阅读说明：本技术 一种延长三文鱼保鲜期的方法 (Method for prolonging freshness date of salmon ) 是由 陈卫 崔昊昕 江峰 胡海梅 于 2021-08-24 设计创作，主要内容包括：本发明公开了一种延长三文鱼保鲜期的方法,包括：将三文鱼片放置在温度保持在4℃的复配保鲜剂中浸泡20～30min后,用食品级塑封袋密封包装,然后间隔放置在蓄冷盒内,最后将蓄冷盒放置在预先设定的冰箱区域内,保持蓄冷盒中心空气温度的积分均值在4.0℃,其温度波动在±0.3℃内。以本发明方法保藏三文鱼,放置在冷藏4℃可以保鲜10-12天,且三文鱼肉片的理化指标、微生物指标以及感官特性均达到食用的要求,方便三文鱼的流通和货价期的延长,减少三文鱼原料的浪费,提高了城市三文鱼供应链的安全性。(The invention discloses a method for prolonging the freshness date of salmon, which comprises the following steps: the salmon fillet is placed in a compound preservative kept at 4 ℃ for soaking for 20-30 min, then is packaged in a food-grade plastic package bag in a sealing mode, and then is placed in a cold storage box at intervals, finally the cold storage box is placed in a preset refrigerator area, the integral mean value of the central air temperature of the cold storage box is kept at 4.0 ℃, and the temperature fluctuation is kept within +/-0.3 ℃. The salmon preserved by the method can be preserved for 10-12 days after being placed and refrigerated at 4 ℃, and the physical and chemical indexes, the microbial indexes and the sensory characteristics of the salmon fillet all meet the edible requirements, thereby facilitating the circulation of the salmon and the extension of the shelf life, reducing the waste of salmon raw materials and improving the safety of the urban salmon supply chain.)

1. A method for prolonging the freshness date of salmon is characterized by comprising the following steps: the salmon fillet is placed in a compound preservative kept at 4 ℃ for soaking for 20-30 min, then is packaged in a food-grade plastic package bag in a sealing mode, and is then placed in a cold storage box at intervals, and finally the cold storage box is placed in a preset refrigerator area, the integral mean value of the central air temperature of the cold storage box is kept at 4.0 ℃, and the temperature fluctuation is kept within +/-0.3 ℃;

in the compound preservative, the solvent is water, and the effective components comprise citric acid monohydrate, cyanidin-3-O-rutinoside and tea polyphenol, wherein the concentration of the citric acid monohydrate is 1.5-2.5 g/L, the concentration of the cyanidin-3-O-rutinoside is 0.25-0.75 g/L, and the concentration of the tea polyphenol is 2.5-3.5 g/L.

2. A method according to claim 1, characterized in that the food grade plastic bags are 240mm x 170mm in size and are pre-treated with uv light sterilization.

3. The method as claimed in claim 1, wherein the soaked salmon sides are removed with sterile absorbent paper before being sealed and packaged in food-grade plastic bags.

4. The method of claim 1, wherein the salmon fillet is rectangular.

5. The method of claim 1, wherein the mass of each salmon fillet is 300 g.

6. The method of claim 1, wherein boned and skinned salmon fillets are used.

7. The method of claim 1, wherein the soaking time is 25 min.

8. The method according to claim 1, wherein the concentration of citric acid monohydrate is 2g/L, the concentration of cyanidin-3-O-rutinoside is 0.5g/L, and the concentration of tea polyphenol is 3g/L in the compound preservative.

Technical Field

The invention relates to the technical field of salmon preservation and storage, in particular to a method for prolonging the freshness date of salmon by combining a compound preservative for reducing temperature fluctuation and impact.

Background

Salmon (Salmon), also known as Salmon or Salmon, widely distributed in high latitude regions of northern hemisphere, belonging to the class of teleost Salmoniformes of the class of teleost fishes in cold water region, and having delicious meat quality and good taste, and is a high-quality raw material for making tattoos. Salmon, as an important raw edible fish, is increasingly popular with consumers due to its delicious and fine taste, high protein, low calorie and rich unsaturated fatty acid. The salmon can not be separated from a cold chain for transportation, and in the final stage of the cold chain, the salmon is peeled and divided into salmon fillets for sale until consumers purchase the salmon fillets to home, and the salmon fillets are separated from fish bodies in the process, so that the quality of the salmon fillets is easy to lose due to the characteristics of high protein and high fat.

