How to Extract Vitamin C: Methods from Natural Sources to Industrial Synthesis

December 17, 2025 •

4 min read

The human body is unable to produce its own vitamin C (ascorbic acid), requiring it to be obtained from external sources, primarily through diet. The process of extracting this vital antioxidant varies widely, from simple kitchen-based methods using common fruits to highly complex, multi-step industrial and laboratory procedures.

Quick Summary

Isolating ascorbic acid involves a range of techniques, including solvent-based extraction from plants, and industrial-scale chemical and fermentation syntheses. This process is challenging due to vitamin C's high instability, requiring controlled conditions to prevent oxidation.

Key Points

Natural Sources: Extracting vitamin C from natural sources like fruits and vegetables requires acidic solvents and careful handling due to its instability.
Industrial Synthesis: Large-scale vitamin C production relies heavily on the two-step fermentation process, which starts with glucose and uses bacteria to achieve high yields.
High Instability: Vitamin C is highly sensitive to heat, light, and oxidation, which can cause rapid degradation and a loss of potency during extraction.
Green Extraction: Techniques such as ultrasound-assisted (UAE) and microwave-assisted extraction (MAE) use physical energy to disrupt plant cells and improve extraction efficiency with reduced environmental impact.
Purification is Key: Regardless of the method, the final extracted vitamin C needs to be purified to remove other compounds and stabilize it for its intended use.
Pre-treatment is Crucial: Before extraction, methods like freeze-drying or low-temperature drying are preferred to preserve the vitamin C content in the raw plant material.

Understanding Ascorbic Acid Stability

Before delving into the extraction methods, it's crucial to understand why vitamin C extraction requires careful handling. Ascorbic acid is a highly unstable, water-soluble compound. It is sensitive to heat, light, and especially oxygen, which can cause rapid oxidative degradation and a loss of its nutritional value. For this reason, extraction procedures often take place in a weakly acidic, low-oxygen environment to preserve the final product.

Extracting Vitamin C from Natural Sources

Extracting vitamin C from fruits and vegetables is a common practice in both laboratory and small-scale food production. The process typically involves disrupting the plant cell walls to release the ascorbic acid into a suitable solvent, followed by purification.

Conventional Solvent Extraction (CSE)

This traditional method involves macerating or grinding the plant material and soaking it in an acidified aqueous solution. The acidic solvent helps stabilize the vitamin C and inhibits enzymatic degradation. Common procedures include:

Preparation: Fresh fruits or vegetables are washed, peeled, and chopped. The material is often ground into a pulp to maximize the surface area.
Acidic Solution: A weak acid, such as metaphosphoric acid or oxalic acid, is used as the extraction solvent. A typical ratio might be 1 part solid to 10 parts solvent.
Extraction: The plant material is mixed with the solvent and stirred for a set period, often under low light and temperature to minimize degradation.
Purification: The mixture is then centrifuged or filtered to separate the solid pulp from the liquid extract containing the vitamin C.

Green Extraction Techniques

To improve efficiency and reduce environmental impact, modern techniques utilize physical energy to assist extraction.

Ultrasound-Assisted Extraction (UAE): This method uses high-frequency sound waves to create cavitation bubbles in the solvent. When these bubbles collapse, they create microjets that disrupt cell walls, releasing intracellular compounds like vitamin C without excessive heat.
Microwave-Assisted Extraction (MAE): MAE uses microwave energy to rapidly heat the solvent and matrix. This increases the internal pressure within the plant cells, causing them to rupture and release their contents more efficiently. Using a nitrogen atmosphere during MAE can further prevent oxidation.
Supercritical Fluid Extraction (SFE): SFE employs a fluid in a supercritical state, most commonly carbon dioxide ($CO_2$), as the solvent. It is a very clean method, as the $CO_2$ can be easily separated from the final product by depressurization. However, pure $CO_2$ has low polarity, so co-solvents like ethanol are needed to effectively extract water-soluble vitamin C.

Industrial Production: Chemical and Fermentation Processes

For large-scale, commercial production of vitamin C, methods based on chemical synthesis and fermentation are used. These processes are designed for high yields and purity.

The Reichstein Process

Developed in the 1930s, this classic method uses a multi-step conversion starting from glucose.

