CN112042806B

CN112042806B - Preparation method of pea protein isolate

Info

Publication number: CN112042806B
Application number: CN202011010862.4A
Authority: CN
Inventors: 王倩
Original assignee: Nanjing Fenchem Biological Technology Co ltd
Current assignee: Nanjing Fenchem Biological Technology Co ltd
Priority date: 2020-09-23
Filing date: 2020-09-23
Publication date: 2021-07-09
Anticipated expiration: 2040-09-23
Also published as: CN112042806A

Abstract

The invention discloses a preparation method of pea protein isolate, belonging to the technical field of pea processing. The invention combines the alkaline treatment and the jet cooking, improves the yield and the purity of the pea protein isolate, and effectively improves the solubility and the water retention of the pea protein isolate. The content of the pea protein isolate prepared by the invention is more than 90 percent, and the pea protein isolate can be used for food additives and nutriments.

Description

Preparation method of pea protein isolate

Technical Field

The invention belongs to the technical field of pea processing, and particularly relates to a preparation method of pea protein isolate.

Background

Peas are one of the edible beans that are widely grown around the world. The starch content in peas is 48-52%, the protein content is 21-28%, the fat content is 1-2.7%, and the crude fiber content is 4.5-8.4%. The utilization of peas in food in China mainly focuses on the utilization of starch in the peas to make vermicelli, sheet jelly and the like, and pea protein is generally used as feed.

In recent years, the rise of plant-based foods has met the health demands of modern consumers. The importance of plant-based food products in replacing food products of animal origin and their role in environmental protection are becoming increasingly appreciated. Soybeans, lentils, peanuts, almonds, algae blue, quinoa and the like are good sources of plant-based proteins, and pea proteins are widely concerned by people. The pea protein can be used as a food additive to replace part of animal protein, such as applied in the processing of ham sausage products. The pea protein has rich and balanced amino acid composition and rich lysine, and can be used as nutriment for infant and pregnant woman. And for the bigger beans and peanuts, pea protein is low-sensitive and non-transgenic, and is relatively high-quality and safe plant protein.

The pea protein prepared by the traditional alkali-soluble acid-precipitation method has poor solubility, and the application of the pea protein in the food industry is limited. Jet cooking is a hydrothermal treatment technology, and the principle is that water-insoluble starch particles or macromolecular protein chains are dispersed through high temperature and high shearing force generated by violent collision of high-pressure steam and materials, so that extraction and structural recombination of starch, protein and other substances are realized. Foreign scholars prepare soymilk by using jet cooking and find that the method can improve the recovery rate of soybean protein. Research shows that the wheat protein and corn syrup treated by the jet cooking can improve the solubility, the emulsion stability and the foaming property of the wheat protein.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a preparation method of pea protein isolate.

The technical scheme is as follows: in order to achieve the purpose, the invention provides the following technical scheme: a method of producing pea protein isolate comprising: soaking peas in water, and grinding to obtain pulp; conveying the slurry to a centrifugal sieve by a pump, and centrifugally filtering to remove slag to obtain a supernatant; adjusting the pH value of the supernatant to be alkaline, leaching, and centrifuging to obtain a centrifugate; carrying out jet cooking on the centrifugate, cooling, and carrying out acid precipitation separation to obtain protein precipitate; neutralizing the protein precipitate, homogenizing under high pressure, and spray drying.

Preferably, the pH of the supernatant is adjusted to be alkaline, and the pH is adjusted to be 8.0-9.0; the leaching is carried out at the temperature of 25-50 ℃ for 30-60 min.

Preferably, the jet cooking reaction conditions of the jet cooking are 120-150 ℃, the time is 40-80 s, and the treatment concentration of the feed liquid is 3-6% (w/v).

Preferably, the jet cooking reaction condition of the jet cooking is 140 ℃, the time is 60s, and the treatment concentration of the feed liquid is 4% (w/v).

Preferably, the acid precipitation separation is to adjust the pH value of the feed liquid to 4.0-4.5, precipitate for 20-40 min, and perform centrifugal treatment for 10-30 min at a rotating speed of 3000-6000 r/min.

Preferably, the peas are soaked in water and ground into pulp, the material-liquid ratio is 1: 20-1: 30, and the soaking time is 12-48 h.

Preferably, the inlet temperature of the spray drying is 170-180 ℃, and the outlet temperature of the spray drying is 70-90 ℃.

Preferably, the solubility is greater than 80%, the yield is greater than 80%, and the purity is greater than 90%.

Preferably, the pea protein isolate is light yellow.

