RU2133778C1 - Method of production of lactulose concentrate - Google Patents

Abstract

FIELD: food industry. SUBSTANCE: invention relates to production of lactulose showing bifidogenic properties. Method involves preparing a lactose solution at its content 20-65%. Reducing agent is added to lactose solution in order to prevent lactulose oxidation, for example, sodium sulfite and a catalyst of reaction and they are added at amount 0.1-0.5 g-mole/1 kg lactose. Then alkali is added to the solution and alkaline isomerization is carried out at pH 10.5-12.0, at 80-105 C followed by cooling the isomerized solution and its purification from reagents by electrodialysis. The purified lactulose solution is condensed if necessary. EFFECT: simplified and accelerated process. 2 cl, 2 ex

Description

 The invention relates to the food industry and is intended to produce lactulose with bifidogenic properties.

A known method for producing lactulose syrup, comprising preparing an aqueous alkaline lactose solution, isomerizing lactose at a temperature of 70-100 ^o C, thickening the isomerized solution, crystallizing lactose and separating the lactose alkaline solution from lactulose syrup, using catholyte obtained by electrolysis to prepare the alkaline lactose solution water and having a pH of 10.5-12.5, and the concentration of lactose in the initial solution is 1.0-5.0% (RU, 2092563, 1997).

 With some advantage of the method, due to the use of catholyte obtained by electrolysis of water, it has a significant drawback, consisting in the length of the process associated with multiple crystallization of the condensed and cooled isomerized solution, which leads to a decrease in productivity and an increase in the cost of additional equipment.

There is also known a method for the production of lactulose concentrate, which involves the preparation of lactose solutions with a concentration of 18-22%, its purification from suspended particles, the introduction of sodium hydroxide (NaOH) in a heated lactose solution in the amount of 2.6-3.2 kg per 1 ton of lactose solution for adjusting the pH to 10.8-11.2. After that, the solution is thermostated at a temperature of 85-95 ^o C for 5-7 minutes and cooled to 15-25 ^o C. The solution obtained after isomerization is subjected to electrodialysis to remove the introduced alkali. After reaching 45-55% demineralization, the solution is refined to remove dyes using activated carbon as adsorbent, filtered to remove charcoal and re-subjected to electrodialysis in order to deeply purify the solution from mineral impurities. The purified solution is concentrated in a vacuum evaporator to a dry matter concentration of 57-55%, cooled, crystallized and lactose crystals are removed by centrifugation. The remaining solution (centrate) is again concentrated on a vacuum evaporator to a dry matter concentration of 58-62% and the crystallization of excess lactose is again carried out. The solution obtained after removal of lactose crystals enriched with lactulose is pasteurized, packaged and packaged (see Technological Instructions for the Production of Lactulose Concentrate, 01.01.96, p. 1-9).

 An advantage of the above method is the implementation of demineralization by electrodialysis.

 But the method has such disadvantages as multioperation, the presence of such lengthy processes as crystallization and refining.

The closest technical solution to the proposed one is a method for the production of lactulose concentrate, which provides for the preparation of an aqueous solution of lactose with its content of 60-65%, the introduction of an alkaline or alkaline earth sulfate reducing agent in the amount of 0.05-0.5 mol per 1 kg of monohydrate into it to prevent lactose oxidation lactose, alkaline isomerization of the latter at 80-110 ^o C, cooling, the introduction of a crystalline seed into the solution to accelerate the crystallization of non-isomerized lactose, followed by removal of the crystal lactose fishing from solution. After that, the solution is subjected to ion exchange treatment to remove sulfites. The purified solution is concentrated, cooled and crystallized again. After removal of the lactose crystals, a lactulose concentrate is obtained (AU 288595, 03/10/71).

 The advantage of this method is that the use of weakly alkaline sulfites leads to a slight formation of coloring by-products of the isomerization reaction, although the degree of lactose isomerization in lactulose is less than when using strong alkalis with an equivalent concentration.

