JP3910593B2 - Liquid sterilization apparatus and milk sterilization method - Google Patents

Description

  The present invention relates to a liquid sterilization apparatus and a milk sterilization method using the sterilization apparatus.

  As a method for sterilizing milk, a low temperature holding sterilization method (LTLT method), a high temperature short time sterilization method (HTST method), and an ultra high temperature heat treatment method (UHT method) are known, but in recent years, the UHT method has become mainstream. It has become. There are two types of UHT methods, an indirect heat sterilization method and a direct heat sterilization method.

The indirect heat sterilization method is characterized by using a heat exchanger such as a plate heat exchanger or a tubular heat exchanger as a heating means in the operation of heating milk to the sterilization temperature. It is a method of heating through a hot wall. In the indirect heat sterilization method, sterilization conditions of 130 ° C. and 2 seconds are frequently used in Japan.
On the other hand, in the direct heat sterilization method, milk is heated in direct contact with steam. As this direct heat sterilization method, there are a method in which steam is blown into milk (injection method) and a method in which milk is discharged into a container filled with steam (infusion method).

Non-Patent Document 1 and Patent Documents 1 and 2 below describe a sterilization method and apparatus combining heat sterilization and centrifugation.
Non-Patent Document 1 below describes a method for separating and removing contained bacteria using ultrahigh-speed centrifugal force and further using a pasteurization method as a milk sterilization method.
In Patent Document 1 below, there is an apparatus configured to attach a centrifugal separator to a heat sterilization apparatus, take out raw milk in the middle of the heat sterilization process, remove bacteria in the raw milk, and return to the heat sterilization process again. Are listed. In the heat sterilization process, an indirect heat sterilization apparatus equipped with a heat exchanger is used.
In Patent Document 2 below, for example, a concentrated partial stream containing microorganisms is separated from a liquid stream such as milk by centrifugal separation, and the concentrated partial stream is degassed, and then the concentrated partial stream is heated and sterilized. And a method for joining the original liquid stream is described.
Supervised by Yukichi Tsugo, “City Milk Industry” 2nd edition, Earth Publishing Co., Ltd., April 30, 1969, p250 JP-A-57-146544 JP 58-63375 A

In the indirect heat sterilization method, the temperature of the milk is gradually raised in the heat exchanger to reach a predetermined sterilization temperature, and is maintained at the sterilization temperature for a predetermined time, and then gradually cooled. Accordingly, a sterilizing effect can be obtained even during temperature rise and cooling in the heat exchanger, but at the same time, heat denaturation of milk occurs.
On the other hand, in the direct heat sterilization method, the temperature is raised almost instantaneously from the preheating temperature (for example, 75 to 85 ° C.) to the sterilization temperature, and after being kept at the sterilization temperature for a predetermined time, the preliminary heat sterilization is quickly performed by vacuum evaporation. Since it is cooled to the heating temperature, the bactericidal effect during temperature rise and cooling cannot be obtained, and the heat denaturation of milk is also small. Therefore, in order to obtain a sterilizing effect equivalent to that of the indirect heat sterilization method in the direct heat sterilization method, it is necessary to set the sterilization temperature to be about 5 to 10 ° C. higher than that of the indirect heat sterilization method. Often set.
In this way, the direct heat sterilization method is less heat-denatured during heating and cooling than the indirect heat sterilization method, and a good flavor can be obtained, but the sterilization temperature is set higher than the indirect heat sterilization method. It is necessary to do. That is, in the direct heat sterilization method, since it is difficult to set the sterilization temperature to a temperature equal to or lower than the indirect heat sterilization method, even if it is intended to further improve the flavor by reducing thermal denaturation, There were technical limitations.

The present invention has been made in view of the above circumstances, and it is possible to set the sterilization temperature to a temperature equal to or lower than that of the indirect heat sterilization method even though it is a direct heat sterilization method. It is an object of the present invention to provide a liquid sterilization apparatus capable of suppressing the denaturation of the liquid and obtaining a sufficient sterilization effect, and an apparatus for producing a container-containing liquid product provided with the sterilization apparatus.
In addition, the present invention makes it possible to set the sterilization temperature to a temperature equal to or lower than that of the indirect heat sterilization method even though it is a direct heat sterilization method, further minimizing flavor deterioration due to heating. It is an object of the present invention to provide a milk sterilization method capable of obtaining a sufficient sterilization effect and a method for producing a milk product in a container using the sterilization method.

