JP7109752B2 - Processing method of aged fish - Google Patents

Description

The present invention relates to a method for processing aged fish.

It has long been known that vinegar has an antibacterial effect on many microorganisms (see, for example, Non-Patent Documents 1 and 2). The antibacterial action of vinegar is divided into bactericidal action and bacteriostatic action by acetic acid. The bactericidal action of acetic acid is disclosed, for example, in Non-Patent Documents 3 and 4.

However, most of the bactericidal effects of vinegar disclosed in the above documents are evaluated from the number of bacteria before and after immersing each food in vinegar or the change in spoilage products produced by the growth of bacteria. Little mention is made of the effects of food quality on food quality.

Minoru Ameyama, Shigeru Otsuka (editors). Series <Science of Food> Science of Vinegar. Asakura Shoten Co., Ltd., Tokyo, October 1, 1994 3rd printing. 4. Food Chemistry of Vinegar 178-202 Toshio Matsuda (Author), Chemistry of Food Microbial Control. Co., Ltd. Sachi Shobo, Tokyo, 1998/2/25 First edition 1st printing. IV Substances not primarily intended for food preservation or sterilization 2 Organic acids and their salts 104-132 Toshisada Shimizu, Ryoichi Suzuki, Akira Degawa. "On the Survival Period of Several Pathogenic Bacteria and Food Poisoning Bacteria in Seasonings". Journal of Japan Food Industry Association, Vol. 9, 1962, 10-12. Etsuzo Tsuburaya, Kunihiko Shibata, Yoshiya Kawamura, Hiroyuki Masai. "About the bactericidal action of mixed vinegar". Journal of Japan Food Industry Association, Vol. 28, 1981, 387-392

By the way, the use of vinegar for fresh fish has long been known in the processing of pickled marine products such as shime mackerel. , It is common to pickle in the final stage of processing. In such a method, the fish meat is directly exposed to vinegar, so that the pH of the fish meat is immediately lowered, which accompanies acid denaturation of the fish meat proteins, making the fish meat cloudy and accompanied by a decrease in water retention. From the above, there is a problem that the conventional pickling conditions cannot be applied as they are as a processing technique for improving the storage stability of fresh fish while maintaining raw quality, that is, as a method for processing aged fish.

The present invention has been made in view of the circumstances described above, and one of its objects is to provide a highly safe method for processing aged fish that retains its raw quality.

A method for processing aged fish according to one aspect of the present invention includes a raw vinegar immersion step of immersing fresh fish in vinegar containing acetic acid, a salting step of washing the fresh fish immersed in vinegar and immersing it in salt water, and a drying step of drying the soaked fresh fish.

According to the present invention, it is possible to provide a highly safe aged fish processing method that retains raw quality.

FIG. 4 is a diagram showing changes in acetic acid concentration in skin and muscle of fresh fish due to immersion in raw vinegar. FIG. 4 is a diagram showing changes in acetic acid concentration in the skin of fresh fish immersed in raw vinegar, which accompanies washing with water and immersion in salt water. FIG. 4 is a diagram showing the effect of salt concentration during raw vinegar immersion treatment on acetic acid concentration in the skin of fresh fish after water washing and salt water immersion. FIG. 4 is a diagram showing changes in fish body weight ratio due to drying. FIG. 4 is a diagram showing the inhibitory effect of immersion in raw vinegar on the increase in the number of bacteria in the skin of stored fresh fish. FIG. 4 is a diagram showing changes in K ion concentration in red sea bream aged fish meat with the passage of time after death. FIG. 4 is a diagram showing changes in Na ion concentration in aged red sea bream fish meat over time after death. FIG. 4 is a diagram showing an increase in the concentration of total free amino acids in aged red sea bream meat with the passage of time after death.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[First embodiment]
The present embodiment provides a highly safe aged fish processing method that maintains raw quality by appropriately controlling the following three conditions (1) to (3) for processing aged fish. is one purpose. In the following description, vinegar containing about 4.2% acetic acid is called raw vinegar.
(1) Raw vinegar immersion time and salt concentration contained in raw vinegar when immersing fresh fish in raw vinegar from which gills, viscera, heads and scales have been removed (2) Raw vinegar immersion (3) Drying conditions for salted fresh fish

Through such a series of processing treatments, the progress of putrefaction that occurs during refrigerated storage of fresh fish is greatly retarded, and the increase in the free amino acid concentration in the fish meat and the slight increase in the salt concentration in the fish meat improve the taste as sashimi. strengthened. In addition, the sashimi has a soft texture, which further enhances the taste of the sashimi. Each of the conditions (1) to (3) will be described in detail below.