The shelf life and quality of meat products are influenced by a number of interrelated factors including temperature, oxygen content, endogenous enzymes, water content, light and microbial action. The determination of meat quality parameters has been very important in all processes in the food industry, the quality of meat including many attributes such as colour, texture, pH, tenderness and freshness. Due to the action of tissue enzymes and microorganisms, spoilage of meat products is a complex dynamic process, the denaturation of which is usually accompanied by changes in internal properties (chemical composition) and external properties (color, texture, odor, etc.).

To reduce biochemical degradation and microbial action, different preservation methods are used to store meat and fish products. Chilled fresh meat is commercially important and is a meat product that is widely consumed, and therefore it is important to ensure its quality and safety. Refrigeration and freezing (including storage above or below freezing) by lowering the temperature has been the traditional preservation method for meat products and is currently the most common means to meet the storage needs of a wide range of consumers. In addition, the biological preservative is more and more concerned by people due to the characteristics of safety, health, high efficiency and the like. The common biological antistaling agent is mostly natural products extracted from animals, plants and microorganisms. However, there are many weak links in the cold chain from slaughter to consumer purchase, including frequent voltage fluctuations and temperature abuse. This can lead to reduced product quality, reduced shelf life, spoilage and export rejections, product recalls, and the like. Therefore, cryopreservation has been identified by the meat industry organizations as a priority area for improvement.

The Chinese patent publication No. CN106650291A discloses a model for predicting shelf life of salmon, which is used for researching salmon quality indexes stored at different temperatures, and the model for predicting shelf life of salmon is established according to the salmon quality indexes of volatile basic nitrogen (TVB-N), freshness index K value, thiobarbituric acid (TBA) and the total number of colonies reacting to microbial changes, so that the residual shelf life of salmon within the temperature range of 0-20 ℃ can be predicted. However, the evaluation temperature is ideal and is different from the temperature change in the actual storage process.

Also, for example, the chinese patent publication No. CN101371671B discloses a method for prolonging the shelf life of pork by using ice temperature preservation. According to the preservation characteristics of pork, the designed technical scheme of pork ice temperature preservation comprises the following steps: trimming raw meat, packaging the raw meat, determining the ice temperature, placing the raw meat in an ice temperature box, and controlling the temperature in the ice temperature box. The method for preserving the pork ensures that the ice temperature preservation temperature of the pork is set to be-1 ℃, the fluctuation is controlled within +/-0.5 ℃, the first-grade freshness period of the pork is 19 days, the freshness period of the pork is prolonged by 15 days compared with the freshness period of the pork at 4 ℃, and a longer shelf life is provided for the pork preservation. But the technical means is single, and the temperature condition is difficult to control by consumers in the daily storage process.

The Chinese invention patent with the publication number of CN108112683A provides a bacteriostatic fresh-keeping method and a fresh-keeping box for cold fresh fish. The method comprises an air-conditioning packaging box, bacteriostatic fresh-keeping water-absorbing packing paper arranged on the inner bottom wall of the air-conditioning packaging box and air-conditioning package filling air filled in the air-conditioning packaging box. The bacteriostatic fresh-keeping method for the cold fresh fish meat comprises the following steps: 1) soaking absorbent paper in a fresh-keeping solution prepared from a natural fresh-keeping agent, a fresh-keeping auxiliary agent and water, and then drying and sterilizing to prepare bacteriostatic fresh-keeping absorbent packing paper for inhibiting microorganisms in fish meat; 2) the antibacterial fresh-keeping water-absorbing packing paper is placed on the inner bottom wall of the modified atmosphere packaging box, the cold fresh fish is placed on the inner bottom wall, the modified atmosphere packaging box is filled with modified atmosphere package filling gas, and the modified atmosphere packaging box is packaged and then refrigerated. The patent technology can play a role in inhibiting bacteria, preventing color deterioration and prolonging the shelf life of the product, but the storage method is complex, the cost is high, and the quantity of the contained meat is small.