In order to solve the above problems, the present invention provides a preheating device that preheats a liquid, a sterilization centrifuge that sterilizes the liquid that has passed through the preheating device by centrifugation, and the sterilization centrifuge. A cooling device that cools the liquid that has passed through the separation device, a holding tank that stores the liquid that has passed through the cooling device, and a direct heating sterilization device that sterilizes the liquid supplied from the holding tank by a direct heat sterilization method. A liquid sterilization apparatus is provided.

  Further, the present invention is characterized by comprising the liquid sterilization apparatus of the present invention, a supply tank provided in the previous stage of the sterilization apparatus, and a container filling apparatus for filling the container with the liquid that has passed through the sterilization apparatus. An apparatus for manufacturing a liquid product in a container is provided.

In addition, the present invention has undergone a preheating step for preheating milk, a sterilization centrifugation step for sterilizing the milk subjected to the preheating step by centrifugation, and a sterilization centrifugation step. A cooling step for cooling the milk, a step of storing the milk after the cooling step in a holding tank, and the milk supplied from the holding tank by direct heat sterilization method at 120 ° C. for 2 seconds to 130 There is provided a milk sterilization method characterized by comprising a direct heating sterilization step in which a heat sterilization process is performed under sterilization conditions at a temperature of 2 ° C. or a sterilization condition to which a thermal history equivalent thereto is applied .

  The present invention also includes a step of storing milk in a supply tank, a step of sterilizing milk supplied from the supply tank using the milk sterilization method of the present invention, and the sterilization treatment. And a step of filling milk into a container. A method for producing a milk product in a container is provided.

According to the liquid sterilization apparatus of the present invention, it is possible to minimize the denaturation of components due to heating and to obtain a sufficient sterilization effect.
According to the apparatus for producing a liquid product in a container of the present invention, a liquid product in a container that is sufficiently sterilized with little modification of components due to heating of the contents can be obtained.
According to the milk sterilization method of the present invention, a sufficient sterilization effect can be obtained while maintaining a good flavor while minimizing the denaturation of components due to heating of milk.
According to the method for producing a milk product in a container of the present invention, a milk product in a container that is excellent in flavor with little degeneration of components due to heating of milk and is sufficiently sterilized is obtained.

FIG. 1 is a schematic configuration diagram showing an embodiment of a production apparatus for a liquid product in a container provided with a sterilization apparatus according to the present invention. In this figure, the solid line indicates the flow of the liquid, and the broken line indicates the transmission of the control signal.
The present invention is not limited to milk and can be applied to various liquids, but is particularly suitable for milk.

Milk in the present invention is milk (raw milk, milk) as defined by a ministerial ordinance of milk ("Ministerial ordinance on ingredient standards of milk and dairy products", Dec. 27, 1951, Ministry of Health and Welfare No. 52). , Special milk, raw goat milk, raw sheep milk, pasteurized goat milk, partially skimmed milk, skimmed milk, processed milk, etc.), and various beverages handled according to milk, such as concentrated milk, skimmed milk, etc. Concentrated milk, sugar-free milk, sugar-free defatted milk, sweetened milk, sweetened defatted milk, lactic acid bacteria drink, milk drink, lactic acid bacteria drink which is the main milk source, and the like are also included. Preferably it is milk.
In this embodiment, milk will be described as an example.

The apparatus for producing a milk product in a container according to this embodiment includes a supply tank 1, a heat exchanger 2, a sterilization centrifuge 3, a holding tank 4, a direct heating sterilizer 5, a sterilized milk tank 6, and a container filling device. 7 is a schematic configuration.
The supply tank 1 stores liquid to be sterilized, and a temperature adjustment function is provided as necessary to maintain a suitable storage temperature of the liquid.
In the present embodiment, raw milk (raw milk) is stored in the supply tank 1. A suitable storage temperature of the raw milk is 5 ° C. or less, preferably 4 ° C., and the supply tank 1 is provided with a heat retaining means.