<(1) Raw vinegar immersion time and salt concentration contained in raw vinegar>
Regarding the processing of aged fish, if fresh fish covered with skin is the target, in order to control the permeation of acetic acid into the fish meat and maintain the quality of the raw fish meat, Basic knowledge of the permeation properties of acetic acid is essential. In the present embodiment, in order to obtain such findings, red sea bream and horse mackerel are the target fish species, and gills, internal organs, heads, and scales are removed from these fish and washed. It was immersed in twice the amount of raw vinegar containing. The skin of 2 cm×4 cm of red sea bream or 2 cm×3 cm of horse mackerel was removed from the fish taken from the raw vinegar at regular intervals. In addition, the muscles under the peeled skin were also collected. Table 1 shows the mean and standard deviation of the weight of the collected skin and muscle. Table 1 also shows the thickness (mm) of each sample estimated based on the weight.

Fish skin consists of epidermis, dermis, and subcutaneous fat underneath. For example, according to the following non-patent document, the thickness of red sea bream skin is 0.52 mm to 1.35 mm, although it varies depending on the degree of growth of the fish. . According to this, the thickness of the skin of the red sea bream and horse mackerel shown in Table 1 is greater than the thickness of the skin shown in the following non-patent literature, so the skin collected in this experiment has the underlying layer. It is thought that muscle (fish meat) is partly contained.
<Non-Patent Literature>
Fumiko Kamiyanagi, "Penetration of salt into fish meat -differences due to fish body size-". Japanese Journal of Home Economics, Vol. 41, 1990, 621-628.

Fig. 1 (a: red sea bream, b: red horse mackerel) shows changes in the acetic acid concentration (mM/kg) in the skin and underlying muscle associated with immersion in raw vinegar in such a sampling accuracy. The acetic acid concentration in the skin of both fresh fish increased with the lapse of time immersed in raw vinegar.

On the other hand, the concentration of acetic acid in the underlying muscles did not increase at all during the immersion in raw vinegar for 30 minutes or less in either red sea bream or horse mackerel. was detected for the first time.

The above results indicate that the penetration of acetic acid into the muscle underlying the skin is minimized if the raw vinegar immersion treatment is performed for 30 minutes or less.

Next, Table 2 shows the result of examining the influence of the salt concentration in the raw vinegar used for this raw vinegar immersion on the permeability of acetic acid to the muscle through the skin.

In this experiment, red sea bream was used and the raw vinegar immersion time was fixed at 5 minutes. The thickness of the 2 cm × 3 cm skin and underlying muscle taken from the fish body was 1.27 mm ± 0.25 mm (n = 20) and 2.14 mm ± 0.54 mm (n = 20), respectively. Among these sampling accuracies, there was no difference in the acetic acid concentration in the skin between no salt added and 3%, but it tended to increase when the salt concentration added to raw vinegar was 3% or more. .

On the other hand, no acetic acid concentration was detected in muscle under the skin until the salt concentration was 20%, and a small amount of acetic acid was detected in fish meat treated with raw vinegar containing saturated salt. This result indicates that the permeation of acetic acid into the muscle under the skin is very small or negligible regardless of the salt concentration in the raw vinegar used for the raw vinegar immersion treatment.

<(2) Water washing and salting time of fresh fish immersed in raw vinegar>
Red sea bream soaked in raw vinegar for 5 minutes is immersed in tap water twice the weight of the fish body for 30 seconds, and then immersed in 3% saline for 0-60 minutes. show.

