JP5054591B2 - Method for judging the safety of cooked foods stored at refrigerated temperatures - Google Patents

Description

  The present invention relates to a method for determining the safety of a cooked food stored at a refrigerated temperature. According to the present invention, the safety of cooked food stored at a refrigerated temperature can be determined easily and accurately in a shorter time than before, thereby eliminating the risk of food poisoning and the like. It is possible to quickly supply cooked foods with excellent properties to the market.

  There is no need to cook at home due to the increase in double-working households, single-person households, elderly households, etc., and various foods that can be eaten as they are simply by purchasing them and taking them home or just heating them in a microwave oven etc. Cooked foods have been widely sold in recent years due to their convenience and demand has been increasing. Examples of such cooked foods include various cooked foods sold in department store basements, supermarkets, convenience stores, and the like. In addition, cooked food is not only sold as a single dish, but also used as a food material to be packed in take-out lunches sold in stores, etc., and also used in restaurants, etc. It has become.

Cooked foods such as prepared dishes are usually stored and distributed at a refrigerated temperature of 0 to 10 ° C, and depending on the type of food, when kept at a refrigerated temperature, including during distribution, In general, the expiration date is about 1 to 2 days after production.
If cooked foods such as prepared dishes that are stored and distributed at refrigerated temperatures contain a lot of harmful microorganisms such as bacteria at the manufacturing stage, the harmful microorganisms may be stored before the expiration date even if stored at refrigerated temperatures. May multiply and cause food poisoning.
The demands and regulations on food safety and hygiene are becoming stronger, and this is no exception for cooked foods such as prepared dishes. From this point, it is required to perform a safety inspection before shipment even for cooked foods stored and distributed at refrigerated temperatures.

For the safety inspection of cooked foods stored at refrigerated temperatures, as with other foods, a portion of the cooked food is collected as a sample and the sample is free of harmful microorganisms such as bacteria. 2. Description of the Related Art Conventionally, a method of inoculating and culturing an agar medium or the like containing a growth promoting component and counting the number of colonies of harmful microorganisms formed on the medium by visual observation or the like has been widely used.
However, in the case of this method, in order to form colonies that can be counted by visual observation, it is usually necessary to carry out culture for 2 to 3 days. Therefore, even if the safety inspection of cooked food stored at a refrigerated temperature is started immediately after its manufacture, the safety inspection of the cooked food is completed and the safety is confirmed. If you try to ship food, it will be shipped after more than 2 days of production, and the taste, flavor, appearance, etc. of the food may be considerably degraded at the time of shipment compared to immediately after production. . In addition, since it took a long time to inspect the safety, the period between the time of shipment and the expiration date is shortened and cannot be sold in the market, resulting in a decrease in sales.

  Instead of the above-mentioned method for determining the safety of food by counting the number of colonies formed by culturing using an agar medium, etc., the amount of heat generated from a sample such as food is measured to determine the amount of microorganisms in the food sample. A method and apparatus for measuring the presence / absence and the active state of microorganisms are known (Patent Document 1). This Patent Document 1 describes that the amount of heat generated from a sample is measured while maintaining the sample at a constant temperature within a range of 25 to 40 ° C. (paragraph 0013 of the cited document 1). In all the examples of Patent Document 1, the sample is maintained at 30 ° C., and the calorific value from the sample is measured over a long time of 50 hours or more.

  In the case of the method described in Patent Document 1, the operation is simpler than the method of counting the number of colonies formed in the medium, and the inspection time is slightly shortened. However, when the present inventors applied the method described in Patent Document 1 to a cooked food stored at a specific temperature called a refrigeration temperature and tried to determine its safety, Suitable for judging the safety of cooked foods that are stored at refrigerated temperatures where it still takes 48 hours or more to be judged and is required to be distributed and sold to the market as soon as possible after production. Turned out not to. In addition, the safety determination result performed according to the method of Patent Document 1 may not always match the actual safety of cooked food stored at a refrigerated temperature, and there is actually no problem with safety. However, it has been found that there is a possibility that the result may be that the safety is not achieved, or that the safety may be obtained although there is a problem with the safety.

Japanese Patent Laid-Open No. 2003-125797

An object of the present invention is to provide a method capable of quickly and accurately determining the safety of a cooked food stored at a refrigerated temperature with a simple operation and in a shorter time than before. is there.
It is an object of the present invention to provide a highly reliable safety determination method that has no discrepancy between the determination result and the actual safety of the cooked food stored at the refrigeration temperature.

