JPH0150381B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for lowering the gelling temperature of whey proteins obtained from milk, particularly casein whey or cheese whey proteins. Protein is essential in human food because it can be a source of essential amino acids. However, in the field of foods that require functions such as gelation, foaming, emulsification, or thickening, many proteins
In addition to its nutritional properties, it is widely used for its physical properties. However, these physical properties, taken together, are often known as the functional properties of a protein. Casein, egg white, gelatin and gluten are all examples of proteins that utilize their functionality rather than their nutritional properties.
In recent years, a lot of research has been carried out in the direction of recovering protein from milk whey. Although there is no dispute that whey protein is nutritionally superior, commercially available whey protein is However, due to its low physical properties, there were limitations in utilizing the functionality of whey protein. According to the method currently in use,
Although it is possible to produce whey products containing more than 90% whey protein, these products tend to be rather limited in their functionality. This is because the whippability and gelling properties are generally inferior to those of egg whites and whole eggs, and the viscosity is inferior to that of casein, gelatin or soybean. Whole whey protein is a globular protein and can be used functionally. However, the specific functionality of commercially available whey proteins is currently generally at the following level. In other words, this functionality is not at a level that can be advantageously compared as equivalent to the functionality of proteins from other sources. A method has been proposed to improve the whippability of whey protein by hydrolyzing it at a specific pH level and decomposing whey protein into peptides and amino acids while controlling it. However, with this method,
It was found that this had a negative effect on the gelling properties of whey protein. To improve the whippability of an aqueous solution containing dissolved cheese whey protein, especially a cheese whey protein concentrate obtained by gel-filtering cheese whey from which lactose contained therein has been partially removed, as follows. has also been proposed. That is,
The above-mentioned protein-containing aqueous solution is heated at a temperature range of at least 90°C and 99°C or below for about 5 minutes or less, preferably about 0.1 minute, under conditions of pH 5 to 8.5, preferably 6 to 7.5. It was proposed that the aqueous cheese whey protein solution be whipped within 8 hours after being cooled to below .degree. C. and heat treated to improve the whippability of the aqueous cheese whey protein solution. However, the aqueous solution produced in this manner is said to be unsuitable for use in place of egg whites used in the food field, which requires the thermosetting or coagulating properties of egg whites. The present invention aims to provide the following method. The method is a method of improving the gelling property of whey protein so that the gelling point of whey protein is lower than that of undenatured whey protein. Here, the following was discovered. That is, so that interactions between partially denatured (modified) protein molecules occur at lower temperatures than those that occur between undenatured protein molecules,
It has been found that it is possible to change the structure of whey proteins and, as a result, lower the gelling temperature of the proteins. Additionally, the following was discovered: That is, these proteins are held at a constant high temperature for a sufficient period of time, and the pH of the protein processing system is maintained at a constant level so that protein precipitation, coagulation, or gelation does not occur during the high temperature period. It was also found that if this was done, partial denaturation of the above-mentioned protein would occur. According to the present invention, a method for lowering the gelling temperature of milk-derived whey protein is provided, and the method comprises the following steps. That is, protein concentration 0.5-10W/V%
(e.g. g/l) is maintained at a high temperature of at least 70°C at an alkaline pH to increase the mercapto groups (sulphy-dryle gioup) that can participate in the reaction, and this high temperature treatment To prevent protein precipitation, gelation, and coagulation despite high temperatures,
This process consists of appropriately selecting two conditions: the high temperature maintenance time and the pH of the solution, and then cooling the solution obtained in this way. In order to partially denature proteins within a reasonable amount of time, it is necessary to maintain the temperature at 70°C or higher.