The skin thickness sampled in this experiment had a mean value of 1.42 mm ± 0.31 mm (n = 20). The acetic acid concentration in the skin was 30-50 mM/kg after immersion in raw vinegar with 3% salt concentration for 5 minutes, but decreased to 14-38 mM/kg after rinsing with water for 30 seconds. Variation in acetic acid concentration was observed in the skin after washing with water, but the variation in acetic acid concentration was reduced by subsequent immersion in 3% saline (ie, salting). In addition, the acetic acid concentration in the skin gradually decreased after 30 minutes from the start of salting, and decreased to around 10 mM/kg after 60 minutes of salting.

In the same experiment, the acetic acid concentration in the muscles under the skin was also examined, but acetic acid was not detected in the muscles immediately after immersion in raw vinegar for 5 minutes, and even after washing with water and salting for 1 hour. Not detected. This result shows that the acetic acid concentration in the skin of fresh fish immersed in raw vinegar containing 3% sodium chloride for 5 minutes can be reduced to 10 mM/kg or less by washing with water and salting for 1 hour.

In addition, FIG. 3 shows the acetic acid concentration of red sea bream skin that was subjected to 30 seconds of water washing and 1 hour of salting after being immersed in raw vinegar of different salt concentrations for 5 minutes. The skin thickness sampled in this experiment averaged 1.38 mm ± 0.21 mm (n = 12).

As already shown in Table 2, the acetic acid concentration of red sea bream skin immediately after immersion in raw vinegar for 5 minutes tends to increase as the salt concentration in the raw vinegar increases (more specifically, the concentration of acetic acid added to raw vinegar However, after washing with water and salting for 1 hour (60 minutes), the acetic acid concentration in the red sea bream skin decreased to 10-20 mM/kg.
In addition, the acetic acid concentration in the red sea bream skin that was washed with water and salted for 1 hour (60 minutes) did not change much depending on the salt concentration during the raw vinegar immersion treatment.

From this result, the acetic acid concentration of the skin tends to increase with the raw vinegar immersion treatment, but it is greatly reduced by the subsequent washing with water and salting for 1 hour, and the acetic acid concentration of the skin finally reaches 10-15 mM/. It has been confirmed that the weight is within the range of kg.

From the above results, it was confirmed that most of the acetic acid that penetrated the skin of fresh fish immersed in raw vinegar can be removed by subsequent washing and salting, and that 60 minutes of salting time is sufficient.

Based on the above, vinegar with a salt concentration adjusted to 0%-saturated concentration and having a temperature of 10° C. or less was used for the raw vinegar immersion treatment. Also, the conditions for removing acetic acid from the fresh fish immersed in raw vinegar required washing with tap water, and the salting time was 1 hour.
It should be noted that the salting is preferably immersed (salting) in a 1-3% saline solution at 10° C. or less in order to avoid imparting an excessive salty taste due to permeation of salt.

<(3) Drying conditions>
The technology to improve the storage stability of food by drying reduces the amount of water that can be used for the growth of microorganisms by concentrating the hydrating components dissolved in the water in the food by reducing the water content in the food. based on that. That is, by lowering the water activity of the water contained in the food. Generally, the drying process of solid matter containing water is roughly divided into two stages. One of them is characterized by the evaporation of water from the food surface that occurs in the early stages of drying, and this period is called the constant rate drying period. The second is the decreasing rate drying period, in which water evaporates at a slower rate than the constant rate drying period. In the drying of fresh fish covered with skin, after the constant-rate drying period, the decreasing-rate drying continues for a certain period. The water content of the fish meat is maintained high for a certain period of time. In other words, by manipulating the decreasing rate drying period after the constant rate drying period, the water activity of the skin is greatly reduced while maintaining a high water content in the muscle (fish meat) part, which is the main edible part of fresh fish. It is possible to bacteriostatic the existing bacteria on the skin. However, when fresh fish that has reached the declining rate drying period is stored in an airtight condition, the moisture in the fish meat gradually migrates to the skin over time, and the skin regains moisture. The problem is that if the skin cannot completely absorb the moisture transferred from the fish meat, the excess moisture leaks out (that is, drips are generated), and the drips become a perfect breeding ground for bacteria. Therefore, it is necessary to carefully set the conditions even during the falling-rate drying period.

