JP4282746B1 - Method for producing frozen fish that can be cooked frozen and frozen fish - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing frozen fish and a frozen fish that are delicious even when cooked frozen, are soft, do not have a foul odor, do not produce a card, and save labor for cooking.
SOLUTION: A fish body is immersed in an alkaline aqueous solution adjusted to pH 7.1 or more and 11.5 or less at atmospheric pressure and room temperature for a predetermined time, and the alkali-treated fish body is frozen.
[Selection figure] None

Description

  The present invention relates to a method for producing frozen fish that can be cooked frozen and to frozen fish.

  Frozen fish is cooked over the hands of consumers after being stored and stored for a certain period of time using, for example, a frozen storage technique described in Patent Document 1. Consumers devise various ideas for cooking frozen fish, but the common place for preparation before cooking is to use frozen or half-thawed frozen fish.

For example, Non-Patent Document 1 describes that by thawing frozen fish well, it is possible to provide a taste and appearance comparable to fresh fish and shellfish.
JP 11-164649 A "Professional Menu Handbook" by Yasuko Nagako, Frozen Food Newspaper, published July 31, 1997, pages 8-18

  However, frozen fish have unique problems not found in fresh seafood. According to the said nonpatent literature 1, in order to produce the problem of the following (i)-(iV), it was necessary to start cooking after thawing frozen fish half or thawed completely.

(i) An ice film (glaze) on the surface
(ii) Hard and hard
(iii) The fishy odor unique to fish remains
(iV) Water-soluble protein (curd) appears significantly when heated, resulting in white turbidity and poor appearance. For example, if glaze adheres to the surface, it will interfere with seasoning and heating, so it takes a long preparation time before cooking. It takes time and effort.

  In addition, the water-soluble protein exudes from the cells together with moisture during thawing and heating, so that there is a drawback that the body becomes stiff, is puffy (not juicy), and the taste is halved.

  Moreover, when freezing and thawing | decompressing conventional frozen fish many times, there exists a problem that freshness falls and it is worried about the raw odor of fish.

  Furthermore, when a conventional frozen fish is heated, the card may adhere to the surface, the appearance is impaired, the appearance is deteriorated, and the commercial value is lowered.

  Because of these drawbacks, frozen fish tend to be refrained by consumers as they tend to be hard to cook and have a bad taste and appearance.

  The present invention has been made in order to solve the above-mentioned problems, can solve the problem of glaze when cooking, is delicious even when frozen while being frozen, is soft, does not smell, does not come out of cards, and hassle of cooking An object of the present invention is to provide a method for producing frozen fish and a frozen fish that can eliminate the above.

The method for producing frozen fish that can be cooked while frozen, according to the present invention, includes: (a) a step of immersing the fish body in an alkaline aqueous solution adjusted to pH 8.6 or more and 11.5 or less at atmospheric pressure and room temperature for 30 minutes or more ; and b) a step of freezing the alkali-treated fish body.

The frozen fish that can be cooked while frozen according to the present invention is immersed in an alkaline aqueous solution adjusted to pH 8.6 to 11.5 at an atmospheric pressure and room temperature for 30 minutes or more at pH 8.6 to 11.5. It consists of a fish body frozen after being adjusted to the following .

  The important terms in this specification are defined as follows.

  The “curd” refers to a phenomenon in which a water-soluble protein in fish meat is solidified by heating and adheres to the surface, and the white turbid unnecessary matter that impairs the appearance, or a phenomenon that appears on the surface of the fish meat.

  A “glaze” is a thin ice film that covers the surface of a fish to preserve its quality (freshness), taste (grease) and nutrition at each stage where frozen fish is produced, stored and distributed. That means.

  “Chlorella extract” refers to a chlorella extract. The chlorella extract contains various water-soluble components extracted from chlorella powder using various extraction methods, such as amino acids, peptides, water-soluble vitamins, saccharides, nucleic acids, water-soluble proteins, and the like.

  “Mackerel” is a general term that includes all kinds of mackerel such as mackerel and sesame.

  According to the present invention, frosting can be prevented by water retention and vacuum packaging, so there is no need to attach glaze to the fish. Because it is not necessary to remove the glaze, it can be boiled, baked or cooked while frozen. In addition, the water retention of the fish is increased, making the body juicy and soft.