The inventors have made various studies in order to achieve the above object. In a cooked food stored at a refrigerated temperature, the number of general viable bacteria is preferably 1.0 × 10 ⁵ cfu or less per gram of the cooked food when the cooked food is actually eaten. (“Bento and sanitary hygiene standards”)
Therefore, in food stored at a refrigerated temperature after cooking, it is possible to easily and quickly confirm that the number of viable bacteria at the shipping stage is 1.0 × 10 ⁵ cfu / g or less and is safe. In order to do this, we have continued to study various inspection methods.

As a result, the method of inoculating a culture with a sample collected from a cooked food stored at a refrigerated temperature and incubating the culture to count the number of colonies formed on the culture is time consuming and time consuming. It has been found that it is not suitable for determining the safety of food that must be shipped and stored at refrigerated temperatures.
On the other hand, the method of measuring the amount of heat generated from a sample as described in Patent Document 1 is simpler and can reduce the time than the method of forming a colony, but is described in Patent Document 1. If the method is applied as it is as a method for judging the safety of cooked foods stored at refrigerated temperatures, the safety cannot be judged accurately yet in a short time, and special measures and improvements are required. It turned out to be.

  Under such circumstances, the present inventors have further studied. As a result, nutrients that promote the growth of microorganisms that grow in low-temperature regions of 0 to 10 ° C., especially heat-resistant bacteria that grow at 0 to 10 ° C. (particularly Bacillus spp.) A constant temperature within a specific temperature range of 15 to 28 ° C., which is lower than that employed in the example of Patent Document 1 by adding nutrients that promote the growth of the genus Clostridium and Streptococcus The calorific value is measured over time while maintaining the temperature, and when safety is determined by the degree of calorific value at a predetermined time, heating stored at a refrigeration temperature within 12 to 20 hours from the start of the calorific value measurement. It has been found that the safety of cooked foods can be confirmed quickly and accurately. In particular, it has been found that as long as the cooked food is stored while being kept at a refrigerated temperature, it can be determined more quickly than before whether there is no problem with safety at least within the expiration date.

Further, the present inventors, in making the above-mentioned determination, determine by the magnitude of the value of the calorific value itself at a predetermined time within the above 12 to 20 hours, the calorific value up to the predetermined time It has been found that a method of determining by the magnitude of the integral value can be adopted.
Furthermore, when adopting the above-described determination method, the present inventors fill a container with a predetermined amount of cooked food stored at a refrigerated temperature, and have a sensor for measuring the calorific value thereof. A heat sink, an air circulation tank surrounding the outside of the heat sink, a constant temperature water circulation tank surrounding the outside of the air circulation tank, and a means for keeping the temperature of the heat sink constant including a heat insulating layer surrounding the outside of the constant temperature water circulation tank It is found that it is preferable to use a calorific value measuring device equipped with a measuring tank, and to accommodate and carry a container filled with cooked food stored at a refrigeration temperature in the heat sink of the measuring tank in the calorific value measuring device. Based on these various findings, the present invention has been completed.

That is, the present invention
(1) A method for judging the safety of cooked food stored at a refrigerated temperature, which promotes the growth of microorganisms that propagate in a low temperature region of 0 to 10 ° C. on a cooked food stored at a refrigerated temperature. Add the nutrients to fill the container, place the container filled with cooked food in the measuring tank of the calorific value measuring device, and maintain the temperature of the measuring tank at a constant temperature in the range of 15 to 28 ° C The calorific value is measured over time, and the cooked food is determined according to the amount of calorific value at a predetermined time (TA) 12 to 20 hours after the container filled with the cooked food is placed in the thermostat. It is a method for determining the safety of a cooked food stored at a refrigeration temperature of 0 to 10 ° C., wherein the safety is determined.

And this invention,
(2) The determination method according to (1) above, wherein the microorganism that propagates in a low temperature region of 0 to 10 ° C is a heat-resistant bacterium that propagates at 0 to 10 ° C;
(3) The determination method according to the above (1) or (2), wherein a filling amount of the cooked food stored at a refrigerated temperature in the container is 1 to 3 g per 10 ml of the internal volume of the container;
It is.

Furthermore, the present invention provides
(4) Judgment of safety by the amount of heat generated at a predetermined time (TA)
(A) If the measured value of the calorific value at a predetermined time (TA) does not exceed the reference value, the safety is determined to be acceptable, and if the measured value exceeds the reference value, the safety is determined to be unacceptable. Do by doing;
(B) The integrated value (ΔHa) of the calorific value from the time (T0) to the predetermined time (TA) when the container filled with the cooked food stored at the refrigeration temperature is placed in the measurement tank is the reference By determining that the safety is acceptable if the integrated value is not exceeded, while determining that the safety is unacceptable if the integrated value is exceeded; or
(C) When a certain time has elapsed since the container filled with the cooked food stored at the refrigeration temperature was placed in the measurement tank (TB) [However, the time (TB) is before the time (TA). If the integral value (ΔHb) of the calorific value between the current time point and the predetermined time point (TA) does not exceed the standard integral value, the safety is judged to be acceptable, while the standard integral value By determining that the safety is unacceptable if
The determination method according to any one of (1) to (3).