The setting of drying conditions in this embodiment will be described with reference to FIG.
FIG. 4 shows changes in weight when red sea bream, from which gills, heads, internal organs and scales have been removed, is dried in a drying cabinet at 4° C. to 5° C. while air is circulated.
The vertical axis in FIG. 4 is the ratio of the fish weight at each drying time to the weight of the fish before drying as 100%. The fish weight ratio decreased with the lapse of drying time, and the fish weight ratio decreased linearly during the initial period of 2 to 3 hours after the start of drying.

The period during which the rate of decrease in the initial weight ratio is the fastest is the "constant rate drying period". The decrease in the weight ratio during the constant-rate drying period is due to the sudden evaporation of water from the skin on the surface of the fish body.

As the drying time progressed further, the fish weight ratio decreased further, but the rate of decrease in the fish weight ratio was slower than the rate of decrease in the fish weight ratio during the initial constant rate drying period. This drying period is the "falling rate drying period". The rate of decrease in the fish body weight ratio during the declining rate drying period is not constant, and slows down step by step as the drying time elapses. Taking FIG. 4 as an example, the drying period can be divided into the I falling rate drying period up to 12 hours of drying, the II falling rate drying period from 12 hours to 40 hours, and the III falling rate drying period after that.

The decrease in the fish body weight ratio accompanying such drying depends on many factors such as the shape and size of the fish, the temperature and humidity in the drying chamber, and the flow of air. It is difficult to define with Therefore, the drying conditions recommended in the present invention are the III falling-rate drying period corresponding to 40 hours of drying in FIG. The condition of the fish before the end of the second declining-rate drying period is that the skin is extremely dry, but the underlying muscle (fish meat) remains highly hydrated. Therefore, when the muscle is sealed and refrigerated after drying, the moisture in the muscle gradually moves to the dry skin side, and the skin regains moisture. Since there is a limit to the amount of water that the skin can hold, when the limit is exceeded, excess water leaking out of the skin leaks (ie, drips). The dripping environment is not preferable because it is a suitable place for bacteria. On the other hand, dripping is prevented by drying up to the III decreasing rate drying period. From the above results, the recommended condition for the drying treatment in the present invention is the III decreasing rate drying period. In addition, focusing on the fish weight ratio, it is desirable to dry until the fish weight ratio becomes less than 90%. Moreover, the drying temperature is preferably set to 10° C. or less from the viewpoint of maintaining the freshness of fresh fish and the accuracy of temperature control of drying equipment.

The main features of the method for processing aged fish according to the present embodiment described above are summarized in the following three points. By combining these three points, it becomes possible to produce aged fish that can be eaten raw with guaranteed safety.
(1) The time period for immersing the fresh fish in the dressing in the original vinegar is set so that the acetic acid in the vinegar does not permeate into the fish meat layer below the skin of the fresh fish.
(2) In order to remove the acetic acid that has permeated the skin of the fresh fish of dress, surface washing with tap water and salting treatment are incorporated as treatments after immersion in vinegar.
(3) Low-temperature drying conditions are set to prevent dripping from the skin after drying while maintaining a high moisture content in the muscle (fish meat).

<Example 1>
In Example 1, in order to clarify the influence of the drying period (degree of drying) on the progress of putrefaction of fresh fish, a study was conducted using red sea bream that was intentionally not immersed in raw vinegar. The details of the implementation were as follows: Red sea bream (body length 36-40 cm, body weight 1.3-1.6 kg/tail) was used as a live fish. After that, the internal organs and scales were removed and salted in 3% saline (5°C) for 1 hour. Furthermore, it was dried for 0 to 4 days in a low-temperature storage at 5° C. while being ventilated and hung with its tail upward to prepare samples with different degrees of dryness. After drying, the entire fish body was simply wrapped by covering it with a water-absorbing sheet and plastic wrap, and stored at a low temperature while being hung at 5°C. The qualitative changes in the odor emitted from the samples were sensory evaluated on a daily basis, and the results are shown in Table 3.