  The raw material milk in the supply tank 1 is preheated in the heat exchanger 2 and then sent to the sterilization centrifuge 3 where sterilization is performed by centrifugation. The sterilized milk that has been sterilized is cooled in the heat exchanger 2, temporarily stored in the holding tank 4, and then sterilized by the direct heating sterilizer 5. The sterilized milk after the sterilization treatment is stored in the sterilized milk tank 6 and then filled in the container by the container filling device 7 to become a milk product in a container.

  A first pump 11 is provided in the flow path from the supply tank 1 to the heat exchanger 2, and a second pump 12 is provided in the flow path from the holding tank 4 directly to the heating sterilizer 5. Yes. In addition, the liquid amount in the holding tank 4 is measured by the level meter 15, and a signal for controlling the flow rate in the first pump 11 is transmitted from the level controller 16 according to the measurement result. . Thereby, the flow rate of the raw material milk flowing out from the supply tank 1 is controlled so that the liquid amount in the holding tank 4 is maintained at a predetermined amount. For example, an inverter 17 is used to control the first pump 11.

The heat exchanger 2 of this embodiment serves as both a preheating device and a cooling device.
Inside the heat exchanger 2, there are a cooling water flow path 2a, a hot water flow path 2b, a raw material milk flow path 2c through which raw milk flows from the supply tank 1 to the sterilization centrifuge 3 and a sterilization centrifuge 3 The sterilized milk flow paths 2d through which the sterilized milk flows toward the holding tank 4 are provided through a partition wall.
A thermometer 18 is provided in the flow path from the heat exchanger 2 toward the sterilization centrifuge 3. Further, a steam flow path 2e for supplying steam into the hot water flow path 2b is provided, and a valve 13 provided in the steam flow path 2e from the temperature controller 19 according to the measurement result of the thermometer 18. A signal for controlling the opening and closing of the camera is transmitted. Thereby, the temperature of the warm water in the warm water flow path 2b is controlled, and as a result, the temperature of the raw material milk flowing into the sterilization centrifuge 3 can be controlled.

  In the heat exchanger 2, the raw milk in the raw milk flow channel 2c is heat-exchanged by contacting through the partition wall in the order of the sterilized milk in the sterile milk flow channel 2d and the hot water in the hot water flow channel 2b. , And preheated to a predetermined temperature. The temperature t1 of the raw material milk before flowing into the heat exchanger 2 is the storage temperature of the raw material milk in the supply tank 1, and is raised to the temperature t2 by heat exchange with the sterilized milk in the sterilized milk channel 2d. Further, the temperature is raised to a temperature t3 by heat exchange with the hot water in the hot water flow path 2b. The t2 is, for example, about 45 to 60 ° C., preferably about 53 ° C. The t3 is a temperature at which the raw milk is supplied to the sterilization centrifuge 3 and is, for example, about 50 to 75 ° C., preferably about 65 ° C.

  On the other hand, the sterilized milk in the sterilized milk flow path 2d is heat-exchanged by contacting the raw milk in the raw material milk flow path 2c and the cooling water in the cooling water flow path 2a in this order through the partition wall, so that a predetermined temperature is reached. To be cooled. The temperature of the sterilized milk before flowing into the heat exchanger 2 is substantially equal to the temperature (t3) at which the raw milk is supplied to the sterilization centrifuge 3. The sterilized milk is cooled to a temperature t4 by heat exchange with the raw milk in the raw milk flow channel 2c, and further cooled to a temperature t5 by heat exchange with the cooling water in the cooling water flow channel 2a. The t4 is, for example, about 9 to 24 ° C., preferably about 11 ° C. The t5 is preferably the storage temperature of the raw material milk in the supply tank 1, as is the case with t1.

The sterilization centrifuge 3 is a device that selectively removes most of microorganisms, particularly bacteria, from raw material milk by centrifugal force using the specific gravity difference between milk components and microorganisms. According to this, spore-forming bacteria can be effectively removed among bacteria.
For example, a continuous centrifugal separator that applies centrifugal force by rotating the rotating cylinder at a high speed while the raw milk flows at a predetermined flow rate in the rotating cylinder (bowl) can be suitably used. In order to effectively perform sterilization, an apparatus having a centrifugal force of about 5000 to 10000 G and a centrifugal force greater than that of a normal centrifuge (for example, about 4000 to 5000 G) used for cream separation or the like is preferable.

