How to extract pectin from watermelon rind?

(1) raw material processing Selected fresh watermelon rind cleaned, put into the steamer to steam until the watermelon rind becomes soft, there are water droplets precipitation shall prevail, the purpose of steaming is to kill the pectinase in the living cells, in order to prepare for the next step in the pressing.

(2) pressing the raw material will be steamed through the bag into the press, as far as possible, dry, in order to remove the water in the tissue cells, which is due to the juice contains sugar and inorganic salts and other substances, if these substances are not removed, it will affect the purity of pectin.

(3) hydrolysis of the dried raw materials in corrosion-resistant containers, add water 3 to 4 times the acid pH to 2.0 or so, heated to boiling, keep a few minutes to hydrolyze pectin. This process should be carefully operated, master the acidity, temperature and time, otherwise pectin is not easy to hydrolyze.

(4) filtration with a cloth bag wrapped filter residue press, collect the filtrate, the filtrate for the second decomposition, that is, the filtrate plus 2 times the water, adjust the pH to 2.0 or so with the same hydrolysis, filtration, discard the filtrate, the merger of two filtrates.

(5) Concentration Add 0.3% to 0.5% of activated carbon in the filtrate, and decolorize it at a temperature of 55 to 60 degrees Celsius for 30 minutes, and then collect the filtrate after filtration. Then the decolorized filtrate is concentrated by vacuum until the total solid reaches about 8%.

(6) alcohol precipitation in the concentrate, add 90% ethanol (add amount for the concentration of liquid volume of 1 times), and then gently stirring, then will see a pectin flocculation out, after a few minutes of standing can be flocculated pectin into a fine cloth bag, extrusion of liquid pressure (should be recycled, ethanol extraction of the liquid) and then squeezed the pectin, with 5% ethanol solution washing (amount of pectin for about 90 times)

(7) drying The pectin will be squeezed in an enameled tray, 65 ~ 75 ℃ constant temperature oven baked to the moisture content of 8% or less, and then after grinding and crushing, 60 mesh sieve.

(8) grading and packaging After analyzing and testing the products according to different grades can be packaged in polyethylene plastic bags.