The present invention also provides:
(5) A heat sink having a sensor in which a measurement tank of a calorific value measuring device contains a container filled with cooked food stored at a refrigerated temperature and measures the calorific value of the cooked food filled in the container; An air circulation tank that surrounds the outside of the heat sink, a constant temperature water circulation tank that surrounds the outside of the air circulation tank, and a means for maintaining a constant temperature of the heat sink that includes the heat insulating layer that surrounds the outside of the constant temperature water circulation tank, A container filled with cooked food is stored in the heat sink of the measurement tank, the calorific value is measured, and the safety of the cooked food stored at the refrigeration temperature is determined. (1) to (4) Any judgment method; and
(6) The specific heat capacity of the cooked food stored at the refrigerated temperature is the same as that of the food that has been added to the container added with nutrients that promote the growth of microorganisms that propagate in the low temperature range of 0-10 ° C. Use the product without heat of reaction as a reference, and subtract the measured calorific value from the reference (reference) as the noise from the calorific value measured for the cooked food. The determination method according to any one of (1) to (5), wherein the amount is measured;
It is.

In the case of the determination method of the present invention, whether the cooked food stored at the refrigerated temperature has no growth of harmful microorganisms such as bacteria or the like and can be safely eaten at least until its expiration date. Can be accurately determined by a simple operation in a shorter time than in the past.
In the case of the determination method of the present invention, the safety of cooked food stored at a refrigerated temperature can be determined in a short time, so that the cooked food can be shipped after the safety determination is finished. Thus, the market confidence of the cooked food to be shipped can be maintained, and the purchaser can use or eat the cooked food with confidence until the expiration date.

The present invention is described in detail below.
The present invention is a method for determining the safety of a cooked food stored at a refrigerated temperature.
Here, the “refrigeration temperature” in the present invention generally means a temperature of 0 to 10 ° C. The “cooked food stored at a refrigerated temperature” targeted in the present invention is a constant temperature within a range of 0 to 10 ° C. (for example, a constant temperature such as 2 ° C., 5 ° C., 7 ° C. or 10 ° C.). Cooked food that is stored in the oven, or cooked food that is stored at a fluctuating temperature within the range of 0-10 ° C (when the temperature fluctuates within the range of 0-10 ° C during storage). It may be.
In the present invention, “stored at a refrigerated temperature” means refrigerated storage in a stationary state, refrigerated storage in a moving state (distribution, transfer, shipment, sale, etc.), and refrigerated storage in a stationary state. Includes refrigerated storage with both refrigerated storage in the mobile state.
Furthermore, the “cooked food stored at the refrigeration temperature” in the present invention is a food that is stored, distributed, transported, shipped, and sold in a state maintained at the refrigeration temperature after cooking. Any one is acceptable. In addition, the “cooked food” in the present invention may be a food that has been cooked up to the final stage so that it can be eaten as it is or can be eaten simply by heating it with a microwave oven or the like. It may be a food that has been cooked up to this stage.

Typical examples of “cooked foods stored at refrigerated temperatures” include various cooked prepared dishes (boiled foods, fried foods, fried foods, grilled foods, seasoned foods with heat cooking, salads with heat cooking, etc.) Stored, distributed, transported, shipped, sold at refrigerated temperature, cooked food materials other than prepared dishes (for example, boiled bamboo shoots, boiled soybeans, boiled lotus root, etc.) stored at refrigerated temperature, distributed, Examples include those that are transported, shipped, and sold.
More specifically, for example, pumpkin boiled, Chikuzen boiled, meat potato, boiled beans, boiled bamboo shoots, boiled simmered carrots, boiled carrots, boiled sweet potatoes, boiled potatoes, shiitake mushrooms Boiled food, boiled radish, boiled seafood, various cooked Chinese-style boiled meat, meat dumplings, fried food, tempura, fries, cutlet, fried tofu, grilled fish, grilled meat, kinpyra, stir-fried vegetables, fried noodles, salmon flowers, Examples include steamed products such as potato salad, boiled hijiki and shumai, which are stored, distributed, transported, shipped and sold at refrigerated temperatures.

