goat's milk and ewe's colostrum.

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The aim of research was to evaluate changes of physico-chemical characteristics, somatic cell count and curd quality during lactation and their relationship in Lacaune ewes. The study was carried out on eighteen ewes of the second lactation on an organic farm in Valašská Bystřice (Czech Republic). It was found that the stage of lactation significantly affected almost all monitored traits except pH value, titratable acidity, somatic cell count and curd quality. The content of total solids, fat, total protein, casein, Ca and P was significantly increased, while daily milk yield and the content of lactose were decreasing with the advancement of lactation. The stage of lactation had a significant effect on the coagulation time that was extended with advanced lactation. Length of the coagulation time was positively correlated with contents of total protein, casein and Ca. In contrast, the curd quality was not affected by the stage of lactation and no significant correlation between the curd quality and other parameters were found, except for the coagulation time (r=0.40). It could be concluded that Lacaune ewes had a satisfactory milk yield and physico-chemical and technological characteristics of milk under relatively extensive nutrition.

Biogenic amines are aliphatic, aromatic or heterocyclic alkalic substances with a biological impact on live organisms. They may cause serious problems to sensitive persons in combination with some medicaments or in case of higher intake. They are present in non-fermented food, usually coming from contaminating microflora, and especially in fermented food where biogenic amines might be produced by microbiota used for procedure. The genus Enterococcus spp. can occur in cheese because their resistance to pasteurizing temperatures is much higher compared to other mesophilic microorganisms. Previous studies have targeted the occurrence and problems of enterococci isolated from cow and sheep milk. The aim of this study was to detect decarboxylase activity of enterococci isolated from goat milk and cheese and to see how the particular temperatures involve decarboxylase activity using a rapid and inexpensive screening method. In this study, bacteria Enterococcus faecium, E. mundtii, E. durans were isolated from 9 samples of goat milk and cheeses. Colonies of bacteria were inoculated on diagnostic medium fortified with amino acids (lysine, arginine, phenylalanine, histidine, tyrosine and tryptophan) and acidity indicator. Changes in colour detected decarboxylase activity of enterococci. The only positive reactions were determined in samples containing arginine and tyrosine. Cultivation of bacteria was confirmed by PCR. All of the tested microorganisms showed significant activity of tyrosindecarboxylase and arginindecarboxylase which was regulated by temperature and influenced by duration of cultivation. The test of decarboxylase activity using colour changes is suitable for a relatively rapid and inexpensive detection of microorganisms that are able to produce biogenic amines.