Method for producing skim milk powder

Abstract

The present invention relates to a method for producing skim milk powder which is suitable as a raw material for fermented milk. Fermented milk which is one of food utilizing lactic acid bacteria contains live lactic acid bacteria, and as a raw material for the fermented milk, animal milk such as cow milk or skim milk powder prepared from such animal milk is sometimes used. Therefore, skim milk powder having better fermentability of lactic acid bacteria is desired. In order to use skim milk powder as a raw material for fermented milk, it is desired to increase the free fatty acid content without bringing about a deterioration of flavour. The method for producing skim milk powder from skim milk, comprises subjecting the skim milk to homogenization treatment under a temperature of 30 to 55°C at a homogenization pressure of 5 to 50 MPa using a homogenizer, storing the skim milk subjected to the homogenization treatment for a period of 12 to 96 hours at a temperature of 10°C or lower, after storing the skim milk, sterilizing the skim milk at a temperature of 80 to 130°C and subsequently drying the skim milk to obtain the skim milk powder. Furthermore, the amount of free fatty acids in the skim milk powder is increased as compared with a comparative skim milk powder produced by a method not comprising the homogenization treatment.

Description

Skim milk powder manufacturing method

[0001] The present invention relates to a method for producing skim milk powder suitable as a raw material for fermented milk.

[0002] Fermented milk, a type of food that uses lactic acid bacteria, contains live lactic acid bacteria, and animal milk such as cow's milk or skim milk powder prepared from such milk may be used as raw materials for the fermented milk. Therefore, skim milk powder with better fermentability of lactic acid bacteria is required.

[0003] Milk fat, the fat content in cow's milk, is composed of many different fatty acids. Most of these are saturated fatty acids, but a wide range of short-, medium-, and long-chain fatty acids are also included, and it is known that long-chain fatty acids with 14 to 18 carbon atoms, such as palmitic acid, myristic acid, stearic acid, and oleic acid, are particularly abundant. Milk fat in raw milk is dispersed as large and small spherical particles (fat globules) covered by a fat globule membrane composed of phospholipids. When the fat globule membrane is damaged by external factors such as stirring, lipase in the raw milk acts to hydrolyze part of the fat, liberating the constituent fatty acids (Non-Patent Documents 1 and 2).

[0004] Such free fatty acids often cause unpleasant odors and tastes, which can be problematic in terms of product management. However, it has been confirmed that an increase in the amount of free fatty acids improves the fermentation ability of lactic acid bacteria.

[0005] Skim milk powder is made by removing cream (milk fat) from raw milk and then removing almost all of the water, so its fatty acid content is much lower than that of raw milk. Therefore, in order to use it as a raw material for fermented milk, it is necessary to increase the free fatty acid content.

[0006] DEETH, HC and FITZ-GERALD, CH: Some factors involved in milk lipase activation by agitation, J. Dairy Res., 44: 569-583. 1977BHAVADASON, MK, ABRAHAM, M. j. and GANGUL, NC: Influence of agitation on milk lipolysis and release of membrane-bonud xanthine oxidase, J. Dairy Sci., 65: 1692-1695. 1982

[0007] To provide a method for producing skim milk powder having an increased amount of free fatty acids without causing deterioration in flavor.

[0008] The present inventors have found that by homogenizing skim milk under specific temperature conditions in the production process of skim milk powder, the amount of free fatty acids increases without causing deterioration in flavor.

[0009] That is, the present invention relates to the following 1) to 11). 1) A method for producing skim milk powder, comprising a step of homogenizing skim milk powder at a temperature of 30 to 55°C in a step of producing skim milk powder from skim milk. 2) The method of 1), in which the homogenization is carried out at 43 to 53°C. 3) The method of 1) or 2), in which the homogenization is carried out using a homogenizer at a homogenization pressure of 5 to 50 MPa. 4) Any of the methods of 1) to 3), in which the amount of free fatty acids in the skim milk powder is increased. 5) The method of 4), in which the amount of free fatty acids having 14 or more carbon atoms when stored for 24 hours at 10°C or below after homogenization is increased by 20% or more compared to when stored for 24 hours without homogenization. 6) The method of 4) or 5), in which the rate of increase in fatty acids having 12 or less carbon atoms when stored for 24 hours at 10°C or below after homogenization is lower than the rate of increase in fatty acids having 14 or more carbon atoms. 7) Any of the methods 4) to 6), wherein the amount of free fatty acids having 14 or more carbon atoms when stored for 24 hours at 10°C or less after homogenization is 300% or more of the amount of free fatty acids having 12 or less carbon atoms. 8) Skim milk powder produced by any of the methods 1) to 7). 9) A method for increasing the amount of free fatty acids in skim milk powder, characterized by homogenizing under temperature conditions of 30 to 55°C in the process of producing skim milk powder from skim milk. 10) The method of 9), wherein the amount of free fatty acids having 14 or more carbon atoms when stored for 24 hours at 10°C or less after homogenization is increased by 20% or more compared to milk stored for 24 hours without homogenization. 11) The method of 9) or 10), wherein the rate of increase in fatty acids having 12 or less carbon atoms is lower than the rate of increase in fatty acids having 14 or more carbon atoms.