Has the advantages that: the invention has the advantages that the invention has the following advantages,

1. in the traditional process, pea protein and starch are separated by directly standing or centrifuging after pea is soaked and ground into pulp. The invention provides an alkali treatment method, namely adjusting the pH of a mixed solution of protein and starch after grinding to 8.0-9.0, and leaching for 30-60 min at 25-50 ℃. Since the isoelectric point of pea protein is around 4.5, the protein is more soluble in alkaline environment. In addition, the alkali can loosen the compact starch structure in the peas, is favorable for releasing carbohydrates tightly combined with pea proteins, and simultaneously has a destructive effect on secondary bonds of protein molecules, thereby promoting the separation of the protein and the starch. Because the higher pH value can cause the color of the protein to be deepened, the protein has obvious alkaline taste, and the yield, the solubility and the protein purity of the protein are comprehensively considered, the pH value is controlled to be 8.0-9.0, and the time is 30-60 min.

2. The jet cooking treatment provided by the invention is characterized in that after materials are mixed with steam, under the environment of high temperature and high pressure of the steam and high-speed shearing of a generator nozzle, original insoluble protein in the materials is continuously dissolved out and depolymerized, and the insoluble or insoluble molecules are solubilized, so that the solubility of pea protein is improved. In addition, due to the change of the protein structure, the peptide chain and the polar group originally concealed in the protein are turned to the surface, and the water binding capacity is improved. Researches find that the pH value of the feed liquid can influence the treatment effect of the jet cooking, and the higher pH value can improve the dispersibility and the dissolubility of the protein. The method combining the alkaline method and the jet cooking improves the solubility of the pea protein isolate to 88.11 percent, the protein yield is close to 85 percent, the purity is about 92 percent, and the water retention is improved. The finally prepared pea protein isolate was sieved through a 100 mesh sieve to obtain a light yellow powder.

Drawings

FIG. 1 is a flow chart of the preparation of pea protein isolate according to the invention;

FIG. 2 is a graph showing the results of the protein solubility and water-holding capacity measurements in example 1 and comparative examples 1, 2 and 3;

FIG. 3 is a graph showing the results of the measurement of the protein yield and purity in example 1 and comparative examples 1, 2 and 3.

Detailed Description

The present invention will be further described with reference to the accompanying drawings.

Specific examples of the present invention are defined as follows:

1. protein purity: the protein content adopts GB 5009.5-2016 Kjeldahl method;

2. protein solubility: expressed as the nitrogen solubility index. Preparing the prepared protein sample into 1% (w/v) dispersion, adjusting the pH to 7.0, stirring at room temperature for 1h, centrifuging at 8000r/min for 20min, and determining the protein content of the supernatant by adopting a Kjeldahl method. The Nitrogen Solubility Index (NSI) is calculated as follows:

3. protein water retention: dispersing 1g of the prepared protein sample in 20mL of water, carrying out water bath at 80 ℃ for 60min, cooling to 30 ℃, centrifuging at 8000r/min for 10min, measuring the volume Vml of the supernatant, and calculating the water binding capacity of the pea protein isolate. The calculation formula is as follows:

4. protein yield: the ratio of the isolated pea protein content to the protein content of the raw material.

Example 1

Step A1: soaking raw material peas in water, grinding the mixture into slurry, wherein the ratio of the raw material to the slurry is 1:25, and the soaking time is 36 hours; go to step A2;

step A2: conveying the slurry to a centrifugal sieve by a pump, centrifugally filtering and removing slag, and transferring the obtained supernatant to the step A3;

step A3: adjusting the pH of the supernatant to 8.0, leaching at 40 deg.C for 40min, pumping the mixed solution into a horizontal decanter centrifuge for centrifuging, and transferring the obtained centrifugate to step A4;

step A4: placing the centrifugate in a jet cooking generator, cooling the centrifugate at the feed liquid concentration of 4% (w/v) and the reaction temperature of 140 ℃ for 60s, and transferring to the step A5;

step A5: adjusting the pH value of the feed liquid to 4.5 by using 1mol/L HCl, precipitating for 30min, centrifuging at the rotating speed of 5000r/min for 20min to obtain a precipitate, and transferring to the step A6;

step A6: redissolving the protein precipitate with water, adjusting the pH value to 7.0 by using 2mol/L NaOH, homogenizing under high pressure, and transferring to the step A7;

step A7: pumping the homogenized protein solution into a drying tower for spray drying, crushing and sieving with a 100-mesh sieve to obtain light yellow powder, and packaging. The inlet temperature was 176 ℃ and the outlet temperature was 80 ℃.