The holding tank 4 temporarily stores the sterilized milk sterilized by the sterilization centrifuge 3 before supplying the sterilized milk directly to the heating sterilizer 5, and the sterilized milk is preferably stored at its preferred storage temperature. That is, a heat retaining function for holding at t5 (t1) is provided.
As described above, the amount of liquid in the holding tank 4 is kept constant.

In the centrifugal separator 3 for sterilization of this embodiment, since the raw material milk is centrifuged in the apparatus, a sludge (separate) containing bacteria separated from the raw milk is generated. Is configured to be discharged as discharged liquid at regular intervals. The discharged liquid is discharged by opening / closing a discharge valve (not shown). As the discharge valve is opened / closed, the flow rate of the sterilized milk flowing out from the sterilization centrifugal separator 3 varies.
On the other hand, in the present embodiment, the sterilized milk flowing out from the sterilization centrifuge 3 is temporarily stored in the holding tank 4 and the liquid amount in the holding tank 4 is kept constant, thereby directly The flow rate of the sterilized milk fed to the heating sterilizer 5 is configured not to fluctuate. In order to effectively prevent fluctuations in the flow rate of the sterilized milk fed to the direct heating sterilizer 5, the amount of the sterilized milk stored in the holding tank 4 is preferably about 100 to 200 liters. .
In this embodiment, the sterilized milk that has undergone the sterilization centrifugation step is quickly cooled to a preferable storage temperature (t1, t5), and in the holding tank 4, a preferable storage temperature (t1, t5). It is comprised so that it may be hold | maintained. Therefore, even if a relatively large amount of sterilized milk is stored in the holding tank 4 as described above, and the retention time of the sterilized milk is relatively long, bacterial growth and quality deterioration of the sterilized milk during storage are prevented. Can be prevented.

The direct heating type sterilizer 5 uses either a method in which pressurized steam is blown into sterilized milk (injection method) or a method in which sterilized milk is released into a container filled with steam (infusion method). It may be used. More preferred is an infusion system.
In this embodiment, an infusion type direct heating sterilizer 5 is used. The infusion type direct heating sterilizer 5 is configured to be sterilized by the following procedure, for example. First, the sterilized milk fed from the holding tank 4 directly to the heating sterilizer 5 is heated to an intermediate temperature. This intermediate temperature is about 75 to 85 ° C, preferably about 75 to 80 ° C. Next, the sterilized milk is diffused into the heating container filled with pressurized steam. At this time, the sterilized milk comes into contact with the steam and the steam flows into the sterilized milk, whereby the sterilized milk is instantaneously heated to a predetermined sterilization temperature. The heated sterilized milk passes through a holding tube having a predetermined length, is maintained at a sterilization temperature for a predetermined time, is sterilized, and becomes sterilized milk. Thereafter, the high-temperature and high-pressure sterilized milk is sent to a suction chamber that is sucked so as to be in a predetermined negative pressure state. In this suction chamber, the sterilized milk is boiled under reduced pressure. As a result, the steam that flows in at the time of heating is removed and the temperature decreases, and the temperature quickly decreases to near the intermediate temperature before the sterilization treatment. Thereafter, it is cooled to a preferred storage temperature, that is, about t5 (t1) and stored in the sterilized milk tank 6.
Further, after boiling under reduced pressure in the suction chamber and quenching, homogenization may be performed at a predetermined homogenous pressure with a homogenizer.

  In the infusion type direct heating sterilizer 5, as described above, the sterilized milk is instantaneously heated to a predetermined temperature by dispersing the sterilized milk in the pressurized steam, and thus is mixed. When the ratio of the flow rate of the pressurized steam and the flow rate of the sterilized milk varies, the heating temperature varies. In this embodiment, while fixing the 2nd pump 12 provided in the flow path which goes directly from the holding tank 4 to the heating-type sterilizer 5 to a predetermined rotation speed, the liquid amount in the holding tank 4 is kept at a predetermined amount. As a result, the flow rate of the sterilized milk fed from the holding tank 4 directly to the heating sterilizer 5 is kept constant.

