Tin in food

H. Cheftel, Tin in Food,]o m. EAO/WHO Eood Standards Program, 4th Meeting of the Codex Committee on Pood Additives, PEPT, 1967, oint PAO/WHO Pood Standards Branch (Codex Alimentarius), EAO, Rome. 

High tin concentrations in food may cause short-term acute health effects in some people, including stomach upsets, abdominal cramps, nausea and/or diarrhoea. These short-term effects may occur in some individuals at concentrations above 200 mg/kg.33 The UK Tin in Food Regulations 1992 limit the maximum amount of tin in food sold in the UK to 200 mg/kg.34 Fortunately, concentrations of tin in most foods are well below 10 mg/kg, although canned foods may contain higher concentrations as a result of slow dissolution of the tin coating used on some cans to protect the steel body of the can from corrosion. Tomato-based products tend to have high levels of tin as nitrate in the food accelerates corrosion of the tin. A survey of canned tomato products sold in the UK in 1998/1999 found that 98% of the products tested were below the 200 mg/kg limit.35... 

AOAC. 1984b. Tin in food Atomic absorption spectrophotometric method. In AOAC official methods of analysis, 474. 

Steering Group on Food Surveillance (1985) The Working Party on the Monitoring of Foodstuffs for Heavy Metals. Survey of Aluminium, Antimony, Chromium, Cobalt, Indium, Nickel, Thallium, and Tin in Food, pp. 1-76. Ministry of Agriculture, Fisheries and Food Surveillance Paper No. 15, HMSO, London, UK. 

The earliest methods for tin analysis, namely, gravimetric and titrimetric methods, are now mainly of historical interest. Being essentially macro methods, laborious in application, they are limited and mainly useful for levels of tin in food in the 50-100 ppm range or above. The use of colorimetric analysis is associated with problems of specificity, sensitivity, and stability of the tin complexes formed. Nowadays, methods for tin analysis in biological media include the various atomic spectroscopic techniques (atomic absorption spectrometry, atomic emission spectroscopy, and inductively coupled plasma atomic emission spectrometry) as well as electrochemical and neutron activation procedures. 

Tin occurs in all humans organs. Although a growth-promoting effect was detected in rats, it is disputed. The natural level of tin in food is very low, but it can be increased in the case of foods canned in tinplate cans. Very acidic foods can often dissolve substantial amounts of... 

The natural content of tin in foods is very low and mean concentrations are <1 mg/kg in most foods (meat 0.007, meat products 0.18, offal 0.014, poultry 0.006, fish 0.032, milk 0.003, dairy products 0.297, eggs 0.003, fresh fruit 0.019, green vegetables 0.003,... 

Tests have shown that considerable quantities of tin can be consumed without any effect on the human system. Small amounts of tin are present in most hquid canned products the permitted limit of tin content in foods is 300 mg/kg in the United States and 250 ppm in the UK, which far exceed the amount in canned products of good quaUty (19) (see also Tin compounds). 

Boron, as barium metaborate, is marketed as a mildew preventative for paints (273). Borax is used as a wood preservative, and an organic boron, 2,2 -(l-methyltrimethylenedioxy)-bis(4,4,6-trimethyl)-l,3,2-dioxaborinane (Biobor JF) [14697-50-80] is a biocide for jet fuel (274). Whereas tin metal is used to coat steel cans used as food containers, organic tin in the form of tributyl tin compounds have proven to be powerfiil antimicrobials, and have found use in antifouHng coatings for ship bottoms, paints, and wood preservatives (275). 

Steel coated with tin (tinplate) is used to make food containers. Tin is more noble than steel therefore, well-aerated solutions will galvanically accelerate attack of the steel at exposed areas. The comparative absence of air within food containers aids in preserving the tin as well as the food. Also the reversible potential which the tin-iron couple undergoes in organic acids serves to protect exposed steel in food containers. 

Procedure (tin in canned foods). The procedure provides for the removal of interfering copper by the addition of diethylammonium diethyldithiocarbamate in chloroform reagent. ... 

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. 

Mercury, tin, lead, arsenic, and antimony form toxic lipophilic organometallic compounds, which have a potential for bioaccumulation/bioconcentration in food chains. Apart from anthropogenic organometallic compounds, methyl derivatives of mercury and arsenic are biosynthesized from inorganic precursors in the natural environment. 

