Food cans

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. 

Canned and Semimoist Foods. Canned and dry foods are nutritionally comparable on a moisture-free basis. Some canned foods are basically dry foods to which gravy, moisture, and flavor enhancers have been added. Almost all animals tend to prefer moist foods to dry, and canned foods are desirable for geriatric dogs and cats, particularly those having gum and dental deterioration. Canned foods can be gulped by dogs and consumed quickly by cats. 

Extmsion processing is highly automated. Some extmders may process over 9 t/h, and in one Ralston Purina plant (Davenport, Iowa) 30 extmders were operating in a single location. With computer assistance, one person can operate many different extmders, and several different foods can be produced simultaneously. These maybe different formulations or different colors and shapes to be packaged singly or combined into one variety pack. The differences in variety may be attributable only to added colors or different shapes. 

A persistent idea is that there is a very small number of flavor quaUties or characteristics, called primaries, each detected by a different kind of receptor site in the sensory organ. It is thought that each of these primary sites can be excited independently but that some chemicals can react with more than one site producing the perception of several flavor quaUties simultaneously (12). Sweet, sour, salty, bitter, and umami quaUties are generally accepted as five of the primaries for taste sucrose, hydrochloric acid, sodium chloride, quinine, and glutamate, respectively, are compounds that have these primary tastes. Sucrose is only sweet, quinine is only bitter, etc saccharin, however, is slightly bitter as well as sweet and its Stevens law exponent is 0.8, between that for purely sweet (1.5) and purely bitter (0.6) compounds (34). There is evidence that all compounds with the same primary taste characteristic have the same psychophysical exponent even though they may have different threshold values (24). The flavor of a complex food can be described as a combination of a smaller number of flavor primaries, each with an associated intensity. A flavor may be described as a vector in which the primaries make up the coordinates of the flavor space. 

Epoxy phenoHc coatings either are made by blending of a soHd epoxy resin with a phenoHc resin or are the products of the precondensation of a mixture of two resins. A three-dimensional stmcture is formed during curing which combines the good adhesion properties of the epoxy resin with the high chemical resistance properties of the phenoHc resin. The balanced properties of epoxy phenoHc coatings have made them almost universal in their appHcation on food cans. 

Food processing operations can be optimi2ed according to the principles used for other chemical processes if the composition, thermophysical properties, and stmcture of the food is known. However, the complex chemical composition and physical stmctures of most foods can make process optimi2ation difficult. Moreover, the quaUty of a processed product may depend more on consumer sensory responses than on measurable chemical or physical attributes. 

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. 

Acid foods generally require the simplest equipment for heat preservation. The food can be heated to 100°C and filled hot into suitable containers. The containers are sealed, inverted to sterilize the closure, held at the filling temperature for a short time to ensure that the package is thoroughly heated, and then cooled. Tomato sauces, jellies, fmits, fmit juices (qv), and pickles are routinely preserved in this fashion. 

Pleasant odors of flowers, fmit, or food can reheve the depression of hospital patients, whether they are aware of the scents or not. 

Pet Foods and Commercial Animal Feeds. Eor many years, it has been known that stable, long-shelf-life, intermediate-moisture pet foods can be prepared through the use of 0.1—0.3 wt % sorbates. In these products, the antimicrobial effectiveness of sorbates is enhanced by a combination of moderate heat treatment, pH adjustment, and reduced water activity via humectants such as propylene glycol, or by adjusting sugar and salt content. These techniques have been reviewed extensively (138,139). 

The efficient recovery of volatile nitrosamines from frankfurters, followed by gc with chemiluminescence detection, has been described (133). Recoveries ranged from 84.3 to 104.8% for samples spiked at the 20 ppb level. Methods for herbicide residues and other contaminants that may also relate to food have been discussed. Inorganic elements in food can be deterrnined by atomic absorption (AA) methods. These methods have been extensively reviewed. Table 8 Hsts methods for the analysis of elements in foods (134). 

Rich sources of vitamin A include dairy products such as milk cheese, butter, and ice cream. Eggs as well as internal organs such as the Hver, kidney, and heart also represent good sources. In addition, fish such as herring, sardines, and tuna, and in particular the Hver oil from certain marine organisms, are excellent sources. Because the vitamin A in these food products is derived from dietary carotenoids, vitamin A content can vary considerably. Variation of vitamin A content in food can also result from food processing and in particular, oxidation processes (8). 

A component of polycarbonate plastics and epoxy resins used to line food cans... 

Phenolic resins are useful surface coating materials. Resols are useful for stoving lacquers for coating chemical plant, textile equipment, razor blades, brassware cuid food cans. Phenolic resins are used with poly(vinyl formal) as a flexible, tough and solvent-resistant wire enamel. Oil-soluble resins based on synthetic phenols form the basis of some gloss paints. 

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. 

Two-piece food cans may be made by a draw-redraw process, in which lacquer is first applied to and cured on sheet. Blanks are then cut from the sheet and the can is drawn from the blank in two or three stages. The lacquer deforms with the drawing process and lubricates the draw. It then becomes the interior protective coating. Although epoxy-phenolic solvent-borne lacquers are used, even better drawing properties are obtained from organosols. These are dispersions of colloidal polyvinyl chloride powder in solutions of other mixed resins in solvent, e.g. chosen from epoxy, polyester, vinyl and phenolic. 

Energy values of food can be estimated on the basis of the content of carbohydrate, protein, and fat ... 

Incorporating a proportion of SCP into manufactured foods can disguise unpleasant flavours or textures. Food technologists have a wide array of flavourings at their disposal, which can be used to produce particular flavours. If this cannot be done it might be possible to use the SCP as feed. 

To appreciate the potential changes in food cans, it is necessary to describe briefly the steel-based materials used in modern can manufacturing operations. The tin can is made from a special grade of thin gage, low carbon, cold-rolled steel, which is generally referred to as a tin mill product. The base steel is coated with either tin, a chromium-chromium oxide system, or it is just cleaned and oiled. It may also be coated with organic coatings. 

TFS-CT or TFS-CCO is a primary material for cemented and welded beer and carbonated beverage containers (20-22) and can be used in sanitary food cans. It is currently used for ends on soldered sanitary food cans and is a candidate for drawn containers which do not require soldering. 

There are several areas to consider when discussing the future of the food can. Anti-pollution legislation, new can-making technologies, and public safety aspects will have a pronounced effect on food container design. 

Cemented and Welded Cans. Beer and carbonated beverage cans, made by the now familiar cementing (22) and welding (20) processes, are shown in Figure 8. These processes could also be used for sanitary processed food cans. Enameled TFS materials are used for these cans. Corrosion performance of the enameled, cemented, and welded cans is similar to that of enameled soldered cans for products which do not require the cathodic protection usually supplied by the tin coating. 

Process particulate pickup may significantly increase the risk of boiler foaming. This kind of problem happens in the crossover of hot to cold water during manufacturing processes, as in rubber tire factories, food can cookers and retorts, plastic injection molding, and the like). 

Some simple foods can be preservatives in their own right. Honey, salt, sugar, lactic acid, and vinegar are all examples of foods that inhibit microbial action. Some health professionals recommend consuming phytoestrogens from foods such as soybeans to achieve various health benefits. The phytoestrogens in the paraben family, found in blueberries, kill molds and fungi and are often added to food as preservatives. 

Methylquinoxaline 4-oxide (264) selectively from 2-methylquinoxaline 1,4-dioxide (265) (ascorbic acid, H2O, 90°C, 5 h 58% homologs likewise) the natural amino acids in foods can also reduce such quinoxaline N-... 

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