In Table 3, the undried samples gave off a putrid odor on the sixth day after death and were judged to be putrid the next day. The number of days after death when the smell of putrefaction was detected increased with the increase in the drying period, and rotting was observed on the 14th day of the 87.1% dry weight ratio sample after drying for 4 days. This result shows that even a red sea bream sample that has had its gills, internal organs, and scales removed and washed with water, and immersed in 3% saline for 1 hour, will reach initial putrefaction 6 days after death. It is shown that. It also indicates that the rotting of red sea bream, from which major bacterial contamination sites have been removed, is delayed by the drying treatment for four days, which corresponds to the third decreasing-rate drying period. Here, the number of general bacteria in the skin (3 cm × 3 cm) of the skin (3 cm × 3 cm) 7 days after death of the undried sample and the sample dried to a dry weight ratio of 88% (measured using a standard agar medium containing 3% salt) ) were 1.6×10 ⁹ CFU/cm ² and 9.1×10 ² CFU/cm ² respectively. Therefore, the results in Table 3 mean that the growth of bacteria existing on the red sea bream skin was greatly suppressed by the drying treatment corresponding to the III decreasing rate drying period. The above results indicate that the drying conditions corresponding to the III decreasing rate drying in the present invention are one of the important control points for producing safe aged fish.

<Example 2>
In Example 2, the drying conditions were fixed to the III decreasing rate drying period, and the progress of putrefaction was compared with and without the raw vinegar immersion treatment in the previous stage. The content of the implementation was to destroy the medulla oblongata and exsanguinate live red sea bream (body length 36-40 cm, body weight 1.3-1.6 kg/tail), decapitate it, and perform spinal cord destruction treatment. After that, the internal organs and scales were removed, and the samples treated with raw vinegar were immersed in raw vinegar containing 3% common salt for 5 minutes. Subsequently, it was salted for 1 hour in a 3% saline solution (5°C) regardless of the presence or absence of raw vinegar treatment. Further, it was dried in a low-temperature storage at 5°C while being ventilated and hung with the tail upward until it reached about 88% of the pre-drying weight, which corresponds to the III decreasing rate drying period (it took 2 days). After drying, the entire fish body was simply wrapped by covering it with a water-absorbing sheet and plastic wrap, and stored at a low temperature while being hung at 5°C. Changes in the odor of the samples were sensory evaluated every week, and the number of general bacteria on the skin of the stored samples was measured in the same manner as in Example 1. The results are shown in FIG.

In FIG. 5, the increase in the number of general bacteria in the red sea bream skin that was not immersed in raw vinegar was suppressed in this experiment because the skin was dried to the extent recommended in the present invention. Nevertheless, storage at 5° C. for 2 weeks increased the general bacterial count of the skin to 10 ⁸ CFU/cm ² , at which point organoleptic spoilage was perceived. In contrast, the increase in the number of general bacteria in the skin of red sea bream immersed in raw vinegar was clearly slow. Moreover, the sample stored at 5°C for 3 weeks did not rot, and the fish meat could be eaten raw as sashimi. Such a clear putrefaction retarding effect by the raw vinegar immersion treatment corresponded to the effect of reducing the growth rate of general bacteria on red sea bream skin to 1/3.

<Example 3>
Using red sea bream, the effect of vinegar immersion time on the decay retardation effect of vinegar immersion was investigated. Table 4 shows the results.

The concentration of salt contained in the raw vinegar used in this example was 3%, and the immersion times in the raw vinegar were 5 minutes and 30 minutes. After immersion in raw vinegar, it was washed with water and salted in 3% saline for 1 hour, and then dried to the dry weight ratio shown in the same table. The dried sample was vacuum-packaged with a gas-barrier packaging material (Meiwa Pack BA type, barrier Ny 15 μm//LLD 70 μm) and stored in ice water. Each sample was organoleptically intact after being stored for 27 days counted from the date of raw material acquisition. The number of general bacteria on the skin of these samples was 470 CFU/g for the sample immersed in raw vinegar for 5 minutes, and 505 CFU/g for the sample immersed in raw vinegar for 30 minutes, which were extremely low. This result indicates that even a 5-minute immersion treatment in raw vinegar provides a sufficient spoilage retarding effect.

<Example 4>
Using red sea bream, the effect of salt concentration in raw vinegar on the spoilage retardation effect of immersion in raw vinegar was investigated. Table 5 shows the results.