  The sterilized milk tank 6 stores the sterilized milk flowing out from the direct heating sterilizer 5 before feeding it to the container filling device 7, and the sterilized milk is stored at its preferred storage temperature, that is, t5 (t1). A heat retention function is provided to hold the

  The container filling device 7 fills and seals sterilized milk in an appropriate container such as a bottle or a paper pack, and a known container filling device can be used. If a device for aseptically filling the container is used as the container filling device 7, so-called long life milk can be produced.

In order to manufacture a containerd milk product using the containerized milk product manufacturing apparatus having such a configuration, first, raw milk as raw material milk is supplied to the supply tank 1 and stored. The raw milk is then preheated to a temperature t3 by passing through the heat exchanger 2. This is sent to the centrifugal separator 3 for sterilization, where sterilization treatment by centrifugation is performed. The conditions at the time of the sterilization treatment are preferably within a range of about 5 to 20 seconds with a centrifugal force of 5000 to 10000 G. Even if the centrifugal force is small and the treatment time is short, the sterilization effect is insufficient. On the other hand, if the centrifugal force is too large or the processing time is too long, the apparatus becomes unnecessarily large and very expensive. Moreover, as above-mentioned, the temperature (t3) of the raw material milk at the time of the disinfection process by centrifugation has preferable about 50-75 degreeC, for example, about 65 degreeC is suitable. If the temperature of the raw material milk during the sterilization treatment is too high, internal scoring occurs, and if it is too low, a sufficient sterilization effect cannot be obtained.
It is preferable to remove spore-forming bacteria present in the raw milk at a sterilization rate of 85 to 90% by sterilization treatment in the sterilization centrifuge 3.
The sterilization rate here is obtained by a known method. The method is described in detail, for example, in Daamen, CBGet al: NIZO Reports R124 & R127 (1986).

  Next, the sterilized milk that has been sterilized by centrifugation is passed through the heat exchanger 2, cooled to a temperature t5, temporarily stored in the holding tank 4 at a low temperature t5, and then directly heated sterilized. The solution is sent to the device 5.

And in the direct heating type sterilizer 5, sterilization is performed by the direct heating sterilization method. The sterilization condition at this time is a range of heating conditions of 120 ° C. for 2 seconds to 130 ° C. for 2 seconds, preferably 120 ° C. for 2 seconds to 129 ° C. for 2 seconds, or a thermal history equivalent to this range. It is preferable to use heating conditions. If the heat history applied to the sterilized milk is smaller than the above range, the sterilization effect becomes insufficient, and if it is large, sufficient sterilization effect can be obtained only by heating without sterilization. I can't enjoy it.
By such direct heat sterilization treatment, microorganisms such as general bacteria, psychrophilic bacteria, Escherichia coli, mold, yeast and the like are sufficiently killed, and a sufficient sterilization effect is obtained in combination with the sterilization effect by the previous centrifugation.

Alternatively, the sterilization condition in the direct heating sterilizer 5 may be a heating condition in which the F value is 0.026 to 0.259 (min).
Here, the sterilization efficiency in the sterilizer can be generally expressed by an F value (unit: minute) calculated by the following mathematical formula (1). In the formula, t represents the sterilization time (second), and T represents the sterilization temperature (° C.).
F = t / 60 × 10 ^{{(T-121.1) / 10}} (1)
In addition, when a plate-type or tubular-type heat exchanger is used in the indirect heat sterilization method, a sterilization effect is generated not only in the holding tube held at the sterilization temperature but also in the heating part and the cooling part in the heat exchanger. Therefore, it is known that the F value needs to be calculated in consideration of the temperature and the residence time in the heating part and the cooling part (for example, “About the bactericidal effect in the plate heat exchanger” by Hideo Shigaraku et al. Papers, 17, p. 220-224 (1991)).
Since this embodiment uses the direct heat sterilization method, the F value can be obtained using the sterilization temperature and the sterilization time in the direct heating type sterilizer 5.

  Thereafter, the sterilized milk that has undergone the sterilization process in the direct heating sterilizer 5 is temporarily stored in the sterilized milk tank 6 while maintaining a low temperature of about t5 (t1). And a milk product with a container is obtained by filling a container with a well-known method.