[0010] According to the method of the present invention, it is possible to obtain skim milk powder having an increased content of free fatty acids without causing deterioration in flavor.

[0011] In the present invention, "skim milk powder" refers to skim milk obtained by removing cream from raw milk, which is then pasteurized, concentrated and dried to form a powder.

[0012] The raw milk used as a raw material may be any of cow's milk, goat's milk, sheep's milk, buffalo milk, horse's milk, camel's milk, etc., and there are no particular limitations on its properties as long as they are those commonly known in the dairy processing industry.

[0013] The method for removing the cream component to obtain skim milk (also referred to as "cream separation") is not particularly limited in terms of the type of separator or its operating conditions, and may be a continuous process or a batch process. A preferred separation method is one that uses a cream separator and is carried out at 10 to 65°C.

[0014] The method for producing skim milk powder of the present invention is a step of producing skim milk powder from skim milk, which includes a step of homogenizing the skim milk at a temperature of 30 to 55° C. The step of producing skim milk powder from skim milk refers to the steps of sterilization, concentration, and drying to powder, which are generally carried out in the production of skim milk powder, in this order.

[0015] The homogenization treatment may be carried out by any means that can mix and stir the entire skim milk, but a preferred method is to use a homogenizer, and the homogenization pressure at this time is 5 to 50 MPa (50.986 to 509.86 kgf / cm). ２ ), preferably 8 to 30 MPa, more preferably 12 to 24 MPa.

[0016] The homogenization treatment is carried out under temperature conditions of 30 to 55°C. Homogenization under such temperature conditions increases the amount of free fatty acids. The homogenization temperature may be 30 to 55°C, preferably 35 to 50°C, more preferably 43 to 53°C, and even more preferably 45 to 51°C. The temperature can be adjusted by any method, such as a tank type, a tubular type, a plate type, or a direct steam type.

[0017] The homogenization treatment is carried out at least before the sterilization step in which lipase is inactivated, but it is preferable to store the treated skim milk for a certain period of time after the homogenization treatment in order to increase the free fatty acid content. The storage time is preferably 12 to 96 hours, more preferably 24 to 48 hours. The temperature during storage is preferably 10°C or lower. In order to control the amount of free fatty acids, a step of heating and holding the skim milk at 50 to 60°C for about 20 to 60 minutes before storage can also be included, depending on the fat content in the skim milk.

[0018] The sterilization treatment can be carried out under general heating conditions employed in the production of skim milk powder, for example, treatment in a sterilizer at 80 to 130° C. for 1 to 30 seconds. The apparatus for the heat treatment is not particularly limited as long as the above heating conditions can be employed as a sterilizer, and any of batch, tubular, plate, and direct steam types may be used, but a plate type sterilizer or direct steam type sterilizer is preferably used, which allows stable and easy control of the above heating conditions, has good production efficiency, and is capable of mass production.

[0019] In the concentration step, for example, the solution is concentrated under reduced pressure at a temperature of 50 to 90° C. to a solids concentration of 40 to 50% using an MVR vapor compression concentrator or a vacuum concentrator.

[0020] The resulting concentrate is preheated to 50 to 80°C and then spray-dried in a chamber to obtain powdered skim milk.

