Milk analysis composition

Newburg, D.S., and Nenbauer, S.H. 1995. Carbohydrate in milks analysis, quantities, and significance. In Handbook of Milk Composition, ed. R.G. Jensen, pp. 273-349. San Diego, CA Academic Press. 

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. 

F rom an analysis of variance with a general linear model including the effect of diet (D) and batch (B), lactation stage (S) and their interactions as fixed effects. Repeated measurements of milk chemical composition were analysed using an unstructured covariance structure wilh sows within bateh as a subject. Statistical significance P<0.05, ... 

In a study completed during the early development of f.a.b.-m.s., both f.d. and f.a.b. were used to characterize 101 fractions containing neutral oligosaccharides isolated from human milk. Samples were examined as their peracetylated alditols. In subsequent work, the structures of two minor acidic oligosaccharides from human milk were investigated. The per-methylated derivatives were analyzed by f.a.b.-m.s., and their compositions and sequences were defined by the f.a.b. data. Methylation analysis and partial formolysis were the other principal methods used. 

Recent applications of HPAEC-PAD are many and varied. A representative list includes quantitation of polyglucose metabolites in plasma of dialysis patients,148 analysis of heat-treated milk,149 carbohydrate content in lipopolysaccharides,150 phosphorylated sugars in tissue samples,151 composition of soybean meal,152 carbohydrate composition of recombinant modified tissue plasminogen activator,153 analysis of cyclization products from an enzyme reaction,154 carbohydrate content of glycoconjugate vaccines,155 and monitoring of patients with rheumatoid arthritis.156... 

Some samples may change on standing. For example, the cream separates out from milk samples and the buttery lumps have to be broken up before the analysis. The composition of other samples may change due to, for example, fermentation. 

Olfactorily active compounds carried in human milk have rarely been subjected to chemical analysis (Stafford, Horning and Zlatkis 1976 Pellizari, Hartwell, Harris III, Waddell, Whitaker and Erickson 1982 Shimoda, Ishikawa, Hayakawa and Osajima 2000 Bingham, Sreven-Tuttle, Lavin and Acree 2003), and so far no attempt was undertaken to characterize the volatile composition of human AG secretions. Thus, the degree of their chemical overlap or specificity cannot be evaluated. Here we present preliminary data from such comparative analyses of colostrum and AG secretions from the same women. 

The arterial and veinous systems supplying the mammary gland (Figure 1.5) are readily accessible and may be easily cannulated to obtain blood samples for analysis. Differences in composition between arterial and venous blood give a measure of the constituents used in milk synthesis. The total amount of constituent used may be determined if the blood flow rate is known, which may be easily done by infusing a known volume of cold saline... 

The so-called Ling oxalate titration indicates that CCP consists of 80% Ca3(P04)2 and 20% CaHP04, with an overall Ca P ratio of 1.4 1 (Pyne, 1962). However, the oxalate titration procedure has been criticized because many of the assumptions made are not reliable. Pyne and McGann (1960) developed a new technique to study the composition of CCP. Milk was acidified to about pH 4.9 at 2°C, followed by exhaustive dialysis of the acidified milk against a large excess of bulk milk this procedure restored the acidified milk to normality in all respects except that CCP was not reformed. Analysis of milk and CCP-free milk (assumed to differ from milk only in respect of CCP) showed that the ratio of Ca P in CCP was 1.7 1. The difference between this value and that obtained by the oxalate titration (i.e. 1.4 1) was attributed to the presence of citrate in the CCP complex, which is not measured by the oxalate method. Pyne and McGann (1960) suggested that CCP has an apatite structure with the formula ... 

Most creamery butter is produced by churning sweet cream so that the fat globules coalesce into a soft mass. The federal standard for butter (USDA 1981B) requires not less than 80% milk fat. FAO/WHO standards specify 80% milk fat, as well as no more than 16% water and a maximum of 2.0% nonfat milk solids (FAO 1973). The required fat level is universal. A typical analysis of butter is given in Table 2.3. Whey butter has a similar composition but is derived from the milk fat recovered from cheese whey. 