According to the present embodiment, it is possible to minimize the denaturation of components due to heating, and to obtain a sufficient sterilizing effect, so that the milk product in a container excellent in quality and flavor and highly sterilized. Is obtained.
That is, when the conventional indirect heat sterilization method is used, while the sterilization effect can be obtained even during the temperature rise and cooling in the sterilization apparatus, the denaturation of the component due to heat proceeds, whereas this In the embodiment, since the temperature rise to the sterilization temperature and the cooling are instantaneously performed by the direct heat sterilization method, denaturation of the component due to heat is minimized. At the same time, in the present embodiment, the sterilization temperature in the direct heating sterilization device 5 is raised to a high level by going through both the sterilization step in the sterilization centrifuge 3 and the sterilization step in the direct heating sterilization device 5. Even without it, milk that has been thoroughly sterilized can be obtained. For example, if the sterilization condition in the direct heating sterilizer 5 is 125 ° C. or 130 ° C. · 2 seconds, the bacteria are sterilized and sterilized in the same manner as the normal indirect heat sterilization method (sterilization temperature 130 ° C., sterilization time 2 seconds). Milk can be obtained.
Here, in a general indirect heat sterilization method (sterilization temperature 130 ° C., sterilization time 2 seconds), the F value is calculated in consideration of the temperature and residence time in the heating part and cooling part of the heat exchanger. It will be about 168 (minutes). On the other hand, in this embodiment, a sufficient sterilization effect can be obtained even when the F value of the sterilization condition in the direct heating sterilizer 5 is as small as 0.026 to 0.259 (min) as described above. .

(Examples 1 to 3, Comparative Examples 1 and 2)
Raw milk was sterilized using the manufacturing apparatus of the milk product with a container of the structure of FIG. The temperatures in the heat exchanger 2 and the flow paths before and after the heat exchanger 2 were t1 = t5 = 4 ° C., t2 = 53 ° C., t3 = 65 ° C., and t4 = 11 ° C. As the sterilization centrifuge 3, Westphalia CND130 was used, and the centrifugation conditions were 5070G.
When sterilization treatment was performed under these conditions, the number of viable bacteria before eradication was 198,000, the number of viable bacteria after eradication was 20,500, and the eradication rate was 89.6%.
As the direct heating sterilizer 5, an infusion type apparatus was used.
In each example and comparative example, the sterilization conditions in the direct heating sterilizer 5 were as shown in Table 1 below. The F value under each sterilization condition is shown in Table 1 below. In the direct heating type sterilizer 5, the intermediate temperature before being diffused into the heating container was 80 ° C.
The sterilized milk thus sterilized was examined for the number of viable bacteria when cultured at 25 ° C. for 48 hours. The results are shown in Table 1 below. In the following table, the number of viable bacteria is ∞, indicating that a lot of fungal growth was observed.

(Comparative Examples 3 to 7)
In Example 1, sterilization by the infusion type direct heating sterilizer 5 was performed without sterilization by the sterilization centrifuge 3. In addition, sterilized milk was obtained in the same manner as in Example 1 except that the sterilization conditions were changed as shown in Table 2 below.
About the obtained pasteurized milk, it carried out similarly to Example 1, and investigated the viable count after culture | cultivation. The results are shown in Table 2.

From the results of Tables 1 and 2, when only sterilization by direct heat sterilization was performed, sterilization conditions of 132 ° C. and 2 seconds were necessary, but by sterilization by centrifugation and direct heat sterilization according to the present invention. When both sterilizations were performed, a good sterilization effect was obtained even when the sterilization conditions in the direct heat sterilizer were lowered to 120 ° C. for 2 seconds.
In Comparative Example 6, the number of viable bacteria was 0, which is the same result as Comparative Example 2.
That is, as in Comparative Example 2, if the sterilization conditions are 132 ° C. and 2 seconds, the merit of performing the sterilization treatment in the present invention is poor.
Thus, it is apparent that the range of sterilization conditions suitable for the present invention is in the range of 120 ° C. · 2 seconds to 130 ° C. · 2 seconds.
The conditions lower than 129 ° C. · 2 seconds of Example 2 are more preferable because the effect of reducing the component change due to heating can be obtained.

