RU1793882C - Method for albumin of milk raw material concentrating - Google Patents

Abstract

Usage: in the dairy industry when obtaining protein concentrates by ultrafiltration. The inventive protein is isolated from milk raw materials by continuous ultrafiltration in three stages by means of polymer membranes having a molecular weight cut-off in the first stage of 50 000-67 000 Yes, in the second stage - 20 000-25 000 Yes and in the third stage 5 000-10 000 Yes, at the end of the process, the polymer membranes are regenerated with an aqueous solution, including sodium tripolyphosphate, from 0.12 to 0.20 May. %; alkyl sulfonate - 0.015-0.02 wt.%, sodium hydroxide 0.02-0.25 wt.% and sodium nitrate 0.2-0.25 wt.%, followed by exposure in a washing solution for 2-8 hours. 1 s.p. crystals, 1 tab.

Description

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The invention relates to the dairy industry, and in particular to a method for concentrating protein using the ultrafiltration process from cottage cheese whey, skim milk and other products of the dairy industry.

The closest technical solution is the method of concentrated protein from milk raw materials by continuous ultrafiltration by means of polymer membranes in three stages to obtain protein concentrate and filtrate and subsequent regeneration of elements. Regeneration is carried out by chemical washing. To process the filter elements, an aqueous acid solution is used first, followed by an alkali solution, followed by washing with water.

A disadvantage of the known protein concentration method is increased protein loss. Their concentration in the filtrate reaches 0.2%.

An object of the invention is to reduce protein loss.

The goal is achieved in that according to the method of concentrating protein from milk raw materials by continuous ultrafiltration by means of polymer membranes in three stages to obtain protein concentrate and filtrate and subsequent regeneration of elements, when concentrating at the first stage, polymer membranes having a cut-off by molecular weight of 50,000 67000 Yes, in the second stage -20000-25000 Yes and in the third stage - 5000-10000 Yes.

The regeneration of polymer membranes is carried out by filling them with an aqueous solution, including sodium tripolyphosphate, alkyl sulfonate, sodium hydroxide and

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sodium nitrate in the ratio of components, wt.%:

Tripolyphosphate

sodium 0.12-0.20

Alkyl sulfonate 0.015-0.02 Sodium hydroxide 0.02-0.25

Sodium nitrate 0.2-0.25

Water The rest, followed by exposure to a washing solution for 2-8 hours.

The selectivity of ultrafiltration membranes during separation and concentration of solutions of high molecular weight compounds, including milk protein, is determined mainly by the pore size of the membrane. For ultrafiltration processes, an equivalent indicator is more often used - cut-off by molecular weight. The main part of the protein fractions in milk raw materials is albumin, having a molecular weight of 67,000 Da. In the process of concentrating milk raw materials on an ultrafiltration unit, the protein content increases from 1.8 ± 0.2% in the first stage, to 6.0 ± 0.3% in the second and up to 14.5 ± 0.5% in the third . Moreover, while the selectivity weakly depends on the concentration of protein in the working solution, the absolute protein content in the ultrafiltrate varies over a wide range. The UMP-67 widely used polysulfonamide membrane has a cut-off of 67,000 Da and an albumin selectivity of 95%. With this selectivity, the protein content in the ultrafiltrate in the first stage will be 0.09%, in the second 0.3%, and in the third already 0.75%. Thus, when using the UMP-67 membrane at all three stages, the protein loss in ultrafiltrate increases sharply.

When ultrafiltration membranes with a lower cutoff value are used, the albumin protein selectivity is significantly increased, but the filtrate productivity is slightly reduced compared to the UPM-57 membrane.

The last problem in ultrafiltration units with a feed pump is solved quite simply, since the use of a feed pump circuit allows increasing the working pressure on the membrane by 0.2-0.3 MPa with a slight increase in the total power consumption. However, the use of ultrafiltration membranes with a lower cut-off molecular weight has a lower cutoff limit. This is due to the fact that, in addition to protein fractions, other components are also present in the milk raw materials. This is primarily lactose (milk sugar), which is a valuable food product. Nanofiltration and reverse osmosis membranes are used to remove it. Therefore, when using ultrafiltration membranes with a cut-off of less than 5000 Da (transition region to nanofiltration), a significant part of the lactose begins to linger, thereby disrupting the processing of secondary milk raw materials.

The upper cut-off limit for the concentration of protein from milk raw materials is limited to 67,000 Da. With a larger cut-off, the protein selectivity of ultrafiltration membranes decreases sharply and approaches zero.

It was experimentally established that the optimal cut-off molecular weight in steps for a 3-step installation is: in the first stage, 50,000-67,000 Da, in the second stage 20,000-25,000 Da, in the third stage 5,000-10000 Da. An increase in the number of concentration steps is impractical because the dimensions and metal consumption of the installation increase, and the process reliability decreases.

