Dairy products methods

The physical characteristics of a fat or oil for imitation dairy products are not necessarily dictated by the fat being replaced, but by the composition, processiag methods, and conditions of use of the substitute product. Thus, the selection of the fat or oil is generally developed experimentally. The chemical and physical nature of the components of the system, order of addition, shear iaput, and processiag temperature dictate the final iateractions and the nature of the product. A comparison of the characteristics of milk fat and three different fats that are used ia satisfactory filled and imitation milks are listed ia Table 1 and those that comprise whipped toppiag, ia Table 2. 

For detection residue amounts of tetracyclines in dairy products widely used methods FIPLC, immunoaffinity chromatography, kinetic spectrophotometry, which are expensive and complicated. 

Five synthetic and five natural colorants were identified and quantified in lyo-philized dairy products and fatty foods using an automatic method based on solid phase extraction using a stationary phase followed by RP-HPLC C,g columns for the sequential retention of colorants and diode array detection. Lyophilization of the samples coupled with the separation procedure provided clean extracts despite the complexity of the food matrices and preserved the sample for at least 2 months without changes in colorant concentrations. The detection limits achieved for the colorants were found in a wide range from 0.03 to 75 pg/g of the lyophilized sample, according to the limits established by the European Union. ... 

In summary, the new 2D experiments of relaxation and diffusion appear to offer a new method to identify and quantify the components in dairy products. The two components are well separated in the 2D maps while they can be heavily overlapped in the ID spectrum. We find that some microscopic properties of the products can be reflected in the relaxation and diffusion properties. These new techniques are likely to be useful to assist the characterization of the products for quality control and quality assurance. 

The total-chlorine method for residues of the chlorinated hydrocarbons has also been applied to animal tissues, milk, and dairy products (9). As in the spray-residue determinations, the method does not differentiate between the insecticide and metabolites. 

Effects of organic and conventional feeding regimes and husbandry methods on the quality of milk and dairy products... 

J. Kramer, G. Carter, B. Arret, J. Wilner, W. Wright, and A. Kirshbaum, Antibiotic Residues in Milk, Dairy Products, and Animal Tissues Methods, Reports, and Protocols,... 

If it is required to perform the determination by digestion and distillation, refer to Method 5.6b. Determination of organic plus ammonium-N by digestion and distillation, but use 2 g oven-dry plant sample ground to 1 mm. Also, for the calculation, multiply the sample titre minus blank titre by 0.35 to give the % N in the sample. Multiply the % N by 6.25 to get the % crude protein. This assumes there are 160 g N kg- plant protein. Traditional factors for other products are almonds, 5.18 brazil nuts and peanuts, 5.46 coconuts and tree nuts, 5.30 dairy products, 6.38 wheat, 5.7. Note about 20% of any nitrate present will be included. 

Superoxide dismutase (SOD), an indigenous enzyme in milk, was discussed in section 8.2.10. A low level of exogenous SOD, coupled with catalase, was shown to be a very effective inhibitor of lipid oxidation in dairy products. It has been suggested that SOD may be particularly useful in preserving the flavour of long-life UHT milk which is prone to lipid oxidation. Obviously, the commercial feasibility of using SOD as an antioxidant depends on cost, particularly vis-d-vis chemical methods, if permitted. 

J.C. Bruhn, R.E. Ginn, J.W. Messer, and E.M. Mikolajcik, In Standard Methods for the Examination of Dairy Products (G. A. Richardson, ed.), 15th Edition, American Pubhc Health Association, Washington, D.C., p. 265 (1985). 

Perry, N. A. and Doan, F. J. 1950. A picric acid method for the simultaneous determination of lactose and sucrose in dairy products. J. Dairy Sci. 33, 176-185. 

The number of fatty acids and related compounds in milk lipids grew from 16 in 1959 (Jenness and Patton, 1959) to 142 in 1967 (Jensen et al. 1967) to over 400 in 1983. However, there are only 10 fatty acids of quantitative importance. The amounts (weight percent) as butyl esters prepared by three methods of esterification were determined by Iverson and Sheppard (1977). Because of the widely differing molecular weights of the fatty acids (4 0-18 0), fatty acid compositions of ruminant milk fats are often presented as a mole percent. The nutritionist needs the data calculated in yet another manner weight of fatty acid/100 g or 100 ml of edible portion. Analyses of food fatty acids should always be accompanied by the fat content so that the actual weights of the fatty acids and be calculated. A compilation of this type was made by Posati et al. (1975). Since these analyses were done with methyl esters, the contents of 4 0 are low. Data from Feeley et al. (1975), obtained from careful analyses, are more reliable, and USDA Handbook 8-1 (Posati and Orr 1976) has data for many milk and dairy products. 

Several methods have been introduced which express the degree of oxidation deterioration in terms of hydroperoxides per unit weight of fat. The modified Stamm method (Hamm et at 1965), the most sensitive of the peroxide determinations, is based on the reaction of oxidized fat and 1,5-diphenyl-carbohydrazide to yield a red color. The Lea method (American Oil Chemists Society 1971) depends on the liberation of iodine from potassium iodide, wherein the amount of iodine liberated by the hydroperoxides is used as the measure of the extent of oxidative deterioration. The colorimetric ferric thiocyanate procedure adapted to dairy products by Loftus Hills and Thiel (1946), with modifications by various workers (Pont 1955 Stine et at 1954), involves conversion of the ferrous ion to the ferric state in the presence of ammonium thiocyanate, presumably by the hydroperoxides present, to yield the red pigment ferric thiocyanate. Newstead and Headifen (1981), who reexamined this method, recommend that the extraction of the fat from whole milk powder be carried out in complete darkness to avoid elevated peroxide values. Hamm and Hammond (1967) have shown that the results of these three methods can be interrelated by the use of the proper correction factors. However, those methods based on the direct or indirect determination of hydroperoxides which do not consider previous dismutations of these primary reaction products are not necessarily indicative of the extent of the reaction, nor do they correlate well with the degree of off-flavors in the product (Kliman et at. 1962). 

Two variations of the thiobarbituric acid (TBA) method have been widely used to determine the degree of lipid oxidation in dairy products (Dunkley and Jennings 1951 King 1962). These methods, of approximately equal sensitivity, are based on the condensation of two mole-... 

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