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Toxic Effects of Tinplate Corrosion and Mitigation Measures in Canned Foods

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Tin metal is widely used in packed canned foods and beverages packaging, largely due to less toxicity, corrosion resistivity, lubricity, lacquer ability, formability, solderability, and weldability. The integrity of tinplate (tin-iron alloy) comprises a coating of tin over both faces of carbon steel using various electrolytic processes. Moreover, for solid foods and beverages, 250 mg/kg for tin and 150 mg/kg for iron are recommended as maximum limits. Both the elements are toxic above these permissible concentrations. The excess doses of tin can induce serious digestive disturbances, gastrointestinal upsets, cancer in bones and tissues. The factors affecting corrosion failure and mitigation techniques for the prevention of corrosion in tin plate cans are discussed in this chapter.
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TOXIC EFFECTS OF TINPLATE
CORROSION AND MITIGATION
MEASURES IN CANNED FOODS
SHUBHRA PAREEK, DEEPTI JAIN, and DEBASIS BEHERA
CHAPTER 9
ABSTRACT
Tin metal is widely used in packed canned foods and beverages packaging,
largely due to less toxicity, corrosion resistivity, lubricity, lacquer ability,
formability, solderability, and weldability. The integrity of tinplate (tin-iron
alloy) comprises a coating of tin over both faces of carbon steel using various
electrolytic processes. Moreover, for solid foods and beverages, 250 mg/kg
for tin and 150 mg/kg for iron are recommended as maximum limits. Both
the elements are toxic above these permissible concentrations. The excess
doses of tin can induce serious digestive disturbances, gastrointestinal
upsets, cancer in bones and tissues. The factors affecting corrosion failure
and mitigation techniques for the prevention of corrosion in tin plate cans
are discussed in this chapter.
9.1 INTRODUCTION
Transportation of processed food is an important consideration the shelf-
life of foods. Moreover, excessive demand for agriculture production, food
commodities has fueled the establishment of packaging industry throughout
the globe. Tin (Sn) is a very ductile metal with a white color. It cannot be
dissolved in water due to its low solubility [6]. Along with its use for food
safety, tin also finds its application in bronze, brass, and pewter and shows
anti-corrosive properties [20, 24, 41].
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Tin cans can form signicant compounds with a combination of other
elements. The chemical reaction of Sn with oxygen, sulfur, or chlorine results
in inorganic-tin compounds. In addition, it forms organic-tin with carbon
or carbon derivatives. The inorganic tin (Sn) compounds have their distinct
applications as food additives, toothpaste, aromatic perfumes, coloring
agents, soaps, and dyes [39, 47].
Organic compounds are mainly used in plastic, paints, food packages,
pesticides, rodent repellants (mice and rats), and wood-preservative industries.
The organic, inorganic, and metallic forms of tin are found in water, air, and
soil, whereas the organic form of tin is purely from anthropogenic sources
[52, 57]. A large amount of tin is used to produce cans and container. Since tin
is naturally present in soil, therefore, small concentrations of tin (<2 ppm) are
commonly reported in fruits, vegetables, dairy products, nuts, sh, poultry,
meat, eggs, and beverages [41].
Humans can be exposed to this metal, if they directly ingest solid foods,
liquid juices or drink from canned food packages contaminated with high
concentrations of Tin. The concentration of tin metal in fast foods (such as
bread and pastas) is in the range of 0.003 to 0.03 ppm. Therefore, to avoid
human exposure to tin through canned foods, lacquered-tin cans are used
in its place. The use of lacquer in tin cans can protect the preserved food
from direct exposure of tin. As reported in literature, lacquered cans are
predominantly used for beverages, alcohols, water, soft drinks, nectars,
fruit juices, tomato puree, and tomato products, etc. In lacquer tin cans, the
concentration of tin is generally <25 ppm [49].