The cryogenic equipment frequently used by consumers such as refrigerators, freezers and the like is a place where commodities are finally stored, however, temperature changes (including temperature fluctuation and temperature impact) inside the cryogenic equipment are often ignored by sellers and consumers, and the temperature changes can obviously reduce the quality of salmon. Patent specification No. CN209672670U discloses a cold storage box convenient for assembly, comprising a lower cover, an upper cover, an inner barrel, an outer barrel and a cold storage barrel; a first flanging is fixed on the peripheral side surface of the lower cover; the upper surface of the lower cover is clamped with an upper cover; a first closed cavity is formed between the lower cover and the upper cover, and a first heat-preserving material and a bagged cold-storage agent are respectively arranged in the first closed cavity from top to bottom; the lower cover is arranged at the inlet of the inner barrel, and the side surface of the top circumference of the inner barrel is fixed with a bending flanging which is in lap joint with the first flanging. The cold storage box forms a box body by clamping a lower cover and an upper cover, the cold storage barrel and a second heat insulation material are relatively fixed by clamping an inner barrel and an outer barrel, cold energy is prevented from leaking by the first heat insulation material and the second heat insulation material, and long-time cold storage of articles is realized by utilizing the principle of cold energy sinking and the phase change temperature of a first cold storage agent; the production cost of the cold storage box is effectively reduced, and the cold storage effect of the cold storage box is improved.

At present, a method capable of reducing temperature fluctuation and impact in low-temperature storage equipment is designed, and a biological preservative with a good effect is combined, so that the method has important practical significance for prolonging the preservation period of salmon and reducing food waste.

Disclosure of Invention

Aiming at the problems of temperature fluctuation, impact and the like commonly existing in the existing low-temperature storage equipment, the problems of juice loss, microorganism growth and the like of meat products can be accelerated, so that the spoilage of salmon is accelerated. The invention provides a method for prolonging the fresh-keeping period of salmon by combining a compound fresh-keeping agent with reduced temperature fluctuation and impact. The cold storage box convenient to assemble is combined in the refrigerator, so that temperature fluctuation and impact generated by low-temperature storage equipment are reduced, a novel compound biological preservative is used for pretreating salmon, and the preservation effect of the method is analyzed by combining various physical and chemical indexes, so that the aim of prolonging the preservation period of the salmon is fulfilled.

A method for prolonging the freshness date of salmon comprises the following steps: the salmon fillet is placed in a compound preservative kept at 4 ℃ for soaking for 20-30 min, then is packaged in a food-grade plastic package bag in a sealing mode, and is then placed in a cold storage box at intervals, and finally the cold storage box is placed in a preset refrigerator area, the integral mean value of the central air temperature of the cold storage box is kept at 4.0 ℃, and the temperature fluctuation is kept within +/-0.3 ℃;

in the compound preservative, the solvent is water, and the effective components comprise citric acid monohydrate, cyanidin-3-O-rutinoside and tea polyphenol, wherein the concentration of the citric acid monohydrate is 1.5-2.5 g/L, the concentration of the cyanidin-3-O-rutinoside is 0.25-0.75 g/L, and the concentration of the tea polyphenol is 2.5-3.5 g/L.

The structure of cyanidin-3-O-rutinoside is shown as the following formula:

according to the compound preservative, citric acid monohydrate can adjust the pH value and osmotic pressure of the salmon fillet, so that an environment which is not beneficial to bacterial reproduction and breeding is generated, and the bacteriostatic and preservative effects are achieved; meanwhile, the added tea polyphenol and cyanidin-3-O-rutinoside (C3R) have strong antioxidant activity and good bacteriostatic activity, and can effectively prevent the oil oxidation of the salmon. The three components act together to keep the quality and flavor of the salmon meat and achieve the effect of fresh-keeping.

The cold storage box can adopt the prior art, preferably adopts the cold storage box disclosed in the patent specification with the publication number of CN209672670U, and has small temperature fluctuation range.