In order to partially denature a protein to a specified degree, the treatment temperature and treatment time are closely related to each other; generally speaking, the higher the temperature, the shorter the treatment time; The lower the value, the longer the processing time required. Although the temperature must be high enough to achieve the desired denaturation, it may be necessary to cleave S-S bonds or other labile bonds present within the protein molecule, even if they are initially The treatment should not be carried out at high temperatures or should not be continued for an excessively long time even at low temperatures, so as to cause extensive cleavage of peptide bonds from the protein or coagulation or precipitation of the protein. The effect achieved by the above-mentioned method of partially denaturing protein molecules is to open up the protein molecule, and as a result, the SH groups or S-S groups present inside the protein molecule are Either one or both can be brought into a state where they can react. These groups are encapsulated within the protein molecule and are not available for reaction when the protein molecule is under natural conditions. It is believed that: That is, by widening the protein molecule, disulfide groups also increase, and as a result, these disulfide groups interact with mercapto groups present in other protein molecules, and this It is believed that it plays at least some role in lowering the gelation temperature. Since the mercapto groups and disulfide groups present on the outside are more readily available for reaction, it is possible to increase the interaction between protein molecules, and as a result, it is thought that the gelation temperature is lowered. This partial modification (modification) treatment is performed by converting the protein into a solution, ie, an aqueous solution. The concentration of protein in this aqueous solution may be within the range of 0.5 to 10 W/V%.
When the concentration is lower than 0.5%, the solution is uneconomical and impractical for carrying out the method. concentration is 10
%, it becomes difficult or impossible to prevent uncontrollable interactions between protein molecules, resulting in insolubilization, precipitation,
It even causes gelation in the processing equipment.
Preferably, the protein is present in the aqueous solution at a concentration of 3 to 5% W/V. It is an essential condition that protein precipitation, gelation, or thermal coagulation does not occur. Therefore, the pH of the solution is maintained at a slightly alkaline level of, for example, about 7.5 to 9. It is preferable to maintain the pH at a level of 8.0. For normal processing, the temperature must generally be below 90° C. to make processing times practical. However, if ultra-high temperature techniques are used, processing times can be much shorter and temperatures can be as high as 120° C. or even higher. Furthermore, in order to partially denature the protein to a certain degree, that is, to lower the gelation temperature to a certain temperature, the time for holding the protein at a high temperature also depends on the concentration of the protein in the aqueous solution. It is something that will be done. Regardless of the elevated temperature employed, the lower the protein concentration, the longer the elevated temperature must be maintained to achieve a given degree of denaturation. Therefore, if ultra-high temperature technology is not used and the whey protein concentration is 3W/V%, the required processing time is:
At 90°C, it takes 30 seconds at most, and at 70°C, it lasts as long as 30 minutes. Whey protein concentration
In the case of 3W/V%, the residence time at high temperature is approximately 3
Preferably, the temperature and other parameters are set to ˜5 minutes. Normally, the temperature should be set to 75
By setting the temperature to ~85°C, the residence time described above can be obtained. To obtain the same degree of partial modification at a given temperature at a concentration lower than 3W/V%,
Furthermore, the processing time will be longer, and if the concentration is higher than 3%, e.g. 5% or 10%, the same degree of partial modification can be achieved at a given temperature. To achieve this, processing times will usually be short. Although the partial denaturation method according to the present invention can be carried out on unconcentrated milk whey, it is usually more suitable to carry it out on whey that has undergone ultrafiltration treatment. The method according to the present invention uses concentrated and separated whey, which contains three proteins.
It is preferable to conduct the experiment at a concentration of ~5 W/V%, preferably 3 W/V%. Fractionated milk whey can also be used, but excessive fractionation may result in some fractions not being applicable to the present method. However, whatever concentration or fractionation technique is used, great care must be taken to avoid complete denaturation of the protein by treating it at high temperatures, among other things: Care must be taken when concentrates from different origins have to be used. A preferred method for carrying out the invention includes:
It is best to adjust the pH to about 8.0 using milk whey with a protein concentration of about 3W/V% and a dilute solution of alkali metal hydroxide such as sodium hydroxide. The temperature of the whey is then raised to 70-90° C. continuously using a heat exchanger or by a batch system for a period of 30 minutes to 30 seconds. After the required time has elapsed, the whey is rapidly cooled and, in some cases, the pH is
6.5 to 7.0, and then concentrate and dry the whey to obtain partially denatured dry whey protein. Low-temperature concentration treatment and spray-drying from a fairly dilute solution should be carried out in order to avoid complete denaturation of the protein by the above-mentioned concentration and drying treatment. Analysis of partially denatured whey protein produced by the method of the present invention revealed that the content of mercapto available for reaction was increased compared to that of undenatured whey protein. When we measured the gelation temperature of a partially denatured protein solution with a protein content of 15W/V% and an undenatured protein solution, we found that the partially denatured protein had a higher
It has been found that gels gel at lower temperatures, and in that case, there is no appreciable decrease in gel strength between gels made from partially denatured proteins and gels made from undenatured proteins. The extent to which the gelation temperature is lowered depends on the combined effect of temperature and treatment time when the concentration of whey protein in the aqueous solution to be treated is constant. When the concentration of whey protein is constant and the treatment temperature is also constant, the rate at which the gelation temperature decreases increases as the treatment time increases; when the concentration of whey protein is constant and the treatment time is constant, , the extent to which the gelling temperature is lowered will be greater if the treatment temperature is not higher. The invention will be further elaborated with reference to the following examples: Example 1 A whey protein concentrate powder (85% protein) was prepared by ultrafiltration and low temperature spray drying process. (containing 8.5% fat and 3% lactose), which was reconstituted with water to obtain a solution with a protein content of 3%. Adjust the pH of this solution to 8.0 using dilute sodium hydroxide.
