CN103518823B - The method of the fresh-keeping fish liver of a kind of fluidisation ice - Google Patents

Abstract

A method for fresh-keeping cod liver with fluidized ice, characterized in that the steps are: 1) pre-treatment: fresh razor clam anglerfish that have just been caught ashore, washed for later use; After the cod liver is taken, it is immersed in fluidized ice. The ratio of fluidized ice to cod liver is 20L:8kg～40L:15kg until the center temperature reaches -1.6°C～0°C. Compared with the prior art, the present invention has the advantages of The reason is that the pretreatment of cod liver with fluidized ice can effectively delay the growth and reproduction of spoilage microorganisms, slow down the growth of the amount of alkaline compounds such as ammonia, and keep the freshness of anglerfish livers good. The fluidized ice precooling method To a certain extent, it can prolong the process of fresh anglerfish liver from neutral stage to spoilage stage. This study can provide technical basis for the processing, storage and long-distance transportation of fresh anglerfish liver, and it is of great significance to improve the economic value of fresh anglerfish liver.

Description

A method of fresh cod liver with fluidized ice

technical field

The invention relates to the technical field of food preservation, in particular to a method for preserving fish liver with fluidized ice.

Background technique

The earliest report of the application of fluidized ice precooling technology in aquatic product processing was Chapman's research on the application of fluidized ice to the onboard precooling of fin whales in 1990. Since then, there have been research reports on the use of fluidized ice to store prawns, bream, sea bass, and turbot. The research results show that because the fluidized ice can control the temperature of the product below 0°C, the shelf life of the product is prolonged, and satisfactory microbial, chemical, and sensory characteristics are obtained, thereby obtaining high-quality and safe aquatic products. At present, fluidized ice is widely used in the fishery fields of the United States, the United Kingdom, Australia, Canada and other countries for fish catch processing on board (precooling, killing, storage, etc.), precooling and raw material storage in the production line of land aquatic product processing plants.

Fluidized ice is an aqueous solution containing suspended ice crystal particles. Under the same temperature and flow rate, fluidized ice with an ice content of 5% to 20% has a cooling capacity of 1.8 to 4.3 times that of frozen water. . Fluid ice pre-cooling can make the body temperature of fish or fish fillets drop rapidly from the outside to the inside, kill some microorganisms on the body surface and inhibit the reproduction of undead microorganisms, slow down the biochemical reactions in the fish body, and reduce the consumption of nutrients in the fish body , to maintain the freshness, edible quality and processing performance of fish to the greatest extent. In developed countries, advanced ice-making equipment units such as fluidized ice machines and ice slurry machines are more common in fishing boats and land applications, and are used in all aspects of aquatic product processing. There are relatively well-known ice machine manufacturers in Canada, Iceland and other countries. Ice temperature storage is a method of storing aquatic products in a temperature zone between below 0°C and the freezing point. In China, ice temperature preservation technology is still in the research stage, and most of the research reports are for fruits and vegetables, beef, and pork. Aiming at the current situation that domestic chilled fresh fish has a short shelf life and inland urban residents are not easy to buy fresh fish products, Gao Hongyan published "Fluidized ice pre-cooling and ice The research in "Experimental Research on Fresh Cod Fillets Stored at High Temperature" shows that the technical method of combining fluidized ice precooling and ice temperature storage is as follows: the caught fish are slaughtered and gills removed, viscera removed and rinsed in cold sea water. And so on, the temperature of the fish body is initially lowered, and the microorganisms on the surface of the fish are removed to a certain extent, so as to prevent fresh fish from spoiling, and then enter the fluidized ice pre-cooling stage, so that the temperature of the center of the fish body quickly drops to -2 ° C ~ 0 ° C, and further Kill harmful bacteria and inhibit biochemical reactions to maintain the freshness of fish; then send them to -4℃～0℃ ice temperature warehouse for storage or enter ice temperature transportation, ice temperature sales and other links. Fluid ice pre-cooling technology and ice-temperature storage compound technology realize that the temperature of fresh fish is always in the same temperature range from pretreatment to storage, transportation and sales. In the processing of fresh cod fillets, satisfactory sensory properties, such as texture, smell, aroma, etc., can be reduced to a certain extent. However, this technology must be combined with fluidized ice precooling and ice temperature storage technology to achieve the technical effect, and there are still technical problems in the promotion of fluidized ice precooling and ice temperature storage combined technology at this stage : 1. The ice-temperature cold chain technology and equipment are not perfect, and the quality management and traceability of ice-temperature chain products are not very clear, especially there are no easy-to-use quality monitoring communication products; Fish is difficult to be generally accepted by consumers. Domestic consumers prefer to eat live fish. To produce fresh fish using this composite technology, it is necessary to remove the viscera and gills of the fish body containing a large number of bacteria in advance to prolong the shelf life. This is different from the consumption habits of the public. There is a distance.

