STANNOUS CHLORIDE

CAS: 7772-99-8 ANTIOXIDANT

Stannous chloride is the inorganic salt of tin(II) chloride (CAS 7772-99-8) used for its antioxidant and colour retention properties in specific food applications.

What It Is

Stannous chloride is an inorganic salt commonly identified as tin(II) chloride with CAS number 7772-99-8 and functional classification as an antioxidant and colour retention agent in food applications. In regulatory and food chemistry contexts it may appear in both anhydrous and hydrated forms and serves technical purposes including the prevention of oxidation-related quality changes in certain foods. The compound exists as white to off-white crystals that dissolve in water and participate in redox reactions due to the tin(II) cation's ability to donate electrons. This additive is recognized under regulatory systems such as the Joint FAO/WHO Expert Committee on Food Additives (JECFA) with the INS designation "512" indicating its registration as a food additive with defined technological functions. In the U.S. Code of Federal Regulations it is d in multiple sections of 21 CFR including 172.180 and 184.1845 for specific uses, notably for colour retention in asparagus and similar products under defined conditions. Although its use is limited compared with many common antioxidants, it has a specific niche role in food processing where oxidative changes need to be minimised. The other chemical names reflect its composition and role, such as tin(II) chloride and tin dichloride. As an antioxidant the compound helps to slow oxidation reactions that can lead to discoloration or off flavours in foods, particularly canned and bottled vegetables. In international additive numbering systems this class of additives is indexed to facilitate harmonized identification across jurisdictions.

How It Is Made

Stannous chloride is prepared industrially by reacting metallic tin with hydrochloric acid, producing tin(II) chloride which can then be crystallised and, if needed for specific applications, dehydrated to form an anhydrous product. This process yields a compound that meets defined purity and stability criteria for its intended use, especially in food-grade applications. The production steps typically begin with high-purity tin metal which is dissolved in an acid medium, often hydrochloric acid, under controlled conditions to form tin(II) chloride in solution. This solution can be concentrated and cooled to precipitate solid crystals of stannous chloride. In some cases the dihydrate form is initially formed and then dehydrated under controlled temperatures to achieve the anhydrous form specified by regulatory authorities. These processes are described in regulatory monographs and compendia that ensure consistency with food additive specifications, such as those referenced in the U.S. Food Chemicals Codex incorporated by regulatory reference. Producers of food-grade stannous chloride must adhere to specifications covering assay, impurity limits and handling criteria. These specifications outline acceptable limits for related substances and heavy metals to assure safety and functionality. As with many inorganic salts used in food technologies, manufacturing involves well‑established practices of crystallisation, purification, and quality verification to ensure that the final product meets both technical and regulatory requirements.

Why It Is Used In Food

Stannous chloride is used in food primarily for its antioxidant and colour retention properties. Oxidative reactions in food systems can lead to undesirable changes such as browning, loss of colour, or development of off‑flavours. The reducing nature of the tin(II) ion allows it to donate electrons to reactive species, thereby interrupting oxidative chain reactions that degrade food quality. This makes it suitable for use in food processing applications where maintaining appearance and sensory attributes is important. Specifically, regulatory provisions such as 21 CFR 172.180 authorise the use of stannous chloride for colour retention in certain vegetables, such as asparagus packed in glass containers with inert liners, in amounts not exceeding defined limits calculated as tin. These authorised uses reflect recognition by food safety authorities that the compound serves a functional role in stabilising colour and slowing oxidation in targeted food categories. In other contexts stannous chloride has been evaluated by expert bodies including the European Food Safety Authority (EFSA) where its technological necessity and limited use were assessed. According to EFSA evaluations, its authorised use is limited to particular food categories with maximum permitted levels set in EU legislation. Because its application is specific rather than broad, stannous chloride is not encountered in most everyday processed foods, and its inclusion on ingredient lists signals its function as a technical aid rather than a flavour or nutritional component.

