(2) Liquefaction: This procedure is very important to improve the yield of maltose, and should be strictly operated. Pump the prepared starch emulsion into the storage tank, the dosage of D- amylase is calculated as 5U/g starch, and IO0~C is liquefied to DE value 1o ~ 12. At the same time, immediately raise the temperature to above 100℃, keep it for 5 minutes, and inactivate the enzyme at high temperature. The starch liquefied liquid after high temperature treatment has good dispersibility and is not easy to coagulate, which is beneficial to saccharification operation.
(3) Saccharification: cooling the liquefied matter to 45-50℃, adjusting the pH to 5.8-6.0, adding isoamylase 20U/g starch and fresh bran, 13 mono-amylase 10U/g starch, and saccharifying for 30-40h to obtain 80%-95% and 5%-650%.
(4) Filter pressing: Its function is to remove impurities in saccharified liquid and ensure the smooth progress of subsequent processes. Filter pressing with a plate-and-frame filter press, and using diatomite or crushed nacre powder as a filter aid until a clear filtrate is obtained.
(5) Decolorization: 0.5 ~ 1.0% of the dry matter of the filtrate is added with powdered activated carbon, and the activated carbon is mixed with the same amount of filtrate before adding, so that the activated carbon can be easily mixed. Decolorization operation conditions: pH 4.5 ~ 5.0, 80℃, 30min, stirring at the speed of 20 ~ 25 rpm, and then using diatomite as filter aid (the dosage is 0.3 ~ 0.5kg/m2), press-filtering with a plate-and-frame filter press. First, mix diatomite with a small amount of saccharified liquid evenly, then pump it into the filter, and the pressure is required to be below 0. 1 MPa, so that diatomite can be uniformly deposited on the surface of the filter, and the filtered filtrate is unclear at first. Return to the decoloring tank until the liquid is clear, close the reflux pipe, and send the filtrate to the storage tank, with the filtration pressure controlled at 0.2 ~ 0.3 MPa.
(6) Ion exchange: impurities such as metal ions, ionic pigments and residual soluble nitrogen-containing substances in the filtrate can be removed by ion exchange, which can further improve the purity and thermal stability of sugar solution and make it colorless and transparent. Ion exchange process: saccharification liquid-column-column-column-column. Choose strong acidic cation resin and strong alkaline anion resin. Before use, the ionic resin is soaked and expanded, and then put into anion column and cation column respectively, and can be used after acid washing, alkali washing and water separation. During the exchange, the flow rate is controlled at about 700kg/h and the temperature is controlled at about 40℃. The service life of resin depends on the impurity content in syrup, and the high impurity quality has a short service life.
(7) vacuum concentration: the vacuum degree is maintained at 0.086-0.092 MPa, the sugar solution temperature is about 50-53℃, the vacuum degree is not lower than 0.066MPa, and the steam pressure is controlled at 0.2-0.3 MPa. Concentrate until the solid content is 40-60%, stop cooking and exhaust, which can be used as raw material for preparing maltitol.
Preparation of maltitol. Under alkaline conditions, nickel catalyst was added according to 8% of starch input, and colorless pure high maltose syrup with solid content of 40% ~ 60% was obtained. Hydrogen gas of 5 ~ 18 MPa was introduced into the autoclave, and under this condition, maltose began to absorb H for hydrogenation reaction. After hydrogenation, maltitol solution was obtained. Then the catalyst in the sugar solution is removed by filtration, and then treated with activated carbon and ion exchange (the operation requirements and steps are the same as above), so that the clarified maltitol can be obtained. Finally, maltitol syrup or granular products can be made by vacuum concentration, spray drying and other processes.
Maltitol has a high melting point and can be dried at a higher temperature. However, due to the high viscosity of maltitol, it must be dried immediately, so it can be produced by full crystallization process, that is, liquid maltitol can be used as raw material to produce powdery solid products by spray drying in molten state.