In recent years, with the change of marine fishery resources, the catch of anglerfish has increased year by year. The anglerfish (Lophius litulon) belongs to the order of anglerfish, also known as choupo, anglerfish, etc. It has become one of the main export aquatic products in my country. Its utilization value highlight. Anglerfish is rich in nutrition and delicious in taste. It is usually sold in the form of dried fish fillets and dried meat sticks. However, the small head and large viscera of anglerfish account for a large proportion, and the proportion of leftovers in the processing process exceeds 60%, of which the liver accounts for as high as 11%. Angler fish heparin is known as "undersea foie gras". It has extremely high nutritional and edible value, and also has high medicinal value. It can clear away heat and detoxify, and also has the effects of insulin-like active peptide. Fresh liver that has not been frozen at all has an excellent taste after cooking, and the better the anglerfish liver, the finer the texture (light orange color, fine blood vessels). In my country, anglerfish livers are mostly limited to the level of rough freezing and rough processing, and after quick-freezing, vacuum-packed products have a lot of blood, which affects the taste. Therefore, it is urgent to study the sensory quality of fresh fish livers, which is a single technology of fluidized ice pre-cooling technology. The impact of the change is of great significance to provide technical basis for the processing, storage and long-distance transportation of fresh anglerfish liver, and to improve the economic value of fresh anglerfish.

Contents of the invention

The technical problem to be solved by the invention is to provide a method for fresh-keeping cod liver with fluidized ice, which has the characteristics of simple preparation process and easy operation.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a method for fresh-keeping cod liver with fluidized ice, which is characterized in that the steps are:

1) Pre-treatment: fresh anglerfish just caught ashore, washed and set aside;

2) Take the liver: After the fresh anglerfish caught in the sea is bled to take the liver, it is immersed in fluidized ice. 0°C.

Preferably, the ratio of the fluidized ice to the cod liver is 30L:10.2kg.

Preferably, the central temperature is -1.6°C.

Since the temperature of the fluidized ice changes with the concentration of the salt solution, the temperature of the fluidized ice is equal to the change of the concentration of the salt solution, and the temperature of the fluidized ice is equal to the freezing point of the salt solution. Conversely, the lower the concentration of salt, the higher the coagulation and fixation. When seafood products are kept fresh and refrigerated, the change process is just the opposite. Because the input of seafood products dissolves the ice, the concentration of ice decreases accordingly, and the salt solution becomes thinner ( Concentration drops), in this case the temperature of the fluidized ice rises, the salt concentration of the fluidized ice is 2-5%, the concentration of the fluidized ice is 10-30%, in order to ensure the refrigeration temperature of the fluidized ice, and according to As measured by the principle of heat balance, as a preference, the salt concentration of the fluidized ice is 2.3%, and the concentration of the fluidized ice is 23%.

Compared with the prior art, the present invention has the advantages that: the fresh anglerfish liver caught in the sea is taken as the experimental object in this paper, and the fish liver is pretreated with fluidized ice, which can effectively delay the growth and reproduction of spoilage microorganisms, making ammonia, etc. The increase in the number of alkaline compounds slows down, which keeps the freshness of anglerfish livers good. The fluidized ice precooling method can prolong the process of fresh anglerfish livers from the neutral stage to the spoilage stage to a certain extent. It is of great significance to provide technical basis for liver processing, storage and long-distance transportation, and to improve the economic value of fresh anglerfish.