At present, the preservation period of the refrigerated salmon in a supermarket at 4 ℃ is only about 3 days, and the salmon used as the tattoo can be generally placed for only 1-2 days. The method disclosed by the invention can effectively inhibit the growth and reproduction of microorganisms and slow down the growth rate of volatile basic nitrogen, so that the freshness date of the salmon is prolonged.

In a preferred embodiment, the food-grade plastic package bag is 240mm × 170mm in size and is subjected to ultraviolet light sterilization treatment in advance.

In a preferred embodiment, before being sealed and packaged by a food-grade plastic packaging bag, excess water on the soaked salmon fillet is removed by using sterile absorbent paper.

In a preferred embodiment, the salmon fillet is rectangular.

In a preferred embodiment, the mass of each salmon fillet is 300 g.

In a preferred embodiment, boned and skinned salmon fillets are used.

In a preferred embodiment, the soaking time is 25 min.

In a preferable example, in the compound preservative, the concentration of citric acid monohydrate is 2g/L, the concentration of cyanidin-3-O-rutinoside is 0.5g/L, and the concentration of tea polyphenol is 3 g/L.

Compared with the prior art, the invention has the following remarkable technical effects:

1. the storage is convenient and fast, and the safety is high.

The cold storage box is convenient to assemble and convenient to take or transfer at any time, raw materials for preparing the preservative are citric acid monohydrate, tea polyphenol and cyanidin-3-O-rutinoside, and the raw materials and the sources thereof are all food grade, are safe and non-toxic, and meet the food safety advocated by the state at present.

2. The influence of temperature fluctuation and impact on the quality of the salmon is reduced.

The salmon is stored by the method and can be kept fresh for 10-12 days at the refrigerated temperature of 4 ℃, and the physical and chemical indexes, the microbial indexes and the sensory characteristics of the salmon fillet meet the edible requirements of the salmon, so that the requirements of consumers on the quality of the salmon are met; after the salmon meat obtains a longer fresh-keeping period, circulation of the salmon and prolongation of the shelf life are more convenient, waste of raw materials in the market and in the hands of consumers is reduced, and the safety of the urban salmon supply chain is improved.

Drawings

FIG. 1 is a schematic plan view of a manner of placing salmon fillets in a cold storage box or a storage room;

FIG. 2 is a schematic view showing a temperature fluctuation pattern in comparative example 2;

FIG. 3 is a schematic view of the temperature shock mode of comparative example 3;

FIG. 4 is a graph showing the results of changes in the volatile basic nitrogen (TVB-N) values of salmon in the cold storage area in example 1 and comparative examples 1 to 4;

FIG. 5 is a graph showing the results of the change in the total number of salmon colonies in the cold storage area in example 1 and comparative examples 1 to 4;

FIG. 6 is a graph showing the result of the change in the sap loss of salmon in the cold storage area in example 1 and comparative examples 1 to 4;

FIG. 7 is a graph showing the results of changes in the values of thiobarbituric acid (TBARS) in salmon in the cold storage area in example 1 and comparative examples 1 to 4;

FIG. 8 is a schematic diagram showing a cycle of change in the refrigerating temperature in a conventional refrigerator according to comparative example 4.

Detailed Description

The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.

The technical scheme of the invention is that salmon is stored by combining the compound preservative under the conditions of different storage temperatures, the conditions of volatile basic nitrogen (TVB-N), total bacterial colony count, juice loss and thiobarbituric acid (TBARS) of the salmon are respectively measured at different time points, and the analysis and comparison of the preservation effect are realized by the following steps: setting the temperature in the storage space, pretreating raw fish meat, packaging the raw fish meat, and placing the raw fish meat. The method comprises the following specific steps:

(1) setting of temperature in storage space: the temperature fluctuation and impact state existing in a common refrigerator and the constant temperature state after the cold storage box is placed are respectively simulated, the probe of the temperature recorder is placed at the central position of the storage space, and the refrigerator parameters are adjusted to enable the temperature change integral mean value to reach a set value.

(2) Pretreatment of raw fish meat: the fresh salmon without bones and skins is divided into rectangles with similar sizes and masses by a uniform dividing method, and the experimental group is further processed by a self-made biological preservative after being divided.