Applications Multidimensional SEC techniques can profitably be applied to soluble polymer/additive systems, e.g. PPO, PS, PC - thus excluding polyolefins. A fully automated on-line sample cleanup system based on SEC-HRGC for the analysis of additives in polymers has been described, as illustrated for PS/(200-400ppm Tin-uvin 120/327/770, Irgafos 168, Cyasorb UV531) [982], In this process, the high-MW fractions are separated from the low molecular masses. SEC is often used as a sample cleanup for on-line analysis of additives in food extracts these analyses are usually carried out as on-line LVI-SEC-GC-FPD. 

Food contamination may result from transmission of lead from glaze, enamel, or tinning on kitchen dishes, or from the lead on surfaces of containers or pipes used for storage, processing and transportation of food products. The occurrence of lead in food can also result from environmental contamination, as plants and animals may assimilate lead during growth and incorporate it into their tissues. The level of lead found in plant tissues is proportional to its concentration in the environment, and in cases of animals, the feed and water supplies also play important roles (Vreman et al., 1988 McLaughlin et ah, 1999 Sedki et ah, 2003). 

At present, Polish standards limit the content of tin only in food products packed in tin-coated containers, and in fruit and vegetable preserves, and products including such preserves, packed in other materials (Dz. U., 2003). The content of tin in products intended for children up to the age of three must not exceed 10 pg per g, and for other products it must not exceed 100 pg per g (for food in tin-coated packing) or 20 pg per g (for food in other types of packing). The Joint FAO/WHO Expert Committee established the PTWI value for tin as 14,000 pg per g (14 mg per g) of body weight (WHO, 1989). 

Tin is anther ancient metal that continues to have a variety of uses. The inorganic form is used in food packaging, solder, brass, and as an alloy with other metals. The organic forms of tin, triethyltin and trimethyltin, are used as fungicides, bactericides, and generally as antifouling agents for boats. 

L. Perring and M. Basic-Dvorzak, Determination of Total Tin in Canned Food Using Inductively Coupled Plasma Atomic Emission Spectroscopy, Anal. Bioanal. Chem. 2002,374, 235. 

Carbon is the definitive nonmetal, considering its vast variety of covalent compounds. The diamond structure (3 2PT, Section 4.4.3) has a network of tetrahedra. The next two elements of the carbon family, silicon and germanium, have the diamond structure, and lead is cubic close-packed. Tin shows an interesting variation. The low temperature form of tin (stable below 13.2°C) is gray tin with the diamond structure. The CN of Sn is 4, the Sn—Sn distance is 2.80 A and a0 = 6.4912. Ordinary tin, the "high temperature form, is white tin. In our time tin is used primarily for tin plate on iron for food containers, tin cans. In earlier periods utensils were often cast tin. In cold climates sometimes a tin utensil would crumble from "tin disease," resulting from conversion of white tin to gray tin. The conversion is slow, but once started, nucleation causes spread of the "disease."... 

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). 

Tin is widely distributed in nature at low concentrations in plants, both marine and land, and animals. It has extensive uses in industry, where organotin compounds are used as heat stabilisers in plastics, salts in glazes in porcelain and oxide coatings used to reduce abrasion of glass containers. The main source of tin in the diet is from tin-plated steel used in the manufacture of cans for foods and beverages. 

Most of the surveys on metals and metalloids in food have concentrated on those elements that are known to be toxic, or where there are possible concerns about their levels in food. In the course of collecting the data, information on other metals is often collected in addition. Other metals that have been included in the UK Government s surveillance are zinc, antimony, chromium, cobalt, indium, nickel, thallium and tin. 

Compounds of antimony are used as fire retardants in plastics and paper, and for veterinary purposes. The metal is found in specialised alloys such as white metal bearings and pewter, which is an alloy of tin, antimony (up to 7.5%) and copper. Concentrations in food are low, generally in the range <0.01 to 0.08 mg/kg, but have been found to be higher in samples of aspic jelly and cream of tartar.40 The... 

With some caveats, the toxicological information required is the same as for other chemical contaminants in our food, irrespective of their source. Chronic effects are the main concern - i.e. low-level long-term exposure to migrating substances. One exception is the migration of tin from tinplate steel into canned tomato products where high tin concentrations in food may cause short-term stomach upsets in some people but without any lasting harm. 

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