Description of drawings

Fig. 1 is the PCA analysis chart of the volatile odor of fluidized ice precooling method (group A) in the storage process of anglerfish liver;

Fig. 2 is the PCA analysis chart of the volatile odor without fluidized ice processing (group B) in the storage process of anglerfish liver;

Fig. 3 hardness change diagram of fluidized ice precooling method (group A) and no treatment with fluidized ice (group B) in the storage process of anglerfish liver;

Fig. 4 The elastic change diagram of fluid ice precooling method (group A) and no treatment with fluid ice (group B) in the storage process of anglerfish liver;

Fig. 5 cohesion change diagram of fluidized ice precooling method (group A) and no treatment with fluidized ice (group B) in the storage process of anglerfish liver;

Fig. 6 Changes in chewiness of anglerfish livers during storage with fluidized ice precooling method (group A) and without treatment with fluidized ice (group B).

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

1. Materials and Instruments

1.1 Main materials

Fresh Anglerfish Liver

1.2 Main instruments

UV-2102PC ultraviolet-visible spectrophotometer, Unico (Shanghai) Instrument Co., Ltd.;

TMS-PRO texture analyzer, American FTC company;

Electronic nose PEN3, Germany AIRENSE company;

Fluid ice preparation apparatus;

Dimethyl sulfoxide (DMSO) was purchased from AMRESCO, USA.

2. Experimental method

2.1 Materials and pretreatment

To compare the effects of fluidized ice precooling method (group A) and no treatment with fluidized ice (group B) in the production process of fresh anglerfish livers on later storage at ice temperature. Fresh anglerfish were caught in the waters of Zhoushan, Zhejiang. The fish livers were bled on board and stored in ice. Shipped to the laboratory for processing the next day.

After weighing and grading, all the experimental cod livers were divided into two groups. Group A was pre-cooled with pre-prepared fluidized ice, and group B and the control group were directly stored at ice temperature. Group A was immersed in fluidized ice (the ratio of ice to anglerfish liver was 30L:10.2kg) until the core temperature reached -1.6°C. Experimental cod livers were packed in polystyrene foam (EPS) insulation boxes, 10 pieces per box (average weight 66.5±6.4g), 5 boxes per group, and shipped to the fishery laboratory cold storage on the same day (storage temperature (-1.5±0.5) °C) for storage. Sensory testing, cod liver texture and electronic nose analysis are conducted once a day in the aquatic laboratory of Zhejiang Ocean University.

The fluidized ice used for the precooling medium in the experiment was prepared by an ice machine produced by Nantong Refrigeration Technology Co., Ltd. The ice concentration was determined to be 23% based on the heat balance principle, and the salt concentration was 2.3%.

2.2 Determination of physical and chemical indicators

2.2.1 Cooking loss rate

A, B two groups of samples were weighed (Y1). After boiling an appropriate amount of water with an induction cooker, put the cod liver into the pot and cook for 5 minutes, remove it, cool to room temperature, absorb the water with absorbent paper, and then weigh it again (Y2). The cooking loss rate is calculated by the following formula:

CL=(Y1-Y2)/Y1×100%

In the formula, CL—cooking loss rate, %; Y1—sample mass before cooking, g; Y2—sample mass after cooking, g.

2.2.3 pH value determination

Take 10.0 g of cod liver, cut it into pieces, put it in a beaker, add 90.0 mL of distilled water, homogenize at high speed for 1.0 min, soak at 4°C for 20 min, filter with filter paper, and measure the pH value of the filtrate with a PHS-25 acidity meter.

2.2.4 Determination of TVBN value

TVBN was determined by the semi-micro Kjeldahl method with some improvements. Accurately weigh 10.00g cod liver, add 100.0mL, 0.60mol/L perchloric acid solution, homogenize at 4°C for 1.0min, filter with filter paper. Accurately draw 5.0 mL of the filtrate, add 1 drop of phenolphthalein indicator, 2 drops of silicone oil, and 5.0 mL of 0.80 mol/L NaOH solution respectively, inject the mixed solution into the reaction chamber of the semi-micro nitrogen analyzer, and cover with a water seal. Steam is fully heated for 6.0min, and the boric acid (0.50mol/L) absorption solution is titrated with 0.01mol/L HCl solution to blue-purple.

2.2.5 Determination of TMA value

It was determined by the colorimetric method of trimethylamine picric acid. Accurately weigh 10.00 g of cod liver, add 70.0 mL of distilled water, homogenize at 4 °C for 1.0 min, add 10.0 mL of 40% trichloroacetic acid, shake for 5 min, and filter through filter paper. Accurately pipette 5.0 mL of filtrate into a stoppered tube, add 1.0 mL of 10% formaldehyde solution, 10.0 mL of toluene (dehydrated with anhydrous sodium sulfate), 10.0 mL of 7.2 mol/L potassium carbonate solution, and shake the cap for 1 min. Let stand for 20min. Accurately absorb (after dehydration) 5.0mL of the supernatant, add 5.0mL of 0.02% picric acid-toluene solution, and measure the absorbance at 410nm.