and the temperature was raised to 90°C and held for 30 seconds, followed by rapid cooling in an ice/water bath.
This solution was then dried with a spray dryer. Analysis of the dried product thus obtained revealed that the mercapto content ranged from 2 × 10 ^-6 μmol/g to 20
It was found that the amount increased to ×10 ⁻⁶ μmol/g. When a solution with a protein content of 15W/V% was prepared and gelled, a hard gel was formed at 25°C.On the other hand, undenatured whey protein produced a hard gel. The only problem was that the temperature needed to be 72 degrees Celsius. Example 2 The same process as in Example 1 was repeated, except that
The whey protein solution was kept at 80°C for 3 minutes. After this treatment, the free mercapto group content is 8.0×
10 ^-6 μmol/g, and the gelation temperature decreased to about 50°C. Example 3 The method of Example 1 was repeated, but the concentration of the whey protein solution was 1 W/V% and kept at 80° C. for 10 minutes. As a result of this treatment, the content of free mercapto groups increased to 9.0×10 ⁻⁶ μmol/g. The 15W/V% aqueous solution of the protein thus treated had a gelation temperature of 50°C. Example 4 The method of Example 1 was repeated, except that the concentration of the whey protein solution was 5% W/V and kept at 80°C for 10 minutes. As a result of this treatment, the free mercapto content increased to 16.2×10 ⁻⁶ μmol/g. The 15W/V% aqueous solution of the protein thus treated had a gelation temperature of 42°C. Example 5 The method of Example 1 was repeated, except that the concentration of the whey protein solution was 10% W/V and kept at 80°C for 10 minutes. As a result of this treatment, the free mercapto content increased to 22×10 ⁻⁶ μmol/g. The 15 W/V% aqueous solution of the protein thus treated had a gelation temperature of 36°C. By varying the parameters of concentration, temperature, and time, various products with gelation temperatures in the range 25-72 °C can be obtained, thus
The number of applications in which whey protein can be used in the food field is greatly increased, and its efficacy is also greatly increased. Furthermore, it is also possible to obtain a product in which both gelling temperature and gel strength are well balanced. Naturally, the products produced by the method according to the invention can also be used in admixture with unprocessed whey protein or materials from other sources.

[Claims]

1 Into a protein-containing solution with a protein concentration of 2% by weight or more,
1. A method for producing a gelled product, which comprises adding 1 unit or more of transglutaminase to 1 g of protein to form a gel.

Claims (1)

The method according to any one of the ranges 1 to 5. 7 The protein concentration in the aqueous solution is substantially
Claims 1 to 6 which are 3W/V%
The method described in any one of paragraphs. 8 The aqueous solution is maintained at a high temperature of 70 to 90°C, and the high temperature maintenance time is 30 seconds at 90°C, 30 minutes at 70°C, and at a temperature within this range. 8. A method according to claim 7, wherein the time is proportional to the above. 9. The method according to claim 8, wherein the aqueous solution is maintained at a high temperature of 75-85°C for 5-3 minutes.