Another type of Tin can is one that is lined and un-lacquered. If the food
is kept in an un-lacquered tin lined can, then there is direct contact of tin
with the food. In this case, the canned food is reported to contain >100 ppm
concentration of Tin due to the reaction of preserved foods with tin metal
that directly or indirectly induces the dissolution of tin into the canned food.
Nowadays, more than 90% of tin plate cans for application of food or food
preservation are lacquered. Some light-colored fruit juices do not require the
use of lacquered tin lined cans. Since tin is helpful in maintaining the actual
color of the fruit juices. However, the corrosion in tin may occur due to the
prolonged contact of packaged food with the tin can [2, 40].
The main purpose of the food industry is to provide a product to the
consumers, which are safe and enriched with nutritional quality. The industry
is taking into consideration all parameters to maintain the quality of foods
and beverages because of the adverse effect of the corrosion caused by the
interaction between the food-products and food wrapping materials. Manu-
factures primarily ensure the integrity of the food product and manufacturing
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of tin plate substrate to boost the shelf-life of the food. However, the tin
plate is formed by a thin layer of electrodeposited tin over low carbon steel
[14, 18, 32]. The goal of these tin plates is to save food against unfavorable
chemical and physical reactions.
The corrosion resistance nature of tin plate cans offers a crucial role in
the shelf-life of preserved-foods, taste, and appearance, etc. In the United
Kingdom, the use of tin cans is around 2.5 million per year. In addition, steel
(25% of worldwide steel) is also utilized in the manufacturing of tin cans [56].
Kamm [23] stated that the corrosion in tinplates depends on the integrity of the
free tin and inter-metallic tin (alloyed tin) and exposed area of steel in tin plate.
The risk of high corrosion in the tin plate is due to a high number of
porosities in the tin coating, which is the reason behind low shelf-life of food
products [28]. Sometimes the uneven or discontinuous tin coating is also
the main cause for galvanic corrosion, which appears due to the presence of
anodic areas or exposed iron (Fe), leading corrosive reaction in tin plate. The
nature of food and its contact time with food-container plays an important
role in corroding tin cans.
The wide pH range of foods, organic acid, nitrates, salt (NaCl), the
concentration of the stored food, storage temperature are also responsible for
the tin corrosion. However, for the improvement of the food quality and the
prevention of the food from the unhygienic issues, bacterial growth, fouling,
and mineral deposition, food packaging industries employed some additives
(such as sanitation, cleaning agents, acids, alkaline, weak or strong reducing
and oxidizing chemicals). These varieties of food additives (vigorous chemi-
cals) in the stored-food act as corrosion accelerating agents (such as nitrates,
sultes, oxygen, and sulfur dioxide) into the canned products [20].
Few literature has reported the degradation of the tin-coating and the
steel-base with the release of hydrogen gas [5]. Hence, it is the necessity of
the food packaging industries to take an initiative to diagnose the problem
and produce some better corrosion retardant metal cans.
This chapter focuses on the toxic effects of corrosion of tin plates on
canned foods and food products. The integrity of the tin plate, tin estimation
techniques, and corrosion mechanism and mitigation methods has also been
elaborated.
9.2 INTEGRITY OF TIN PLATE
Figure 9.1 displays the multilayered metal structure on both sides of the steel
base. The description of different layers work as a safety-guard in tin cans.
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FIGURE 9.1 Structure of multi-layered tin plate (cross-section).
9.2.1 STEEL BASE
These steel plates work as highly corrosion-resistant materials and mostly it
is suitable for those products (such as acidic products), which require longer
shelf-life. The size of the can is considered for the thickness of the steel
sheet. Usually, the thickness is kept between 0.20 to 0.29 mm [24, 34].
9.2.2 TIN-IRON ALLOY
Tin iron alloy is present outside of the steel plate and it is produced during
the flow brightening process on electrolytic tinplate. In this process,
diffusion of tin and metal takes place into the steel sheet. The tin alloy layer
has the thickness of around 10 to 30%. This layer works as a preventive
layer against the corrosion mechanism. The more continuous and compact
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is the layer, the more will be the protection. Sometimes, the corrosion is
generated in steel plate due to the creation of pores in uneven alloy layer.