2.2.6 Electronic nose analysis

Accurately weigh 5.0±0.2 g of anglerfish liver, cut it into pieces, transfer it to an odor collection bottle, and seal it with a cap. Electronic nose measurement parameters: ①The equilibrium temperature of the collection bottle is 25°C, and the time is 20 minutes; ②The system warm-up time is 30 minutes; ③The sampling time interval is 1.0s, the sample measurement time is 60s, and the sensor cleaning time is 60s; ④The gas collection method is automatic dilution, and the sensor room The flow rate is 300ml/min. Using the Winmuster data vectorization program that comes with the PEN3 electronic nose system, multivariate statistical analysis was performed on the collected volatile odor information. Specifically, principal component analysis (Principal-Component-Analysis, PCA)

2.2.7 Texture Analysis

The hardness, elasticity, cohesiveness and chewiness of anglerfish liver samples were determined by TMS-PRO physical property analyzer. TPA characteristic test parameters: ① The measurement site is the tissue at a distance of 3.0 cm from the center of the fish liver; ② A flat-bottomed cylindrical probe P/50 with a diameter of 50 mm is selected; ③ The test speed is 1.0 mm/s, and the compression deformation of the sample is 30%.

3 Results and Analysis

Moisture is the most important chemical component in meat, and its content and distribution are directly related to the color, texture, flavor and other edible qualities of meat or meat products. The prolongation change trend of group B is relatively smaller than that of group B, indicating that fluid ice pretreatment has a protective effect on the eating quality of anglerfish liver.

It is generally believed that fish body (cod liver) pH ≤ 6.5 is fresh fish, pH 6.5-6.8 is slightly degraded and edible, pH 6.8-7.0 is the critical value, and pH ≥ 7.0 is seriously corrupted. The pH changes of anglerfish liver in different treatment groups are shown in Table 1. The pH value of fresh cod liver was about 6.30. After 5 days of storage in group B, the pH reached the critical value, and the cod liver softened severely, and the color turned black and had obvious odor. After 7 days of storage in group A, the pH of cod liver also reached the critical value for consumption. During the storage period, the activity of endogenous enzymes in the fish liver is enhanced, coupled with the growth and reproduction of specific spoilage microorganisms, which decompose proteins to generate alkaline compounds such as ammonia, resulting in a significant increase in pH. Because fluidized ice pretreatment (group A) delayed the growth and reproduction of spoilage microorganisms, the growth of alkaline compounds such as ammonia slowed down, so the pH of group A increased slowly.

TVBN is widely used as an important indicator to judge the degree of corruption of aquatic products. As shown in Table 1, the TVBN value of fresh anglerfish liver is 2.71mg/100g (cod liver). Fluid ice pretreatment (group A) effectively inhibited endogenous enzyme activity and the reproduction of related spoilage microorganisms, thus showing a slow increase in TVBN value, and the freshness of anglerfish liver samples remained good at 7 days. But group B reached 37.25mg/100g after storage for 5 days (standard limit 30mg/100g, GB/T18108).

The TMA content of fresh anglerfish liver was about 1.20 mg/100 g (fish liver); during the 7-day storage of group B, the rate of increase of TMA in samples was faster (Table 1). During the 7-day storage of group A, the TMA content of the samples did not exceed 5.0mg/100g, and the freshness remained good.

As shown in Figures 1 and 2, the storage group A: the cumulative contribution rate of PC1 and PC2 was 86.84%, the distribution of PCA analysis results was relatively concentrated, and the discrimination effect was relatively poor; the storage group B: the contribution rate of PC1 reached 93.09%, and the PC1 and PC2 The cumulative contribution rate of PC2 is 94.51%, so its principal component analysis can better reflect the original high-dimensional matrix data information. The change trend of volatile odor substances in group A and storage group B was basically the same, that is, the odor components of the samples were distributed along the PC1 axis to the right, and along the PC2 axis first upward, then downward, and then upward. In addition, combined with the change of TVBN, the time of fish corruption: 5 days in group B and 7 days in group A. The inflection point of the significant change of the sample odor substances can be found by analyzing the template by electronic nose PCA, which also appeared in group B storage 5d and A storage group 7d, and the change trends of the two have a high synchronization. It shows that the treatment of group A can prolong the shelf life of anglerfish liver.