[0021] The skim milk powder thus obtained has an increased free fatty acid content compared to ordinary skim milk powder not subjected to the predetermined homogenization treatment. In this case, the content of long-chain fatty acids having 14 or more carbon atoms is higher than that of fatty acids having 12 or fewer carbon atoms, which are thought to cause flavor deterioration. Therefore, even when the free fatty acid content is increased, there is almost no deterioration in flavor; rather, the mellowness and richness of the fatty acids are enhanced, resulting in an improved flavor. That is, the total free fatty acid content in the skim milk powder of the present invention is preferably 0.02 to 0.15% by mass, more preferably 0.04 to 0.08% by mass. Furthermore, after homogenization and storage at 10°C or below for 24 hours, the content of free fatty acids having 14 or more carbon atoms is preferably 300% or more, and more preferably 400% or more, of the content of free fatty acids having 12 or fewer carbon atoms. The upper limit is not particularly limited, but examples include 600% or less, or 450% or less. Furthermore, the amount of free fatty acids having 14 or more carbon atoms when the milk is stored at 10° C. or below for 24 hours after homogenization is preferably increased by 20% or more, and more preferably by 40% or more, compared to when the milk is stored at 10° C. or below for 24 hours without homogenization. The upper limit is not particularly limited, but examples include 110% or less, 85% or less, 50% or less, and 45% or less.

[0022] <Quality Evaluation Test of Skim Milk> 1 ml of a methanol solution of tridecanoic acid (50 μg / ml) as an internal standard and 15 ml of acetonitrile were added to 3.5 g of the sample listed in Table 1. After stirring and centrifugation, 3.5 ml of the supernatant was collected, the acetonitrile was removed using a centrifugal evaporator, and the volume was adjusted to approximately 5 ml with methanol and filtered through a 0.45 μm filter. One volume of an acetone solution of ADAM (9-Anthryldiazomethane, manufactured by Funakoshi Co., Ltd.) (1 mg / ml) was added to 5 volumes of this solution. The mixture was left to stand at room temperature in a dark place for at least 90 minutes and analyzed by high-performance liquid chromatography. Nine types of standards were used: butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid. The sum of these nine free fatty acids was used as the total free fatty acids. Analysis was performed under the following conditions. Analysis conditions Column: Unison UK-C8 manufactured by Imtakt Column temperature: 30°C Flow rate: 1.0 ml / min Mobile phase: Solution A was acetonitrile / water = 65 / 35, Solution B was acetonitrile / water = 85 / 15, and Solution A was 100% from 0 to 9 minutes, Solution B was 0 to 100% linear gradient from 9 to 28 minutes, and Solution B was 100% from 28 to 46 minutes. Injection volume: 10 μl Excitation wavelength: 365 nm Fluorescence wavelength: 412 nm

[0023] <Flavor Evaluation Test> Three experienced sensory evaluation panelists evaluated the flavor of the samples, and conducted absolute evaluations of palatability and free descriptions.

[0024] Example 1 Raw milk was separated into cream and skim milk using a centrifugal cream separator (manufactured by Elecream) at a separation temperature of 45°C. The separated skim milk was cooled, heated to 48°C, and homogenized at a homogenization pressure of 12 MPa. The homogenized skim milk was stored at 10°C or below for 0, 24, and 48 hours, and then heated to 80°C to obtain samples, which were then evaluated for quality.

[0025] Comparative Example 1 Raw milk was separated into cream and skim milk using a centrifugal cream separator (manufactured by Elecream) at a separation temperature of 45°C. The separated skim milk was cooled, and then stored at 10°C or below for 0, 24, and 48 hours. The skim milk was then heated to 80°C and the quality of the obtained samples was evaluated.

[0026] Comparative Example 2 The quality of samples obtained in the same manner as in Example 1, except that the temperature immediately before homogenization was 10°C or lower, was evaluated. The results are shown in Table 1. As can be seen from Table 1, the total free fatty acid content (total FFA) in the skim milk powder of Example 1 was 0.0303 to 0.0419% by mass. Furthermore, in Example 1, the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours after homogenization was 495% of the amount of free fatty acids having 12 or less carbon atoms, which was a 43% increase compared to the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours without homogenization (Comparative Example 1). Furthermore, as in Comparative Example 2, when the homogenization treatment was performed at 10°C or lower, no increase in the amount of free fatty acids was observed.

[0027]

[0028] Example 2 Samples were obtained in the same manner as in Example 1 except that the cream separation temperature was 48°C and the homogenization pressure was 24 MPa, and the quality was evaluated.

[0029] Comparative Example 3 A sample was obtained in the same manner as in Comparative Example 1 except that the cream separation temperature was set to 48°C, and the quality was evaluated.

