ADIPIC ACID

CAS: 124-04-9 FLAVORING AGENT OR ADJUVANT, LEAVENING AGENT, PH CONTROL AGENT

Adipic acid is a dibasic organic acid used in foods to regulate acidity, extend leavening and contribute mild tart flavor qualities.

What It Is

Adipic acid is a straight-chain organic dibasic acid that functions as a food additive with multiple technological roles including as a flavoring agent or adjuvant, leavening agent, and pH control agent. It has the Chemical Abstracts Service (CAS) registry number 124-04-9 and is known by other chemical names such as hexanedioic acid and 1,4-butanedicarboxylic acid. In food science contexts, adipic acid appears as a white crystalline solid with acidic properties that contribute to taste and acidity regulation. The designation "E355" is associated with adipic acid under the International Numbering System (INS) for food additives in jurisdictions where E numbers are used, indicating its recognition and listing in food additive inventories. Adipic acid’s inclusion in regulatory lists and inventories reflects its historical recognition and continued use as a functional acidulant and process aid in diverse food categories.

How It Is Made

Commercial production of adipic acid for food and industrial use involves chemical synthesis starting from petrochemical feedstocks. A common method oxidizes cyclohexane to a mixture of cyclohexanone and cyclohexanol, which is then further oxidized with nitric acid to produce adipic acid. This multistep oxidation process yields a purified organic acid that is recovered and refined to meet specifications for industrial or food-grade use. Food-grade adipic acid typically undergoes additional purification and testing to ensure consistency with established quality criteria for acidity regulators and food processing aids. Although industrial-scale synthesis remains the predominant source, research continues into sustainable production pathways that may involve bio-based substrates or catalysts. The resulting adipic acid product is a crystalline solid that exhibits the physicochemical characteristics needed for its functions in food systems.

Why It Is Used In Food

Adipic acid is used in food primarily for its functional contributions to acidity control, flavor enhancement, and texture modification. As an acidulant, it helps adjust the pH of food and beverage formulations to achieve desired tartness and stability, particularly in dry mixes and confections where balanced acidity enhances taste perception. In leavening systems, adipic acid reacts with alkaline ingredients like sodium bicarbonate to release carbon dioxide, contributing to leavening action in baked goods. Its buffering capacity supports stable pH levels in gelatin desserts, jams, and similar products, helping maintain consistency in texture and shelf stability. The technical versatility of adipic acid allows it to perform multiple roles within food formulations, providing formulators with a tool for achieving specific sensory and functional outcomes in finished products.

Adi Example Calculation

To illustrate how an acceptable daily intake (ADI) can be applied in a hypothetical scenario, consider an ADI range set at 0-5 mg per kilogram body weight per day. For an adult weighing 70 kilograms, the upper bound of the ADI range corresponds to up to 350 mg of adipic acid per day from all dietary sources. This example is solely to demonstrate how an ADI range is interpreted and does not imply that a specific individual’s exposure should approach this level. Typical food product formulations and consumption patterns are designed so that dietary exposure to adipic acid remains within safe limits well below this illustrative amount when used according to regulatory guidelines.

Safety And Health Research

Scientific and regulatory evaluations of adipic acid focus on hazard identification and exposure assessment to determine safe use levels in food. Toxicological data reviewed by expert committees such as JECFA have informed the establishment of an acceptable daily intake (ADI) range of 0-5 mg per kilogram body weight for adipic acid and its alkali metal salts, based on animal studies and dietary exposure estimates. These evaluations consider endpoints such as gastrointestinal effects in studies where high dietary levels were administered, and conservative safety factors are applied to account for interspecies and intraspecies variability. Regulatory bodies require that food-grade adipic acid meet defined purity criteria and are used in accordance with good manufacturing practices to ensure that consumers are not exposed to levels beyond safety thresholds. Adipic acid’s metabolic fate and potential for systemic toxicity have been reviewed in connection with its widespread use, and ongoing assessments by expert committees help ensure that emerging data are considered in risk management decisions.