Adi Example Calculation

To illustrate how intake from a food additive might be contextualised, consider a hypothetical example where a food product is processed using stannous chloride at the maximum permitted level for colour retention. If a product contains the additive at a level representing X mg tin per kilogram of food, and a consumer eats Y kilograms of that product in a day, the daily intake of tin from that source would be X multiplied by Y. This figure can then be compared with conservative intake benchmarks developed through toxicological assessment. For example, if a regulatory authority sets a conservative intake threshold of Z mg of tin per kilogram bodyweight per day based on toxicological and exposure data, the calculated daily intake from the food product can be divided by a hypothetical bodyweight to express intake relative to that threshold. If the resulting value remains below the threshold, the use is considered to be within safe bounds. Such calculations emphasise that authorised use levels and realistic consumption patterns inform safety assessments, rather than focusing on intrinsic toxicity at doses far above typical exposure. They illustrate why regulatory frameworks set limits on use levels and why exposure assessment is integral to determining if an additive’s use is acceptable.

Safety And Health Research

Safety assessments for stannous chloride and related tin compounds have focused on questions of exposure and potential effects arising from ingestion at levels above typical food additive uses. Expert evaluations consider toxicological data, mechanisms of action, and human exposure patterns to determine whether authorised uses present safety concerns. For example, JECFA evaluations note that at high tin concentrations acute manifestations such as gastric irritation have been observed in certain individuals, providing context for establishing safety frameworks. The European Food Safety Authority’s scientific opinion on stannous chloride (E 512) considered available toxicity and exposure data within the EU context. EFSA’s assessment indicates that absorption of stannous chloride from the gastrointestinal tract is low and that authorised uses do not raise concerns with respect to genotoxicity or carcinogenicity at permitted levels. Such assessments incorporate data from animal studies and human observations where available, helping to inform regulatory decisions about safe use levels and conditions. Regulatory reviews also consider the potential for effects such as irritation or systemic toxicity at significantly higher doses than would occur from normal consumption of foods containing authorised levels of the additive. By evaluating both chemical properties and biological data, expert panels such as EFSA’s ANS Panel help to characterise risks and ensure that authorisations remain appropriate within the scope of intended use.

Regulatory Status Worldwide

In the United States stannous chloride is listed in the Code of Federal Regulations (CFR) with specific allowances for use under defined conditions. For example, 21 CFR 172.180 authorises its use for colour retention in certain packed vegetable products, subject to maximum levels calculated as tin. Additionally, 21 CFR 184.1845 recognises stannous chloride (anhydrous and dihydrated) as a substance meeting food additive specifications when prepared and used in accordance with regulatory criteria. These regulatory entries reflect formal authorisations under U.S. food additive regulations. In the European Union stannous chloride is identified under the food additive designation E512 and has been evaluated by the European Food Safety Authority (EFSA). EFSA’s scientific opinion on stannous chloride as food additive E512 indicates that its authorised uses and use levels are safe under current conditions and that exposure estimates remain below thresholds of concern when used as permitted. Maximum permitted levels in EU legislation are established in accordance with Annex II of Regulation (EC) No 1333/2008. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has considered tin and related compounds including stannous chloride in the context of overall tin exposure, noting data on potential acute effects at high tin concentrations. JECFA evaluations provide background on safety assessment but do not by themselves confer regulatory status; rather, they inform national and regional regulatory decisions. Collectively these regulatory evaluations illustrate that stannous chloride’s use as a food additive is subject to specific conditions and limits designed to ensure safety.

Taste And Functional Properties

Stannous chloride itself does not contribute a discernible flavour profile to foods; its role is functional rather than sensory. In aqueous solutions the compound dissociates to release tin(II) ions which participate in reduction reactions, counteracting oxidation that would otherwise contribute to quality deterioration in foods, such as the browning of plant tissues or off‑odor formation. Because its purpose is chemical stabilization, any impact on taste is indirect; by slowing oxidative reactions it helps to preserve the original sensory characteristics of the food. In functional terms, stannous chloride is soluble in water and participates effectively at low concentrations, which is typical of many food processing additives. Its behaviour is influenced by factors such as pH and the composition of the food matrix. In systems where oxidation is a concern, the tin(II) ion shifts to a more oxidised state, tin(IV), while neutralizing reactive oxygen species or radicals that could otherwise alter food components. This redox chemistry underlies its effectiveness as an antioxidant and colour retention agent. Because it is not used for flavour enhancement or nutritional fortification, stannous chloride appears on ingredient lists for its technological effect. Its impact on food quality derives from its chemical properties rather than from imparting taste, texture, or aroma. In practical formulations it is typically applied at levels that achieve the desired stabilising effect while minimising any potential interactions with other formulation ingredients.