(Comparative Example 8)
The same raw milk as in Example 1 was used to sterilize by indirect heat sterilization to obtain sterilized milk. A commercially available sterilizer equipped with a plate heat exchanger was used as the heating means, and the sterilization conditions were 120 ° C. and 2 seconds (F value = 0.125). Sterilization by centrifugation was not performed. About the obtained pasteurized milk, it carried out similarly to Example 1, and investigated the viable count after culture | cultivation. The results are shown in Table 3.
(Comparative Example 9)
In Comparative Example 8, the sterilization conditions were changed to 130 ° C. and 2 seconds (F value = 1.168) to obtain sterilized milk. About the obtained pasteurized milk, it carried out similarly to Example 1, and investigated the viable count after culture | cultivation. The results are shown in Table 3.
In the above Comparative Example 8 and Comparative Example 9, the F value indicates a value that also takes into account the heat history during temperature rise and cooling in the heat exchanger. Without taking these into account, the F values in the case where the history of only the state maintained at 120 ° C. and 130 ° C. are formed are 0.026 and 0.259, respectively.

(Evaluation of physicochemical properties)
For the pasteurized milk obtained in Example 3 and the pasteurized milk obtained in Comparative Examples 7 to 9, respectively, furosine content (μg / g), lactulose content (mg / 100 g), rennetability (seconds), and Absorbance (OD ₄₂₀ ) at ₄₂₀ nm (nanometer) was measured. It is known that these parameters are values that vary depending on the degree of heating that the measurement object has received. Each measuring method is as follows. The measurement results are shown in Table 4 below.

[Measurement of furosine content (μg / g)]
A known method can be employed for measuring the furosine content. For example, since it is described in Japan Milk Industry Technical Association, “Raw Milk Functional Component Analysis Project Implementation Report, Development of a Method for Specifying Raw Milk Use Ratio”, March 2000, it is cited below.
Using a micropipette, 1 ml of the sample was weighed into a test tube with a screw cap with Teflon (registered trademark) packing in which 5 ml of hydrochloric acid had been weighed in advance, and immediately stirred and attached to a heating block. Process for 10 hours (process after heating block is completed within 72 hours). After heating, the sample is filtered with a membrane filter (0.45 μm) to remove insoluble matters. 2 ml of the filtrate is dispensed into a concentration tube using a micropipette and concentrated to dryness on a rotary evaporator (heating temperature is 45 to 50 ° C.). Dissolve the dried solid in the concentrating tube completely with 2 ml of water, add 1 ml of the internal standard substance for furosine measurement, and filter with a membrane filter (0.45 μm) to obtain a high-performance liquid chromatograph (HPLC) injection sample. . The injection sample prepared by pretreatment in this way is injected into 10 μl HPLC using a microsyringe or an autosampler, and the peak areas of furosine and the internal standard substance for furosine measurement are determined.
The value of furosine content increases as the component change by heating increases.

Hereinafter, the lactulose content, rennetability, and OD ₄₂₀ can be measured by known methods. For example, Iwatsuki et al., “Effect of sterilization conditions on sensory characteristics of milk”, Journal of Japanese Society for Food Science and Technology, Vol. 46, No. 8, August 1999, p535-542, quoted below. To do.

[Measurement of lactulose content (mg / 100 g)]
5 g of the sample is diluted 10-fold with water, extracted with ultrasound for 10 minutes, and filtered through an ultrafiltration membrane (Millipore) with a molecular weight cut off of 10,000. Then, it measures by the arginine fluorescence method by the anion exchange chromatography of a borate complex ion. Measurement with a fluorescence detector is performed at an excitation wavelength of 320 nm and a measurement wavelength of 430 nm.
The value of the lactulose content increases as the component change due to heating increases.

[Measurement of rennetability (seconds)]
After holding 50 ml of the sample in a constant temperature bath at 37 ° C. for 5 minutes, 2 ml of 1% rennet solution (HA-LA Rennet POWDER (including NaCl), CHR.HANSEN'S, Denmark) is added, and the solidification time at 37 ° C. (seconds) ).
The value of rennetability increases as the component change due to heating increases.

[Measurement of OD ₄₂₀ ]
Hold 22 g of sample at 37 ° C. for 30 minutes, add and dissolve 8 g of sodium chloride, filter, and add 10 ml of acidic saturated brine (4 ml of glacial acetic acid to 1 liter of saturated brine) to 1 ml of filtrate. The absorbance at 420 nm (disposel, optical path length 10 mm, room temperature) is measured using a spectrophotometer (U-2000 type double beam spectrophotometer, manufactured by Hitachi, Ltd.).
The value of OD ₄₂₀ decreases as the component change due to heating increases.

