Preparation method of lactulose

Abstract

The invention discloses a preparation method of lactulose. The preparation method comprises the following steps: preparing lactulose syrup, decoloring by use of activated carbon, performing nanofiltration purifying and concentrating, and performing ion exchange to remove residual salt, wherein a nanofiltration membrane for membrane separation is a polyamide membrane with molecular cut off more than 250Da, and the method for removing the residual salt comprises the following steps: adding boron-removal resin in syrup when pH is in range of 7-10, then adding cation exchange resin, and finally regulating the pH value of the syrup as neutral by use of anion exchange resin. The method has the advantages that the content of the lactulose relative to the total sugar can achieve 75-80% by virtue of catalytic isomerization, the color value removal rate of the activated carbon decoloring can achieve 80%; the salt removal rate of the nanofiltration purifying can achieve 97% and more, and the monosaccharide removal rate can achieve 100%; finally the purity of the lactulose relatieve to the total sugar is greater than 90%, and the yield of the lactulose is more than 70%.

Description

technical field [0001] The invention belongs to the field of functional sugars, in particular to a method for preparing lactulose combined with nanofiltration technology. Background technique [0002] Lactulose (also known as isomerized lactose, lactulose) is a disaccharide composed of a molecule of galactose and a molecule of fructose connected by β-1,4 glycosidic bonds. It has the functions of regulating intestinal health, improving human immunity, and promoting nutrition. Absorption and other beneficial effects are important raw materials for medicine, food and feed industries. However, the monosaccharides (glucose and galactose) and lactose present in low-purity lactulose (50-70% to total sugar) will affect its efficacy. In addition, the pigment and residual salt produced by side reactions will cause drug and food safety issues, so it is necessary to establish a method for preparing high-purity lactulose that is easy to industrialize. [0003] At present, the method of...

AI Technical Summary

Problems solved by technology

At present, the main industrial desalination technologies include ion exchange desalination and membrane separation desalination. The amount of ion exchange desalination resin is large, the adsorption of sugar is serious, and a large amount of acid-base regeneration is required; after the membrane separation technology removes most of the salt in the lactulose syrup, further The removal of residual salt requires the consumption of a large amount of deionized water

Removal of monosaccharides is another difficulty in the purification of lactulose syrup. At present, the main industrial monosaccharide separation technologies include industrial column chromatography and membrane separation. The cost of column chromatography separation equipment is high and the operation requirements are high. It has not been widely used in the industrial production of functional sugars.

[0005] In addition, in the application number 201110081858.1 filed by the applicant on April 1, 2011, and the invention name is a preparation method of high-purity lactulose, the disadvantage is that in order to completely convert lactulose, finally obtain a purity of up to 97% (for the total sugar) lactulose syrup, which limits the ratio of NaOH to lactose, but at the same time reduces the yield of lactulose to 50-55%, and the degree of side reactions such as hydrolysis and pigmentation increases