(3) Packaging the raw fish: and removing excessive water from the pretreated salmon fillet by using sterile absorbent paper, and sealing and packaging by using a food-grade plastic package bag.

(4) Placing the raw fish: the salmon is respectively placed in designated spaces according to the preset temperature fluctuation and impact setting, and is taken out at different time points, and the fresh-keeping effect of the salmon is determined and analyzed.

Example 1

The fresh salmon without bones and skins is divided into rectangles with similar sizes and masses according to a uniform dividing method, and the weight of a salmon sample is about 300 g. And (3) soaking the well-divided salmon fillet in a compound preservative kept at 4 ℃ for 25min, taking out and packaging. The components of the preservative are as follows: 2g/L of citric acid monohydrate; cyanidin-3-O-rutinoside 0.5 g/L; 3g/L of tea polyphenol; the solvent is water.

And removing excessive water from the pretreated salmon fillet by using sterile absorbent paper, and sealing and packaging by using a food-grade plastic package bag. The salmon is placed in a cold storage box at intervals (the placement mode is shown in figure 1), and then the cold storage box is placed in a preset refrigerator area, the integral mean value of the air temperature in the center of the cold storage box is kept at 4.0 ℃, and the temperature fluctuation is within +/-0.3 ℃.

The experiment was sampled 5 times in 15 days, taken out on days 0, 5, 9, 12 and 15, and analyzed for freshness effect by measuring volatile basic nitrogen (TVB-N), total number of colonies, sap loss, and thiobarbituric acid (TBARS).

Volatile basic nitrogen (TVB-N) was measured according to the semi-trace nitrogen determination method of GB 5009.228-2016 national food safety Standard for volatile basic nitrogen determination. During storage, the protein is decomposed by the action of the enzyme and bacteria in the muscle to generate volatile ammonia and alkaline nitrogen-containing substances such as amines. Such materials are volatile, with higher levels indicating more amino acid damage. According to the regulation in NY/T842-2012 "Green food Fish": the content of the seawater fish volatile basic nitrogen is less than or equal to 15mg/100 g. As shown in the attached figure 4, the TVB-N of the salmon refrigerated by the preservative and the constant temperature of 4 ℃ is more than 15mg/100g on days 11 to 13, and the average value on day 15 is 16.80mg/100 g.

The total number of colonies is determined according to GB4789.2-2016 (national food safety Standard for food microbiology test) for total number of colonies. The colony count is a very effective parameter for evaluating the quality and shelf life of meat products. According to the international food microbiology commission regulations: international Commission on Microbiological specificities for Foods (ICMSF) (1986). Sampling planes for fish and shells. microorganisms in Foods 2. Sampling for Microbiological analysis: primary and specific applications, the total number of colonies of fresh fish must be ≤ 6lg CFU/g. As shown in the attached figure 5, the total number of colonies of the salmon refrigerated by the preservative and the constant temperature of 4 ℃ on days 10 to 13 exceeds 6lg CFU/g, and the average value on day 15 is 6.559lg CFU/g.

Reference to juice loss, eni, o.,T.,&t. (1982) Minced fish production from capelin (Mallotus villosus) -a new method for typing, skinning and removal of fat from small fat fish species journal of Food Science 47(2) p.347-349,354. The juice loss is one of the indexes for measuring the water holding capacity of meat. The juice loss of meat stored at 4 ℃ is continuously increasing. As can be seen from the attached figure 6, the average value of juice loss of the salmon refrigerated by the preservative and the constant temperature of 4 ℃ in 15 days is 2.213%.

Thiobabituric acid (TBARS) assay reference Siu G M, Draper H H.A SURVEY OF THE MALONALDEHYDEDYDE CONTENT OF RETAIL MEATS AND FISH [ J ]. Journal OF Food, 2010,43(4): 1147-. TBARS is widely used for determining the degree of oxidative rancidity of lipid substances in foods, particularly the degree of oxidative rancidity of fat in meat and aquatic products. The total thiobarbituric acid of the salmon is in a continuous rising trend, and as can be seen from the attached figure 7, the mean value of the thiobarbituric acid of the salmon which is kept at the constant temperature of 4 ℃ and refrigerated by the preservative on the 15 th day is 1.799 mg/kg.