In carrying out the determination method of the present invention, a portion of a cooked food stored at a refrigerated temperature (hereinafter sometimes simply referred to as “refrigerated storage cooked food”) is collected as a sample. Nutrients that promote the growth of bacteria that grow in a low temperature region of 10 ° C. are added and filled into containers.
By adding the nutrients to the sample made of the refrigerated storage cooked food, the safety of the refrigerated storage cooked food can be reliably determined in 12-20 hours shorter than the conventional time. When the calorific value is measured by filling only the refrigerated storage cooked food without adding the nutrients, it is difficult to determine whether the refrigerated storage cooked food is safe in 12 to 20 hours. Therefore, a long time of 40 hours or more is usually required for safety judgment as in the conventional method.

Addition of nutrients to a sample made of refrigerated storage cooked food may be performed at any stage before filling the sample into the container or after filling the sample into the container.
“Nutrients that promote the growth of microorganisms that propagate in the low temperature range of 0 to 10 ° C.” added to the sample may be nutrients that adhere to food and promote the growth of microorganisms that propagate in the low temperature range of 0 to 10 ° C. Any of them may be used, but among them, the growth of heat-resistant bacteria that proliferate in a low temperature range of 0 to 10 ° C. (in particular, one or more bacteria selected from the genus Bacillus, Clostridium, and Streptococcus) is promoted. It is preferable to add the nutrients to be used in a short time and with high reliability because it is possible to reliably determine whether the refrigerated storage cooked food is safe.
As such nutrients, those containing proteins (among them, proteins derived from livestock meat and / or soy proteins are preferred) are preferable. Specific examples include “Nutrient Broth” manufactured by Oxoid, “Tryptic Soy Broth” manufactured by Bacto. "Brain Heart Infusion Broth" manufactured by Difco.
The amount of nutrients added to the sample may vary depending on the type of sample (food that has been refrigerated, cooked and cooked), the type of nutrient, etc., but promotes the growth of thermotolerant bacteria that grow in the low temperature range of 0 to 10 ° C. In the case of the nutrients mentioned above, generally, the nutrient is added at a ratio of 0.5 to 1.5 g, particularly 0.6 to 1 g, with respect to 1 g of the sample prepared from the refrigerated storage cooked food. However, if bacteria or other substances adhere to food that has been cooked and stored in a refrigerator, the growth of the bacteria is promoted, and the calorific value associated with the growth is reliably measured in a short time. It is preferable because it can be surely performed in a short time.

  When filling a sample collected from a refrigerated storage cooked food into a container, if the sample size is too large, it becomes difficult to accurately measure the calorific value, so it is preferable to fill the sample with a size of 10 mm or less. It is more preferable to fill with the size of.

Furthermore, when filling the sample collected from the refrigerated storage cooked food into the container, it is preferable to fill the sample in an amount of about 1 to 3 g per 10 ml of the internal volume of the container.
Alteration and decay of refrigerated cooked food is generally caused by aerobic microorganisms attached to the refrigerated cooked food, but the container is filled with a sample of refrigerated cooked food And oxygen in a container decreases and it becomes difficult to judge safety | security correctly. Specifically, even if there is a lot of microorganisms (mainly aerobic microorganisms) attached to food that has been cooked and stored in a refrigerator and must be judged to have a safety problem, The growth of aerobic microorganisms adhering to refrigerated and cooked foods is suppressed because the inside of the container becomes deficient as it grows, preventing normal growth of microorganisms. The amount of generated heat becomes small, and the amount of generated heat is small, so that it is easy to make an erroneous determination that “there is less adhesion of microorganisms and it is safe”.
On the other hand, if the amount of the sample made of food that has been refrigerated, stored and cooked in a container is too small, it becomes difficult to accurately measure the calorific value, making it difficult to accurately determine safety.

The container filled with the sample containing the refrigerated storage cooked food and the nutrients may be any container that is made of a heat conductive material and can be completely sealed, such as a metal container, a glass container, and the like. Can do.
The size of the container is not particularly limited, and can be determined according to the size of the measurement tank in which the container is disposed. Generally, a container having an internal volume of about 30 to 40 ml is preferably used.
It is preferable that the sample consisting of the refrigerated storage cooked food and the nutrients in the container are filled flat in the container from the viewpoint of more accurate calorific value measurement.

  Samples made of refrigerated cooked foods are filled into a container together with nutrients that promote the growth of bacteria that grow in a low temperature range of 0 to 10 ° C., and then sealed, and the container is kept within a range of 15 to 28 ° C. It is placed in a measurement tank maintained at a temperature, and the calorific value is measured over time. A predetermined time (TA) after 12 to 20 hours have passed since a container filled with refrigerated storage cooked food is placed in the measurement tank. ) To determine the safety of refrigerated and cooked foods based on the amount of heat generated.

