Erythorbic Acid

Erythorbic Acid (CAS Number: 89-65-6) Supplier in Europe

Erythorbic acid, also known as isoascorbic acid or D-araboascorbic acid, is a stereoisomer of ascorbic acid (vitamin C). This compound was initially synthesized from sucrose through a fermentation process, and today it plays a significant role as an antioxidant in the food industry.

Its antioxidant properties contribute to preserving color and preventing the change of flavor and aroma in processed foods. Erythorbic acid is recognized by the E number E315 and is considered safe for consumption by various food safety authorities around the world.

While erythorbic acid shares structural similarities with ascorbic acid, its vitamin C activity in humans is substantially less. Consequently, it is not used as a vitamin supplement.

Instead, its primary function is to improve the shelf life and stability of food products by slowing down the oxidation of food constituents.

It is commonly found in canned and preserved fruits, beverages, processed meats, and even some baked goods.

Manufacturers favor erythorbic acid due to its efficiency in small quantities and its minimal impact on taste.

Chemical Structure

Erythorbic acid, also known as isoascorbic acid or D-araboascorbic acid, possesses a specific chemical structure that can be attributed to its efficacy as an antioxidant. This compound is recognized as a stereoisomer of ascorbic acid, commonly referred to as vitamin C.

The molecular formula of erythorbic acid is C_6H_8O_6.

The structure of erythorbic acid is characterized by a lactone ring—a cyclic ester that includes a six-membered ring with the following key functional groups and characteristics:

• A primary alcohol group (-OH) positioned at the 4^th^ carbon.
• An enediol moiety, which involves two adjacent alcohol groups on the 2^nd^ and 3^rd^ carbons.
• A keto group (=O) at the 3^rd^ carbon in its oxidized form, differing from ascorbic acid’s aldehyde group.

These functional groups play significant roles in erythorbic acid’s antioxidant activities. They are capable of donating electrons to neutralize free radicals, thus preventing oxidative stress.

Erythorbic acid shows a spatial configuration that mirrors that of L-ascorbic acid but displays different optical activity due to its distinct arrangement of atoms.

The compound exists as a white to light yellow crystalline powder and is highly soluble in water, which is attributable to its hydrophilic groups.

The compound’s molecular conformation is stabilized by internal hydrogen bonding, which also impacts its chemical reactivity. Despite similar attributes to ascorbic acid in antioxidant properties, erythorbic acid is not recognized as a vitamin by the human body due to differences in biological activity.

Production and Synthesis

Erythorbic acid is produced on an industrial scale due to its application as a food preservative and antioxidant. Synthetic methods facilitate its production for commercial use.

Industrial Synthesis

On the industrial front, erythorbic acid is manufactured through a process that stems from the reaction of methyl 2-keto-D-gluconate with sodium methoxide. The key steps are as follows:

1. Esterification: Methyl 2-keto-D-gluconate is first esterified using methanol.
2. Isomerization: The ester undergoes double bond isomerization to produce an isomeric compound.
3. Reduction: The isomer is then reduced, yielding erythorbic acid.

This route offers a cost-effective and efficient way to produce erythorbic acid in large quantities.

Laboratory Methods

In a laboratory setting, more precise and controlled synthesis methods are employed for the production of erythorbic acid. These include:

• Stereo-Specific Synthesis: Initially, D-glucose is converted into D-sorbitol, which then undergoes a stereo-specific oxidation to give L-sorbose.
• Oxidation: The L-sorbose is subsequently oxidized in the presence of a catalyst, typically platinum or palladium, to produce erythorbic acid.

This method provides erythorbic acid in higher purity but is less commonly used on a commercial scale due to higher costs and more demanding reaction conditions.

Properties

Erythorbic acid, recognized for its preservation capabilities, is commonly used in the food industry. The properties of this compound are divided into physical and chemical characteristics that define its applications and efficacy.

Physical Properties

Erythorbic acid appears as a white to slightly yellow crystalline powder. It is odorless and has a slightly tart flavor.

Solubility plays a crucial role in its use as a food additive; it is highly soluble in water (up to 40 g/100 mL) and moderately soluble in ethanol. The melting point of erythorbic acid is approximately 166°C when anhydrous.

Property	Description
Appearance	White to slightly yellow crystalline powder
Odor	Odorless
Taste	Slightly tart
Solubility in Water	Highly, up to 40 g/100 mL
Solubility in Ethanol	Moderate
Melting Point	About 166°C (anhydrous)

Chemical Properties

Erythorbic acid, with the chemical formula C_6H_8O_6, is an isomer of ascorbic acid (vitamin C) but does not exhibit vitamin C’s physiological activity.

It demonstrates antioxidant properties by acting as an oxygen scavenger, which makes it valuable in preventing the oxidative deterioration of foods, thereby extending shelf life.

Additionally, it exhibits a high reactivity with oxygen, and its efficacy is impacted by factors such as pH, where it is most stable at a pH below 6.

Property	Description
Chemical Formula	C_6H_8O_6
Isomerism	Isomer of ascorbic acid; lacks vitamin C activity
Antioxidant	Acts as oxygen scavenger
Stability	Most stable at pH below 6

Food Industry Applications

Erythorbic acid is used primarily in the food industry for its capabilities to preserve and maintain the freshness of foods.

Preservative Functions

Erythorbic acid helps to prevent food spoilage caused by oxygen, which can occur in a variety of food products. Specifically, it:

• Prevents microbial growth: By inhibiting the effects of oxygen on food, erythorbic acid reduces the likelihood of microbial growth, thus extending the shelf life of processed foods.
• Maintains color and texture: It is commonly added to meats and other products to preserve their natural color and prevent the fats within them from becoming rancid, thereby maintaining the desired texture.

Antioxidant Mechanisms

The effectiveness of erythorbic acid as an antioxidant is due to its chemical properties, which allow it to:

• Donate electrons: It can donate electrons to free radicals, which neutralizes them and prevents oxidative damage to food molecules.
• Regenerate other antioxidants: Erythorbic acid has the ability to regenerate other antioxidants, like vitamin E, thus maintaining their active role in protecting food products from oxidation.

Regulatory Status

Erythorbic acid is widely recognized by food safety authorities as a safe preservative and antioxidant, but its use is subject to specific regulatory controls.

FDA Regulations

The U.S. Food and Drug Administration (FDA) classifies erythorbic acid as generally recognized as safe (GRAS). It permits its use in food with the following specifications:

• Function: Antioxidant, Preservative
• Maximum Allowed Levels:
  • Meat products: 550 ppm
  • Other products: As needed in accordance with good manufacturing practice

Compliance with these standards ensures that food products containing erythorbic acid are safe for consumption in the U.S.

EU Food Safety

The European Union’s approach towards erythorbic acid, categorized as E315, involves both approval and regulation:

• Approval: Listed as an approved food additive
• Usage Limitations:
  • Fruit and vegetables: 300–500 mg/kg
  • Beverages: 100–300 mg/L

These guidelines, enforced by the European Food Safety Authority (EFSA), ensure that European consumers are protected from excessive intake.