The concentration of salt contained in the raw vinegar used in this example was 3%, 10% and saturated concentration, and the immersion time in the raw vinegar was 10 minutes. After immersion in raw vinegar, it was washed with water and salted in 3% saline for 1 hour, and then dried to the dry weight ratio shown in the same table. The dried sample was vacuum-packaged with a gas-barrier packaging material (Meiwa Pack BA type, barrier Ny 15 μm//LLD 70 μm) and stored in ice water. None of the red sea bream stored for 26 days counted from the date of raw material acquisition was sensory decayed. After 26 days, the number of general bacteria on the skin of each red sea bream was 10,150 CFU/g for the red sea bream soaked in raw vinegar containing 3% salt, and 6 for the red sea bream soaked in raw vinegar containing 10% salt. , 350 CFU/g, and 1,410 CFU/g for red sea bream immersed in raw vinegar containing saturated sodium chloride. This result indicates that the higher the salt concentration in the raw vinegar, the better the spoilage retarding effect of the raw vinegar immersion treatment.

<Example 5>
Using amberjack, we examined the effect of immersion in raw vinegar to delay spoilage. Table 6 shows the results.

The concentration of salt contained in the raw vinegar used in this example was 3%, and the immersion time in the raw vinegar was 5 minutes. After the raw vinegar immersion treatment, it was washed with water and salted in 3% saline for 1 hour, and then dried to the dry weight ratio shown in Table 6. The dried sample was vacuum-packaged with a gas-barrier packaging material (Meiwa Pack BA type, barrier Ny 15 μm//LLD 70 μm) and stored in ice water. The amberjack stored for 21 days counted from the date of raw material acquisition did not spoil organoleptically. The skin general bacterial count of that sample was very low at 5,285 CFU/g. Although the examples of the present invention were carried out mainly using red sea bream, it indicates that the same anti-corruption effect can be expected for different fish species.

<Example 6>
Immerse in raw vinegar containing 3% salt for 5 minutes, wash with tap water, salt in 3% salt water for 1 hour, and then dry until it corresponds to the III decreasing rate drying period. The fish species did not rot after storage in ice water for 3 weeks, and sashimi cooked from the fish was fully edible raw.
(Fish species)
Horse mackerel, chub mackerel, yellowfin, yellowtail, Spanish mackerel, sea bass, John Dory, tangfish, conger eel, gurnard, pheasant grouper, striped trevally, krill trevally, striped bream, greater amberjack, brown sea bream, red sea bream

<Example 7>
In order to clarify the qualitative characteristics of the aged fish according to this embodiment, changes during low-temperature storage of various components that contribute to the taste of the fish meat part, which is the main edible part of the aged fish prepared using red sea bream. about

First, the change in K or Na ion concentration in fish meat, which contributes to salty taste, was compared with and without raw vinegar immersion treatment. The content of the implementation was to destroy the medulla oblongata and exsanguinate live red sea bream (body length 36-40 cm, body weight 1.3-1.6 kg/tail), decapitate it, and perform spinal cord destruction treatment. After that, the internal organs and scales were removed, and the samples treated with raw vinegar were immersed in raw vinegar containing 3% common salt for 5 minutes. Subsequently, it was salted for 1 hour in a 3% saline solution (5°C) regardless of the presence or absence of raw vinegar treatment. Further, it was dried in a low-temperature storage at 5°C while being ventilated and hung with the tail upward until it reached about 88% of the pre-drying weight, which corresponds to the III decreasing rate drying period (it took 2 days). After drying, the entire fish body was simply wrapped by covering it with a water-absorbing sheet and plastic wrap, and stored at a low temperature while being hung at 5°C. Every week, the fish was taken out of the low-temperature storage, cut into three pieces, and the skin was removed from the fillet. Changes in K and Na ion concentrations in the collected back meat and tail meat are shown in Figures 6 and 7, respectively.