[0030] Comparative Example 4 The quality of samples obtained in the same manner as in Comparative Example 2 was evaluated, except that the cream separation temperature was 48°C and the homogenization pressure was 24 MPa. The results are shown in Table 2. As can be seen from Table 2, the total free fatty acid content (total FFA) in the skim milk powder of Example 2 was 0.0300 to 0.0431% by mass. Furthermore, in Example 2, the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours after homogenization was 413% of the amount of free fatty acids having 12 or less carbon atoms, which was a 46% increase compared to the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours without homogenization (Comparative Example 3). Furthermore, as in Comparative Example 4, when the milk was homogenized at 10°C or below, no increase in the amount of free fatty acids was observed.

[0031]

[0032] Example 3 The quality of samples obtained in the same manner as in Example 1 was evaluated, except that the cream separation temperature was set to 15°C and the milk was kept at 52°C for 20 minutes after homogenization and before storage.

[0033] Example 4 The quality of samples obtained in the same manner as in Example 1 was evaluated, except that the cream separation temperature was set to 15°C and the milk was kept at 52°C for 60 minutes after homogenization and before storage.

[0034] Comparative Example 5 The quality of samples obtained in the same manner as in Comparative Example 1 was evaluated, except that the cream separation temperature was set to 15°C. The results are shown in Table 3. As can be seen from Table 3, the total free fatty acid content (total FFA) in the skim milk powder of Example 3 was 0.102 to 0.117% by mass. Furthermore, in Example 3, the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours after homogenization was 420% of the amount of free fatty acids having 12 or less carbon atoms, which was a 105% increase compared to the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours without homogenization (Comparative Example 5).

[0035] Furthermore, as shown in Table 3, the total free fatty acid content (total FFA) in the skim milk powder of Example 4 was 0.095 to 0.104% by mass. Furthermore, in Example 4, the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours after homogenization was 415% of the amount of free fatty acids having 12 or less carbon atoms, which was an 81% increase compared to the amount of free fatty acids having 14 or more carbon atoms when the milk was stored for 24 hours without homogenization (Comparative Example 5).

[0036]

[0037] Flavor Evaluation Test The flavors of the samples obtained in Example 1 and Comparative Example 1 were evaluated.

[0038]

[0039] The samples obtained in Examples 1 and 2 were directly heat-sterilized in a UHT sterilizer (MicroThermics) at 125°C for 9 seconds, and then cooled to below 10°C. The sterilized skim milk was concentrated under reduced pressure using a centrifugal thin-film vacuum evaporator, Evapol CEP-L (Okawahara Seisakusho), at a vacuum of 70 cmHg and an evaporation temperature of approximately 40°C, until the solids concentration rose to approximately 47%. Powdered skim milk powder was obtained by spray-drying the concentrated skim milk using a spray dryer PSD52 (APV) at a hot air temperature of 180°C and while controlling the flow rate of the concentrated skim milk so that the exhaust air temperature was 85°C.

Claims

1. A method for producing skim milk powder, comprising a homogenization step at a temperature of 30 to 55°C in the process of producing skim milk powder from skim milk.

2. The method according to claim 1, wherein the homogenization is carried out at 43 to 53°C.

3. The method according to claim 1 or 2, wherein the homogenization is carried out using a homogenizer at a homogenization pressure of 5 to 50 MPa.

4. The method according to any one of claims 1 to 3, wherein the amount of free fatty acids in skim milk powder is increased.

5. The method of claim 4, wherein the amount of free fatty acids having 14 or more carbon atoms when the milk is stored at 10°C or below for 24 hours after homogenization is increased by 20% or more compared to when the milk is stored for 24 hours without homogenization.

6. A method according to claim 4 or 5, in which the rate of increase in fatty acids having 12 or less carbon atoms is lower than the rate of increase in fatty acids having 14 or more carbon atoms when the milk is stored at 10°C or below for 24 hours after homogenization.

7. A method according to any one of claims 4 to 6, wherein the amount of free fatty acids having 14 or more carbon atoms in the milk after homogenization and storage at 10°C or below for 24 hours is 300% or more of the amount of free fatty acids having 12 or less carbon atoms.

8. Skim milk powder produced by the method according to any one of claims 1 to 7.

9. A method for increasing the amount of free fatty acids in skim milk powder, which comprises homogenizing the skim milk powder at a temperature of 30 to 55°C during the process of producing skim milk powder from skim milk.

10. The method of claim 9, wherein the amount of free fatty acids having 14 or more carbon atoms when the milk is stored at 10°C or below for 24 hours after homogenization is increased by 20% or more compared to when the milk is stored for 24 hours without homogenization.

11. The method according to claim 9 or 10, wherein the rate of increase in fatty acids having 12 or less carbon atoms is lower than the rate of increase in fatty acids having 14 or more carbon atoms.