(sensory evaluation)
Sensory evaluation was performed on the pasteurized milk obtained in Example 3 and the pasteurized milk obtained in Comparative Example 7. The panel was evaluated by three panelists: “Delicious, Neither Satisfactory, Not Delicious” by 20 male and female panelists with excellent taste and milk drinking habits. The results are shown in Table 5 below.

From the results of Tables 1 and 2, the following was found. That is, in the present invention, if the sterilization conditions (Examples 2, 3 and Comparative Example 2) apply a heat history higher than the sterilization conditions (Example 1) of at least 120 ° C. for 2 seconds, the viable cell count is calculated. Although sterilization conditions (Comparative Example 2) exceeding 132 ° C. and 2 seconds can be reduced to 0, even if the conventional direct heat sterilization method (Comparative Examples 6 and 7) without a sterilization step, The number can be zero. Therefore, it is recognized that the preferred implementation range of the present invention is in the range of 120 ° C. · 2 seconds to 130 ° C. · 2 seconds.
Moreover, according to Table 4, compared with Comparative Examples 8 and 9 showing the conventional indirect heat sterilization method, Example 3 and Comparative Example 7 showing the direct heat sterilization method have fewer component changes due to heating. .
In addition, among the direct heat sterilization methods, Example 3 according to the present invention has less component change due to heating than Comparative Example 7 which is a conventional standard sterilization condition. This is also supported by sensory evaluation.
From the above, it has been found that the present invention is superior to both the conventional direct heat sterilization method and the conventional indirect heat sterilization method.

(Comparative Example 10)
The same raw milk as in Example 1 was used, and sterilization was performed by a high-temperature and short-time sterilization method (HTST method) at 75 ° C. for 15 seconds to obtain sterilized milk.

(sensory evaluation)
Sensory evaluation was performed on the pasteurized milk obtained in Example 3 and the pasteurized milk obtained in Comparative Example 10. The evaluation was performed in three stages: “no wrinkles, neither can be said, there are wrinkles”, with 14 panelists of men and women who have excellent taste and a habit of drinking milk tasting sterilized milk. received. The results are shown in Table 6 below.

  From the results shown in Table 6, it was felt that Example 3 according to the present invention was clearly less habitable than Comparative Example 10 sterilized by the HTST method, and more delicious milk was obtained.

It is the schematic block diagram which showed one Embodiment of the manufacturing apparatus of the liquid product with a container which concerns on this invention.

Explanation of symbols

1 Supply tank 2 Heat exchanger (preheating device, cooling device)
3 Centrifugal Separation Device 4 Holding Tank 5 Direct Heating Sterilizer 6 Sterilized Milk Tank 7 Container Filling Device

Claims (4)

A preheating device for preheating the liquid;
A sterilization centrifuge for sterilizing the liquid that has passed through the preheating device by centrifugation;
A cooling device for cooling the liquid that has passed through the sterilization centrifugal separator ;
A holding tank for storing the liquid that has passed through the cooling device ;
A liquid sterilization apparatus comprising: a direct heating sterilization apparatus that sterilizes a liquid supplied from the holding tank by a direct heat sterilization method. A liquid sterilizer according to claim 1 ;
A supply tank provided in front of the sterilizer;
An apparatus for producing a liquid product in a container, comprising: a container filling device that fills a container with the liquid that has passed through the sterilization device. A preheating step for preheating milk,
A sterilization centrifugation step for sterilizing the milk that has undergone the preheating step by centrifugation;
A cooling step of cooling the milk that has undergone the sterilization centrifugation step;
Storing the milk after the cooling step in a holding tank;
Direct heating type in which the milk supplied from the holding tank is sterilized by direct heat sterilization under sterilization conditions of 120 ° C. · 2 seconds to 130 ° C. · 2 seconds or sterilization conditions to which a thermal history equivalent thereto is applied A method for sterilizing milk characterized by comprising a sterilization step. Storing milk in a supply tank;
A step of sterilizing the milk supplied from the supply tank using the milk sterilization method according to claim 3 ;
A method for producing a milk product in a container, comprising: filling the container with the milk after the sterilization treatment.

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