The temperature of the measuring tank when the calorific value is measured over time needs to be a constant temperature within the range of 15 to 28 ° C., and should be a constant temperature within the range of 15 to 25 ° C. preferable.
If the temperature of the measuring tank at the time of calorific value measurement is higher than 28 ° C (especially 30 ° C or more), only microorganisms that grow at the refrigeration temperature will proliferate during refrigerated storage of refrigerated and cooked foods. In addition, since microorganisms that do not inherently grow at refrigerated temperatures (0 to 10 ° C.) and that do not cause problems when refrigerated are stored also grow and generate heat at the same time, the measured calorific value grows when stored at refrigerated temperatures. It becomes uncorrelated with the amount of microorganisms, and when the refrigerated storage cooked food that is the object of determination is stored at the refrigeration temperature, there is no growth of microorganisms and it is impossible to determine at least whether it is safe until the expiration date. On the other hand, if the temperature of the measuring tank at the time of calorific value measurement is lower than 15 ° C., even if microorganisms that grow at refrigerated temperature are considerably attached to the refrigerated storage cooked food, It takes a long time to reach the specified calorific value that is the criterion for the presence or absence of safety, and accordingly, it takes a long time to judge the safety of refrigerated, cooked and cooked foods. In addition, accurate determination cannot be made.

As the above-mentioned “predetermined time point (TA)” which is the reference time point for judging the safety of the refrigerated storage cooked food, the container filled with the refrigerated storage cooked food and nutrients is placed in the measurement tank. Within a range of 12 to 20 hours, select a time point at which the determination can be made more accurately according to the expiration date, type, cooking method, cooking conditions, etc. of the refrigerated storage cooked food. TA) ".
The predetermined time (TA) can be generally determined as follows.
That is, in a refrigerated storage cooked food whose expiration date is Y days after the refrigerated storage cooked food is manufactured (cooked), the refrigerated storage cooked food is stored at a refrigeration temperature of 0 to 10 ° C. (for example, 10 ° C. ) Refrigeration so that the number of viable bacteria at the time when Y day has passed after storage is over the safe range (for example, a number exceeding 1.0 × 10 ⁵ cfu per gram of refrigerated storage cooked food) Using the stored cooked food (refrigerated preserved cooked food with safety problems), the refrigerated preserved cooked food is filled into a container together with the nutrients according to the determination method of the present invention, The calorific value was measured over time by placing it in a measuring tank maintained at a constant temperature within the range of 28 ° C. (for example, 25 ° C.), and when the calorific value suddenly increased or the calorific value reached its peak. Point in time You can decide by a point (TA) ", it is preferable that the time when the heat generation amount reaches the peak and" predetermined time (TA) ".
In the case of the determination method of the present invention, the “predetermined time point (TA)” that is a reference time point for determining safety is the refrigerated storage cooked food in the measurement tank of the calorific value measuring device. Since it is the time within the range of 12 to 20 hours after the placement, the safety of the refrigerated storage cooked food can be determined at an early stage.

In determining the safety of the refrigerated storage cooked food according to the amount of heat generated at the “predetermined time point (TA)”,
(A) If the measured value of the calorific value at a predetermined time (TA) does not exceed the reference value, the safety is determined to be acceptable, and if the measured value exceeds the reference value, the safety is determined to be unacceptable. how to;
(B) The integrated value (ΔHa) of the calorific value from the time (T0) to the predetermined time (TA) when the container filled with the refrigerated storage cooked food is placed in the measuring tank exceeds the standard integrated value. The safety is judged to be acceptable if not, and the safety is judged to be unacceptable if the standard integral value is exceeded;
(C) When a certain time has elapsed since the container filled with the refrigerated storage cooked food was placed in the measuring tank (TB) [However, the time (TB) is the time before the time (TA). ] And the integrated value (ΔHb) of the calorific value between the time point and the predetermined time (TA) is judged to be acceptable if the integrated value (ΔHb) does not exceed the standard integrated value, and exceeds the standard integrated value. If the safety is judged to be unacceptable;
And so on.

In the methods (a) to (c) described above, the reference value of the calorific value and the integrated value of the calorific value standard are determined according to the type of food that has been refrigerated, cooked and cooked, the length of its expiration date, etc. it can.
Further, the time point (TB) in the above (c) may be a fixed time point 1 to 10 hours before the predetermined time point (TA), particularly a fixed time point 2 to 8 hours before.
Of the methods (a) to (c) described above, the method (a) described above is based on the measurement value of the calorific value itself at a predetermined time point (TA) (the measured calorific value is a standard calorific value). There is an advantage that it is possible to easily determine the safety of refrigerated, cooked and cooked foods simply by checking whether the quantity value is exceeded.
The methods (b) and (c) are also methods that can be easily implemented after the method (a).

