Protein milk, composition

Milk composition expressed in terms of the contents of water (or total solids = 100 - water), fat, protein, lactose, and ash is called gross composition. Protein is often calculated as crude protein by multiplying total N by 6.38, but sometimes it is corrected to true protein 6.38 (TN -NPN) in a few studies, casein and whey protein have been calculated separately. Lactose should be expressed on an anyhydrous basis, but as pointed out previously, this has not always been done. For bovine milk the sum of fat, true protein, anhydrous lactose, and ash would be expected to fall about 0.2-0.3 percentage units short of the total solids contents because of the materials (citrate, NPN, and mis-... 

Seasonal Variation and the Influence of Temperature. In temperate latitudes, rather characteristic seasonal variations in milk composition are commonly observed. Both fat and solids-not-fat contents are lower in summer than in winter. In the survey by Overman (1945) of individual cows at the University of Illinois, monthly extremes for fat were 4.24 and 3.81% in January and August and for protein were 3.61 and 3.37% in January and July, respectively. Nickerson (1960) found significant seasonal differences in 18 components of bulk milks from six areas in California. Seasonal differences in fat and protein contents were similar to those observed in Illinois. Seasonal variations in milk composition could conceivably be caused by differences in temper-... 

Mather, I. H., Weber, K. and Keenan, T. W. 1977. Membranes of mammary gland. XII. Loosely associated proteins and compositional heterogeneity of bovine milk fat globule membrane. J. Dairy Sci. 60, 394-402. 

Milk composition is not constant and is influenced by the timing of feeding and duration of nursing postpartum. Human milk contains about 2-3% fat and a large number of proteins. The pH of milk tends to be lower than that of plasma. Most water-soluble substances are excreted into the milk by simple diffusion, and lipid-soluble compounds are transported along with lipid molecules from plasma into the mammary gland. The amount of a certain substance transferred to the milk depends on the physicochemical properties of the... 

As it can be seen in Table 13.2, human milk composition is quite different from that of cow s milk. Casein and mineral contents are lower in human milk than in cow s milk, whilst the lactose content is higher in the former. With regards to fatty matter, both types of milk present similar contents, but the total protein is over three-fold higher in cow s milk. 

Proteins The total amount of proteins in milk is much higher during the colostrum period than in that of mature milk (once milk composition is already stable). The protein content is 12 and 35 g l-1 in human and cow s milk, respectively. This higher protein content is directly related to the higher growth rate of calves. The chemical contents of the principal proteins present in human and cow s milk are summarized in Table 13.4. 

Fat is a major component in most cheese types, but its level and importance differ markedly with variety. Inter- and intra-variety differences in fat content are affected by a number of factors, including milk composition (particularly ratio of protein to fat), and the cheesemaking process (recipe, manufacturing procedure and technology), which control the levels of milk fat and moisture retained in the cheese curd and the moisture content of the cheese. The ratio of protein-to-fat in the cheese milk is probably the principal factor influencing fat content, as it controls the relative proportions of two of the three major compositional components in cheese, namely protein and fat the third major component is moisture. Owing to the inverse relationship between the percentage of moisture and fat in cheese, as discussed in Section... 

Q12 Human milk is a bluish-white fluid with approximately 88% water, 6-8% carbohydrate (lactose), 3-5% fat and 1 -2% protein. The composition of milk varies from day to day and changes during a single feed the milk is watery at the start of a feed to satisfy thirst, but the fat content of the milk increases towards the end of the feeding period. 

TABLE 18. Effect of Supplemental Protein and Fat on Feed Intake, Body Weight Change, Milk Yield, and Milk Composition (98)... 

We have recently studied the effect of the protein membrane composition on partial coalescence in 20% milk-fat emulsions (16). Emulsions were produced consisting of 20% fat (from sweet butter, 80% fat), and 0.085, 0.17, 0.25, 0.50, 0.75, 1.0, 1.5, or 2.0% whey protein isolate (WPI, 88% protein Protose Separations, Teeswater, ON, Canada). The emulsions were heated to 70 or 90°C for 30 min. 

The structure and textural characteristics of fresh, acid-curd products are influenced by many factors, e.g., milk composition (levels of fat and protein), processing parameters (heat and homogenization treatments), conditions of gel formation (incubation temperature, rate of acidification, addition of rennet, final pH), and further curd treatments. 

Mating of C females with B6 males caused pronounced modification of milk composition milk from C females that had given birth to hybrids contained a higher percentage of proteins and lipids compared to the control C females that mated with a C male (Figure 2). There were no effects of gestation type on milk composition in B6 females. 

Typical values for the lactose, ash and major mineral content of different breeds is given in Table 16.6. Strain and individuality of the cows have an important effect on milk composition, and many Holstein cows may average more than 40 g fat/kg and 33 g protein/kg over a lactation, whereas some Channel Island cows may not match these figures. Typical ranges in composition within four breeds are given in Table 16.7. 

Assessment of milk composition is a more difficult task than assessment of milk yield, since there are five main variables to consider. Modern analytical methods allow for routine milk analysis on a large scale, and values for fat, lactose and protein contents of herd bulk milks are now readily available. AVhen analytical results are not available, assumptions are often made concerning the quantitative relationships between constituents, which allow composition to be predicted from the content of a single, easily determined constituent, usually fat. 

Raw log (1/r) spectra of nonhomogenized cow s milk samples are shown in Figure 9.3.1. Because of strong absorbance by O-H groups in water, two bands around 1445 and 1930 nm dominate the spectra. The characteristic absorption bands of fat and other milk components such as protein and lactose are very weak in comparison with the water bands and are difficult to visualize. This fact has required the application of multivariate analysis to extract the spectral information connected with milk composition. 

The accuracy of SCC determination in composite cow s milk by NIR spectroscopy has allowed health screening of cows and differentiation between healthy and mastitic milk samples. It has been found that SCC determination by NIR milk spectra is based on the related changes in milk composition. The most significant factors that influence NIR spectra of milk are the alteration of milk proteins and changes in ionic concentration of mastitic milk. 

Emulsions were composed of 3% proteins (milk proteins in powdered form), 9% fat, and 0.5% emulsifier. The model food emulsions were flavored with an aroma mixture at 0.04%. The composition of food model emulsions is indicated in Table 1. Because of the confidential nature of this project, a more detailed description of the fats used cannot be made available. 

Bequette, B.J., N.E. Sunny, S.W. El-kadi and S.L. Owens, 2006. Application of stable isotope and mass isotopomer distribution analysis to the study of intermediary metabolism of nutrients. J. Anim. Sci. 84 (E.Suppl.), E50-E59. Brun-Lafleur, L., L. Delaby, F. Husson and and R Faverdin, 2010. Predicting energy x protein interaction on milk yield and milk composition in dairy cows. J Dairy Sci. (accepted for publication). 

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