ADIPIC ANHYDRIDE
Adipic anhydride (CAS 2035-75-8) is a chemical compound used in industrial applications and referenced in United States food additive regulation 21 CFR 172.892 as a modifier in food starch, functioning as an acid anhydride in certain processing contexts.
What It Is
Adipic anhydride is an organic chemical compound identified by the CAS number 2035-75-8 and used in specific food processing roles. The compound is structurally an anhydride derivative of adipic acid and is referenced by names such as 2,7-oxepanedione and hexanedioic acid anhydride in chemical nomenclature. This substance is included under United States food additive regulation 21 CFR 172.892 as a permitted component in the modification of food starch, where it serves technological functions during processing. Although its inclusion in food regulation indicates lawful conditions of use under defined limits, adipic anhydride itself is not widely recognized as a direct consumable ingredient in common foods and is primarily used for processing applications.
How It Is Made
Adipic anhydride is typically synthesized through dehydration reactions of adipic acid or related precursors. In industrial chemistry settings, anhydrides are formed by removing water from their corresponding dicarboxylic acids under controlled conditions, which often involve catalysts and elevated temperatures to facilitate ring closure or anhydride formation. The manufacturing processes for adipic anhydride are designed to achieve a high degree of purity suitable for industrial applications. In food processing contexts where this compound is permitted, specifications ensure that any residual reagent or byproduct is within safe limits for the specific technological purpose. Because adipic anhydride can react with alcohols and amines, typical facilities managing this synthesis employ standard safety precautions to minimize exposure and control reaction pathways.
Why It Is Used In Food
In food technology, adipic anhydride’s primary role is in modifying food ingredients such as starch. Within the code of federal regulations (21 CFR 172.892), adipic anhydride is permitted for use in treating starch to alter its physical characteristics, such as improving stability, texture, or performance during cooking and processing. The compound’s chemical reactivity allows it to esterify hydroxyl groups on starch molecules, resulting in modified starch structures that can withstand specific processing conditions. These modifications help manufacturers achieve desired functional attributes in finished products, such as thickening, gelling, or improved water retention. The use of adipic anhydride and similar agents is restricted to levels reasonably required to achieve the intended effect, consistent with good manufacturing practice.
Adi Example Calculation
Because a specific numeric acceptable daily intake (ADI) for adipic anhydride is not available from the primary authoritative registries, an illustrative example calculation using an ADI cannot be provided. Typically, if an ADI mg/kg body weight value were established, a calculation could show how the theoretical daily intake for an individual of a given body weight compares to that ADI. In the absence of a clearly documented numeric ADI, regulatory frameworks instead focus on setting usage conditions and limits under which the compound can be used safely during processing. As a result, consumers are protected by limiting the extent to which adipic anhydride can be present in modified food ingredients.
Safety And Health Research
Adipic anhydride’s safety profile has been examined primarily in the context of its intended technical function and regulatory conditions of use. Regulatory frameworks such as 21 CFR 172.892 establish limits for its use in processing food ingredients like starch, with restrictions designed to minimize residual reagent in the finished product. Scientific evaluations of chemical additives typically consider endpoints including acute toxicity, chronic toxicity, genotoxicity, reproductive and developmental outcomes, and exposure levels from dietary sources. While detailed toxicological assessments specific to adipic anhydride’s dietary exposure under approved conditions are not extensively documented in public regulatory summaries, its permitted use in modified starch contexts implies that regulators have determined the compound can be used safely within those specific processing parameters. Adipic anhydride should be handled with care in industrial and laboratory settings due to its potential for irritation upon contact or inhalation, consistent with chemical safety data available through databases such as the European Chemicals Agency (ECHA) classification and lab safety resources.
