Production Of High Purity Lactulose

It is complex and difficult to purify the lactulose syrup prepared by chemical catalyst though it could provide high yield for lactulose. This paper aimed to design a process which could be easily applied in the industrial production. In this study, a spectrophotometric method for lactulose determination has been proposed, and the conditions to produce lactulose by H3BO3/NaOH system were optimized. Through the pilot experiments by an M 8-5 membrane, we acquired the appropriate operating parameters for nanofiltration. We obtained high purity lactulose by using an ion-exchange resin column. A novel process to produce high purity lactulose has also been described in this paper.Firstly, lactulose decomposes to galactose and fructose when heated with sulfuric acid (75%, w/v). The fructose transfers to hydroxymethylfurfural which reacts with color developing reagent (cystine hydrochloride and tryptophan). The maximum adsorption wavelength of the coloring matter is 518 nm. The lactulose could be quickly quantified by this spectrophotometric method. Then we investigated the optimum temperature, reaction time, the amount of lactose and boric acid which respectively were 70℃,70 min,3.62 g and 20.0 g. The yield and purity of lactulose were 75%-80% and 78%.Secondly, the H3BO3/NaOH system was tested in a pilot system. A membrane, M 8-5, was chosen as the pilot membrane due to the high retention of total saccharide and low retention of salts. In addition, by investigating the characteristics of the M 8-5 membrane it was found that this membrane could be used in the desalination of lactulose syrup in industry. In a diafiltration mode, when the Vc/Vf was 3.125, more than 90% of the salt was removed with a total sugar loss less than 10%. Moreover, D403 resin could effectively adsorb the residual boric acid in the syrup. The concentration of boric acid was controlled under the safe level.Thirdly, a column which packed by HZ-001 resin (Ca2+) could effectively separate the lactulose and lactose. A separation factor of 0.538 was obtained when the temperature was 15℃, the L/d was 93.75 and the volume velocity was 0.15 BV-h"1. The lactulose with a high purity (>98%) was successfully collected and the recovery was 84.5%. The NMR-C13 spectra fully corresponded to that of the standard sample which purchased from Sigma Company.Finally, in order to produce a kind of lactulose syrup which did not contain lactose, we investigated the NaAlO2 system and H3BO3/NaOH system. By changing the reaction conditions we found that both systems could produce lactulose syrup with high Pu [Clactulose/(Clactulose+Clactose)] values. In the H3BO3/NaOH system, this kind of syrup was subjected to nanofiltration in an M 8-19 membrane. When the Vc/Vf was 4.8, a recovery of 42.7 and a purity of 97.2% were acquired simultaneously.