COPPER SULFATE

CAS: 7758-98-7 NUTRIENT SUPPLEMENT, PROCESSING AID

Copper sulfate (CAS 7758-98-7) is a copper-containing inorganic compound used in food as a nutrient supplement and processing aid under current good manufacturing practice.

What It Is

Copper sulfate is a copper-containing inorganic compound identified by the Chemical Abstracts Service number 7758-98-7. It appears in various solid forms, most commonly as the pentahydrate (blue crystals) and as an anhydrous powder. In food regulatory contexts, the compound is affirmed as a direct food substance and is used as a nutrient supplement and a processing aid under conditions that align with current good manufacturing practice. Copper sulfate may also be referred to by other chemical names listed in regulatory records, reflecting its copper(II) ion form and sulphate composition. The compound’s inclusion in direct food regulations indicates its recognized role in contributing essential copper for nutritional purposes and functioning within manufacturing processes where the additive’s effects on the food matrix are technologically justified. Within scientific databases, copper sulfate’s chemical identifiers account for both its hydrated and anhydrous forms, and the compound participates in coordination chemistry involving the copper(II) ion. In aqueous environments, copper sulfate dissociates into copper and sulfate ions, which can interact with other components in food formulations or processing systems. It is considered a micronutrient in human nutrition, as copper is an essential trace element required for enzyme activity, iron metabolism, and connective tissue formation. However, the compound’s use in food is strictly regulated and limited to conditions where it serves specified functional roles, reflecting both technological need and safety considerations.

How It Is Made

Copper sulfate is typically manufactured through well‑established inorganic chemical processes. One common method involves the reaction of sulfuric acid with metallic copper or copper(II) oxide to form copper(II) sulfate in solution. The resulting solution is then crystallized to yield the hydrated or anhydrous forms of the salt, depending on processing conditions. In industrial settings outside food production, the compound is often prepared to meet specific purity criteria for its broad range of applications. In the context of food grade production, sourcing and manufacturing must adhere to purity standards that are suitable for their intended nutritional or processing uses. Regulatory guidelines require that the substance must be of a purity appropriate for direct human food use, meaning that impurities are controlled to levels that will not adversely impact food safety or quality. Manufacturers typically conduct analytical tests to verify identity, concentration, and the absence of prohibited contaminants. These specifications are documented in international compendia for food additive standards, where monographs specify acceptable purity ranges and analytical methods. Good manufacturing practice ensures that ingredient handling, storage, and processing align with established safety protocols to maintain consistent quality in food applications.

Why It Is Used In Food

Copper sulfate is used in food primarily for two technical functions: to act as a source of the essential trace element copper and to serve as a processing aid under current good manufacturing practice. As a nutrient supplement, copper sulfate contributes trace amounts of elemental copper that support biological functions when food formulations are designed to address nutritional needs. Copper, as an essential micronutrient, plays roles in enzyme systems, metabolic pathways, and the maintenance of physiological processes, although the additive itself is incorporated at levels consistent with regulatory allowances. As a processing aid, copper sulfate can influence certain manufacturing steps where its chemical properties facilitate technological objectives without leaving significant residues in the final product. Processing aids are substances that affect the process but are not intended to have a direct functional effect in the finished food. Regulatory frameworks distinguish these roles and allow use based on good manufacturing practices, which ensure that the additive performs a necessary technological function and that any presence in the finished food is incidental and safe. The dual function reflects both nutritional and processing considerations within food science and product development, particularly in formulations where trace copper may be beneficial or where the compound’s properties aid in production efficiency.

Adi Example Calculation

To illustrate how acceptable daily intake concepts work without assigning a specific numeric ADI for copper sulfate itself, consider a hypothetical scenario based on a provisional copper intake range referenced by international evaluations. Suppose an adult weighing 70 kilograms consumes foods containing trace copper from various sources. If a provisional tolerable intake range for copper was articulated in terms of elemental copper, a regulator might use a reference range expressed per kilogram of body weight. For example, a notional range of trace copper exposure could be expressed in terms of copper milligrams per kilogram body weight. In this hypothetical example, a 70 kg adult at the upper end of such a range might be associated with exposure up to a level calculated by multiplying the individual’s body weight by this reference value. For instance, if a provisional reference intake range were expressed at a certain milligram per kilogram body weight, multiplying that value by 70 kg yields an estimated maximum daily intake of copper from all dietary sources. The result would represent the upper boundary of intake considered within a provisional safe range. It is important to recognize that this exercise uses a theoretical reference range rather than an official ADI specific to copper sulfate itself, and that actual regulatory guidance would frame such calculations in the context of total dietary exposure from all sources rather than isolating a single additive. This illustrative calculation underscores how body weight, provisional intake metrics, and total exposure considerations interplay in regulatory assessments of trace elements and related compounds. It also highlights why regulatory agencies emphasize comprehensive evaluations of all sources of exposure and adherence to good manufacturing practices for additives like copper sulfate used in food.