Electrochemically, the alloy layer is considered as cathodic layer compared
to iron and tin [23, 34].
9.2.3 TIN COATINGS
The most common use of electrolytic tin coating inside the can is to provide
an appropriate coating on the specific side of the tin, which is more aggres-
sive. This enables the low consumption of tin and the significant decrease in
packaging cost. The weight of the tin coating is ranges from 2.8 to 11 g/m2
in food cans [25, 55].
9.2.4 TIN FREE STEEL (TFS)
There are various alternative materials, such as chromium oxide and chromium.
These materials are replacing tin due to their low-price range and easy
availability. Chromium oxide and chromium (Cr) are known to be appropriate
coatings. Notwithstanding, tin-free steel is sometimes not suitable for the acid
products due to the acceleration of filiform corrosion in the enamel films [36,
38]. Additionally, the use of Cr in place of tin causes a deleterious impact on
cellular metabolic pathways in the human body because of its carcinogenic
nature, when it is present in hexavalent oxidation state (Cr (VI)). Thus, there is
a need to find alternatives for promising materials in place of TFS.
9.2.5 PASSIVATION OF LACQUERED LAYERS
During the manufacturing process of tin plate, the tin oxide film can be formed
on the tin plate. The tin plate containing tin oxide causes failures in adhesion
of the coating material, discoloration of yellow surface and difficulty in
soldering. For the protection of tin plate from uncontrolled oxidation, the
grouping of unwanted sulfide stains is generated by some acidic foods; and
to withstand from future-corrosion problems during storage process and for
the improvement of lacquer adhesion, the passivation treatment (coating of
lacquer) process is carried out on the tin plate [11, 12].
Passivation is the action of treating the metal with a protective layer to
protect the metal against the chemical reactivity of the surface with the stored
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food. Three different kinds of important passivation layers are used for the
safety of tin plate against tin oxide: (1) cathodic layer of sodium dichromate
(CLSD), which works as an effective protective lm for tin oxides; (2) lm of
sodium dichromate dip (FSDCD), provides ordinary protection is contrary to
the oxide lm having limited stability of the storage; and (3) cathodic lm of
sodium carbonate (CFSC), works as a least effective protective layer among
three layers. The passivation layer provides a barrier between the tin plate
and stored food, ceases staining from Sulfur-containing foods, improves
lacquer adhesion, and inhibits the degradation of the tin oxide [13, 29, 30].
9.2.6 OIL FILM
A lubricating oil film on tin plate surface minimizes friction due to the
abrasion, which helps in handling of tin plates during its processing and
production. Oil film undergoes polymerization, evaporation, and soap
formation, when food is preserved for a long time, leading to complications
in the application of lacquer processing due to uneven wetting on the metal
surface [35, 50].
9.2.7 WELDING AND SOLDERING OF TIN PLATES
Soldering of the metal follows steps, such as designing of metal parts, fitting
of metals (so that they can combine), polishing of joining parts of metal,
de-greasing of joining-parts of the metal, use of soldering flux to help wet the
surface, use of the solder itself and elimination of spare solder, and cooling
of the metal joints. The soldering a tin can use 2/98 and 40/60 (tin and lead
%) of tin-lead alloys. Tin in alloys is used in very low concentrations due
to its high price range and high melting point during the soldering process.
There are two best techniques for welding: rolling and welding. Both are
cost-effective and speedy techniques. The best use of welded cans is for
storing aerosols and beverages [34].
9.2.8 ORGANIC COATINGS IN CANS
The best property of the organic tin coatings inside the can is to protect the
contents of the can and stop the interaction between the can and product. The
interior coating exhibits good efficiency and it should possess characteristics,
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such as The solutions for the coatings materials should be pigment-free
for the best results. It is a dispersive resinous matter of organic materials.
Following considerations are necessary for best results [33, 34, 50]:
Interior organic can coatings should have the tendency to work as a
preventive layer between can and its stored food.