The apparatus for performing the determination method of the present invention is not particularly limited, and any calorific value measuring apparatus that can smoothly carry out the above-described determination method of the present invention can be used.
Among them, the determination method of the present invention includes a heat sink and a heat sink having a sensor for storing a container filled with a refrigerated storage cooked food to which nutrients are added and measuring a calorific value of the refrigerated storage cooked food filled in the container. Smoothly implemented by using a calorific value measuring device comprising an air circulation tank that surrounds the outside of the air circulation chamber, a constant temperature water circulation tank that surrounds the outside of the air circulation tank, and a measurement tank that surrounds the outside of the constant temperature water circulation tank can do.
As an example of the measuring tank in such a calorific value measuring apparatus, there can be mentioned a measuring tank A as shown in FIG.
In FIG. 1, A is a measuring tank, 1 is a container filled with refrigerated storage cooked food with added nutrients, 2 is a sensor 2, 3 for measuring the calorific value of the refrigerated storage cooked food filled in container 1. Is a heat sink, 4 is an air circulation tank, 5 is a constant temperature water circulation tank, 6 is a heat insulation layer, and 7 is a fan.
The calorific value measuring apparatus described above is commercially available, for example, as “Biothermoanalyzer H201” manufactured by Nippon Medical Chemical Co., Ltd. The commercially available calorific value measuring device is usually equipped with a computer at the same time, and the measured calorific value is automatically taken in, analyzed, and displayed in a graph.

  When performing the determination method of the present invention using the calorific value measuring device as described above, temperature irregularities and fluctuations that cannot be prevented by the measurement tank itself may occur. Therefore, noise such as temperature irregularities and fluctuations may occur. In order to accurately measure the calorific value based on refrigerated food that has been cooked and stored refrigerated, the specific heat capacity is equal to that obtained by adding the above nutrients to the food that has been refrigerated and cooked and filled in the container. The heat without the reaction heat is used as a reference (8 in FIG. 1), and the calorific value measured for the control (reference) is used as noise to offset (subtract from) the calorific value measured for container 1 The method of measuring in this way is preferably employed.

The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to the following examples.
In the following example, the measurement of the number of general viable bacteria adhering to the refrigerated storage cooked food was performed as follows.
[Measurement of general viable count]
10 g of refrigerated storage cooked food was weighed, 90 g of sterilized water was added, and a stocking solution was prepared that was stomached at 8 times / second for 60 seconds with a masticator (manufactured by IUL Instruments). The sample stock solution was diluted 10-fold as necessary. Next, 0.1 ml of the sample stock solution was dispensed on the surface of a sterilized standard agar medium (manufactured by Eiken Chemical Co., Ltd.) contained in a sterilized petri dish, and this was uniformly spread on the medium using a large rod. This was cultured at 35 ° C. for 48 hours, and the number of colonies after 48 hours of culture was counted to obtain the number of general viable bacteria (cfu / g).

Example 1
(1) Carrots, beef bowls, dried shiitake mushrooms, dried salmon mushrooms, and onions are each finely chopped, and an appropriate amount of oil is added to the kettle and heated. Stir well while mixing, add seasonings (sugar, soy sauce, miso, sake, soup stock) and stir. The whole kettle was put in a refrigerator and cooled to 10 ° C. or less over about 3 hours. When 10 g of this camellia flower was collected and the number of viable bacteria was measured by the method described above, it was a low value of less than 100 cfu / g.
(2) (i) 100 g of the camellia flower obtained in (1) above was refrigerated for 8 days in a refrigerator at 10 ° C., then taken out of the refrigerator and the number of viable bacteria was measured by the method described above. When it exceeded 10 ⁵ cfu / g (actually 1.1 × 10 ⁵ cfu / g) and the expiration date was 8 days, there was a problem in terms of safety.
(Ii) 100 g of the camellia flower obtained in (i) above was collected, put in an autoclave (temperature 121 ° C.) and sterilized for 15 minutes, and then the number of viable bacteria was measured by the method described above. The value was less than low.
(Iii) Collect 100 g of the camellia flower obtained in (1) above, put it in an autoclave (temperature 121 ° C.) and sterilize it for 15 minutes, and store it in a refrigerator at a temperature of 10 ° C. for 8 days. After taking out and measuring the number of viable bacteria by the above-mentioned method, it was a low value of less than 100 cfu / g, and the blossoms sterilized by autoclave had fungi even when the expiration date was 8 days or 8 days later. The number was very small and passed as a refrigerated preheated food.
(3) were taken UNOHANA 100g obtained in (i) above (1), where after standing at a temperature 25 ° C. 18 hours to measure the number of viable microorganisms in the manner described above, 5.4 × 10 ⁴ cfu / g.
(Ii) 100 g of the camellia flower obtained in the above (1) is collected, put in an autoclave (temperature 121 ° C.) and sterilized for 15 minutes, and left at a temperature of 25 ° C. for 18 hours. When the viable cell count was measured, it was a low value of less than 100 cfu / g.
(4) The results of (1) to (3) above are shown in Table 1 below.