As shown in Figures 3 to 6, the hardness, elasticity, cohesiveness and chewiness of anglerfish liver decreased with storage time and temperature, and the hardness of group B showed a relatively slow change at the beginning stage (0-5d) , and the rate of decline was significantly accelerated in the later period. The hardness of group A is always higher than that of group B, mainly due to the endogenous enzymes and ATPases of fish liver tissue, etc., and the activity of group B remains high under the treatment conditions, resulting in severe myofibrillar proteolysis, and the reproduction of microorganisms on the surface of fish liver , Accelerated the process of cod liver autolysis and corruption. Elasticity reflects the degree of recovery of the sample after the deformation is removed when the sample is subjected to an external force. During the storage of anglerfish liver, the elastic change of group B was relatively slow at the beginning stage (0-5 days), and the rate of decline was significantly accelerated in the later period. The elasticity of group A was always higher than that of group B, which may be related to the effective inhibition of endogenous enzyme degradation ability by fluidized ice pretreatment, less actomyosin denaturation, and greater binding force between muscles.

Cohesion reflects the property of a sample to resist damage and maintain its integrity through tight connections, ie the cohesive force that pulls the sample together. Chewiness is the energy required to simulate cod liver chewing into a swallowing state, that is, the so-called bite force. In group B, the change of cohesion and chewiness was relatively slow at the beginning stage (0-5 days), and the rate of decline was significantly accelerated in the later period. The cohesion and chewiness of group A are always higher than those of group B, which may be due to the continuous decline in the binding force between the liver cells of group B anglerfish, so that the tissue becomes loose; on the other hand, the low temperature denaturation of the sample protein is serious, resulting in more Non-polar hydrophobic groups, resulting in a decrease in cohesion and chewiness.

In summary, this method of fluidized ice precooling can reduce the TVBN value of fresh anglerfish liver at the initial stage of ice storage to a certain extent. If the hygienic requirements of fluidized ice are taken into consideration during production, such as timely replacement or disinfection, the measured TVN and TVC values can be reduced. Texture data showed that the sensory properties of anglerfish liver pre-cooled by fluidized ice were significantly different from those of the control group during storage at ice temperature. The texture properties of group A did not change much over time. However, the hardness, elasticity, cohesiveness and chewiness of the control group decreased to varying degrees with the prolongation of storage time. Electronic nose PCA analysis showed that the preservation period of group A was significantly longer than that of group B. The fluidized ice precooling method can prolong the process of fresh anglerfish liver from neutral period to spoilage period to a certain extent. Fluid ice pre-cooling and ice-temperature storage techniques have obtained satisfactory sensory properties, such as texture, smell, aroma, etc., in the processing of fresh anglerfish liver. Judging from the acceptable limit of sensory characteristics, the shelf life of fresh anglerfish liver was up to 7 days. It can be inferred that the fresh anglerfish liver processed by this method can meet the needs of long-distance transportation and has good edible quality if it is equipped with an appropriate ice-temperature cold chain.

Claims (6)

1. A method for fresh-keeping cod liver with fluidized ice, characterized in that the steps are: 1) Pre-treatment: fresh anglerfish just caught ashore, washed and set aside; 2) Liver extraction: Fresh anglerfish caught in the sea were bled to take the liver, and then immersed in fluidized ice. The ratio of fluidized ice to fish liver was 30L:10.2kg until the central temperature reached -1.6°C to 0°C. 2. The method for fresh-keeping cod liver with fluidized ice according to claim 1, characterized in that the central temperature is -1.6°C. 3. The method for fresh-keeping cod liver with fluidized ice according to claim 1, characterized in that the concentration of said fluidized ice is 10-30%. 4. the method for fresh-keeping cod liver with fluidized ice according to claim 3, is characterized in that the concentration of described fluidized ice is 23%. 5. The method for fresh-keeping cod liver with fluidized ice according to claim 1, characterized in that the salt concentration of the fluidized ice is 2-5%. 6. the method for fresh-keeping cod liver with fluidized ice according to claim 5, is characterized in that the salt concentration of described fluidized ice is 2.3%.