  Further, according to the present invention, since the water-soluble protein (card) that is seen after heating does not appear, it becomes possible to provide a cooked product that has an excellent appearance and a clean appearance.

  In addition, since the solidification of the protein after heating is reduced, the heating rate is increased by molecular vibrations, and it becomes easy to get burnt, and the heating time can be shortened.

  Furthermore, according to the present invention, the raw odor of fish is eliminated by the deodorizing effect of the chlorella extract. Moreover, the taste of fish can be effectively drawn out by the seasoning effect of the chlorella extract.

  Furthermore, according to the present invention, water retention can be strengthened by immersion in an aqueous solution in which saccharides are dissolved, muscle fibers can be prevented from being broken, and the qualities can be protected.

  The method for producing frozen fish that can be cooked frozen according to the present invention includes (a) a step of immersing a fish body in an alkaline aqueous solution adjusted to pH 7.1 or more and 11.5 or less at atmospheric pressure and room temperature for a predetermined time, and (b) Freezing the alkali-treated fish body. In addition, the frozen fish that can be cooked while frozen according to the present invention is frozen after being immersed in an alkaline aqueous solution adjusted to pH 7.1 or higher and 11.5 or lower at atmospheric pressure and room temperature for a predetermined time.

  In the present invention, it is necessary to adjust the alkaline aqueous solution to pH 7.1 or more and 11.5 or less. This is because when immersed in a neutral or acidic solution having a pH lower than 7.1, the water retention capacity of the cells is lowered and the water-soluble protein exudes from the cells, and the body becomes dry and hard ((2) in FIG. 1). . Also, the water-soluble protein that has oozed out on the surface becomes a cloudy card when heated and adheres to the surface of the fish body, and deteriorates the appearance ((1) C in FIG. 1). On the other hand, when immersed in a strongly alkaline solution having a pH exceeding 11.5, the taste of the meat becomes bitter. Furthermore, it is most preferable to adjust the pH of the alkaline aqueous solution to a range of pH 9.8 ± 1.2 (pH 8.6 to 11.0). pH 9.8 is where the water retention of the cells is optimal, the gap between muscle fibers spreads, moisture enters the gap between the spread muscle fibers, and the flesh becomes soft and juicy (see FIG. 3). (4), FIG. 6, FIG. 7).

  In the present invention, the fish body is soaked in an alkaline aqueous solution at atmospheric pressure and room temperature. However, even if it is at room temperature, it is necessary to perform minimum temperature management according to changes in the air temperature. For example, it is desirable to control the temperature so that the temperature (core temperature) of the fish body is preferably plus 1 to 25 ° C., more preferably plus 3 to 10 ° C., and most preferably plus 3 to 5 ° C. Therefore, it is desirable that the soaking process is performed in an air-conditioned room whose temperature is adjusted by an air conditioner. Further, in the present invention, the pressure at the time of soaking is set to atmospheric pressure, but the present invention is not limited to 1 atmospheric pressure, and may be under a reduced pressure slightly below 1 atmospheric pressure according to changes in weather. The pressure may be slightly higher than the atmospheric pressure.

  In the present invention, the alkaline aqueous solution contains, by mass%, sodium hydrogen carbonate 0.1 to 5.0%, sodium carbonate 0.1 to 5.0%, and trisodium citrate 0.01 to 1.00%. Is preferred. This is because if the sodium hydrogen carbonate content is less than 0.5%, the sodium carbonate content is less than 0.5%, and the trisodium citrate content is less than 0.1%, the desired alkalinizing effect on the fish meat cannot be obtained. On the other hand, when sodium hydrogen carbonate exceeds 5.0%, sodium carbonate exceeds 5.0%, and trisodium citrate exceeds 1.00%, fish meat becomes bitter.

  The three components of sodium hydrogen carbonate, sodium carbonate, and trisodium citrate can be adjusted to a desired value by changing the blending ratio, and water can be provided with a buffering force to maintain the pH on the alkali side. There is an effect of increasing the compatibility and increasing the water retention. In addition to these main components, chlorella, saccharides, salt and the like described later can be further added to the alkaline aqueous solution.