Acceptable Daily Intake Explained

An acceptable daily intake (ADI) represents an estimate of the amount of a substance that can be consumed daily over a lifetime without appreciable risk, based on current knowledge and exposure assessments. For stannous chloride and related tin compounds, expert evaluations have considered measures such as provisional tolerable weekly intake (PTWI) in the past, reflecting the idea that intake over a longer period should remain within safe bounds. In regulatory reviews such as those conducted by EFSA, exposure assessments estimate typical intake levels from authorised uses and compare them with thresholds that have been characterised through toxicity data. These assessments help determine whether authorised uses could plausibly lead to intakes exceeding conservative safety thresholds. Because stannous chloride’s authorised uses are limited and exposure at permitted use levels is low, evaluations have not identified safety concerns that would necessitate withdrawal or tightening of existing limits. It is important to note that ADIs and related intake metrics are tools used by regulators to ensure safety under defined conditions of use. They are not recommended intake levels for consumers but rather benchmarks to guide regulatory decisions and product formulations. In the case of stannous chloride, current regulatory frameworks incorporate such safety evaluations to manage exposure while permitting technological use.

Comparison With Similar Additives

Stannous chloride’s technological role as an antioxidant and colour stabiliser places it in a class with other additives that serve to slow oxidative changes or preserve sensory qualities in foods. For example, organic acid antioxidants such as ascorbic acid and erythorbic acid are widely used to protect colour and flavour in a broad range of food products; unlike stannous chloride, these organic compounds are also nutrients or nutrient analogues and have broader applications. Phenolic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are synthetic compounds used primarily in lipid‑rich foods to inhibit oxidation. These substances are authorised under regulatory frameworks with defined maximum levels tailored to specific food categories. Their use profiles differ from that of stannous chloride in that they address oxidation in fats and oils, whereas stannous chloride’s use is more narrowly focused on colour retention in specific products. Chelating agents like calcium disodium EDTA also contribute to oxidative stability by binding metal ions that catalyse oxidation. While their mechanism differs from the redox chemistry of tin(II) ions, chelators serve to slow oxidative processes by limiting catalytic activity. The choice among these additives in formulation depends on the food matrix, processing conditions, regulatory permissions, and desired functional outcomes, illustrating how multiple technological tools exist for achieving stability in processed foods.

Common Food Applications Narrative

Stannous chloride’s use in foods is narrow and specific, reflecting its designation as a technological additive for antioxidant and colour retention purposes. In food processing, oxidative reactions can cause changes in appearance and quality; for instance, green vegetables such as asparagus may lose their vibrant colour or develop off‑colours over time. Under authorised conditions, stannous chloride helps to stabilise the visual quality of these products, which can be important for consumer acceptance and marketability. In food categories where it is permitted, manufacturers may add stannous chloride in controlled amounts during processing to maintain the desirable colour and delay oxidative effects that can occur during heat processing, storage, or prolonged shelf life. Although its use is not widespread across all food types, it is found in certain canned or bottled vegetable products processed under conditions that make oxidation control a priority. Regulatory frameworks specify both the categories where it may be used and the maximum levels that ensure safety and efficacy. Because its functional role is chemical rather than sensory, stannous chloride does not contribute to taste or aroma but supports overall product quality by counteracting oxidation. Its presence in ingredient lists is typically found in products where maintaining the original appearance is necessary, and food processors select it for its targeted utility rather than broad functionality.

Safety & Regulations

FDA

  • Approved: True
  • Regulation: 21 CFR 172.180 and 21 CFR 184.1845

EFSA

  • Notes: EFSA re-evaluation describes safety at authorised use levels without specifying a numeric ADI.
  • Approved: True
  • E Number: E512

JECFA

  • Notes: JECFA evaluations discuss provisional intake thresholds but do not assign a numeric ADI in the d entry.
  • Ins Number: 512

Sources

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