Metal Food Cans

An essential requirement for the use of polymeric barriers in food packaging is the absence of any additive or residual monomers which can transfer potentially toxic components in any way to the contents of the package and impart an off-flavor to the product or present a health hazard. They must have little or no extractives which is particularly important to avoid odor or taste being imparted to food in the coated container. A variety of special purpose additives, which must be acceptable for use in food-contact applications, are used in coating systems. These additives include pigment dispersants, suspension agents, defoamers, emulsifiers, and rust prevention concentrates. 

The most common metal materials used for metal food cans are aluminum, tinplate, and electrolytic chromium-coated steel. The traditional cylindrical can is a three-piece can widely used for heat-processed foods, which consists of the can body and 

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What is BPA and what is it used for BPA is a precursor of resistant polycarbonate and epoxy plastics. It was first synthesized in 1888 (Fig. 4.26). Commercial use of BPA began when epoxy resins were developed in the 1950s. Epoxy resins are used as protective covering layers on metals (food cans, pipelines), dental adhesives, DVDs, cell phones, contact lenses, car parts, and sports equipment. In shopping receipts, BPA is a slightly acidic activator that causes color change when pressure or heat is applied. Because of its widespread use, BPA is produced on a vast scale, 5.4 million t a year. 

Other A OTHER <1 Polycarbonate (refillable plastic bottles, baby bottles, metal food can liners, consumer electronics, lenses) nylons (clothing, carpets, gears) biodegradable resins (food and beverage packaging) mixed plastics and blends (electronics housing, plastic lumber), etc. 

Since the 1990s, many studies have been dedicated to determining which consumer products contain BPA, and how much is released from these products into food and beverages under normal conditions of use (von Goetz et al. 2010). In particular, studies have focused on the levels of BPA released from baby bottles, food-contact papers, and epoxy resins used both for dental sealants and the linings of metal food cans (Schug et al. 2012 Carwile et al. 2011). These studies confirm... 

Industrial Analysis UV/Vis molecular absorption is used for the analysis of a diverse array of industrial samples, including pharmaceuticals, food, paint, glass, and metals. In many cases the methods are similar to those described in Tables 10.6 and 10.7. For example, the iron content of food can be determined by bringing the iron into solution and analyzing using the o-phenanthroline method listed in Table 10.6. 

Some metals used as metallic coatings are considered nontoxic, such as aluminum, magnesium, iron, tin, indium, molybdenum, tungsten, titanium, tantalum, niobium, bismuth, and the precious metals such as gold, platinum, rhodium, and palladium. However, some of the most important poUutants are metallic contaminants of these metals. Metals that can be bioconcentrated to harmful levels, especially in predators at the top of the food chain, such as mercury, cadmium, and lead are especially problematic. Other metals such as silver, copper, nickel, zinc, and chromium in the hexavalent oxidation state are highly toxic to aquatic Hfe (37,57—60). 

These replaceable cartridges or packs are the most commonly used however, there are cartridges of wire mesh, sintered or porous metal which can be removed, cleaned, and replaced. Usually, the fine pores of the metal become progressively plugged and the cartridges lose capacity. They are often used for filtering hot fluids, or polymers with suspended particles, pharmaceuticals, and foods (liquids). In the case of polymers and other applications a special solvent and blow-back cleaning system may be employed. 

There have been numerous reports of possible allergic reactions to mercury and mercury salts and to the mercury, silver and copper in dental amalgam as well as to amalgam corrosion products Studies of the release of mercury by amalgams into distilled water, saline and artificial saliva tend to be conflicting and contradictory but, overall, the data indicate that mercury release drops with time due to film formation and is less than the acceptable daily intake for mercury in food . Further, while metallic mercury can sensitise, sensitisation of patients to mercury by dental amalgam appears to be a rare occurrence. Nevertheless, there is a growing trend to develop polymer-based posterior restorative materials in order to eliminate the use of mercury in dentistry. 

Requirements for cans for beer and soft drinks differ from those for food cans in that (a) only low tin and iron contents can be tolerated in the product and (t>) the anticipated shelf-lives are much shorter. Specialised lacquering techniques including striping the seams are used to give complete cover to the metal. For soft drinks it is sometimes possible to select colouring matters and acids least likely to give rise to corrosion troubles, and rapid methods of testing formulations have been devised . Steel quality is also controlled by special tests. 

This type transfers heat from the process liquid to the cooling water across a large number of thinly spaced corrugated plates. They find particular application in food and beverage industry applications or for smaller heat loads in hotels or hospitals. Plate and frame types are widely used because of their compact design and availability of various construction materials. Because localized corrosion and metal wastage can occur within the crevices (crevice... 

Farhan FM, Hibibi N, Mofidi J, et al. 1979. Direct determination of traces of heavy metals in canned vegetables by are spectrography. J Agric Food Chem 27 637-638. 

The foods can be protected against lipid oxidation either by the addition of antioxidants or by packaging in vacuum or inert gases to exclude oxygen. The antioxidants can be of various types. They can work as "chain-breakers" that interfere with the free radical chain reaction, as "metal inactivators", that bind otherwise pro-oxidative metals, or as "peroxide destroyers", which react with hydroperoxides to give stable products by nonradical processes (1). 

Radium is a naturally-occurring silvery white radioactive metal that can exist in several forms called isotopes. It is formed when uranium and thorium (two other natural radioactive substances) decay (break down) in the environment. Radium has been found at very low levels in soil, water, rocks, coal, plants, and food. For example, a typical amount might be one picogram of radium per gram of soil or rock. This would be about one part of radium in one trillion (1,000,000,000,000) parts of soil or rock. These levels are not expected to change with time. 

The presence of elements known to have adverse health effects in humans such as lead and arsenic is obviously undesirable in food. Environmental sources are the main contributors to contamination of food with most metals and other elements. Some elements (e.g. arsenic) are present naturally but the major sources of other elements (e.g. lead) in the environment are from pollution from industrial and other human activities. The presence of metals and other elements in food can also be the result of contamination from certain agricultural practices (e.g. cadmium from phosphate fertilisers) or manufacturing processes (e.g. tin in canned foods). 

The risk to health from chemicals in food can be assessed by comparing estimates of dietary exposure with recommended safe levels of exposure. For most metals and other elements, these are the Provisional Tolerable Weekly Intakes (PTWIs) and the Provisional Tolerable Daily Intakes (PTDIs) recommended by the Joint Expert Committee on Food Additives of the Food and Agricultural Organisation of the United Nations and the World Health Organisation International Programme on Chemical Safety (JECFA). The European Commission s Scientific Committee on Food has established other relevant safe levels. These are Acceptable Daily Intakes (ADIs) for chemicals added to food, and Tolerable Daily Intakes (TDIs) for chemical contaminants. The use of the term tolerable implies permissibility rather than acceptability. All the above recommendations are estimates of the amount of substance that can be ingested over a lifetime without appreciable risk, expressed on a daily or weekly basis as appropriate. 

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