  In the present invention, it is preferable to immerse the fish in an aqueous solution containing a chlorella extract having a concentration of 0.1 to 20% by mass for a predetermined time before the freezing step (b). Chlorella is an active ingredient having both a deodorizing action and a seasoning action. This is because if the chlorella concentration in the chlorella extract-containing aqueous solution is less than 0.1% by mass, the desired deodorizing effect and seasoning effect cannot be obtained. On the other hand, when the chlorella concentration in the liquid exceeds 20% by mass, the effect is saturated. Here, the deodorizing action refers to the property of eliminating the odor of fish meat. Seasoning action refers to the property of further extracting the original taste of fish meat. The seasoning effect of chlorella has a role to enhance the taste of fish meat when combined with a seasoning such as salt. The immersion time in the chlorella solution is preferably the same as the immersion time (30 minutes or more and 48 hours or less) in the alkalizing treatment. This is because it is possible to add and mix the chlorella extract in an alkaline aqueous solution and soak it. Of course, the chlorella solution can be separately soaked separately from the alkaline aqueous solution. The timing of immersing the chlorella solution may be before or after the alkaline aqueous solution immersing process.

  In the present invention, it is preferable to immerse the fish in a saccharide-containing aqueous solution having a concentration of 0.01 to 20% by mass for a predetermined time before the freezing step (b). Saccharides are an active ingredient having an action of protecting muscle fibers and an action of increasing water retention. As the saccharide, trehalose, reduced starch syrup, maltose, lactose, sucrose and the like can be used. When the saccharide concentration in the liquid is less than 0.01%, desired muscle fiber protection effect and water retention effect cannot be obtained. On the other hand, when the saccharide concentration in the liquid exceeds 20% by mass, the effect is saturated. The immersion time in the saccharide solution is preferably the same as the immersion time (30 minutes to 48 hours) in the alkalizing treatment. This is because it is possible to add and mix saccharides in an aqueous alkali solution and soak it. Of course, the saccharide solution can be separately soaked separately from the alkaline aqueous solution. The timing of immersing the saccharide solution may be before or after the alkaline aqueous solution immersing process.

  Sodium chloride can be contained in the alkaline aqueous solution in an amount of 0.1 to 5.0% by mass. Salt has a preservation and seasoning effect. Salt is also contained in the chlorella extract. When the salt concentration is less than 0.1%, the desired storage effect and seasoning effect cannot be obtained. On the other hand, if the salt concentration exceeds 5.0%, the fish becomes salty and the taste of fish is impaired. In addition, it is most preferable that the salt concentration is about 1.0% in order to obtain the preservation effect and the seasoning effect, and further obtain the seasoning effect with the chlorella.

  In the present invention, in the alkali treatment step (a), the immersion time in the alkaline aqueous solution can be 30 minutes or more and 48 hours or less. The soaking time can be from 30 minutes to 48 hours, more preferably from 30 minutes to 180 minutes (3 hours), and most preferably from 1 hour to 180 minutes (3 hours). For most fish species, a sufficient effect can be obtained by soaking for 3 hours or less, but the soaking time can be extended beyond 3 hours depending on the type of fish and the fish body. However, the effect of the soaking process is saturated in 48 hours, and further soaking is unacceptable from the viewpoint of productivity, so the longest soaking time is set to 48 hours. On the other hand, if the soaking time is less than 30 minutes, the effect of the present invention cannot be obtained or is difficult to obtain. Increasing the osmotic pressure of the alkaline aqueous solution to the fish body by increasing the temperature and pressure at the time of soaking may further reduce the soaking time, but the increase in temperature and pressure may cause damage to the cells and deterioration Can not be adopted.

  In the present invention, in the alkali treatment step (a), it is desirable to immerse the thawed fish in an alkaline aqueous solution. The above deodorizing effect is particularly effective when the frozen fish is used as a raw material. Of course, fresh fish may be used as a raw material in the present invention.

  In the present invention, in the freezing step (b), it is desirable not to glaze the surface of the fish body by vacuum packaging. Because there is no glaze, you can cook and bake it while it is frozen.

  In the present invention, it is desirable to remove bone from the fish before the alkali treatment step (a). This is because the bone removal process facilitates the infiltration of the alkaline aqueous solution into the fish body.