Sulfites are good reducing agents. They prevent the oxidation of lactulose and, therefore, the appearance of dark-colored substances. The product is light and transparent. The use of sulfites (Na ₂ SO ₃ ) in the dairy industry is known to prevent dark coloring in syrups of milk sugar (lactose).

 The disadvantages of the known method for the production of lactulose concentrate are as follows.

 Double crystallization of the product and the use of ion-exchange purification are required, which requires additional reagents and rather sophisticated equipment.

 The duration of the crystallization process is 12-48 hours. All things being equal, it leads either to a decrease in productivity or to an increase in production areas with duplicated equipment (dozens of crystallizers, complex technological strapping, etc.), despite the fact that the isomerization process itself lasts 1-30 minutes.

 The technical result of the proposed method for the production of lactulose concentrate is to simplify the method, accelerate it and obtain the final product - lactulose concentrate that meets the requirements of the food industry.

This result is achieved by the fact that in the proposed method for the production of lactulose concentrate, involving the preparation of a lactose solution, the introduction of a reducing agent in it to prevent lactulose oxidation, alkaline isomerization of lactose at a temperature of 80-105 ^o C, cooling and purification of the isomerized solution from the reagents, prepare a lactose solution with its content of 20-65% and the reducing agent is used in an amount of 0.1-0.5 g-mol per 1 kg of lactose, while the reaction catalyst in the same amount and the isomeric process are introduced before isomerization ization is conducted at a pH 10,5-12,0. The isomerized solution is purified by electrodialysis.

 When using an initial solution of lactose with a small content after electrodialysis, thickening of the lactulose solution should be carried out.

 The method is as follows.

An aqueous solution of lactose is prepared with its content of 20-65% at a water temperature of 80-100 ^o C. Then a reducing agent is introduced into it to prevent the oxidation of lactulose in an amount of 0.1-0.5 g-mol per 1 kg of lactose.

 The lower limit of lactose concentration during isomerization in the initial solution is 20% due to the fact that at lower concentrations, the energy costs for subsequent thickening of the solution sharply increase to a dry matter content of 55-65%.

The upper limit of 65% is due to the fact that with a further increase in concentration, due to the low solubility of lactose, even at a temperature of 105 ^o C, it is difficult to obtain a homogeneous solution.

 As the reducing agent, alkali or alkaline earth metal sulfites, for example sodium sulfite, can be used.

 With the introduction of a reducing agent, the redox potential in the reaction mixture decreases, which reduces the oxidation of lactulose to organic acids. Consequently, the loss of lactulose is reduced, organic acids do not so quickly neutralize the alkaline reaction of the medium, as a result of which the isomerization process takes longer. The low concentration of dyes removes the problem of refining the solution using adsorbents.

The solution is thoroughly mixed at a temperature of 80-105 ^o C and the catalyst is added to it in an amount of 0.1-0.5 g-mol per 1 kg of lactose and then alkali to achieve a pH of 10.5-12.0.

 Soluble substances, for example borates, aluminates, can be used as a catalyst.

 The lower limit of the amount of catalyst - 0.1 g mol per 1 kg of lactose is associated with insufficient effectiveness of its action, and the upper limit - 0.5 g mol per 1 kg of lactose with the need for subsequent removal of this reagent from the solution.

 For the same reasons, the selected range of values for the reducing agent (0.1-0.5 g mol per 1 kg of lactose).

The lactose is alkaline isomerized at a temperature of 80-105 ^° C. for 1-25 minutes at a pH of 10.5-12.0. After isomerization, the solution is rapidly cooled. The lower temperature limit of 80 ^o C is due to the fact that at lower temperatures the isomerization process is delayed in time, and the upper limit of 105 ^o C is the maximum achievable temperature for a solution containing 65% solids, i.e. this is its boiling point under normal conditions.

 The lower limit of the pH value of 10.5 is due to the attenuation of the process of isomerization of lactose into lactulose as the pH decreases below this indicator, and the upper one - 12.0, a significant increase in the rate of lactulose oxidation when this value is exceeded.

