Preserved milk

Milk is sold preserved in its natural state, i e pasteurised or sterilised and even Jrozen 1 also condensed, -with or without addition of sugar, and also in the form of cakes and powder. 

Pasteurised or sterilised milk is recognised by the tests already given (p. 29) it has the same composition as natural milk, and should not contain antiseptics or other preservative agents. 

Condensed milks are mostly condensed to one-third of their volume. Their composition varies somewhat, atcording to the degree of concentration and to the addition of sugar (see later). Good products should be slightly yellowish, should have no unpleasant smell or cheesy flavour and should be homogeneous and show no clots, fat drops or crystals (lactose). 

Condensed milk is usually sold in soldered tins. The analysis should be made immediately after opening, since such products readily change, especially when little or np sugar has been added. Of special importance are tests for antiseptics and other preservatives (see Milk, No. 11) and heavy metals, and bacteriological examination. 

Milk in cakes or milk powder consists of milk reduced by special methods to the dry state the former often contains added sugar. 

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Minzner, R. A., Jr. and Kroger, M. 1974. Physicochemical and bacteriological aspects of preserved milk samples and their effect on fat percentages as determined with the Milko-tester. J. Milk Food Technol. 37, 123-128. 

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. 

A 30 or 40 per cent by volume hydrogen peroxide is used as bleach for silk, wood, Wool, bones, teeths, feathers, mother of pearl, hom, hair, coral, gelatine, oils and fats. In medical science it is an excellent disinfectant and is also essential for sterilizing water for municipal use and preserving milk. Apart from this, hydrogen peroxide is used in the chemical industries for the manufacture of persalts and in laboratories for oxidation. 

Oxidoreductases Glucose oxidase Aspergillus niger Increase gluten strength Improve shelf life Preserve milk Indirect enzymatic bleaching Tooth paste... 

Dr. Penington, who devised a method of heat-preserving milk (prior to pas-... 

Horses, also, about tbe works develop ulcerations if tbe salt get into wounds or cracks in tbe legs and tbe animals may lose tbeir hoofs. Cases of poisoning by chromates are rare. They have been recorded by J. Maschka, E. 0. MacNiven, W. A. McLach-lan, J. J. Bloomfield and W. Blum, A. M Crorie, G. Wilson, J. T. Gadsby, A. D. Walker, G. Leopold, 0. von Linstow, and R. C. Smith. The symptoms are severe gastro-intestinal inflammation, accompanied by depression, stupor, and death. The subject was discussed by A. Hebert, H. Becker, L. Lewin, etc. The objectionable uses of chromates for preserving milk, etc., was discussed by... 

Ayurvedic (Uttarakhand and Himachal Pradesh, India) swam Germicide to preserve milk and other dairy products. Lichen is dried and burned, and milk is exposed to the smoke (Sharma 1997)... 

If food can be heated quickly to a temperature of I3I°C a lethaUty equivalent to 6 min at I2I°C can be accumulated in 36 s. This rapid heating and cooling of hquid foods, such as milk, can be performed in a heat exchanger and is known as high temperature—short time (HTST) processing. HTST processing can yield heat-preserved foods of superior quahty because heat-induced flavor, color, and nutrient losses are minimized. 

Aseptic processing systems have found wide use for packing juices and milk products for the retail market and for the bulk preservation of tomato paste and fmit sHces for use as ingredients. Further information on aseptic processing can be found in the Hterature (2). 

Milk has been a source for food for humans since the beginning of recorded history. Although the use of fresh milk has increased with economic development, the majority of consumption occurs after milk has been heated, processed, or made into butter. The milk industry became a commercial enterprise when methods for preservation of fluid milk were introduced. The successful evolution of the dairy industry from small to large units of production, ie, the farm to the dairy plant, depended on sanitation of animals, products, and equipment cooling faciUties health standards for animals and workers transportation systems constmction materials for process machinery and product containers pasteurization and sterilization methods containers for distribution and refrigeration for products in stores and homes. 

Clarification and homogenization precede evaporating and dryiag. Homogenization of whole milk at 63—74°C with pressures of 17—24 MPa (2500—3500 psi) is particularly desirable for reconstitution and the preservation of quaUty. 

Tinned copper and copper alloys Copper itself has a fair corrosion resistance but traces of copper salts are often troublesome and a tin coating offers a convenient means of preventing their formation. Thus copper wire to receive rubber insulation is tinned to preserve the copper from sulphide tarnish and the rubber from copper-catalysed oxidation, and also to keep the wire easily solderable. Vessels to contain water or foodstuffs, including cooking vessels, water-heaters and heat exchangers, may all be tinned to avoid copper contamination accompanied by possible catalysis of the oxidation of such products as milk, and discolouration in the form of, for example, green stains in water and food. 

Lactic acid is what gives the sour taste to spoiled milk and to sauerkraut. It is used in foods to add tartness, and to preserve freshness in... 

Ruas Madiedo, P., Bada Gancedo, J. C., Fernandez Garcia, E., Gonzalez de Llano, D., and Reyes Gavilan, C. G. D. L. (1996). Preservation of the micobiological and biochemical quality of raw milk by carbon dioxide addition a pilot-scale study. /. Food Prot. 59, 502-508. 

Singh, R. K., Nielsen, S. S., Chambers, J. V., Martinez-Serna, M., and Villota, R. (1991). Selected characteristics of extruded blends of milk protein raffinate or nonfat dry milk with com flour. /. Food Process. Preserv. 15, 285-302. 

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