Safety And Health Research

Regulatory evaluations of substances like copper sulfate focus on safety endpoints relevant to both chemical properties and biological effects. For copper sulfate, the assessment of safety encompasses its dissociation into copper ions and sulfate, the essential micronutrient nature of copper, and potential toxicity at elevated doses. JECFA’s evaluation did not allocate a numerical ADI but highlighted a provisional dietary requirement and maximum tolerable intake range for copper, reflecting the element’s role as a necessary nutrient and the importance of balancing intake to avoid deficiency or excess. These kinds of evaluations consider a range of toxicological data that inform international safety benchmarks. Within the United States regulatory framework, the inclusion of copper sulfate as a GRAS substance under 21 CFR 184.1261 reflects the conclusion that its use as a nutrient supplement and processing aid is safe when applied under current good manufacturing practice. This determination takes into account factors such as the compound’s purity, the levels of use in food, and the overall exposure consumers may experience from its use in food products. Safety evaluations generally review available toxicological evidence, including studies on copper’s biological handling, metabolism, and effects across doses, to delineate conditions under which consumption does not pose appreciable health risk. Because copper is an essential trace element, nutritional science also considers the implications of adequate intake and potential deficiency alongside toxicity thresholds. While excessive intake of copper compounds can lead to adverse effects, regulated food uses of copper sulfate are designed to deliver trace copper within safe and nutritionally relevant bounds. The balance of evidence supports regulatory allowances that align technological function with consumer safety, ensuring that exposure remains within limits that do not raise concerns under authorized conditions of use.

Regulatory Status Worldwide

In the United States, copper sulfate is affirmed as a generally recognized as safe (GRAS) direct human food ingredient under 21 CFR 184.1261 when used as a nutrient supplement and as a processing aid in accordance with current good manufacturing practice. This regulation specifies that the ingredient is used with no limitation other than good manufacturing practice and must meet appropriate purity standards for its intended use. The regulation also notes that copper sulfate may be used in infant formula under specific provisions of the Federal Food, Drug, and Cosmetic Act, reflecting its allowance in specialized formulations where micronutrient contribution is relevant. The FDA’s listing in the CFR affirms evaluation and acceptance of these functions within the scope of direct food use. At the international level, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) has evaluated cupric sulfate, assigning it an International Numbering System (INS) designation of 519. The JECFA evaluation notes that no numerical acceptable daily intake (ADI) was allocated but references a provisional dietary requirement and maximum tolerable intake range for copper expressed on a body weight basis, recognizing copper’s essential micronutrient role. Codex Alimentarius includes copper sulfate in its General Standard for Food Additives database with the corresponding INS number and functional class information, supporting its recognized status within an international regulatory framework. These designations provide a basis for member countries’ food additive regulations, although specific conditions of use and allowable food categories may vary by jurisdiction. In other regions such as the European Union, there is no specific E number established for copper sulfate as a food additive under EU food additive regulations. EFSA’s role in assessing food additives would apply if copper sulfate were proposed for authorization on the Union list, but to date there is no published EFSA opinion or E number tied to copper sulfate for direct food use in the EU. This reflects differences in regulatory pathways and approval processes across global food safety authorities.

Taste And Functional Properties

Copper sulfate itself is not used for flavor enhancement or taste modification in foods; its sensory impact at regulated use levels in food is not typically a driver of its inclusion. The compound is understood to dissociate in aqueous environments, releasing copper and sulfate ions, but it does not impart a characteristic taste profile that would be described or exploited in food formulations. In functional terms, copper sulfate’s solubility in water and its ability to deliver copper ions make it suitable for applications where trace mineral supplementation is desired or where processing objectives require its presence. From a physicochemical standpoint, the functional properties of copper sulfate are rooted in its ionic behavior and stability under typical food processing conditions. The compound dissolves readily, allowing for homogeneous distribution of copper ions in solutions or mixtures. Heat and pH can influence its solubility and the form it takes in a food matrix; these factors are considered when integrating the additive into specific food systems. The stability and behavior of the additive under processing conditions are important for food technologists to understand so that its technical contributions can be predictable and aligned with manufacturing goals. The sensory neutral nature of copper sulfate at regulated use levels differentiates it from additives that are included for flavor, aroma, texture, or color.