The most significant feature of the interior organic tin coatings is not
to participate in any taste or color of the stored food.
It should withstand the physical-deformation and possess good chemical
resistivity.
The lacquer should be flexible, evenly spread and entirely cover the
surface.
The lacquer must adhere uniformly on the surface of the metal.
Failures in adhesion may occur due to the mechanical distortion at the
time of heat treatment or corrosion.
9.3 TECHNIQUES FOR ESTIMATION OF TIN IN CANNED FOODS
It is very important to determine the concentration of tin to validate the
contamination process. Determination of tin also helps in maintaining the
quality, taste, and safety of the stored food. This section explores various
methods for evaluation of the concentration of tin in canned food [29, 46].
9.3.1 UV-VIS SPECTROSCOPY
The UV-Vis-spectrum is used to evaluate the tin concentration in food by
using a pair of quartz cuvettes in UV-Vis spectrophotometer. The fresh stock
solution of tin is prepared by dissolving the tin metal in concentrated H2SO4.
Further, the solution is diluted in the ratio of 1:1 with water. Thereafter, the
sample solution (named as the working solution) is considered for the test.
The UV-Vis absorption spectrum of the working solution is recorded with its
corresponding reference solution [26].
9.3.2 X-RAY FLUORESCENCE SPECTROMETRY (XRF)
In this technique, the XRF spectrometer contains an X-Ray tube of rhodium
anode. The XRF measurement is carried out on a pellet sample, prepared by
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using a drop of tin-contaminated food. Furthermore, the pellet is treated with
wavelength-dispersive method [37].
9.3.3 INDUCTIVELY COUPLED PLASMA ATOMIC-EMISSION
SPECTROMETRY (ICPAES), FLAME ATOMIC ABSORPTION
SPECTROMETRY (FAAS), AND FURNACE ATOMIC ABSORPTION
SPECTROMETRY (FAS)
In these techniques, the contaminated sample is nebulized under the flame of
acetylene and nitrous oxide with a highly sensitized nebulizer [35, 38, 39].
Specifically, FAAS method is used predominantly because of its ease of use in
the estimation of tin. Nevertheless, in FAS technique, the level of the sample
used contains a very low concentration. In spite, in ICPAES technique, the
level of the sample used contains a relatively high concentration [30, 43].
9.3.4 HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY
(HPLC) OR GAS CHROMATOGRAPHY (GS)
The GC provides a very selective separation of organotin compounds because
of its high detector quality and resolution. HPLC is also commonly used as
an analysis technique for the isolation of organo-tin compounds. However,
the HPLC technique is superior to GS, because it does not require any step
of derivatization after the process of extraction [30].
9.3.5 POLAROGRAPHY OR VOLTAMMETRY TECHNIQUE
Estimation of tin is also carried out by polarography technique or voltam-
metry technique. It analyzes tin from the solution of oxidizable or reducible
substance [30].
9.4 TYPES OF FOODS AND BEVERAGES STORED IN TIN CANS
Many food materials are stored in tin cans for maintaining their taste, color,
odor, and composition for a prolonged time. These food materials may be:
vegetables, pickles, fruits, soft drinks, beer, beverages, cereals, milk-dairy
products, fish-crustaceans, meet-poultry-eggs, condiments-sugar-oil [1, 7].
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9.5 TOXIC EFFECTS OF TINPLATE CORROSION ON FOODS
Toxic effects of canned food have been reported by many investigators
[8, 16, 21, 22, 42]. Systematic attempts have been implemented to collect
significant information on the intake of different contaminants by WHO,
UNEP (United Nations Environment Program), and FAO in the program
of monitoring of contaminated food. The toxic effects of some organic tin
compounds are observed to be as poisonous as cyanide, but specific toxicity
for inorganic tin is almost unidentified [22].
