Product Overview

Ascorbic acid, also known as Vitamin C, typically appears as a flaky or sometimes needle-like monoclinic crystal, odorless, sour in taste, and easily soluble in water with strong reducing properties. It participates in complex metabolic processes in the body, promotes growth, and enhances resistance to diseases. It can be used as a nutritional supplement, antioxidant, or wheat flour improver. However, excessive supplementation of Vitamin C can be harmful rather than beneficial, so it must be used rationally. In the laboratory, Vitamin C is used as an analytical reagent, such as a reducing agent or masking agent.

Production Process of Ascorbic Acid

Industrial Production

Vitamin C production methods are broadly divided into three categories: chemical synthesis, combined chemical and biosynthesis (fermentation), and biosynthesis (fermentation). Recently discovered yeast fermentation for synthesizing Vitamin C, although promising, has not yet reached industrial production levels.

Chemical Synthesis

In 1933, the Reichstein and Ault research teams independently published methods for chemically synthesizing Vitamin C, but due to the long synthesis route and low yield, these methods did not achieve industrial-scale production.

Combined Chemical and Biosynthesis

Since 1937, based on the inventions of Reichstein and Grussner, a method for producing Vitamin C starting from glucose using a combination of chemical and fermentation methods, known as the "Reichstein procedure," was established. This marked the beginning of large-scale industrial production of Vitamin C. This method, after continuous improvement and refinement, has been widely applied globally, with an overall yield exceeding 60%. Due to the low cost and easy availability of glucose, the chemical stability of intermediate compounds, particularly diacetone-L-sorbose, and continuous improvements in the production process, along with the high quality of the product, the "Reichstein procedure" remains the primary method for Vitamin C production abroad. This method uses D-sorbitol as the raw material and requires four major reaction steps to obtain the Vitamin C product.

  • D-sorbitol is fermented by Gluconobacter melanogenus (or weak oxidizing Acetobacter suboxydans) to produce L-sorbose.
  • L-sorbose reacts with acetone to produce diacetone-L-sorbose.
  • Diacetone-L-sorbose is oxidized to diacetone-2-keto-L-gulonic acid sodium salt, which is then acidified to produce diacetone-2-keto-L-gulonic acid.
  • Diacetone-2-keto-L-gulonic acid is converted to Vitamin C.

Despite the extensive research from the 1960s onward aimed at shortening the "Reichstein procedure," no substantial progress was made.

Biosynthesis (Fermentation)

2-Keto-L-gulonic acid (2-KGA) is the direct precursor for synthesizing Vitamin C, with the final step being a chemical transformation. There are at least six known pathways starting from glucose to produce 2-KGA. Among these, only the second pathway, developed by China as the "two-step fermentation method," has achieved industrial production.

Preparation of Vitamin C

2-Keto-L-gulonic acid is lactonized at the C-4 position and enolized at the C-2 position to obtain Vitamin C, catalyzed by acid or base. In industrial production, the alkaline conversion method is commonly used, where 2-KGA is catalyzed by methanol with sulfuric acid, then converted to Vitamin C sodium salt by NaHCO₃. This is acidified by hydrogen ion exchange resin, then dried under reduced pressure at 50-55°C to obtain crude Vitamin C.

Application Scenarios for Ascorbic Acid

Nutritional supplement, antioxidant, analytical reagent, etc.

1. Food Industry

  • Freshness preservation of fruits and vegetables
  • Anti-browning
  • Improving protein properties
  • Inhibiting fat oxidation
  • Reducing nitrite content
  • Supplementing SO₂
  • Stabilizing tea polyphenols and improving the quality of black tea

2. Analytical Chemistry

Vitamin C can be used as a reagent for determining arsenic, iron, iodine, bismuth, calcium, magnesium, titanium, tungsten, antimony, and phosphorus, and as a standard substance for determining acid anhydride. It can also be used as a reducing agent, masking agent, or chromatography reagent.

3. Agriculture, Forestry, and Animal Husbandry

  • Poultry farming
  • Aquaculture

4. Pharmaceutical Uses

  • Indications
  • Pharmaceutical formulations

Packaging and Storage of Ascorbic Acid

Storage Conditions: Vitamin C rapidly oxidizes in air and alkaline media, so it should be sealed in brown glass bottles and stored in a cool, dry place away from light, separate from strong oxidizers and strong bases.

Packaging: Bulk: 25kg/drum, samples: 1kg/aluminum foil bag, or as per customer requirements.

Shipping Method: Courier or logistics, domestic delivery within three days by courier, within five days by logistics. Quoted prices generally include domestic shipping costs.

Shelf Life: Two years.

Plant Sources

Ascorbic acid is widely distributed in green leafy plants such as spinach, beet greens, and broccoli. It is also found in animal products (liver, kidneys, egg yolks), fruits (citrus, kiwi), and yeast, but is less abundant in root vegetables, corn, rice, and pork. Among green leafy vegetables, those with high ascorbic acid content include plants like eastern edible aster, hog peanut leaves, wild vegetables like wild asparagus, and others, with respective contents of 36.195, 23.478, 20.137, 67.600, 59.553, 22.032μg/g.

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