JPS59196032A - Method for preventing denaturation of krill and for keeping its freshness - Google Patents

Abstract

PURPOSE:To prevent the denaturation of krill, and to keep the krill at a fresh state, by using an alcohol such as ethanol as a refrigerant as well as a protein- denaturating agent, a dehydration agent and a defatting agent. CONSTITUTION:Krill is immersed in an ethanol soluting having controlled temperature and concentration to adjust the rate of freezing, the degree of denaturation of protein, the dehydration degree, the defatting degree, and the deactivation rate of enzyme. The temperature of ethanol is varied within the range of 5- -50 deg.C. The krill is suspended in the ethanol solution and frozen to prevent the disintegration of the tissue and prevent the autodigestion. The immersed krill is stored at a low temperature if necessary after removing alcohol therefrom.

Description

[Detailed description of the invention] Antarctic krill (Eupha s) of the Southern Ocean
The estimated resource amount of Perba (ia 5 u Perba) is said to be between 1 billion tons and 5 billion tons, and the appropriate catch is said to be more than 5 tons, making it the largest unused protein resource for humankind. development is underway.

It has been known for a long time that the body tissues of crabs and shrimp, especially the liver, have strong protease activity, and krill is also thought to have strong enzymes and lipase. Autolysis phenomena such as color deterioration and loss of extract components occur. For this reason, currently 90% of the catch is boiled in seawater on board and then frozen (boil freezing), and 10% is immediately frozen (main freezing). In the current method, small catches such as krill are preserved in a thick layer by freezing or other means, but krill, whose supporting tissue is softer than that of fish, suffers from the external pressure applied during this process. Body tissue is easily destroyed, and as a result, enzymes from internal organs and blood diffuse into the meat tissue and promote autolysis. Therefore, even during frozen storage, melanin is produced from body component tyrosine by the action of the oxidative enzyme tyrosinase. It is difficult to maintain freshness, such as the body surface turning black and a significant loss of product value, and it is not possible to prevent the generation of the odor characteristic of krill when thawing. Currently, consumption as a fresh food has not been expanded, and most of the consumption is as fishing bait for recreational fish. Boiling treatment can prevent autolysis and blackening caused by autologous enzymes and reduce dripping, but it is not perfect.
Furthermore, since the protein is thermally denatured, the degree of denaturation of the protein is large, and the range of secondary processing and utilization is narrowed, making it impossible to increase consumption. In other words, in order to mass consume krill, the biggest issue is not the secondary processing method on land, but the method to maintain freshness and prevent denaturation during the several months period from capture at sea to secondary processing on land. .

A fundamental solution would be possible if it were possible to perform secondary processing at sea as on land, but this is not possible when considering the situation of mass processing on board ships in the Southern Ocean.

Taking these points into consideration, the present invention reduces the degree of protein denaturation compared to the conventional boil freezing method, and reliably eliminates autolysis, blackening, and
This provides a simple primary treatment and preservation method that can prevent odor generation and the like.

To explain the present invention in detail, alcohol such as ethanol is used as a refrigerant and as a protein solidifying, dehydrating, and degreasing agent. ℃ to adjust the degree of protein denaturation, etc. The collected fresh krill is immersed in cooled ethanol, and the krill is rapidly frozen in a suspended state due to the specific gravity of the ethanol.At the same time, protein coagulation on the body surface, surface dehydration, surface defatting, and enzyme inactivation are performed by ethanol permeation. This is a method for maintaining the freshness of krill by storing it in its original state at a low temperature to prevent krill from denaturing and maintain good freshness.

The present invention differs from conventional methods in that (1) ethanol is used as a refrigerant for krill and as a protein coagulation, dehydration, defatting, and enzyme inactivation agent, and the temperature and concentration of ethanol are adjusted to allow the krill to be immersed in freezing; Good frozen storage is possible by adjusting the speed, degree of protein denaturation, degree of dehydration, degreased bottom, and degree of enzyme inactivation. That is, the salt brine of the brine immersion type conventionally used in skipjack fishing boats and the like has a concentration of 22 to 23% and is cooled to a minimum temperature of about -17°C. Salt infiltrates the frozen bonito subcutaneously up to the 5th subcutaneous level, and the salt concentration in the meat layer up to 5m+n subcutaneously is 0.48 to 3.75%. And this subcutaneous 5
It has been observed that when the salt concentration in the inner layer up to +nm is 2% or more, browning of the flesh color and rancidity of lipids become significant. The degree of salt infiltration into the fish body is influenced by the brine temperature.