In canned foods and canned beverages involving vegetables and fruit
juices, the highest level of the tin is found to be 200 mg/kg and 100 mg/
kg, respectively [16]. The permitted permissible limit is about 250 and
150 mg/kg for solid food and beverages, respectively. The unfavorable
gastrointestinal health issues have been observed in some clinical trials at
very high concentration of 700 ppm of tin [42].
If an adult consumes tin-contaminated food on a daily basis and
accumulates tin in the range of 8 to 16 mg, then this concentration would
affect the gastrointestinal (GI) functions adversely. Additionally, it causes
incurable health issues [16]. The chronic effect of inorganic tin causes
nausea, gastric irritation, diarrhea, vomiting, and abdominal discomfort, if
the concentration of tin is >200 mg/kg in ingested food [29]. According to
the European Union Legislation (EUL), the chronic level of tin may vary
from 50 to 200 mg/kg for baby canned-foods and infant canned-foods [10].
9.6 CORROSION AND SUBSEQUENT CONTAMINATION OF
CANNED FOODS IN TIN CANS
The quality of the tin cans and dissolution of tin inside the stored food is
severely affected by chemical, environmental, and other factors. The chem-
ical factors are responsible for the dissolution and internal tin mobilization to
packaged food containing nitrates and oxidizing agents. The environmental
factors, such as, temperature leads to the disintegration of external tin. Other
factors are composition, integrity (quality of steel) and volume of the tin can.
Tin dissolution can be understood by the corrosion mechanism [42]. The
corrosion is a deterioration of a metal or degradation of the metal quality via
electrochemical or chemical reaction (Eqn. (1)). In this procedure, metal,
and alloys tend to convert itself into their most stable (thermodynamically
stable) state [48, 49]. In food cans, corrosion takes place due to the anodic
disintegration process of the tin can with the formation of ions [19].
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1
[][]Metal Metal ne
+−
 → + (1)
The corrosion-mechanism in tin cans is the result of electrochemical
reactions, which occur in an aqueous medium by the formation of galvanic
cells, which are formed during the coupling of two metals having different
dissolution pressures. Dissolution takes place at the anode (more active
metal), which further protects the cathodic metal (passive metal). When
metal possesses a small size at the anodic surface and more current densities,
then metal gets deeply corroded by pitting corrosion [19, 34].
9.7 CORROSION MECHANISM: ELECTROCHEMICAL PROCESSES
IN LACQUERED CANS
The study of corrosion mechanism in lacquered food cans (Figure 9.2) has
been extensively reviewed.
FIGURE 9.2 Corrosion mechanism of tin can in the presence of liquid juice: (A) Non-defected
coating of lacquer; (B) formation of pores in lacquer-coating; and (C) dissolution of iron and
tin into the cannedfood.
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The layer of lacquer protects the food from direct exposure of tin
(Figure 9.2(A)). Through these pores, tin directly encounters food material
resulting anodic dissolution of tin as shown in Eqn. (2) (Figure 9.2(B)). The
corrosion-mechanism in tin cans may trigger due to the formation of pin
pores under the layer of lacquer. The exposure of tin with food increases with
time due to detachment of lacquer, and leads to the formation of large-sized
pores and cracks, which ultimately result in the dissolution of iron (Eqn.
(4)) from tin-alloy layer (FeSn2) into the food (Figure 9.2(C)). Moreover,
the occurrence of corrosion is aggressively increased by the vigorous attack
of corrosion accelerating agents (nitrates). In terms of electrochemistry, the
cathodic reaction takes place at lacquer surface, as shown in Eqn. (4), where
protons present in organic food, take up electrons released during the dissolu-
tion of tin (anodic reaction) at the tin surface. After the complete dissolution
of tin into the food, the anodic reaction again starts at tin-iron alloy surface
and further the iron dissolution occurs into the food (Figure 9.2(C)).
1. Mechanism of Tin Dissolution (Anodic Reaction‑I):
2
(2)
4
2. The Reaction At Lacquer Surface (Cathodic Reaction):
2
22
He H
+−
+  → (3)
3. Mechanism of Iron Dissolution (Anodic Reaction‑II)
3
3Fe Fe e
+−
 → +
(4)
For the safety of corners of the tin cans, seam stripes must be used, and the
metal should possess zero dissolution. If the example is taken of the carbonated
beverages or beer, the whole area inside the can should be re-lacquered after
the manufacturing procedure [33, 39, 51].