  The fish species to which the present invention is applied are widespread regardless of whether they are red fish (sardine, mackerel, sanma, bonito, etc.), white fish (flounder, flounder, etc.), and intermediate fish (aji, isaki, etc.). For various fish, such as mackerel (Norwegian), mackerel (made in Japan), sardine, sanma, bonito, golden garai, karasu galley, mandarin, assistant sect, white thread, cocoon, sawara, red A wide range of fish, rockfish, sword fish, catfish, Nile perch, oyster crab. Moreover, although the form of the fish body to which this invention is applied has various forms, such as a round, a dress, a fillet, and a fillet, this invention is applicable also to those all forms.

  Next, an example of the manufacturing method of the frozen fish of this invention is demonstrated.

  Here, an example using frozen fish as a starting material will be described, but the present invention is not limited to this, and fresh fish that is not frozen can also be used as a starting material. First, thaw or half-thaw frozen fish. The thawing conditions are controlled so that the temperature (core temperature) at the center of the fish body is minus 2 ° C. or more and plus 5 ° C. or less. Grate three thawed fish and remove major bones. The skin may be left on or peeled off. For example, when processing mackerel, the skin can be peeled off before being soaked, and the penetration of the alkaline aqueous solution into the fish can be accelerated. The mackerel thin skin is located on the outermost surface of the skin, and even if this is removed, the mackerel's unique striped pattern remains, so that the mackerel's original appearance can be maintained as it is.

  Next, the fish is immersed in a predetermined alkaline aqueous solution. The frozen fish meat is first frozen. The primary freezing condition is controlled so that the temperature (core temperature) at the center of the fish body is minus 10 ° C. or less, preferably minus 18 ° C. or less. Fish meat is processed to the desired size in the primary frozen state. Filled with processed vacuum fillet in a special vacuum packaging bag and vacuum packed. Secondary freeze the bagged fish. The secondary freezing condition is controlled so that the temperature (core temperature) at the center of the fish body is minus 15 ° C. or less, preferably minus 18 ° C. or less. The secondary frozen fish meat packed in the vacuum packaging pack in this way is further packed in a shipping box.

  Hereinafter, embodiments of the present invention will be described in comparison with comparative examples with reference to the accompanying drawings and tables.

  FIG. 1 is an appearance photograph showing mackerel samples (after heating) of Examples and Comparative Examples adjusted to various pHs. FIG. 2 is a photograph showing the measured values displayed on the pH meter when the pH of the mackerel sample in FIG. 1 is measured. FIG. 3 is a photomicrograph showing cell structures of mackerel samples (raw and heated) of Examples and Comparative Examples adjusted to various pHs. FIG. 4 is a photomicrograph showing cell structures of mackerel samples (raw and after heating) of the examples to which saccharides were added.

  An example of the components (mass%) of the alkaline aqueous solution is shown below.

Sodium bicarbonate; 1.20%
Sodium carbonate; 1.26%
Trisodium citrate; 0.24%,
Other additives; 0.30%
[Card Evaluation]
The presence or absence of card generation from the fish sample was evaluated by visual inspection. Various samples were prepared by immersing the mackerel in aqueous solutions having various pH values and adjusting the pH to pH 4.5, pH 7.0, pH 9.8, and pH 11.5, respectively. As a fish sample of the example, a frozen mackerel that was not thawed was used, and as a fish sample of the conventional example, a mackerel that was heated after thawing was used. Each frozen mackerel sample was heated in a steam convection oven at 260 ° C. for 270 seconds.

  In the sample (pH 4.5) in FIG. 1 (1) C, a card (white viscous material) was formed and adhered to the back side of the abdomen, and an appearance defect was recognized. The appearances of the other samples were all good.

  As shown by surrounding circles in the cell tissue photographs of the sample before heating and the sample after heating in FIG. 3 (1), the conventional example (without alkaline immersion treatment, pH 7.0) is the cause of the card that impairs the appearance. It was found that there was a lot of water-soluble protein. In the tissue, dark colored portions indicate muscle fibers, and light colored portions indicate proteins having no structure, that is, water-soluble proteins. Moreover, a white part is a space | gap and shows that there existed moisture in this part.

  On the other hand, it was recognized that the four patterns ((2), (3), (4), and (5) in FIG. 3) that were soaked in the alkaline solution had a small amount of water-soluble protein causing the card. From this, the example sample is almost free of water-soluble protein, and it is possible to prevent the exposure of the card, which looks bad like the conventional example sample. Further, in the sample of the example, the protein coagulation after heating is reduced, so that the heating speed is increased by molecular vibration, the scorch is easily formed, and the heating time can be shortened.

