Pasteurized Skimmed Milk

MUk protein standardizatiop (concentration of pasteurized skimmed milk). Milk protein standardization is designed to maintain the protein level in the milk constant all year round for automated cheese making. It basically involves concentration of pasteurized skimmed milk. It has been one of the major commercial successes in using inorganic membranes for food applications. In commercial production, microfiltration alpha-alumina and zirconia membranes with a pore diameter of 0.1 to 0.7 pm (mostly 0.2 pm) are used. Skimmed milk pasteurized at 70 C is typically concentrated to a volume concentration factor of 2 to 5 [Attia et al., 1988 van der Horst et al., 1994]. The volume concentration factor is the ratio of the initial feed volume to the retentate volume. Thus the higher the factor is, the more concentrated the product becomes. 

Nonfat dry milk—This product is prepared by removing water from pasteurized skim milk. Federal standards of Identity require that It contain not more than 5% by weight of moisture and not more than 1.5% by weight of milkfat unless Indicated. Except for small losses of ascorbic acid, thiamin, vitamin B-12, and biotin, the processing has no appreciable effect on the nutritive value of the milk. Due to Its low moisture content. It can be kept for long periods. 

Definition Obtained from fresh and pasteurized skimmed milk by acid coagulation of casein... 

An immunoassay was developed to determine the penicillinase stable isoxazolyl penicillins cloxacillin and dicloxacillin in milk by Usleber et alJ The assay detected lOpgkg" of cloxacillin and 30pgkg of dicloxacillin with recoveries of 102% and 84%, respectively. The calibration curve was prepared by fortifying skimmed milk powder (lOOgL ) with standards. Fortified samples were prepared in pasteurized milk and analyzed directly after decreaming by centrifugation. This immunoassay was performed with minimal sample preparation, probably because the extensive water solubility of the penicillins prevents problems associated with more lipid-soluble analytes. 

Pasteurized processed cheese foods =S44 >23 As for pasteurized blended cheese, but with the following extra optional ingredients (milk, skim milk, buttermilk, cheese whey, whey proteins - in wet or dehydrated forms)... 

The viscosity of milk and creams tends to increase slightly with age, due in part to changes in ionic equilibria. Heating skim milk to an extent that denatures most of the whey proteins increases its viscosity by about 10%. Homogenization of whole milk has little effect on its viscosity. The increase in the volume fraction of fat on homogenization is compensated by a decrease in the volume fractions of casein and whey proteins because some skim milk proteins are adsorbed at the fat-oil interface. Pasteurization has no significant effect on the rheology of whole milk. 

Microbiological tests have indicated that penicillin G is stable to heat. Pasteurization temperatures and times commonly applied to milk and milk products are inadequate for inactivation of tlie antibiotic if it is present (26-29). At 71 C, a total of 1705 min was required to inactivate completely penicillin G in milk, whereas at boiling temperatures or above, all data indicated that a portion of tire penicillin activity in milk survived boiling for 60 min or autoclaving at 15 psi steam pressure for 15-30 min (26, 29). Milk from treated cows retained some of its antimicrobial activity even after conversion to dried skim milk powder (30). 

Lowfat Milks. Per capita consumption of lowfat and skim milk has increased substantially over the past decade. In the United States it represented almost 30% of the total fluid milk consumed in 1980. Milk with the fat content reduced below that of whole milk falls into the general category of lowfat or skim milk. Most lowfat milks contain a designated amount of fat between 0.5 and 2.5% frequently, 1 to 2% additional milk solids with vitamin D are added. The milk is pasteurized, homogenized, packaged, and refrigerated until sold. In the United States most states allow lowfat milks with fat contents of 0.5,1.0,1.5, or 2.0% but require that the percentage be shown on the label. 

Skim Milk. After all or most of the milk fat is removed from whole milk by continuous centrifugal separation, the resulting skim milk is fortified with 2000 International Units (IU) of vitamin A per quart and often with additional milk solids and vitamins, then pasteurized, packaged, and refrigerated until sold. The addition of vitamin D is optional but, when added, it must be not less than 400 IU/quart, and this must be shown on the label. 

Sour cream is prepared by mixing milk fat and skim milk, nonfat solids, and other ingredients. The mix is then pasteurized, homogenized, and cooled to the setting temperature starter and enzymes are then added, and the cream is allowed to ripen. After ripening, it is cooled for 24 hr before packaging. 