In other words, when the brine temperature is high, salt penetration is high;
In addition, slow freezing occurs, resulting in browning of the meat color and denaturation of proteins. In the present invention, we actively utilize this phenomenon and, as an alternative to the conventional boil freezing method, we control the freezing rate of krill and the subcutaneous penetration ring of ethanol by controlling the temperature and concentration of ethanol to prevent protein denaturation by ethanol. This is a treatment method that prevents autolysis and blackening based on autologous enzymes and reduces dripping.

(2) Since krill is frozen while suspended in ethanol, body tissues are not destroyed by external pressure, and enzymes from internal organs and blood do not diffuse into meat tissues, so autolysis does not occur.

(3) By using ethanol as a refrigerant and immersing krill in low-temperature ethanol, instantaneous rapid freezing is possible, and good frozen preservation is possible without the tissue destruction and protein denaturation that occur during slow freezing.

(4) Since protein coagulation is performed using ethanol, secondary processing on land is highly applicable.

(5) Since ethanol is present in the frozen state of krill, it is in a slurry state and is easy to transport and handle.

(6) Since ethanol is used as a refrigerant, freezing operations can be performed easily.

(7) The processing machine is simple and small, making it possible to process large quantities of krill on board.

Next, to explain the present invention in detail, approximately 40% of ethanol with a concentration of 50 to 95% is poured into an ethanol tank insulated with a cold insulating material, etc.
After filling the tank to about 0% and cooling the temperature to 5 to -50℃,
After washing, the caught krill is placed in ethanol while still being washed.

(1) If you want to keep the freshness of krill high and the degree of protein denaturation low, use a freezer such as a brine cooler to keep the ethanol temperature at -20 to -50℃, and freeze the krill from 5℃ to about -20℃ for a long time. By shortening the time and performing rapid freezing, ethanol can only enter the subcutaneous surface, and denaturation of proteins by ethanol can be limited to the surface. Freezing time is about 10 minutes to 2 hours. After the freeze-coagulation process is completed, the ethanol is transferred to another ethanol tank using a pump, etc. The ethanol tank used for the freeze-coagulation process is used for storage, and the temperature inside the tank is lowered to -30 to -50℃ and then frozen. Store.

(2) When storing krill to maintain its freshness as a secondary processing material, the ethanol concentration during soaking should be 70-95% in order to actively coagulate the proteins, dehydrate, degrease, and deactivate the enzymes in the krill using ethanol. Keep the temperature between 5 and -20°C. Krill is soaked and kept in an unfrozen or partially frozen state for 10 minutes to 1 hour, and ethanol is infiltrated into the krill to cause protein coagulation, dehydration, defatting, and enzyme inactivation, and the temperature is then heated to around -30℃ in a brine cooler etc. Either cool and freeze-coagulate it, then store it in a frozen state immersed in ethanol, or transfer the ethanol to another ethanol tank using a pump, etc., and use the ethanol tank used for freeze-coagulation for storage. The inside of the tank is lowered to -30 to 50°C and stored frozen.

Patent applicant Fumio Nishiyo Takashi Yamamoto Masufumi Taguchi

Claims (1)

[Claims] Fresh krill is immersed in alcohol such as ethanol cooled to 5 to -50°C, and kept suspended due to the specific gravity of the alcohol. At the same time, the krill is rapidly frozen, and at the same time, protein coagulation on the surface of the krill body due to alcohol penetration and surface dehydration. , surface degreasing, and enzyme deactivation. At this time, by changing the temperature of the alcohol, the freezing rate of the krill and the depth of penetration of the alcohol can be changed to adjust the protein coagulation, surface dehydration, surface degreasing, and enzyme deactivation on the surface of the krill body. A method for preventing denaturation and maintaining freshness of krill, which is characterized by storing krill at a low temperature after removing alcohol.