Citrus pectin is a natural polysaccharide extracted from the cell walls of citrus fruits like oranges, lemons, limes, and grapefruits.
1. Raw Material Selection
Citrus pectin is mainly extracted from citrus peels (orange, lemon, grapefruit).
- Preferably, dried peels or citrus pomace (the residue left after juice extraction) is used.
- Peels are rich in protopectin, a precursor to pectin.
2. Pretreatment of Peels
Purpose: Remove impurities and prepare for efficient extraction.
- Washing: To remove dirt and pesticides.
- Drying and grinding: Dried peels are ground into small pieces or powder to increase surface area.
- Defatting (optional): Peels can be treated with solvents (like ethanol or acetone) to remove essential oils and lipids, which can interfere with pectin extraction.
3. Acid Extraction
Pectin is soluble in hot acidic water.
- Acid solution: Usually 0.05–0.1 M HCl, citric acid, or nitric acid is used.
- Temperature: 60–90°C (higher temperatures can degrade pectin).
- Time: 30–120 minutes, depending on peel type and acid concentration.
- Principle: Acid hydrolyzes protopectin in the cell walls to soluble pectin.
4. Filtration / Separation
- After extraction, the mixture is filtered or centrifuged to remove insoluble residues.
- The filtrate contains soluble pectin, sugars, and other soluble substances.
5. Precipitation of Pectin
- Alcohol precipitation: Pectin is precipitated by adding ethanol or isopropanol (usually 1:1 or 2:1 ratio with filtrate).
- Pectin forms a gel-like precipitate that separates from the liquid.
6. Washing
- The precipitated pectin is washed with alcohol to remove residual sugars and acids.
7. Drying and Milling
- Drying: Typically in an oven at 40–50°C or by freeze-drying.
- Milling: Dried pectin is ground into a fine powder for use.
8. Optional Refinement
- De-esterification: Adjust the degree of esterification to control gelling properties.
- Standardization: Ensure consistent molecular weight, methoxyl content, and solubility.
Key Parameters Affecting Yield and Quality
- Type of citrus peel (lemon > orange for high methoxyl pectin).
- Acid type and concentration.
- Extraction temperature and time.
- pH of solution (optimal around 1.5–3).
- Alcohol concentration for precipitation.
Summary Flowchart
Raw citrus peel → 2. Wash & grind → 3. Acid extraction → 4. Filtration → 5. Alcohol precipitation → 6. Washing → 7. Drying → 8. Milling → Citrus Pectin Powder