After the end of the isomerization process, as can be judged by the termination of the decrease in the specific rotation rate of the solution, it is cooled to a temperature of 20-60 ^o C and subjected to purification by electrodialysis to remove chemicals from it. After the end of electrodialysis, as judged by the decrease in electrical conductivity to the desired value, the solution with a lactose content in the initial solution of less than 55% is concentrated in a vacuum evaporator to a dry matter content of 55-65%.

 The use of electrodialysis allows the use of a sufficiently large number of reagents for isomerization, which in general greatly simplifies the method and speeds up the process. This leads to increased productivity.

 Example 1

Take 80 kg of water, heat it with steam in a jacketed reactor to 100 ^o C and contribute 5 kg of anhydrous sodium sulfite (Na ₂ SO ₃ ). At the same temperature, 125 kg of refined lactose are introduced into the reactor, after which the temperature drops to 60 ^o C. The resulting suspension, stirring, is heated to 80 ^o C, the catalyst is introduced - 7 kg of sodium aluminate and continued to be heated with constant stirring to 100 ^o C. A 40% sodium hydroxide solution heated to 80 ^° C. is quickly poured into the resulting homogeneous solution until a pH of 11.0 is reached. After the alkali is introduced into the reactor, the steam is shut off, and cold water is supplied to the reactor jacket. After cooling the solution to 30 ^o C it is sent to the Rodnik electrodialysis unit to remove reagents. After 6 hours of installation operation, the reagent content in the solution, determined by the conductometric method, drops from 7.1% to 0.6%. The concentrate obtained in an amount of 180 kg contains 56% solids, of which 41% are lactulose, 9% are lactose, 5% are galactose, and 1% are other. The solids content of the concentrate is such that it does not require thickening.

 Example 2

Take 187 kg of water, heat it in a jacketed reactor with steam to 80 ^o C and add 2 kg of anhydrous sodium sulfite. After dissolution of the latter, 100 kg of refined lactose are introduced into the reactor. At the same time as lactose, a catalyst is added to the reactor - sodium borate in an amount of 2.5 kg. The mixture is again heated to 80 ^° C. and a 40% sodium hydroxide solution heated to 80 ^° C. is quickly added to it until a pH of 11.9 is reached. The resulting mixture was thermostated at 80 ^o C for 20 minutes, after which the steam was closed and cold water was supplied to the jacket. Cooled to 45 ^o C the solution is subjected to purification by electrodialysis. After 3 hours of operation of the Rodnik electrodialysis plant, the content of reagents decreases from 2.4% to 0.1%. The solution has a solids concentration of 29.6%. Then it thickens, resulting in 150 kg of concentrate with a solids content of 58.2%, of which 46.2% is lactulose, 7.1% lactose, 4.3% galactose, 0.2% other.

 The proposed method has undergone pilot industrial testing, which shows that the combined use of strong alkali, a catalyst (for example, sodium borate) and a reducing agent followed by their removal by electrodialysis eliminates the need for long-term crystallization of lactose, since its content is low as a result of a high degree the transition of lactose to lactulose, reaching 75%. Refining is not necessary, since there are negligible coloring materials. Likewise, regeneration of ion exchange resins is not necessary due to their absence.

 Thus, the entire production consists of four operations: preparation of the solution, isomerization, electrodialysis and, if necessary, thickening, which greatly simplifies the method of production of lactulose concentrate in comparison with the known method.

Claims (2)

1. A method of producing a concentration of lactulose, involving the preparation of a solution of lactose, the introduction of a reducing agent in it to prevent the oxidation of lactulose, alkaline isomerization of lactose to lactulose at a temperature of 80 - 105 ^o C, cooling and purification of the isomerized solution from reagents, characterized in that they prepare a lactose solution with its content of 20 - 65% and the reducing agent is used in an amount of 0.1 - 0.5 g-mol per 1 kg of lactose, while the reaction catalyst in the same amount and the process of isomerization of lead are introduced before isomerization ut at a pH of 10.5 to 12.0, and the isomerized solution is purified by electrodialysis.  2. The method according to claim 1, characterized in that when using the initial solution of lactose with a small content after electrodialysis, the final solution of lactulose is thickened.