(5) (i) After 5 g of the camellia flower obtained in (1) above is aseptically cut into a size of about 5 mm, it is filled into a 35 ml glass container (glass vial), where it is used as a nutrient. 3 ml of liquid medium containing meat extract (Oxoid “Nutrient Broth medium”) was added and leveled to prepare a non-sterile persimmon flower sample in a glass container [hereinafter referred to as “non-sterile persimmon flower sample (a)”] .
(Ii) Using the same operation as in (i) above, preparing a bud flower sample in a glass container, placing the container in an autoclave (temperature 121 ° C.), sterilizing for 15 minutes, and sterilizing the strawberry flower in a glass container A sample was prepared [hereinafter referred to as “sterile camellia flower sample (b)”].
(Iii) A sample having a specific heat capacity equal to that of the sample to be measured and not accompanied by fine substance growth or heat of chemical reaction is placed in the center of the heat sink as a reference sample (c), and its calorific value history is measured as noise. The true calorific value was measured by subtracting the noise from the calorific value history of each sample to be measured. This time, as the reference sample (c), the same sample as the “sterilized camellia flower sample (b)” was used.
(Iv) The non-sterile boiled flower sample (a) in the glass container prepared in (i) above, the sterile boiled flower sample (b) and the reference sample (c) in the glass container prepared in (ii) above are heated. Placed in the heat sink of a quantity measuring device (“Biothermo Analyzer H-201” manufactured by Nippon Medical Instruments Co., Ltd.), measured the calorific value of three samples over time while maintaining the heat sink temperature at 25 ° C. When the calorific value history of the sample (c) was subtracted, it was as shown in the graph of FIG.
In the graph of FIG. 2, the voltage output from the sensor 2 for measuring the calorific value is the vertical axis, and this is the calorific value for convenience.

(6) (i) As can be seen from the results of Table 1 above, the buds before sterilization collected from the buds produced in (1) above [for the preparation of non-sterile buds in a glass container (a) [Used camellia flowers] had a viable count exceeding 1.0 × 10 ⁵ cfu / g (actually 1.1 × 10 ⁵ cfu / g) when refrigerated for 8 days in a refrigerator at a temperature of 10 ° C. In addition, it is rejected as a refrigerated storage cooked food whose expiration date is 8 days after manufacture.
Then, when the safety of the non-sterilized camellia flower [non-sterilized camellia flower sample (a); refrigerated camellia flower] which is a rejected product is determined by the method of the present invention, it is seen in the graph of FIG. As described above, the calorific value rises sharply when 16 hours have elapsed after being placed in the measurement tank (heat sink).
(Ii) On the other hand, as seen in the results of Table 1 above, bud flowers collected from the bud flowers produced in (1) above and sterilized by autoclave [for the preparation of sterilized bud flower samples in glass containers (b) Oita blossoms], when stored refrigerated for 8 days in a refrigerator at a temperature of 10 ° C., has a low viable bacterial count of less than 100 cfu / g, and is safely distributed as a refrigerated storage cooked food with an expiration date of 8 days after manufacture. Can be sold.
Then, when the safety of the sterilized camellia flower [sterilized camellia sample (b); refrigerated camellia flower] which is an acceptable product is judged by the method of the present invention, the measurement is performed as shown in the graph of FIG. The calorific value remains extremely low even after 20 hours have passed since it was placed in the tank (heat sink).
(Iii) According to the determination method of the present invention, the result of the graph of FIG. 2 shows the safety of the refrigerated storage cooked food (whether the refrigerated storage cooked food is safe at least until the expiration date). The stored cooked food can be quickly and reliably determined at a predetermined time within 12 to 20 hours (18 to 19 hours in this embodiment 1) after placing the food in the measuring tank of the calorific value measuring device. Is backed up.

