The Process Of Extracting Bixin And Norbixin From Annatto Seeds

The process of extracting bixin and norbixin from annatto seeds is mainly divided into two categories: fat-soluble bixin extraction and water-soluble norbixin preparation. The specific process is as follows (combining traditional solvent extraction with modern optimization technology):

1. Raw material pretreatment

Seed collection and cleaning: Select mature annatto seeds, remove impurities (such as peels, dust, etc.), rinse with deionized water and drain.

Drying and crushing: Place the seeds in a 40-50℃ oven and dry at low temperature (to avoid pigment degradation) to a moisture content of ≤5%, and then crush into 20-40 mesh particles (to increase specific surface area and improve extraction efficiency).

2. Fat-soluble bixin extraction (taking organic solvent extraction as an example)

Bixin is a fat-soluble pigment (insoluble in water, easily soluble in organic solvents such as acetone, hexane, ethanol, etc.), and the core of extraction is solvent extraction-concentration-purification.

1. Extraction steps

Solvent selection: Food-grade solvents (such as acetone and hexane) are preferred to avoid residual risks; the solid-liquid ratio (seed powder: solvent) is usually 1:5-1:10 (mass-volume ratio).

Extraction conditions: Stir and extract for 2-4 hours under light-proof and low temperature (30-40°C) conditions (avoid high temperature causing pigment decomposition); the extraction can be repeated 2-3 times to increase the yield.

Solid-liquid separation: Separate the extract and the residue by filtration or centrifugation (4000-6000rpm, 10 minutes).

2. Concentration and purification

Concentration: The extract is distilled under reduced pressure (40-50°C) to recover the solvent and obtain the crude product of annatto (oil or paste).

Crystallization purification: The crude product is dissolved in a small amount of cold acetone, placed in a 4°C refrigerator for crystallization for 12 hours, filtered and dried to obtain high-purity annatto (purity ≥90%).

3. Preparation of water-soluble norbixin (saponification method)

Norbixin is the saponification product of bismuth (water-soluble, often in the form of sodium/potassium salt), which needs to be converted through alkaline hydrolysis-acidification-separation process.

1. Saponification reaction

Raw materials: crude bismuth or seed powder can be used directly (oil must be removed first).

Alkali solution treatment: Mix the raw materials with 0.5-2% sodium hydroxide (or potassium hydroxide) solution at a ratio of 1:10-1:20, and stir at 40-60℃ for 1-2 hours (to promote the hydrolysis of bismuth ester bonds and generate norbixin salt).

Filtration and impurity removal: After the reaction solution is cooled, filter it to remove insoluble matter (such as cellulose and protein).

2. Acidification precipitation and purification

Adjust pH: Slowly add hydrochloric acid (or citric acid) to the filtrate to adjust the pH to 3-4, and norbixin will precipitate in the form of free acid (yellow precipitate).

Separation and drying: The precipitate is collected by centrifugation (6000rpm, 15 minutes), washed with deionized water until neutral, and vacuum dried (40℃) to obtain the crude product of norbixin.

Refining: The crude product can be dissolved in dilute alkali solution (pH8-9), filtered again and acidified and precipitated, and repeated 2-3 times to improve the purity (purity ≥95%).

Modern optimization technology (optional)

To improve efficiency and safety, the following technologies can be used:

Supercritical CO₂ extraction: Using CO₂ as solvent (adding 5-10% ethanol as entrainer), extracting norbixin at 30-40MPa and 40-50℃, avoiding organic solvent residue, suitable for food-grade pigment production.

Microwave-assisted extraction: Using microwaves to accelerate solvent penetration, shorten the extraction time (10-20 minutes), and increase the yield (10-15% higher than traditional methods).

Key considerations

Avoid light and low temperature: annatto/norannatto are sensitive to light and heat, so the entire extraction process must be kept away from light and the temperature must be controlled below 60°C.

Solvent residue: Food-grade applications require strict control of solvent residue (such as hexane ≤ 25 mg/kg).

pH adjustment: The alkali concentration during saponification should not be too high (≤ 2%) to avoid excessive hydrolysis leading to pigment degradation.

Through the above process, fat-soluble annatto (for coloring oily foods) or water-soluble norannatto (for beverages, cakes, etc.) can be efficiently obtained to meet the application needs of food, cosmetics and other fields