Regulatory Status Worldwide
In the United States, adipic anhydride is referenced within 21 CFR 172.892 as an agent that may be used in modifying food starch, with limitations on the quantity employed to achieve the intended technical effect and restrictions on residual content in the finished additive. Section 172.892 specifies that food starch may be esterified with adipic anhydride, not to exceed 0.12 percent in food starch-modified products, among other modifiers listed in the regulation. This regulatory listing indicates that adipic anhydride is permitted under direct food additive regulations when used in compliance with prescribed conditions. At the international level, authoritative databases such as the Joint FAO/WHO Expert Committee on Food Additives (JECFA) include records of flavourings and additive specifications, but a specific JECFA evaluation or assigned acceptable daily intake for adipic anhydride has not been located in the publicly accessible database entries focused on flavouring specifications. Similarly, the European Food Safety Authority (EFSA) maintains comprehensive food additive evaluation procedures, but specific assessments or E numbers for adipic anhydride are not documented in readily available EFSA lists. As a result, the regulatory status of adipic anhydride outside the United States may depend on national or regional additive lists and the context of modified ingredient use.
Taste And Functional Properties
Adipic anhydride itself is not intended to impart a distinct sensory taste to foods. Its role is functional rather than flavor-enhancing in the conventional sense. Because it participates in chemical modification of other components—such as starch—its influence on sensory properties is indirect, through the physical and textural changes conferred on the food matrix. Functional properties of modified starches treated with adipic anhydride can include improved stability under heat and shear, resistance to retrogradation, and altered gel strength. These changes support consistent performance in processed foods, where texture and mouthfeel are important quality attributes. The compound’s stability and reactivity are leveraged under conditions where controlled esterification of food polymers is required.
Acceptable Daily Intake Explained
An acceptable daily intake (ADI) is a regulatory concept used to estimate the amount of a substance that can be consumed daily over a lifetime without appreciable health risk, based on available toxicological data and safety factors. For many food additives evaluated by expert bodies, ADIs are determined following comprehensive review of studies on toxicity and exposure. In the case of adipic anhydride, a specific numeric ADI value assigned by major regulatory authorities such as JECFA or EFSA has not been clearly documented in publicly available specification listings. Consequently, there is no definitive global ADI expressed for adipic anhydride in the accessible regulatory databases. Within the United States regulatory context, safety considerations are managed through prescribed usage conditions and limits in 21 CFR 172.892, rather than an ADI per se. This reflects an approach where limiting residual levels and controlling conditions of use support safety in the context of food ingredient modification.
Comparison With Similar Additives
Adipic anhydride is one of several acid anhydrides used in the modification of food starches along with other reagents such as acetic anhydride and succinic anhydride, which are also listed in regulatory texts as permitted modifiers under defined conditions. These compounds share the property of reacting with hydroxyl groups in starch to confer functional changes in viscosity, stability, or textural performance. Compared to acetic anhydride, which introduces acetyl groups, adipic anhydride introduces adipate linkages that can impact gel strength and retrogradation resistance differently. Succinic anhydride serves a similar function but with a shorter carbon chain, potentially yielding modified starches with distinct functional characteristics. In each case, regulatory limits and functional roles are outlined to ensure that residual levels in the finished ingredient remain within bounds compatible with safe use under good manufacturing practices.
Common Food Applications Narrative
Adipic anhydride’s use in food is highly specific and focused on ingredient processing rather than direct inclusion in finished consumer products. Within the food industry, starches that have been modified with adipic anhydride are commonly used as functional ingredients across a range of products. Modified starches are found in baked goods, sauces, dressings, soups, and prepared meals, where they provide thickening, stabilization, and texture control. Because adipic anhydride is used at the processing stage to alter starch characteristics, the finished foods may contain traces of the modified ingredient without the additive itself being a discrete label component. The practical result is that consumers encounter the functional benefits of such modification in everyday products like ready-to-eat meals, processed sauces, and bakery items, even though the regulatory listing refers narrowly to the technical role of adipic anhydride in food ingredient preparation.
Safety & Regulations
FDA
- Approved: True
- Regulation: 21 CFR 172.892
EFSA
- Notes: No specific EFSA evaluation or E number identified in available sources
JECFA
- Notes: No specific JECFA entry with numeric ADI available in searchable database
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