Method for extracting pectin from watermelon peel

1. Pretreatment of raw materials: In order to preserve raw materials, raw materials should be treated and quickly heated to 95℃ for 5-7 minutes. The purpose of heat treatment is to passivate pectinase to avoid pectin decomposition and reduce yield, and then dry the raw materials into semi-finished products for preservation.

2. Soaking: Soak the dried skin in water to preliminarily remove aromatic substances, sugar, bitter substances and pigments.

3. Rinse: Soaking on it mainly makes the peel absorb water and soften. By rinsing with plenty of water, various non-colloidal substances such as sugar and pigment can be removed as much as possible to ensure the quality of pectin.

4. Draining and crushing: it can be crushed into a particle size of 3-5 mm with a meat grinder to fully extract pectin.

5. Pectin extraction: The principle of acid extraction method is that the original pectin is hydrolyzed into soluble pectin under dilute acid and heating. When extracting pectin, pH value, temperature, time and acid type have great influence on the quality and quantity of pectin. 1% dilute hydrochloric acid can be added to the raw material in an amount of 4 times, heated to about 90℃, and the solution is in a slightly boiling state, maintained at about 1 hour, and continuously stirred until hydrolysis is completed.

6. Filtering: filtering and removing residues to obtain a thin colloidal pectin solution.

7. Decolorization: The purpose is to fully remove pigment, bitterness and peculiar smell. Multi-purpose activated carbon is used for decolorization.

8. Concentration: In order to produce liquid pectin, the diluted pectin solution must be concentrated to remove a lot of water. Vacuum concentration is adopted in the production, and a double-effect evaporation tank is adopted, with a vacuum degree of 660 mm Hg, a boiling temperature of 45-50℃ and a concentration ratio of 4: 1 or 5: 1. Finally, sodium carbonate (Na2CO3) was used for neutralization, and the pH value was raised to 3.5.

9. canning and sealing: heating canning and sealing.

1 1. sterilization: the causal glue is acidic, and the sterilization temperature should be pasteurized, that is, 70℃ for 30 minutes is enough.

12, and cooling: cooling to obtain a liquid pectin product.