Regulatory Status Worldwide

In the United States, adipic acid is included in the Code of Federal Regulations (CFR) under 21 CFR 184.1009, where it is listed as a food additive permitted for direct addition to food under conditions of good manufacturing practice. It is also referenced in multiple sections of parts 175 and 176 related to indirect food contact substances, reflecting its authorized presence in indirect food contact materials. In the European Union and other regions that adopt INS/E number systems, adipic acid is recognized with INS number 355 and listed in additive inventories that specify its permitted uses and purity criteria. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has evaluated adipic acid and assigned a group acceptable daily intake (ADI) range of 0-5 mg per kilogram body weight based on historical evaluations, including its use as an acidity regulator and flavoring agent. Regulatory frameworks worldwide include specifications for identity, purity, and use conditions that govern how adipic acid may be incorporated into food products.

Taste And Functional Properties

Adipic acid imparts a mild, controlled acidic or tart taste that can enhance fruit and beverage flavor profiles without overwhelming sharpness. Its acidity is less intense than that of some other common food acids, offering a smooth and lingering tart note that is particularly useful in confections, powdered drink mixes, and dry food systems. Functionally, adipic acid acts as a buffering agent to resist pH fluctuations, which supports consistent taste and texture during processing and storage. It also participates in leavening reactions when formulated with alkali leavening agents, contributing to carbon dioxide release and improved volume in baked goods. Adipic acid’s solubility and dissociation characteristics in water influence how it interacts with other ingredients, with its dual carboxylic acid groups enabling effective pH control across a moderate acidity range.

Acceptable Daily Intake Explained

The acceptable daily intake (ADI) is a health-based guideline established by expert bodies to indicate the amount of a substance that can be consumed every day over a lifetime without appreciable health risk. For adipic acid and its salts, JECFA has established an ADI range of 0-5 mg per kilogram body weight. This range reflects comprehensive review of toxicological studies and incorporation of safety factors that account for uncertainties in extrapolating animal data to humans and differences between individuals. The ADI is not a recommended target intake but a benchmark for regulators and food manufacturers to ensure that use levels in food products and estimated dietary exposures remain within safe limits. Products that contain adipic acid are formulated so that normal consumption patterns do not lead to exceeding the ADI when used as intended under good manufacturing practices.

Comparison With Similar Additives

Adipic acid can be compared with other food acids such as citric acid, malic acid, and fumaric acid, which also serve as acidity regulators and flavoring agents. Citric acid offers a bright, sharp acidic taste that is rapidly perceived on the palate, making it suitable for beverages and candy, whereas adipic acid provides a smoother, lingering tart profile that fits dry mixes and confections. Malic acid has a stronger sourness than citric acid and is often used when a more pronounced acidity is desired, while fumaric acid is a strong acidulant with high acidity per unit weight and is useful where intense acidity and buffering are needed. Adipic acid’s moderate acidity and multifunctional roles allow formulators to tailor pH control, flavor balance, and leavening performance when used alone or in combination with other food acids, enabling flexibility across diverse product categories.

Common Food Applications Narrative

Adipic acid appears in a wide range of food and beverage products where acidity regulation, flavor balance, and leavening performance are desired. In powdered drink mixes and flavored beverage concentrates, adipic acid contributes to stable pH and a clean, mildly tart taste that enhances fruit flavors when the product is rehydrated. In gelatin desserts and gummy confections, it supports gel structure and texture while complementing sweetness with subtle acidity. Chewing gums and sour candies often incorporate adipic acid to provide a lasting sour character that complements sugar and other flavor ingredients. Baked goods use adipic acid in combination with bicarbonate leavening agents, helping to release carbon dioxide bubbles that expand and create volume in doughs and batters. Savory products and condiments may include adipic acid to regulate acidity and maintain consistent taste profiles. Across these applications, adipic acid’s multifunctional role supports formulation objectives for sensory quality, stability, and processing performance.

Safety & Regulations

FDA

  • Approved: True
  • Regulation: 21 CFR 184.1009

EFSA

  • Approved: True
  • E Number: E355

JECFA

  • Year: 1977
  • Ins Number: 355
  • Adi Display: 0-5 mg/kg bw
  • Adi Mg Per Kg: 5

Sources

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