Through comprehensive analysis of volatile basic nitrogen (TVB-N), total bacterial count, juice loss and thiobarbituric acid (TBARS), the freshness keeping period of the salmon refrigerated at the constant temperature of 4 ℃ and the preservative is 10-12 days.

Comparative example 1

The fresh salmon without bones and skins is divided into rectangles with similar sizes and masses according to a uniform dividing method, and the weight of a salmon sample is about 300 g. And removing excessive water from the cut salmon fillet by using sterile absorbent paper, and sealing and packaging by using a food-grade plastic package bag. The salmon is placed in a cold storage box at intervals (the placement mode is shown in figure 1), and then the cold storage box is placed in a preset refrigerator area, the integral mean value of the air temperature in the center of the cold storage box is kept at 4.0 ℃, and the temperature fluctuation is within +/-0.3 ℃.

The experiment was sampled 5 times in 15 days, taken out on days 0, 5, 9, 12 and 15, and analyzed for freshness effect by measuring volatile basic nitrogen (TVB-N), total number of colonies, sap loss, and thiobarbituric acid (TBARS).

Volatile basic nitrogen (TVB-N) was measured according to the semi-trace nitrogen determination method of GB 5009.228-2016 national food safety Standard for volatile basic nitrogen determination. During storage, the protein is decomposed by the action of the enzyme and bacteria in the muscle to generate volatile ammonia and alkaline nitrogen-containing substances such as amines. Such materials are volatile, with higher levels indicating more amino acid damage. According to the regulation in NY/T842-2012 "Green food Fish": the content of the seawater fish volatile basic nitrogen is less than or equal to 15mg/100 g. As can be seen from the attached figure 4, the TVB-N of salmon refrigerated at constant temperature of 4 ℃ is over 15mg/100g at 7-9 days, and the average value at 15 days is 21.07mg/100 g.

The total number of colonies is determined according to GB4789.2-2016 (national food safety Standard for food microbiology test) for total number of colonies. The colony count is a very effective parameter for evaluating the quality and shelf life of meat products. According to the international food microbiology commission regulations: international Commission on Microbiological specificities for Foods (ICMSF) (1986). Sampling planes for fish and shells. microorganisms in Foods 2. Sampling for Microbiological analysis: primary and specific applications, the total number of colonies of fresh fish must be ≤ 6lg CFU/g. As can be seen from FIG. 5, the total number of colonies of salmon refrigerated at 4 ℃ on days 8-9 exceeded 6lg CFU/g, and the average value on day 15 was 7.175lg CFU/g.

Reference to juice loss, eni, o.,T.,&t. (1982) Minced fish production from capelin (Mallotus villosus) -a new method for typing, skinning and removal of fat from small fat fish species journal of Food Science 47(2) p.347-349,354. The juice loss is one of the indexes for measuring the water holding capacity of meat. The juice loss of meat stored at 4 ℃ is continuously increasing. As can be seen from the attached figure 6, the average value of the juice loss of salmon refrigerated at constant temperature of 4 ℃ in 15 days is 2.995%

Thiobabituric acid (TBARS) assay reference Siu G M, Draper H. ASURVEY OF THE MALONALDEHYDEDYDE CONTENT OF RETAIL MEATS AND FISH [ J ]. Journal OF Food, 2010,43(4): 1147-. TBARS is widely used for determining the degree of oxidative rancidity of lipid substances in foods, particularly the degree of oxidative rancidity of fat in meat and aquatic products. The total thiobarbituric acid of the salmon is in a continuous rising trend, and as can be seen from the attached figure 7, the mean value of the thiobarbituric acid of the salmon refrigerated at the constant temperature of 4 ℃ on the 15 th day is 2.023 mg/kg.

Through comprehensive analysis of volatile basic nitrogen (TVB-N), total bacterial count, juice loss and thiobarbituric acid (TBARS), the freshness date of the salmon refrigerated at the constant temperature of 4 ℃ is 7-9 days.