Acceptable Daily Intake Explained

An acceptable daily intake (ADI) represents a regulatory benchmark that reflects the amount of a substance that can be ingested daily over a lifetime without appreciable health risk, based on scientific evaluations of available toxicological data. For copper sulfate, international evaluations such as those by JECFA did not assign a specific numerical ADI for the compound itself, but they referenced a provisional dietary requirement and maximum tolerable intake range for copper expressed on a body weight basis, recognizing copper’s essential role in nutrition. These provisional guidance values help inform regulatory thinking about safe exposure levels to elemental copper but are not formal ADIs tied solely to copper sulfate as an additive. In regulatory contexts where ADIs are established, they are derived from detailed toxicological assessments that identify points of departure such as no observed adverse effect levels (NOAELs) in animal or human studies. Safety factors are applied to account for uncertainties and variability in human sensitivity. The result is a conservative estimate that serves as a guide for acceptable exposure. When a compound has very low toxicity and consistent data supporting safety under the conditions of intended use, regulatory bodies may decide that establishing a numerical ADI is unnecessary and instead rely on good manufacturing practice principles. For ingredient users and food technologists, understanding that an ADI may not be numerically defined does not imply a lack of safety; rather, it reflects a regulatory conclusion that, under authorized conditions of use and good manufacturing practice, exposure to the additive does not present appreciable health risk. In such cases, regulatory guidelines emphasize adherence to purity specifications and appropriate usage levels in food products to ensure consumer safety across diverse populations.

Comparison With Similar Additives

Copper sulfate can be compared with other trace mineral additives that serve nutritional or processing functions in food systems. For example, iron sulfate is another inorganic salt used as a source of elemental iron in fortified foods; similar to copper sulfate, iron sulfate must meet purity criteria and is integrated into products to address specific nutritional objectives. Both compounds deliver essential trace minerals but differ in their sensory profiles and functional behavior within the food matrix, with iron often imparting color changes and requiring careful formulation to avoid off‑flavors. Another related additive is zinc sulfate, which provides trace zinc in fortified food and dietary supplements. Zinc sulfate’s role parallels copper sulfate in delivering an essential micronutrient, but differences in solubility, bioavailability, and interactions with other food components can influence formulation strategies. Like copper sulfate, zinc sulfate’s regulatory status is guided by its safety profile and nutritional relevance, and its inclusion is governed by good manufacturing practice and purity standards. These comparisons help illustrate how mineral salts used as nutrient supplements share common regulatory considerations yet may differ in functional attributes. Copper sulfate’s classification as both a nutrient supplement and a processing aid distinguishes it from additives used solely for nutrient fortification or technological effects, highlighting the diversity of roles that trace mineral compounds can play in food science and product development.

Common Food Applications Narrative

In food applications where copper sulfate is utilized, its roles are tied to both its function as a trace mineral supplement and its utility in manufacturing processes. Foods that may incorporate copper sulfate are generally those seeking to address nutritional balance, particularly where trace elements like copper are relevant to dietary formulations. For example, certain fortified food products may include trace minerals to support nutritional labeling claims, and copper sulfate can serve as a defined source of elemental copper within such contexts. Additionally, the compound’s classification as a processing aid means it can be involved in steps of food preparation or ingredient manufacturing where its chemical behavior facilitates technological processes. These uses are governed by regulatory standards that require adherence to current good manufacturing practice, ensuring that any incidental presence in the finished product does not compromise consumer safety. Across categories like baked goods, beverages, and fortified nutrition bars, copper sulfate’s contribution as a source of copper supports comprehensive nutrient profiles while its technical role remains transparent to consumers. These applications reflect a balance between nutritional science and food technology, where trace mineral delivery and process functionality intersect in diverse product formats. The inclusion of copper sulfate in these varied food categories is framed by regulatory allowances that emphasize safety and appropriate usage. It is not a broadly applied additive like sweeteners or emulsifiers; rather, it appears in contexts where its unique attributes are necessary and justified. This careful integration underscores the importance of aligning additive function with consumer needs and regulatory frameworks, ensuring that products leveraging copper sulfate maintain quality and compliance within established food safety regimes.

Safety & Regulations

FDA

  • Approved: True
  • Regulation: 21 CFR 184.1261

EFSA

  • Notes: No specific EFSA food additive approval or E number identified

JECFA

  • Notes: JECFA did not allocate a numerical ADI for copper sulfate
  • Ins Number: 519

Sources

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