9.8 TYPES OF TIN CORROSION
9.8.1 INTERNAL CORROSION
Internal corrosion occurs due to the electrochemical reaction that takes place
inside the can surface after the interaction with the food-content. It generally
happens due to the acidic nature of the food, oxidants, storage temperature,
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and storage duration and presence of oxygen in the can. Internal corrosion
may cause a change in the food quality (taste, odor, and color). Sometimes
leaking, swelling, and vacuum loss also occurs. These factors cause the
toxicological issues in the food.
9.8.2 EXTERNAL CORROSION
External corrosion occurs due to the metal itself, due to: surface-homogeneity
and H2-overvoltage, improper structure during manufacturing, contact with
another metal, environment, corrosive labels, and poor handling [34, 52].
9.8.3 FILIFORM CORROSION
Filiform corrosion takes place under the protected coating of the tin plate
cans. It forms a thread-like structure or filament. This kind of corrosion
usually forms a bulge structure or breaks the coating [17].
9.8.4 PITTING CORROSION
Pitting corrosion occurs at the surface of the tin plate. It takes place, when
some dirt particles meet tin plate and stick to it. There are several examples of
this corrosion: crevice corrosion, water line attack corrosion. When corrosion
begins with the formation of the tiny bubble of air erosion-corrosion [1].
9.9 TOXIC EFFECTS OF TIN COMPOUNDS ON HUMAN HEALTH
Tin is found naturally in low to high concentration. Sometimes, it is impossible
to ignore the exposure of tin compounds due to daily habits of drinking
juice from tin cans (usually highly acidic food). The health effects from the
exposure with tin compounds in humans (conception to maturity) are reported
to be negative.
Children and infants may come in contact with the tin compounds due to
the intake of contaminated soil, tin-canned food, and vegetables. In addition,
the pica behavior is observed in children, in which children eat contaminated
or hazardous dirt. Sometimes in adults, the exposure of tin happens if one of
the family members works in tin manufacturing company so that person may
bring home some tin substances in their outts and tools.
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Inorganic tin may cause acute effects in human health through food products
in tin plate cans. These canned foods generally cause the disturbance in the
digestive system, such as gastrointestinal irritation, abdominal cramp, nausea,
vomiting, diarrhea, headaches, and fever. These acute symptoms may last from
few minutes to weeks. Generally, the concentration of tin in canned foods is
between 200 to 2000 mg/L attributing acute to chronic diseases in humans. The
tin canned products, which are more accountable for human health hazards,
are acidic products, such as vegetables, and fruit juices. This is the main reason
behind the chronic effect of tin compounds on human health [8, 19, 24].
9.10 MITIGATION MEASURES
9.10.1 CONVENTIONAL METHODS
Few possible methods can be employed to avoid direct contact with tin, such
as; the unused part of the tin canned food can be placed in a container instead
of throwing it in an open atmosphere. People can be directly exposed to
organic tin compounds: (1) when they eat seafood from tin contaminated
coastal areas; (2) directly get exposed with the household things, such as
baking papers coated with silicon, plastic polymers, and polyurethane (PU).
However, decreasing the availability of contaminated seafood from coastal
areas and avoiding contact with tin-containing household things can lessen
the effect of tin compounds on human health.
If a person accidentally gets exposed to a large quantity of tin compounds,
then this person should promptly consult a doctor. Few medical tests can
determine the amount of tin in the human body but cannot depict the total
amount of tin in the body. The tin-test cannot be performed regularly at the
hospital or clinic, but the physician or doctor may take the samples and send
it to the particular testing laboratory [8, 24].