  Moreover, even if it is soaked, the water-soluble protein disappears as it moves from pH 7.0 to the acidic side or the alkaline side. This is also clear from the analysis results in Table 1. That is, it was recognized that the protein decreased in the sample after heating in the example as compared with the sample in the conventional example. The more the acid side or the strong alkali side is reached, the more the curd is not generated, but the bitterness appears when the side is too strong, so pH 9.8 shown in FIG. 3 (4) is the most preferred embodiment. .

  Also, from the cell tissue of the sample in FIG. 4, it is recognized that in the sample soaked in an aqueous solution in which saccharides are dissolved, moisture enters between the muscle fibers and the shape of the muscle fibers themselves is kept clean. It was. Therefore, water retention can be strengthened by immersing fish meat in an aqueous solution in which saccharides are dissolved. In addition, the muscle fibers were destroyed and caused the sag due to repeated freezing and thawing as in the conventional product, but in the example sample, the sag is reduced to prevent the muscle fibers from being destroyed. Can do. It can also protect against oxidation of the body due to freezing.

[Evaluation of water retention]
The water retention of fish meat was evaluated by microscopic observation.

  A heated mackerel was used as a fish sample. After heating, the mackerel was immersed in aqueous solutions with various pH values, and various samples were prepared by adjusting the pH to pH 4.5, pH 7.0, pH 9.8, and pH 11.5, respectively. Saba fillet (raw fish before heating) is fixed with paraffin to make a solid sample, cut thinly with a knife in a direction crossing the muscle cells of the same sample to prepare a paraffin section, and the prepared paraffin section is stained. The sample was pasted on a slide, and the structure was observed with an optical microscope. The results are shown in the left column of FIG. Paraffin sections were similarly prepared for the fillets (fish meat after heating) of the same mackerel sample heated, and the tissue was observed with an optical microscope. The results are shown in the right column of FIG.

  As the pH increased, the spacing between the muscle fibers increased in both the pre-heating sample and the post-heating sample, and it was confirmed that moisture entered the gap. It is clear from the moisture analysis results in Table 1 that the water retention improves as the pH increases.

[Evaluation of softness]
The softness of various fish meats was evaluated by the plunger indentation method. The plunger push-in method is a test method that continuously measures the time-dependent changes in load and distortion when the plunger is pushed into fish meat until the load reaches a predetermined set value. The plunger push-in method includes a breaking test method using a wedge-shaped plunger P1 shown in FIG. 5A and a compression test method using a cylindrical plunger P2 shown in FIG. 5B. . Among these, the fracture test method is a test for measuring the force applied when the sharp tip of the wedge-shaped plunger P1 is bitten into the fish meat and the distortion generated at that time, assuming that the fish meat is bitten with the front teeth. The compression test method is a test for measuring the force applied when the bottom surface of the cylindrical plunger P2 is pushed into the fish meat and the strain generated at that time, assuming that the fish meat is bitten with the back teeth.

  A creep meter (Sanden Co., Ltd., break measuring machine; model number RE-3305B) was used as a measuring instrument. Measurement was performed by setting the plunger pushing speed to 1 mm / sec. The target fish species were mackerel galley and assistant sect. All fish species were boiled at 95 ° C. for 10 minutes, cooled to room temperature (30 ° C.), and cut into 2 cm × 2 cm pieces to prepare samples.

(1) Results of evaluation of softness of mackerel FIG. 6 and Table 2 show the results of fracture tests of mackerel samples. The characteristic line E1 in the figure shows the result of the example sample 4-2 subjected to the immersion treatment for 180 minutes, and the characteristic line C1 shows the result of the comparative example sample 6-2 not subjected to the immersion treatment. The former fracture energy was 106661.1 J / m ³ , whereas the latter fracture energy was 205472.7 J / m ³ , and the former fractured at about 51.4% of the latter energy. It was.

FIG. 7 and Table 2 show the compression test results of the mackerel sample. The characteristic line E2 in the figure shows the result of the example sample 4-2 subjected to the immersion treatment for 180 minutes, and the characteristic line C2 shows the result of the comparative sample 6-2 not subjected to the immersion treatment. The former fracture energy was 1,5342.3 J / m ³ , whereas the latter fracture energy was 24145.7 J / m ³ , and the former fractured at about 63.5% of the latter energy. It was.