Acidophilus milk is a sharp, harsh, acidic cultured milk produced by fermenting whole or skim milk with active cultures of Lactobacillus acidophilus. Honey, glucose, and tomato juice may be added as nutrients to stimulate bacterial growth and contribute flavor. Plain acidophilus milk has the same composition as whole milk or skim milk, except that part of its lactose is converted to 0.6 to 1% lactic acid by the culture organisms. Speck (1976), who proposed the addition of L. acidophilus to pasteurized milk (sweet acidophilus milk), described the beneficial effects of implanting the organisms in the human intestines. 

Several types of fluid creams are manufactured and sold directly to consumers. The most significant difference in the creams is the level of milk fat they contain from as little as 10% in half and half to 40% in whipping cream. All commercial creams are produced by centrifugally separating the less dense, higher-fat products from the residual skim milk. Most often, cream with 40% fat is separated and then standardized with skim milk to give creams with the desired fat contents. In some instances, creams with desired fat contents are collected directly from the separator in others, as in plastic cream (made for manufacturing purposes), a 40% cream is pasteurized and reseparated while hot to yield a product with 80% fat. 

Edmondson et al (1971), who studied the enrichment of whole milk with iron, found that ferrous compounds normally caused a definite oxidized flavor when added before pasteurization. Aeration before addition of the iron reduced the off-flavor. The authors recommended the addition of ferric ammonium citrate followed by pasteurization at 81 °C. Kurtz et al. (1973) reported that iron salts can be added in amounts equivalent to 20 mg iron per liter of skim milk with no adverse flavor effects when iron-fortified dry milk is reconstituted to skim milk or used in the preparation of 2% milk. Hegenauer et al. (1979A) reported that emulsification of milk fat prior to fortification greatly reduced lipid peroxidation by all metal complexes. These researchers (Hegenauer et al. 1979B) concluded that chelated iron and copper should be added after homogenization but before pasteurization by a high-temperature-short-time process. 

Homogenization of raw whole milk or cream stimulates lipolysis and thus leads to a decrease in surface tension, but if the product has been previously pasteurized, the effect of homogenization is an increase in surface tension (Trout et aL 1935 Watson 1958 Webb 1933). The reason for such an increase is not known, but suggestions have been made that it results from denaturation or other changes in the lipoprotein complex or from a reduction in the amount of protein available to the milk-air interface because of adsorption on the extended fat surface. The latter explanation seems unlikely in view of the very slight effect of fivefold dilution on the surface tension of skim milk. Another possible suggestion is that homogenization reduces the amount of free fat in the product. 

Surplus milk is commonly stored as frozen skim milk and whole milk concentrate and used as ingredients in ice cream and other formulated food products. There has also been some interest in producing frozen milk concentrates to substitute for pasteurized and sterile fluid milk products (Webb 1970). 

Lipolysis can occur in pasteurised milk as a result of post-pasteurization contamination by lipolytic psychrotrophs. In whole milk, this is a major cause of spoilage while in skim milk, proteolysis is the major cause... 

Enrichment of whole milk before pasteurization with ferrous iron has been reported to give rise to oxidized flavor (Edmondson et al, 1971). Aeration before addition of the iron reduced the effect. Kurtz et al, (1973), however, reported that milk powder can be fortified with iron in amounts equivalent to 20 mg/1 of iron in reconstituted skim milk without development of oxidized flavor. 

Whey is the liquid obtained by separating the coagulum from milk, cream, and/or skim milk in cheese making. Whey obtained from the process in which a significant amount of lactose is converted to lactic acid or obtained from the curd formed by direct acidification of milk is known as acid-type Whey. Whey obtained from the process in which there is insignificant conversion of lactose to lactic acid is known as sweet-type Whey. The acidity of Whey may be adjusted by the addition of safe and suitable pH-adjusting ingredients. The final product is pasteurized and is available as a liquid or dry product. 

Other demonstration tests using alumina membranes with a mean pore diameter of about 1.4 pm and with a cocurrent flow of permeate (to maintain a constant transmembrane pressure, TMP) to process skimmed milk by the cold pasteurization process have witnessed a flux exceeding 7(X) L/hr-m and 99.7% bacteria removal [Malmberg and... 

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