Comparative example 2

The fresh salmon without bones and skins is divided into rectangles with similar sizes and masses according to a uniform dividing method, and the weight of a salmon sample is about 300 g. And removing excessive water from the cut salmon fillet by using sterile absorbent paper, and sealing and packaging by using a food-grade plastic package bag. The salmon is placed in a preset refrigerator area at intervals (the placing mode is shown in figure 1), the integral average value of the air temperature in the center of the area is kept at 4.0 ℃, the temperature fluctuation is +/-2.0 ℃, and the temperature fluctuation cycle curve is shown in figure 2.

The experiment was sampled 5 times in 15 days, taken out on days 0, 5, 9, 12 and 15, and analyzed for freshness effect by measuring volatile basic nitrogen (TVB-N), total number of colonies, sap loss, and thiobarbituric acid (TBARS).

Volatile basic nitrogen (TVB-N) was measured according to the semi-trace nitrogen determination method of GB 5009.228-2016 national food safety Standard for volatile basic nitrogen determination. During storage, the protein is decomposed by the action of the enzyme and bacteria in the muscle to generate volatile ammonia and alkaline nitrogen-containing substances such as amines. Such materials are volatile, with higher levels indicating more amino acid damage. According to the regulation in NY/T842-2012 "Green food Fish": the content of the seawater fish volatile basic nitrogen is less than or equal to 15mg/100 g. As can be seen from FIG. 4, the TVB-N of salmon subjected to fluctuation refrigeration at 4 ℃. + -. 2 ℃ is over 15mg/100g on days 5-6, and the average value on day 15 is 24.73mg/100 g.

The total number of colonies is determined according to GB4789.2-2016 (national food safety Standard for food microbiology test) for total number of colonies. The colony count is a very effective parameter for evaluating the quality and shelf life of meat products. According to the international food microbiology commission regulations: international Commission on Microbiological specificities for Foods (ICMSF) (1986). Sampling planes for fish and shells. microorganisms in Foods 2. Sampling for Microbiological analysis: primary and specific applications, the total number of colonies of fresh fish must be ≤ 6lg CFU/g. As can be seen from FIG. 5, the colony count of salmon subjected to fluctuation refrigeration at 4 ℃. + -. 2 ℃ on days 6-7 exceeded 6lg CFU/g, and the average value on day 15 was 8.047lg CFU/g.

Reference to juice loss, eni, o.,T.,&t. (1982) Minced fish production from capelin (Mallotus villosus) -a new method for typing, skinning and removal of fat from small fat fish species journal of Food Science 47(2) p.347-349,354. The juice loss is one of the indexes for measuring the water holding capacity of meat. The juice loss of meat stored at 4 ℃ is continuously increasing. As can be seen from the attached figure 6, the average value of the juice loss of the salmon refrigerated at the temperature of 4 +/-2 ℃ in the fluctuation way at the day 15 is 3.232 percent

Thiobabituric acid (TBARS) assay reference Siu G M, Draper H H.A SURVEY OF THE MALONALDEHYDEDYDE CONTENT OF RETAIL MEATS AND FISH [ J ]. Journal OF Food, 2010,43(4): 1147-. TBARS is widely used for determining the degree of oxidative rancidity of lipid substances in foods, particularly the degree of oxidative rancidity of fat in meat and aquatic products. The total thiobarbituric acid of the salmon is in a continuous rising trend, and as can be seen from the attached figure 7, the mean value of the thiobarbituric acid of the salmon refrigerated at the temperature of 4 +/-2 ℃ in a fluctuating way on day 15 is 2.270 mg/kg.

Through comprehensive analysis of volatile basic nitrogen (TVB-N), total bacterial count, juice loss and thiobarbituric acid (TBARS), the freshness date of the salmon refrigerated at the temperature of 4 +/-2 ℃ is 5-6 days.

Comparative example 3

The fresh salmon without bones and skins is divided into rectangles with similar sizes and masses according to a uniform dividing method, and the weight of a salmon sample is about 300 g. And removing excessive water from the cut salmon fillet by using sterile absorbent paper, and sealing and packaging by using a food-grade plastic package bag. The salmon was placed in a high-low temperature alternating test chamber at intervals (the placement is shown in fig. 1), the integral mean value of the central air temperature was maintained at 4.0 ℃, the temperature was impacted once every day at +4 ℃, and the temperature fluctuation cycle curve is shown in fig. 3.