Comparative example 1

Step B1: soaking raw material peas in water, grinding the mixture into slurry, wherein the ratio of the raw material to the slurry is 1:25, and the soaking time is 24 hours; go to step B2;

step B2: conveying the slurry to a centrifugal sieve by a pump, centrifugally filtering and removing slag, and transferring the obtained supernatant to step B3;

step B3: separating the supernatant with horizontal decanter centrifuge to obtain starch and centrifugate, and transferring the centrifugate to B4;

step B4: adjusting the pH value of the centrifugate to 4.5 by using 1mol/LHCl, precipitating for 30min, centrifuging for 20min at the rotating speed of 5000r/min to obtain a precipitate, and transferring to the step B5;

step B5: redissolving the protein precipitate with water, adjusting the pH value to 7.0 by using 2mol/L NaOH, homogenizing under high pressure, and transferring to step B6;

step B6: pumping the homogenized protein liquid into a drying tower for spray drying, crushing, sieving with a 100-mesh sieve, and packaging. The inlet temperature was 176 ℃ and the outlet temperature was 80 ℃.

Comparative example 2

Step C1: soaking raw material peas in water, grinding the mixture into slurry, wherein the ratio of the raw material to the slurry is 1:25, and the soaking time is 48 hours; go to step C2;

step C2: conveying the slurry to a centrifugal sieve by a pump, centrifugally filtering and removing slag, and transferring the obtained supernatant to the step C3;

step C3: adjusting the pH of the supernatant to 8.0, leaching at 45 deg.C for 35min, pumping the mixed solution into a horizontal decanter centrifuge for centrifuging, and transferring the obtained centrifugate to step C4;

step C4: adjusting the pH value of the centrifugate to 4.5 by using 1mol/LHCl, precipitating for 30min, centrifuging for 20min at the rotating speed of 5000r/min to obtain a precipitate, and transferring to the step C5;

step C5: redissolving the protein precipitate with water, adjusting the pH value to 7.0 by using 2mol/L NaOH, homogenizing under high pressure, and transferring to step C6;

step C6: pumping the homogenized protein liquid into a drying tower for spray drying, then carrying out spray drying, crushing, sieving with a 100-mesh sieve, and packaging. The inlet temperature was 180 ℃ and the outlet temperature was 80 ℃.

Comparative example 3

Step D1: soaking raw material peas in water, grinding the mixture into slurry, wherein the ratio of the raw material to the slurry is 1:25, and the soaking time is 48 hours; go to step D2;

step D2: conveying the slurry to a centrifugal sieve by a pump, centrifugally filtering and removing slag, and transferring the obtained supernatant to the step D3;

step D3: separating the supernatant with horizontal decanter centrifuge to produce starch and centrifugate, and transferring the centrifugate to D4;

step D4: placing the centrifugate in a jet cooking generator, cooling the centrifugate at the feed liquid concentration of 4% (w/v) and the reaction temperature of 140 ℃ for 60s, and transferring to step D5;

step D5: adjusting the pH value of the feed liquid to 4.5 by using 1mol/L HCl, precipitating for 30min, centrifuging at the rotating speed of 5000r/min for 20min to obtain a precipitate, and transferring to the step D6;

step D6: redissolving the protein precipitate with water, adjusting the pH value to 7.0 by using 2mol/L NaOH, homogenizing under high pressure, and transferring to step D7;

step D7: pumping the homogenized protein liquid into a drying tower for spray drying, crushing, sieving with a 100-mesh sieve, and packaging. The inlet temperature was 180 ℃ and the outlet temperature was 80 ℃.

The peas need to be soaked for a certain time before being ground into pulp, and the soaking time has certain influence on the protein yield and the quality of a final product. If the soaking time is too short, the peas absorb water incompletely and cannot be softened, the bean skins and the bean bodies are not separated thoroughly, and grinding is not thorough during grinding, so that the product purity and the yield are low; the pea is easy to deteriorate due to too long soaking time, the viscosity of the feed liquid is increased, the protein and the starch are not easy to separate, and the purity and the yield of the final product are also reduced. Through tests, the soaking time is finally determined to be 12-48 h.

Comparative example 1 was a blank, comparative example 2 was carried out by applying an alkali pretreatment to the pea protein liquid, comparative example 3 was carried out by subjecting the pea protein liquid to a jet cooking treatment, and example 1 was carried out by subjecting the pea protein liquid to a pretreatment mode combining alkali addition and jet cooking.

