Processing Methods and Technical Key Points for Making MSG from Sweet Potato
The chemical name of MSG is monosodium glutamate, also called sodium glutamate. It is a high-grade seasoning that can both improve cooking flavor and promote appetite and aid digestion. MSG can be produced from sweet potato starch, and the production cost is low.
1. Process flow: preparation of starch hydrolysis sugar -- fermentation -- glutamic acid extraction, neutralization and decolorization -- concentration and crystallization -- drying and sieving -- finished product
2. Key points of process operation:
(1) Preparation of starch hydrolysis sugar: add water to sweet potato starch to make a starch slurry with a concentration of 16 Baume, adjust the pH to 6.2-6.4 with sodium carbonate, and add the prepared liquefying enzyme at a dosage of 5 units per gram of dry starch. Adjust the slurry temperature to 85-90 degC, keep it warm for about 20 minutes, and check with iodine solution; if it turns brownish red or orange-yellow, liquefaction is complete. Then adjust the slurry temperature to 100 degC and hold for 5 minutes to kill the liquefying enzyme. Then lower the slurry temperature to 55-60 degC, adjust the pH to 1.8 with hydrochloric acid, add saccharifying enzyme and keep warm. Check the saccharification endpoint with anhydrous alcohol; when there is no white reaction, saccharification is finished, and heat the saccharified liquid to 100 degC to inactivate the enzyme. Adjust the pH of the hydrolyzed sugar liquid to 4.6-4.8 with sodium carbonate. The neutralization temperature is generally about 80 degC. Then add 0.3% active slurry and stir evenly to decolorize the sugar liquid; the decolorization time should be no less than 30 minutes. After decolorization is complete, filter the sugar liquid to obtain the hydrolyzed sugar liquid.
(2) Fermentation: the fermentation process is divided into: slant activation -- secondary shake flask seed -- secondary tank seed -- fermentation.
Strain B9 is used for glutamic acid fermentation. The slant medium composition is glucose 0.1%, peptone 1%, beef extract 0.5%, salt 5%, agar 2%, pH 7.0. The slant is cultured at 32 degC for 18 hours.
The composition of the primary seed medium is: glucose 2.5%, urea 0.5%, corn steep liquor 3%, magnesium sulfate 0.04%, dipotassium hydrogen phosphate 0.1%, ferric sulfate 2 ppm, manganese sulfate 2 ppm, pH 6.8-7.0. The primary seed is cultured at 32 degC for 12 hours.
The composition of the secondary seed medium is: hydrolyzed sugar 2.5%, urea 0.4, corn steep liquor 3%, dipotassium hydrogen phosphate 0.15%, magnesium sulfate 0.05%, manganese sulfate 2 ppm, pH 6.8-7.0. The secondary seed is cultured at 34 degC for 7-8 hours.
The composition of the medium for the fermentation tank is: hydrolyzed sugar 2.5%, urea 0.6%, corn steep liquor 0.6%, potassium dihydrogen phosphate 0.17%, potassium chloride 0.03%, magnesium sulfate 0.06%, manganese sulfate 2 ppm, pH 6.7-7.0. The culture conditions are: inoculum amount 1%, culture temperature 35-36 degC, culture time about 35 hours.
(3) Glutamic acid extraction: most factories use the isoelectric point method to extract glutamic acid. Adjust the pH of the fermentation broth to 3.22, and glutamic acid becomes supersaturated and crystallizes out.
(4) Neutralization and decolorization: glutamic acid is neutralized with sodium carbonate to make monosodium glutamate, which then has a strong umami taste. The neutralization temperature is 60-65 degC, the concentration of the neutralized liquid is 22 Baume, and the pH is 6.9-7.0. 106 grams of sodium carbonate can neutralize 294 grams of glutamic acid. After neutralization is complete, the neutralized liquid needs to be decolorized. First use glutamic acid to adjust the neutralized liquid back to pH 6.3, heat to 60 degC to fully dissolve the monosodium glutamate, add powdered activated carbon for decolorization, stir for 30 minutes, then allow it to settle naturally or filter it.
(5) Concentration and crystallization: place the decolorized liquid into a vacuum concentration pan, keep the vacuum degree above 60 mmHg, and control the temperature below 60 degC. When the liquid concentration in the pan reaches 32 Baume, start the stirrer, turn off the steam, suck in seed crystals under vacuum to initiate crystallization, and then centrifuge the resulting crystal liquid in a centrifuge.
(6) Drying and sieving: dry the crystalline MSG at 80 degC, then pass it through 8, 12, 20, and 30 mesh sieves. Among these, the 12, 20, and 30 mesh fractions can be used as 99 deg MSG finished product. Large flakes can be crushed into powder and mixed with salt to serve as powdered MSG. The overly fine fraction can be used as small crystalline MSG or as seed crystals.