  From the above, it was confirmed that the mackerel processed by the method of the present invention was soft.

(2) Results of evaluation of softness of glass galley FIG. 9 and Table 3 show the results of fracture tests of glass galley samples. The characteristic line E3 in the figure shows the result of the example sample 7 that has been dipped for 180 minutes, and the characteristic line C3 shows the result of the comparative example sample 8 that has not been dipped. The former fracture energy was 88935.4 J / m ³ , whereas the latter fracture energy was 130230.9 J / m ³ , and the former fractured at about 68.9% of the latter energy. It was.

FIG. 10 and Table 3 show the compression test results of the galley sample. The characteristic line E4 in the figure shows the result of the example sample 7 that has been dipped for 180 minutes, and the characteristic line C4 shows the result of the comparative example sample 8 that has not been dipped. The former fracture energy was 7285.8 J / m ³ , whereas the latter fracture energy was 11739.9 J / m ³ , and the former fractured at about 62.1% of the latter energy. It was.

  From the above, it was confirmed that the body of the glass that was treated by the method of the present invention was soft.

(3) Softness evaluation result of assistant sect Fig. 11 and Table 4 show the fracture test results of the assistant sword sample. The characteristic line E5 in the figure shows the result of the example sample 9 that has been dipped for 180 minutes, and the characteristic line C5 shows the result of the comparative example sample 10 that has not been dipped. The former fracture energy was 311353.8 J / m ³ , whereas the latter fracture energy was 407450.9 J / m ³ , and the former fractured at about 76.4% of the latter energy. It was.

FIG. 12 and Table 4 show the results of the compression test of the sample of the assistant sect. The characteristic line E6 in the figure shows the result of the example sample 9 that has been dipped for 180 minutes, and the characteristic line C6 shows the result of the comparative example sample 10 that has not been dipped. It was found that the fracture energy of the former was 11654.6 J / m ³ , whereas the fracture energy of the latter was 17294.3 J / m ³ , and the former fractured at about 67.4% of the energy of the latter. It was.

  From the above, it was confirmed that the assistants treated by the method of the present invention were soft.

  A conventional sample shown by arrows in FIG. 8A is collagen that connects muscle fibers, that is, collagen fibers. Collagen fiber is a tissue that causes a person to feel hard (a hard texture) when eating fish meat. The collagen fiber cut | disconnected by the part enclosed by the line in FIG. 8 (2) which is an Example sample is recognized. From these facts, it was proved that the example samples subjected to the treatment of the present invention were soft.

[Odor evaluation]
Fish odor (freshness) was evaluated by measuring volatile base nitrogen (VBN) values. It is known that volatile basic nitrogen (VBN) compounds are one type of septic amines produced when seafood rots. VBN compounds contain volatile amines such as ammonia, dimethylamine (DMA), trimethylamine (TMA), piperidine acetaldehyde, etc. Odor that can quantitatively measure these VBN compounds at once (freshness) There is a micro-diffusion method as a determination method. In the micro-diffusion method, VBN generated when the sample is made alkaline is collected in a standard acid solution and quantified. According to the food hygiene inspection guideline RIKEN p269-271 (1991), it is shown that the determination is made as follows according to the quantified VBN value. Also in the present invention, the odor of the sample was evaluated in accordance with such general judgment criteria.

VBN value judgment 5-10 Nmg% (mg / 100 g) → Very fresh fish 15-20 Nmg% (mg / 100 g) → Normal fresh fish 30-40 Nmg% (mg / 100 g) → Early spoiled fish 50 Nmg% (mg / 100g) or more → Corrupted fish meat The case where the VBN value of a fish sample is quantitatively measured by the micro-diffusion method will be briefly described.

  Water and trichloroacetic acid are added to the chopped fish meat sample and homogenized for a predetermined time. The homogenate is rinsed into a volumetric flask with water, mixed at a constant volume, and allowed to stand for a predetermined time. This is filtered through a coarse filter paper, and the filtrate is used as a test solution.

  Boric acid absorbent is injected into the inner chamber of the Conway diffuser, and the above test solution is injected into the outer chamber. Apply a small amount of airtight agent to the lid part and place it on the container of the Conway diffuser. Move it so that the tip of the pipette can be inserted. Pour a saturated solution of potassium carbonate from the pipette into the outer chamber and close the lid to seal.