The nitrogen solubility index NSI may indicate a change in solubility of a protein. As shown in fig. 2, the solubility of the protein was improved by either the alkali pretreatment or the jet cooking treatment alone, since pea protein has an isoelectric point of about 4.5 and is more soluble in an alkaline environment. The pea protein is subjected to the action of high temperature and high shearing force under the jet cooking, the dispersibility of the protein is increased, the granularity is reduced, and the solubility of the protein is obviously improved. In comparison with comparative example 1, in example 1, the solubility of protein was highest by pretreatment with a combination of alkali and jet cooking, which increased from 63.46% to 88.11% in comparative example 1, indicating that the modes of alkali pretreatment and jet cooking pretreatment have synergistic effects.

The water binding capacity of a protein is one of the functional properties of a protein, and refers to the amount of water that a certain amount of dry protein can bind and entrap after sufficient water absorption and centrifugation. As shown in fig. 2, either the alkali treatment or the jet cooking treatment alone can improve the water binding capacity of the protein. Example 1 water retention increased to 410 mL/g. The high-pressure steam in the jet cooking generator collides with materials violently to generate the action of high temperature and high shear force, and can extend a macromolecular protein chain, so that the original insoluble and compact protein structure in the pea protein is dissociated and extended, and the peptide chain and some polar groups originally masked in the pea protein are exposed and turned to the surface, thereby obviously improving the water holding capacity of the protein. As shown in fig. 3, compared with the comparative example 1 in which the supernatant after deslagging is directly subjected to horizontal spiral centrifugal separation, and the supernatant after deslagging is subjected to alkaline pretreatment, the protein solubility of the final product is increased by combining with fig. 2; on the other hand, more protein in the feed liquid is dissolved, the loss of the protein is reduced, and the yield of the protein is increased. Different pH values affect the separation of pea starch and protein differently. Experiments prove that when the pH is 8.0-9.0, the protein and the starch are easy to separate, the protein has only slight alkaline smell, and when the pH is lower than 8.0, the separation effect is not ideal; under the environment that the pH is higher than 9.0, the alkaline taste of the protein liquid is serious, and the protein and the starch are difficult to separate.

The alkali can loosen the compact starch structure in peas, is favorable for releasing carbohydrate tightly combined with pea protein, and has a destructive effect on secondary bonds of protein molecules, thereby promoting the separation of protein and starch. Therefore, the protein purity of comparative example 2 was higher than that of comparative example 1. Comparative example 3 shows that the protein purity is rather reduced by the jet cooking pretreatment alone compared with comparative example 1, because the gelatinization of starch is caused under the high temperature environment provided by the jet cooking, so that the protein is easy to be co-precipitated with the gelatinized starch in the acid precipitation process, and the protein purity is reduced. Compared with the comparison example 1, the pretreatment mode of combining alkali cooking with jet cooking in the example 1 improves the protein yield from 51.59 percent to 84.83 percent and improves the protein purity from 82.15 percent to 92.07 percent. The combination of alkali and jet cooking treatment greatly improves the protein yield, and the final product of example 1 has the protein yield of 84.83%.

The invention combines the alkaline treatment and the jet cooking, improves the yield and the purity of the pea protein, and effectively improves the solubility and the water retention of the pea protein isolate. The pea protein isolate prepared by the invention has the content of more than 90 percent, is light yellow powder, and can be used as food additives and nutriments.

The method comprises the steps of leaching supernatant obtained after pea grinding and centrifugation for 30-60 min in an alkaline environment with the pH value of 8.0-9.0 and the temperature of 25-50 ℃, so that pea protein is fully dissolved, compact starch structures in peas are loosened by alkali, secondary bonds of protein molecules are destroyed, separation of protein and starch is promoted, and then the starch is removed through centrifugation. The invention also provides a method for improving the extraction rate and the solubility of pea protein. The method comprises the step of carrying out jet cooking treatment on the protein solution after starch removal at the temperature of 120-150 ℃ for 40-80 s at the concentration of 3-6% (w/v).

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims

1. A preparation method of pea protein isolate is characterized in that:

step A3: adjusting the pH value of the supernatant to 8.0, leaching at 40 ℃ for 40min, conveying the mixed solution to a horizontal screw centrifuge by a pump for centrifugation, and transferring the obtained centrifugate to the step A4;

step A4: placing the centrifugate in a jet cooking generator, cooling the centrifugate at the reaction temperature of 140 ℃ for 60s, wherein the mass volume percentage concentration of the feed liquid is 4 percent, and transferring to the step A5;

step A7: pumping the homogenized protein liquid into a drying tower for spray drying, and then crushing and sieving by a 100-mesh sieve, wherein the inlet temperature is 176 ℃ and the outlet temperature is 80 ℃;

the obtained pea protein isolate is light yellow, the solubility of the pea protein isolate is 88.11%, the yield is 84.83%, and the protein purity is 92.07%.