The K ion concentration in FIG. 6 was constant regardless of the body part and the elapsed time after death, and there was no difference between the presence and absence of the raw vinegar immersion treatment. If the water content of fish meat parts were reduced during drying and subsequent cold storage, the K ion concentration in fish meat parts would be expected to increase with concentration. However, such an increase in K ion concentration in fish meat was not observed and was constant. Therefore, this result confirms that the moisture content in the fish meat, which is the main edible part, of the aged red sea bream prepared according to the present embodiment is maintained at the same level as that of the fresh fish before processing. It also shows that it is not affected by the raw vinegar soak treatment.

Next, the change in Na ion concentration in FIG. 7 showed no difference between the presence and absence of the raw vinegar immersion treatment, but the concentration increased with the passage of time after death regardless of the measurement site. Since the K ion concentration in the fish meat was constant as shown in FIG. 6, it was determined that the increase in the Na ion concentration in the fish meat was not due to concentration accompanying a decrease in water content. This increase in the Na ion concentration in the fish meat is thought to be due to the diffusion and permeation of Na ions into the fish meat that permeated the skin by salting in 3% saline for 1 hour after the raw vinegar immersion treatment. Since the threshold at which humans can perceive salty taste is 35 mM/kg as salt concentration, the increase in Na ion concentration seen in FIG. 7 is not so large as to impart salty taste to fish meat. On the other hand, it is said that an increase in salt concentration in a range lower than the threshold enhances perception of taste brought about by various free amino acids, inosinic acid, and the like. Therefore, it is considered that this degree of increase in Na ion concentration contributes to enhancing the taste of fish meat.

Furthermore, FIG. 8 shows the change in the total free amino acid concentration of the fish meat portion (back meat) of the aged red sea bream immersed in raw vinegar. Total free amino acid concentration represents the total concentration of the above 17 amino acids Tau, Asp, Glu, Thr, Ser, Glu, Ala, Pro, Val, Met, Ile, Leu, Tyr, Phe, His, Lys, Arg . The total free amino acid concentration increased with the lapse of time after death and reached about twice the initial value after 3 weeks. This increase in total free amino acid concentration is statistically significant (5%). On the other hand, in order to know the details of the increase in the concentration of total free amino acids, 17 kinds of free amino acids were evaluated for sweetness (Thr, Ser, Glu, Ala, Pro) and umami (Asp, Glu) and bitterness (Val, Met, Ile, Leu, Tyr, Phe, His, Lys, Arg) were similarly analyzed statistically, but no significant difference was observed. Therefore, it is considered that the taste peculiar to aged fish contributes to the overall enhancement of taste rather than to a specific taste among the three types of taste derived from free amino acids. .

The above results show that the quality (deliciousness) formation of aged fish progressing while microbial safety is ensured is due to the effect of enhancing the taste sensation due to a slight increase in Na ion concentration and the total amount derived from various free amino acids. It is shown that it is characterized by the above two points of the taste enhancement effect.

The embodiments and the like described above are for facilitating the understanding of the present invention, and are not intended to limit and interpret the present invention. The present invention is not limited to the fresh fish described above, but can be applied to any aquatic animal including shellfish, shrimp, crab, etc., and any animal that can be eaten.

Claims (8)

A raw vinegar immersion step of immersing fresh fish in vinegar containing acetic acid;
A salting step of washing the fresh fish immersed in vinegar and immersing it in salt water;
and a drying step of drying the fresh fish soaked in salt water. 2. The method for processing aged fish according to claim 1, wherein said fresh fish is a fresh dressed fish from which gills, internal organs, heads and scales have been removed. 3. The method for processing aged fish according to claim 1 or 2, wherein the vinegar containing 4.2% acetic acid is used in the raw vinegar soaking step. 4. The method for processing aged fish according to any one of claims 1 to 3, wherein in the raw vinegar immersion step, the fresh fish is immersed in the vinegar for 30 minutes or less. The method for processing aged fish according to any one of claims 1 to 4, wherein the vinegar containing salt is used in the raw vinegar immersion step. 6. The method for processing aged fish according to claim 5, wherein the salt concentration is set between 0% and a saturated concentration. The method for processing aged fish according to any one of claims 1 to 6, wherein in the salting step, the concentration of the salt solution is set at 1-3%. The method for processing aged fish according to any one of claims 1 to 7, wherein in the drying step, the fish is dried at 10°C or less until the weight ratio of the fish is less than 90%.

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