  Next, the Conway diffuser is gently turned in the horizontal direction to mix the test solution in the outer chamber and the saturated potassium carbonate solution, and then left on a horizontal table. The lid is removed after standing for a predetermined time, and the absorbent in the inner chamber is titrated with dilute sulfuric acid. The end point is detected by observing the color change of the solution, and this is used as a titration value. The VBN value is determined using the titration value and a predetermined formula.

  Table 5 shows the results of odor evaluation by VBN measurement using the micro-diffusion method. In any of the samples 11 to 14, the VBN value was less than 10 N mg% (mg / 100 g), and it was confirmed that it was in the numerical range of “very fresh fish meat”. The example samples 11, 12, and 13 immersed in the chlorella extract aqueous solution all had lower VBN values than the comparative sample 14 that was not immersed. Further, it was found that the VBN value was lower when the amount of chlorella added was larger among the sample samples 11, 12, and 13.

From the above, it was confirmed that when immersed in an aqueous solution to which a chlorella extract was added, there was a deodorizing effect, and the effect increased as the amount of chlorella added increased.

The external appearance photograph which shows the mackerel sample (after a heating) of the Example adjusted to various pH and a comparative example, respectively. The photograph which each shows the measured value displayed on the pH meter when measuring the pH of the mackerel sample of FIG. The microscope picture which shows the cell structure | tissue of the mackerel sample (raw and after heating) of the Example and comparative example which were adjusted to various pH, respectively. The microscope picture which shows the cell structure | tissue of the mackerel sample (raw and after heating) of the Example which added saccharides, respectively. (A) is a perspective view which shows the wedge-shaped plunger for a fracture test, (b) is a perspective view which shows the cylindrical plunger for a compression test. The characteristic line figure which shows the fracture test result of a mackerel sample (after heating). The characteristic line figure which shows the compression test result of a mackerel sample (after heating). The microscope structure photograph which contrasts and shows the cell structure of the mackerel sample (raw and after heating) of an Example and a comparative example. The characteristic line figure which shows the fracture | rupture test result of a glass galley sample (after heating). The characteristic line figure which shows the compression test result of a glass galley sample (after heating). The characteristic line figure which shows the fracture test result of a sample (after heating). The characteristic line figure which shows the compression test result of a sample (after heating).

Claims (10)

(A) a step of immersing the fish body in an alkaline aqueous solution adjusted to pH 8.6 or more and 11.5 or less at atmospheric pressure and room temperature for 30 minutes or more ;
(B) freezing the alkali-treated fish body;
A method for producing frozen fish that can be cooked while frozen.   The method according to claim 1, wherein the fish is immersed in an aqueous solution containing a chlorella extract having a concentration of 0.1 to 20% by mass for a predetermined time before the freezing step (b).   The method according to claim 1, wherein the fish body is soaked in a saccharide-containing aqueous solution having a concentration of 0.01 to 20% by mass for a predetermined time before the freezing step (b).   The method according to any one of claims 1 to 3, wherein in the alkali treatment step (a), the immersion time in the alkaline aqueous solution is 30 minutes or more and 48 hours or less.   5. The method according to claim 1, wherein in the alkali treatment step (a), the alkaline aqueous solution is adjusted to a pH range of 9.8 ± 1.2.   The alkaline aqueous solution contains, by mass%, sodium hydrogen carbonate 0.1 to 5.0%, sodium carbonate 0.1 to 5.0%, and trisodium citrate 0.01 to 1.00%. The method according to any one of claims 1 to 5.   The method according to any one of claims 1 to 6, wherein in the alkali treatment step (a), a thawed or semi-thawed fish is soaked in the alkaline aqueous solution.   The method according to any one of claims 1 to 7, wherein in the freezing step (b), the surface of the fish body is not glazed by vacuum packaging.   The method according to any one of claims 1 to 8, wherein bone is removed from the fish body before the alkali treatment step (a). It is composed of a fish that has been frozen after being adjusted to pH 8.6 or more and 11.5 or less by immersing it in an alkaline aqueous solution adjusted to pH 8.6 or more and 11.5 or less at atmospheric pressure at room temperature for 30 minutes or more. Frozen fish that can be cooked while frozen.

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