Glucose to Sorbitol: Glucose is catalytically hydrogenated to produce D-sorbitol.
Sorbitol to Sorbose: The bacterium Acetobacter suboxydans oxidizes sorbitol to L-sorbose through fermentation.
Protection and Oxidation: Remaining hydroxyl groups are protected with acetone, and a catalytic oxidant is used to oxidize the unprotected hydroxyl group.
Cyclization: Acid-catalyzed hydrolysis removes the protective groups and closes the lactone ring, yielding ascorbic acid.

Modern Two-Step Fermentation Process

Prevalent in modern industry, this approach improves upon the Reichstein process by incorporating more fermentation steps.

Glucose to Sorbose: Similar to the Reichstein process, glucose is converted to L-sorbose via fermentation.
Sorbose to 2-Keto-L-Gulonic Acid (2-KLG): A second fermentation step, using genetically modified bacteria such as Erwinia, converts the sorbose to 2-Keto-L-Gulonic acid.
Cyclization: The final step involves the acid-catalyzed cyclization of 2-KLG to form L-ascorbic acid. This process is more cost-effective and environmentally friendly than the traditional chemical route.

Comparison of Vitamin C Extraction Methods


Feature	Natural Extraction (e.g., UAE/MAE)	Industrial Synthesis (Two-Step Fermentation)
Starting Material	Fruits, vegetables, and plant waste rich in ascorbic acid	Glucose, a readily available and inexpensive sugar
Process Scale	Typically small to medium-scale, for niche products or laboratory use	Large-scale, high-volume production for the food, pharmaceutical, and cosmetic industries
Extraction Efficiency	Can be low and highly dependent on the source material's quality, freshness, and processing parameters	High and consistent due to controlled, multi-stage, high-yield processes
Purity of Product	The extract may contain other compounds from the natural source, requiring further purification for higher grades	Produces a highly purified L-ascorbic acid, meeting stringent pharmaceutical and food-grade standards
Environmental Impact	Generally considered a 'green' or sustainable option, especially with modern techniques like UAE/MAE	Involves chemical and fermentation steps that, while improved, can still generate waste products
Cost	Can be expensive per unit of vitamin C due to raw material variability and batch processing	Highly cost-effective at scale due to optimized processes and high efficiency

Conclusion

From the ancient reliance on citrus fruits to prevent scurvy to today's sophisticated industrial processes, the methods to obtain vitamin C have evolved significantly. While simple extraction from natural sources is feasible, it is prone to degradation and lower yields. Industrial methods, particularly the advanced two-step fermentation process, offer a more stable, efficient, and cost-effective solution for large-scale production, ensuring a reliable supply of this essential nutrient for global markets. The optimal method ultimately depends on the desired scale, purity, and application, balancing yield with cost and environmental considerations.

Learn more about modern ascorbic acid production advancements here.

Frequently Asked Questions

At home, you can extract vitamin C by blending fresh citrus peels or other high-vitamin C produce with a weakly acidic solution, such as a mix of water and a small amount of citric acid. The mixture is then strained to separate the liquid extract from the solids.

Using a weakly acidic solution during extraction is crucial for stabilizing vitamin C. Ascorbic acid is prone to oxidation in a neutral or alkaline environment, so the low pH helps protect it from degradation.

The Reichstein process is a classic industrial synthesis method that converts glucose into ascorbic acid through a series of chemical and fermentation steps. It involves converting glucose to sorbitol, then to sorbose via fermentation, and finally cyclizing it chemically into ascorbic acid.

Chemically, synthetic and natural L-ascorbic acid are identical. The bioavailability and effectiveness are considered comparable. The choice often comes down to cost, purity needs, and consumer preference for natural or industrially produced ingredients.

The primary challenge is preventing the degradation of vitamin C, which is highly unstable when exposed to heat, oxygen, and light. This necessitates using low temperatures, acidic conditions, and sometimes inert atmospheres during extraction.

The modern industry primarily uses a two-step fermentation process. This method uses bacteria to convert glucose to sorbose and then to 2-keto-L-gulonic acid, which is then chemically cyclized to produce ascorbic acid.

SFE uses carbon dioxide in a supercritical state as a solvent to extract compounds. For water-soluble vitamin C, a co-solvent like ethanol is added to the supercritical $CO_2$. This 'green' method avoids toxic organic solvents.