During the operation of the ultrafiltration unit, the filtrate productivity of the membranes decreases due to partial clogging of the pores, the formation of a gel layer on the filter surface, and the adsorption of components of milk raw materials on the surface of the membranes.

In the proposed method, the regeneration is carried out by exposing the membranes in a washing solution for 2-8 hours. Membrane productivity is restored to 100% compared to the original. With shorter holding times, i.e. less than 2 hours do not have enough time to go through the processes of sorption and diffusion of contaminants from the membrane surface into the washing solution, and the performance of ultrafiltration elements is not fully restored. A holding time of more than 8 hours does not lead to a further increase in productivity and therefore is not economically feasible.

The optimal composition of the washing solution is determined experimentally, namely, wt.% ::

Sodium tripolyphosphate 0.12-0.20

Alkylsulfonate 0.015-0.020

Caustic Sodium 0.02-0.25

Sodium nitrate 0.20-0.25

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At lower concentrations of sodium tripolyphosphate, alkyl sulfonate, sodium hydroxide, sodium nitrate, the initial productivity is not restored. Within the indicated limits, the degree of restored productivity is 100%. With a further increase in the concentration of the washing solution, an increase in the productivity of the membranes does not occur and is economically unjustified due to the high consumption of detergents.

The drawing shows a diagram of an ultrafiltration unit for concentrating protein from milk raw materials.

It contains a receiving tank 1, a feed pump 2, three concentration concentrating stages, containing circulation pumps 3 / 1-3, filter elements 4 / 1-3, heat exchangers 5 / 1-3, a refractometer 6.

The proposed method for concentrating protein from milk raw materials is implemented as follows.

Example 1. Milk whey containing 0.8% protein after preliminary filtration is subjected to ultrafiltration at a temperature of 55 ° C. At the beginning, it is fed to the first stage of the ultrafiltration unit, which consists of four parallel-mounted sections equipped with roll elements with polysulfonamide membranes, type UPM-67 (TU 6-05-221-939-88), which ensures the concentration of milk proteins with a selectivity of at least 95%.

The resulting filtrate with a protein content of 0.09% is discharged to the filtrate collector, and whey concentrated in the first stage to a protein content of 1.8% is fed to the second concentration stage. The working pressure in the first concentration stage is 0.4 ± 0.01 MPa. Partially concentrated serum enters the second stage, consisting of modules similar to the first stage, but equipped with a UPM-20 polymer membrane (TU 6-55-221-1011-88), which ensures the concentration of milk proteins with a selectivity of at least

Claims (2)

1. A method of concentrating protein from milk raw materials by continuous ultrafiltration by means of polymer membranes in three stages to obtain protein concentrate and filtrate and the subsequent 98.5%. The filtrate obtained in the second stage contains 0.09% protein and 6% protein concentrate. The operating pressure in the second stage is 0.5 ± 0.01 MPA. After the second stage, the concentrate enters the third stage of the installation, the roll elements of which are equipped with a UPM-10 polymer membrane (Start-up note No. 543, approved 16.11.88), which ensures the concentration of milk proteins with a selectivity of at least 98.8%. The working pressure in the third stage is 0.6 ± 0.01 MPa. In the third step, further concentration of the whey takes place to a protein content of 15% and with such concentration is sent to the consumer. The filtrate obtained in the third stage of the ultrafiltration unit contains 0.18% protein. The average protein content in the filtrate after all three steps is 0.093%. The concentration of protein in the concentrate is determined by an RRL refractometer (model 1, passport Kb 2854001 PS). The quality of the filtrate is determined by the M-101 turbidimeter (Passport and test procedure 1E 2834007 PSD1). When the ultrafiltration rate decreases by 30-50%, membrane elements are regenerated. Softened water is used to prepare the washing solution. The washing solution is pumped by the roll elements, kept for 2-8 hours, after which it is superseded by softened water. PRI me R 2. The method of concentration of protein from milk raw materials is carried out analogously to example 1 with the difference that the roll elements are equipped with a cellulose acetate membrane, type UAM-200, UAM-150, UAM-100 (TU 6-05- 221-899-79). The process conditions and test results are summarized in a table. The test results showed that the use of the proposed method of protein concentration will allow to reduce protein loss by more than two times in comparison with the existing method. regeneration of elements, characterized in that, in order to reduce protein loss, when concentrating on the first step, polymer membranes having a cut-off by mol.m are used. 50000-67000 Yes, in the second stage - 20000-25000 Yes, and in the third stage 5000-10000 Yes. 2. The method according to p. 1, characterized in that the regeneration of the polymeric membranes is carried out by filling them with an aqueous solution including sodium tripolyphosphate, alkyl sulfonate, sodium hydroxide and sodium nitrate, in the following ratio, May.%: Comparative characteristics of the claimed and known methods Sodium tripolyphosphate 0.12-0.20 Alkyl sulfonate 0.015-0.02 Sodium hydroxide 0.02-0.25 Sodium nitrate 0.2-0.25 Water The rest, followed by exposure to a washing solution for 2-8 hours.