Processing method for making high-fructose corn syrup from sweet potato

High-fructose corn syrup is a starch sugar crystal made by hydrolysis and isomerization of plant starch, with a unique flavor, and is an important sweetener. Because its composition is mainly fructose and glucose, it is called "high-fructose corn syrup". The production of high-fructose corn syrup is not restricted by region or season, the equipment is relatively simple, and the investment cost is relatively low.

1. Process flow: sweet potato starch - slurry preparation - saccharification - neutralization - decolorization - filtration - resin treatment - evaporation - isomerization - decolorization - resin treatment - evaporation - finished product

2. Key points of process operation:

① Slurry preparation: First add part of the water into the mixing tank, add sweet potato starch under stirring, and after feeding is completed, continue adding water so that the starch milk reaches the specified concentration (40%), then add hydrochloric acid to adjust the pH value to 18.

② Saccharification: The prepared starch milk is sent by an acid-resistant pump to the saccharification tank. After feeding is completed, open the steam valve and raise the pressure to about 2.8 kg/sq cm, maintain this pressure for 3 to 5 minutes, then take a sample and check the saccharification endpoint with 20% iodine solution. When the saccharification liquid turns sauce-red with iodine, it can be discharged for neutralization.

③ Neutralization: The saccharification liquid is transferred to the neutralization tank for neutralization. At the start of stirring, add a measured amount of spent carbon as a filter aid, and gradually add 10% sodium carbonate solution for neutralization. When the pH is 4.6 to 4.8, open the discharge valve and use a pump to send the sugar liquid to the filter. The clear sugar liquid filtered out is immediately cooled to 60°C, and after cooling the sugar liquid is decolorized.

④ Decolorization: Put the clear sugar liquid into the decolorization tank, add a measured amount of activated carbon while mixing, and the decolorization stirring time must not be less than 5 minutes, then send it to the filter, and collect the clear filtrate in a storage tank for later use.

⑤ Resin exchange: Send the filtrate from the first decolorization to the ion exchange filter bed for desalting, purification and decolorization. After the sugar liquid passes through four resin filter beds in the order cation - anion - cation - anion, adjust the pH value in the sugar storage tank to 3.8 to 4.2.

⑥ Evaporation: After resin exchange, the sugar liquid whose pH value has been accurately adjusted is sent by pump to the evaporation tank, maintaining a vacuum degree above 500 mmHg. The heating steam pressure must not exceed 1 kg/sq cm. When the sugar liquid concentration is about 42% to 50%, it can be discharged.

⑦ Isomerization: Pack solid-phase isomerase into an upright heat-preserving reaction column, control the reaction temperature at 65°C, feed the refined sugar liquid from the top of the column, let it flow through the enzyme column for the isomerization reaction, and then discharge it from the bottom of the column, in continuous operation. It can also be fed from the bottom of the column, pass through the enzyme column, and be discharged from the top of the column. Because enzyme activity is at its optimal pH value, it can fully exert its catalytic effect, the reaction speed is fast, the time is short, and the degree of side reactions of sugar decomposition is low. The resulting isomerized sugar liquid is lighter in color and easy to refine. Therefore, during isomerization, the pH value of the sugar liquid should be determined by the model of the isomerase used.

⑧ Secondary decolorization: After the isomerization reaction, the resulting sugar liquid contains colored substances and can produce color, ash and other impurities during storage, so secondary decolorization is required. Send the sugar liquid into the decolorization tank, add a measured amount of fresh activated carbon, and operate in the same way as the first decolorization.

⑨ Secondary resin exchange: The sugar liquid after secondary decolorization needs another resin exchange, in the same way as before. The finally outflowing sugar liquid has a relatively high pH value, and hydrochloric acid can be used to adjust the pH value to 4.0 to 4.5.

⑩ Evaporation and concentration: The refined sugar liquid is concentrated in a vacuum evaporation tank to the required concentration, thus obtaining high-fructose corn syrup. Because glucose is easy to crystallize, in order to prevent crystals from precipitating during storage of the syrup, the sugar liquid must not be evaporated to too high a concentration, and it is generally required to be between 70% and 75% (dry matter concentration).