9.10.2 ADVANCED ANTI-CORROSIVE METHOD
In order to prevent the corrosion from tin food cans, lacquered tin plats are
extensively used, but the efficiency of lacquered tin prominently depends
upon the anticorrosive property of the lacquer and the nature of food inside
the can. When beverages and food are packed in tinplated cans, tin dissolution
may occur due to the exposure of food with tin. There are many mitigation
procedures used for the protection of tin cans from corrosion, such as, the
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use of zinc-plated steel (electro-galvanized cold-rolled steel), stainless steel
(SS), coating of powders, and painting on the tin surface.
The addition of some essential oils (EOs), such as onion essential oil
(OEO) is extensively recommended in coating material of the tin plate
due to its low-cost. The protecting layer of OEO does not participate in
any organoleptic properties of the food. However, the temperature for the
storage should be less than 36°C. The acidic contents, which are attributing
more to the corrosion of tin, such as tomato puree, could be minimized using
the mixture of potassium nitrate (KNO3) in the food content. Mainly, the
corrosion of the tin takes place after 30 days and 20 days at 36°C and 20°C,
respectively due to the action of nitrates. Sometimes, the presence of organic
acid in canned food causes the effect of corrosion. In addition, the presence
of little amount of nitrates (~10 mg) leads to the generation of corrosion in
foodstuff containing less than 7 pH [1, 3, 54].
9.11 GOVERNMENTAL GUIDELINES TO PROTECT HUMAN
HEALTH
The US Federal Government is taking steps ahead for the development of
some regulations and particular recommendations to protect human health.
There are some government agencies (Food and Drug Administration
(FDA); Health and Occupational Safety Administration (HOSA)), which are
helping in the development of regulations regarding toxic products. These
recommendations are providing meaningful guidelines to resolve public
health issues. However, these are hard to implement by the law. The agencies
for disease registry and toxic substances (DRTS) and the National Institute
of Occupational Safety and Health (NI-OSH) are the most esteemed federal
agencies, which help in the development of recommendations for poisonous
substances. Recommendations and regulations could be signified as “not to
exceed” level. That means that the maximum level of toxicity in the water,
food, air, or soil has a fixed level of toxic parameters. If the toxicity level
exceeds this fixed level, then the public health is affected. There is an update
in the recommendations and regulation, when more significant information
is collected. Some rules and regulations related to tin compounds involve the
following considerations [24, 46]:
The US Environmental Protection Agency (US EPA) has restricted the
usage of some organotin compounds in specific paints. The HOSA has
fixed some limit for tin compounds at working places, i.e., 0.1 mg/m3
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and 2 mg/m3 for organo-tin and inorgano-tin compounds, respectively
instead of oxides.
The FDA government manages the usage of organo-tin compounds in
coating materials and packaging.
The FDA has also established some limits on the use of tin (SnCl2) [24].
The NIOSH establishes working place limit of exposure from the
inorganic tin of 2 mg/m3 apart from oxides of tin and for organo-tin
compounds of 0.1 mg/m3 instead of tricyclohexyl-tin hydroxide.
The NIOSH governs that the 25 mg/m3 concentration of tricyclohexyl-
tin hydroxide must be reported as a dangerous concentration to public
health.
9.12 SUMMARY
Changing food habits and increasing packaging of food items, including
beverages, have led to more risks to human health due to corrosion and
contamination of canned foods. A thorough study of the tin plate corrosion
indicates that the bare tin plate is more prone to corrosion than the lacquered
tin plate. Any tiny pores and variation in thickness in the coating material
can attribute more corrosion issues in the base metal. Lacquer restrains the
corrosion mechanism and establishes the composition of the tin plate for a
long-time when tin plate cans are exposed to corrosive media. The literature
cited in this book chapter depicts the permissible limit of the tin in human
being not to be more than 250 and 150 mg/kg for solid food and beverages,
respectively. However, the governmental organization is taking steps to
establish more appropriate regulations to protect human health and safety.
KEYWORDS
corrosion
food packaging industry
gas chromatography
lacquered tin plate
tin canned food
tinplate
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REFERENCES
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