<< Comparative Example 1 >>
(1) When the same operation as (i) to (iv) in (5) of Example 1 was performed without adding nutrients when filling the glass container with camellia flowers in (1) of Example 1, The results were as shown in the graph of FIG. In the graph of FIG. 3, a ′ is a graph in which the calorific value of the non-sterile camellia flower sample (a) to which no nutrient was added was measured over time, and b ′ was a sterile camellia flower sample (b) to which no nutrient was added. It is the graph which measured the emitted-heat amount of time.
In the graph of FIG. 3, the voltage output from the sensor 2 for measuring the calorific value is the vertical axis, and this is the calorific value for convenience.
(2) As shown in the graph of a ′ in FIG. 3, measurement was performed on a non-sterilized camellia flower [non-sterile camellia flower sample (a) (excluding nutrients); When 20 hours have passed since it was placed in the tank (heat sink), the calorific value increased gently, and it took 24 hours or more to determine safety.

  In the case of the determination method of the present invention, it is possible to accurately determine whether the refrigerated storage cooked food can be safely eaten at least until its expiration date, with a simple operation, in a shorter time than before, and safe. Since the cooked food can be shipped immediately after the determination of the sex is completed, the market confidence for the refrigerated cooked food can be maintained, and the refrigerated cooked food can be heated for a long time until the expiration date. Prepared foods can be sold and contribute to sales promotion.

It is a figure which shows an example of the measurement tank in the calorific value measuring apparatus used with the determination method of this invention. 3 is a graph showing the measurement results of the calorific value over time in Example 1; 6 is a graph showing the measurement results of the calorific value over time in Comparative Example 1;

Explanation of symbols

A Measurement tank 1 Container filled with refrigerated storage cooked food 2 Sensor for measuring calorific value 3 Heat sink 4 Air circulation tank 5 Constant temperature water circulation tank 6 Thermal insulation layer 7 Fan 8 Container filled with reference sample

Claims (6)

  A method for judging the safety of cooked foods stored at refrigerated temperatures, wherein nutrients that promote the growth of microorganisms that grow at low temperatures of 0 to 10 ° C. are added to cooked foods stored at refrigerated temperatures The container filled with cooked food is placed in the measurement tank of the calorific value measuring device, and the temperature of the measuring tank is maintained at a constant temperature within the range of 15 to 28 ° C. The safety of the cooked food according to the amount of heat generated at a predetermined time (TA) 12 to 20 hours after the container filled with the cooked food is measured in time and placed in the measurement tank. A method for determining the safety of cooked food stored at a refrigeration temperature of 0 to 10 ° C.   The determination method according to claim 1, wherein the microorganism that propagates in a low temperature range of 0 to 10 ° C is a heat-resistant bacterium that propagates at 0 to 10 ° C.   The determination method according to claim 1 or 2, wherein a filling amount of the cooked food stored at a refrigeration temperature in the container is 1 to 3 g per 10 ml of the internal volume of the container. Judgment of safety by the amount of heat generated at a given time (TA)
(A) If the measured value of the calorific value at a predetermined time (TA) does not exceed the reference value, the safety is determined to be acceptable, and if the measured value exceeds the reference value, the safety is determined to be unacceptable. Do by doing;
(B) The integrated value (ΔHa) of the calorific value from the time (T0) to the predetermined time (TA) when the container filled with the cooked food stored at the refrigeration temperature is placed in the measurement tank is the reference By determining that the safety is acceptable if the integrated value is not exceeded, while determining that the safety is unacceptable if the integrated value is exceeded; or
(C) When a certain time has elapsed since the container filled with the cooked food stored at the refrigeration temperature was placed in the measurement tank (TB) [However, the time (TB) is before the time (TA). If the integral value (ΔHb) of the calorific value between the current time point and the predetermined time point (TA) does not exceed the standard integral value, the safety is judged to be acceptable, while the standard integral value By determining that the safety is unacceptable if
The determination method according to claim 1.   A heat sink having a sensor in which a measurement tank of a calorific value measuring device contains a container filled with cooked food stored at a refrigerated temperature and measures the calorific value of the cooked food filled in the container, and the outside of the heat sink Means for maintaining a constant temperature of the heat sink comprising an air circulation tank that surrounds the air circulation tank, a constant temperature water circulation tank that surrounds the outside of the air circulation tank, and a heat insulating layer that surrounds the outside of the constant temperature water circulation tank, 5. The safety of cooked food that is stored at a refrigerated temperature by measuring a calorific value in a container filled with the cooked food in a heat sink is determined. Judgment method.   The specific heat capacity of the cooked food stored at refrigerated temperature is the same as that of the food that has been added to the container added with nutrients that promote the growth of microorganisms that grow in the low temperature range of 0-10 ° C. A heating value of a cooked food is measured by using a non-accompanied material as a control and subtracting a measured value of the calorific value by the control as a noise from a calorific value measured for the cooked food. The determination method according to any one of the above.

Images