Evaporated milk, lead

Capar SG, Rigsby EJ. 1989. Survey of lead in canned evaporated milk. J Assoc Off Anal Chem 72 416-417. 

Dabeka RW. 1989. Survey of lead, cadmium, cobalt, and nickel in infant formulas and evaporated milks and estimation of dietary intakes of the elements by infants 0-12 months old. Sci Total Environ... 

AOAC Method 979.17 Lead in evaporated milk and fruit juice (1984)... 

The primary focus of these programs has been on the. "tin" can. There are two types of tin cans with which FDA has had concerns the "vent hole" can and the ordinary "sanitary" can. The evaporated milk industry utilizes the "vent hole" can exclusively. In the early 1970 s, an excessive lead content was found in evaporated milk. As a result, FDA initiated a quality assurance program with the evaporated milk industry to ensure compliance with a 0.5 ppm limit on lead in milk. Through cooperative effort, a decline from 0.52 ppm in 1972 to less than 0.10 ppm was achieved. 

In 1979, an advance notice of proposed rulemaking was published by FDA in the Federal Register (44 FR 51233) describing FDA s philosophy on controlling lead in foods. It proposed various steps to expedite the reduction of lead in the food supply. Among these was the establishment of action levels for lead in canned infant foods, such as evaporated milk, formula, and juices, and subsequent action levels for lead in other food products consumed by adults but with priority given to foods fed to children at early ages. Our concern for adult canned foods... 

We have seen figures and tables here showing that the lead level dropped in evaporated milk from 0.5 ppm to less than 0.1, for canned fruit juices from 0.3 ppm to about 0.014 ppm, and finally, for canned infant formula from 0.1 ppm to 0.02 ppm. As children absorb substantially more lead in the early phase of childhood than adults, the US Food and Drug Administration has made a special recommendation for infants and children, to which I referred already above The lead intake from all sources should be less than 100 ig per day for children up to 6 months of age, and should be less than 150 pg per day for children aged between 6 months and 2 years. 

Human exposures to lead in the diet historically comprised a major fraction of overall lead exposures in the United States and elsewhere, especially for adults. However, in a number of instances, such as infant consumption of Pb in evaporated milk from lead-seamed cans, many children also sustained significant dietary Pb exposures. Dietary lead intakes, for purposes of this chapter, are separated from drinking beverages prepared from drinking water, but include foods cooked in tap water containing Pb. 

In 1990, the total milk equivalent consumption of all dairy products was 570.6 lb (259.4 kg), a 13% decline from 1960. But the growth in human population offset per capita decline, with the result that total consumption increased. From Table M-22, several trends are apparent Americans have become weight conscious in recent years leading to a decreased per capita consumption of fluid whole milk and cream and an increased per capita consumption of low-fat milk. Per capita fluid whole milk consumption declined 67% from the period of 1960 to 1990, while per capita low-fat milk consumption increased 313%. Of the manufactured dairy products, per capita consumption of butter declined 41%, and evaporated milk 42%, in the period 1960 to 1990. Per capita total cheese consumption increased 34% in this same period. Per capita consumption of ice cream declined due to the increased popularity of frozen yogurt. 

The U.S. Food and Drug Administration (FDA) reported that in 1979, over 90% of food containers contained lead-soldered seams. The FDA has since sought to reduce a child s daily dietary lead intake by, for example, establishing permissible lead residues in evaporated milk and evaporated skim milk and reducing lead in canned infant formulas, infant fruit, and vegetable juices. By 1986, the percentage of food containers with lead-soldered seams was reduced to 20%. (ATSDR, 1988 CDC, 1985 EPA, 1988). 

As the temperature of the liquid milk increases, its rate of evaporation increases. This will disrupt the equilibrium, making the rate of evaporation greater than the rate of condensation. This leads to an increase in the concentration of water molecules in the gas space above the liquid, which increases the rate of condensation until it increases enough to once again become equal to the rate of evaporation. At this new dynamic equilibrium, the rates of evaporation and condensation will both be higher. 

The trick in using emulsions is based on the fact that one can apply both water and oil (latter is insoluble in water) simultaneously. Further, one can then include other molecules, which may be soluble in either phase (water or oil). This obviously leads to the common observation where we find thousands of applications of emulsions. It is very important to mention here that actually nature uses this trick in most of the major biological fluids. The most striking example is milk. The emulsion chemistry of milk (and other food anulsion systems) has been found to be the most complex (Kristensen, 1997). Paint consists of polymer molecules dispersed in water phase. After application, water evaporates, leaving behind a glossy layer of paint. 

Lactose is the main milk sugar, which reacts with whey proteins, leading to loss of lysine. This reaction (the Maillard reaction) is particularly intense during milk evaporation or drying (see Section 4.7.5.12.3). 

Evaporation and drying leads to more extensive reactions than in UHT milk that include degradation of proteins and thiamine, Maillard reaction between proteins (preferably in bound lysine) and lactose, degradation of 0x0- and hydroxycarboxyhc acids and oxidation of fatty acids. PhosphoKpids of fat particles are particularly susceptible to oxidation. It is therefore mainly alkane-2-ones, lactones and the Maillard reaction products that are responsible for the odour of condensed and powdered mflk. In addition to these compounds, typical aromatic substances are benzalde-hyde, acetophenone, 2-aminoacetophenone, furfiiryl alcohol and benzothi azole. 

Films can be formed by solvent removal as a result of an increase in the polymer concentration in the solution, leading to molecule aggregation and formation of a three-dimensional network. Films that are obtained by skimming of the skin formed on the surface of heated protein milks, result from the polymerisation of heat-denatured proteins associated with solvent evaporation [22, 63]. Coacervation is said to be simple when a... 

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