The ADSA Committee on Milk Protein Nomenclature (Eigel et al. 1984) presented a tentative nomenclature for the new enzyme membrane proteins. While the primary structures of these proteins have not been established, sufficient information exists to obtain an operational definition. The total protein complement of the membrane as observed is dependent upon the past history of the membrane from its formation to its analysis. Both the temperature and the time of storage before analysis can alter the membrane composition and physical state (Wooding 1971). In addition, plasmin has been shown to be associated with preparations of the membrane, and proteolytic products of the membrane protein have been observed in milk (Hoffman et al. 1979 Kanno and Yamauchi 1979). Therefore, one should use fresh warm raw milk for the study of the native MFGM protein. 

The application of several chromatographic procedures to the separation and identification of milk lipids was mainly responsible for these endeavors. The first gas-liquid chromatographic (GLC) analysis of milk fatty acids was published by James and Martin (1956). By 1960, many laboratories were using GLC for routine analysis of fatty acids. For example, Jensen et al. (1962) reported the fatty acid compositions of 106 milk samples taken during 1 year. In comparison, Hansen and Shorland (1952) analyzed only six samples in a year, using distillation of methyl esters. 

They studied the effect of the mass detectors drift tube temperature on the low-molecular-mass TGs. Solutions of 10 mg/ml of tributyrin, tricaproin, tricaprylin, tricaprin, and trilaurin were injected twice at each of the following drift tube temperatures 20,25, 30,45, and 60°C. Five replications of the HPLC analysis were performed for one sample of ewe s milk fat to determine the reproducibility of the HPLC method. The TG composition was estimated in accordance with the method based on the calculation of the equivalent carbon numbers (ECNs) of the HPLC chromatographic peaks and in the molar composition in fatty acids, analyzed by GLC, collected at the HPLC chromatograph outlet. The HPLC fractions were collected every 40 s at the outlet of the column after 14 min there were no peaks before that time. 

If sampling is not followed immediately by analysis, the sample must be treated with a preservative, but not such as to falsify the analytical results use is made of 10% potassium dichromate solution, formaldehyde, hydrogen peroxide, alcoholic solution of phenol, mercuric chloride (about 5% solution), etc., a few drops being added. The last of these preserves milk very well for several days without altering its composition or disturbing the determinations, but its poisonous character necessitates precautions. 

Consequently, a more objective way to measure the habitual intake of milk fat would be the fatty acid composition of adipose tissue. However, this is not routinely performed in larger cohort studies, due to cost and that the procedure is invasive and less tolerated by study participants. Analysis of plasma fatty acid composition is thus a more feasible option for examination to determine dairy intake in the study population. While some groups have separated plasma into its constituent phospholipids and cholesterol esters to analyze serum 15 0 and 17 0 as markers of dairy intake (Smedman et al., 1999), Baylin et al. (2005) found that plasma that was not separated into its constituent cholesteryl ester, phospholipids, and triacylglycerols was still able to reflect habitual dairy intakes comparably to adipose tissue. Thus, whole plasma is an acceptable alternative to fractionated plasma in the absence of adipose tissue for analysis to reflect habitual dairy intakes and may be a cost effective option for consideration when conducting future intervention studies to assess the affect of dairy products on health outcomes. 

Many of the tests described involve physical properties such as refractive index, viscosity or melting point of the fat, of the fatty acids or of the lead salts of the fatty acids. However, there were also many chemical tests such as Reichert, Polenske, iodine, saponification and acetyl values. These all gave information as to the composition of the fat, some information as to fatty acid composition, others as to other non-glyceride components of the fat. Thus the iodine value is a measure of unsaturated fatty acids in the fat, now obtainable in more detail from a fatty acid profile. Similarly the Reichert value is a measure of volatile fatty acids soluble in water. For most purposes this means butyric acid, and so the modem equivalent is the determination of butyric acid in the oil. The modem method for milk-fat analysis is thus carrying out the analysis in a similar way to the Reichert determination, but uses a technique that is less dependent on the exact conditions of the analysis and is thus less likely to be subject to operator error. The Reichert value could be useful, in theory, even if milk fat was not present. Lewkowitsch notes that some other oils do give high values. Porpoise jaw oil has a value almost twice that of milk fat, while some other oils also have significant values. It is unlikely that one would have come across much porpoise jaw oil even in 1904, and even less likely today. 

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