The experiment was sampled 5 times in 15 days, taken out on days 0, 5, 9, 12 and 15, and analyzed for freshness effect by measuring volatile basic nitrogen (TVB-N), total number of colonies, sap loss, and thiobarbituric acid (TBARS).

Volatile basic nitrogen (TVB-N) was measured according to the semi-trace nitrogen determination method of GB 5009.228-2016 national food safety Standard for volatile basic nitrogen determination. During storage, the protein is decomposed by the action of the enzyme and bacteria in the muscle to generate volatile ammonia and alkaline nitrogen-containing substances such as amines. Such materials are volatile, with higher levels indicating more amino acid damage. According to the regulation in NY/T842-2012 "Green food Fish": the content of the seawater fish volatile basic nitrogen is less than or equal to 15mg/100 g. As can be seen from FIG. 4, the TVB-N of the salmon subjected to impact refrigeration at 4 +4 ℃ is over 15mg/100g on days 6-7, and the average value on day 15 is 22.678mg/100 g.

The total number of colonies is determined according to GB4789.2-2016 (national food safety Standard for food microbiology test) for total number of colonies. The colony count is a very effective parameter for evaluating the quality and shelf life of meat products. According to the international food microbiology commission regulations: international Commission on Microbiological specificities for Foods (ICMSF) (1986). Sampling planes for fish and shells. microorganisms in Foods 2. Sampling for Microbiological analysis: primary and specific applications, the total number of colonies of fresh fish must be ≤ 6lg CFU/g. As can be seen from FIG. 5, the total number of colonies of the 4 +4 ℃ impact-refrigerated salmon was more than 6lg CFU/g on days 7 to 8, and the average value on day 15 was 7.810lg CFU/g.

Reference to juice loss, eni, o.,T.,&t. (1982) Minced fish production from capelin (Mallotus villosus) -a new method for typing, skinning and removal of fat from small fat fish species journal of Food Science 47(2) p.347-349,354. The juice loss is one of the indexes for measuring the water holding capacity of meat. The juice loss of meat stored at 4 ℃ is continuously increasing. As can be seen from the attached figure 6, the average value of juice loss of salmon refrigerated at 4 ℃ and 4 ℃ by impact refrigeration at 15 days is 3.629%

Thiobabituric acid (TBARS) assay reference Siu G M, Draper H H.A SURVEY OF THE MALONALDEHYDEDYDE CONTENT OF RETAIL MEATS AND FISH [ J ]. Journal OF Food, 2010,43(4): 1147-. TBARS is widely used for determining the degree of oxidative rancidity of lipid substances in foods, particularly the degree of oxidative rancidity of fat in meat and aquatic products. The total thiobarbituric acid of salmon is in a rising trend, and as can be seen from figure 7, the mean value of the thiobarbituric acid of salmon subjected to impact refrigeration at 4 ℃ and 4 ℃ on day 15 is 2.155 mg/kg.

Through comprehensive analysis of volatile basic nitrogen (TVB-N), total bacterial count, juice loss and thiobarbituric acid (TBARS), the freshness date of the salmon refrigerated at 4 ℃ plus 4 ℃ under impact is 6-7 days.

Comparative example 4

The fresh salmon without bones and skins is divided into rectangles with similar sizes and masses according to a uniform dividing method, and the weight of a salmon sample is about 300 g. And removing excessive water from the cut salmon fillet by using sterile absorbent paper, and sealing and packaging by using a food-grade plastic package bag. Salmon was refrigerated at intervals in a general refrigerator area (the arrangement is shown in fig. 1), the panel temperature was set to 4.0 ℃, and the temperature change cycle was shown in fig. 8.

The experiment was sampled 5 times in 15 days, taken out on days 0, 5, 9, 12 and 15, and analyzed for freshness effect by measuring volatile basic nitrogen (TVB-N), total number of colonies, sap loss, and thiobarbituric acid (TBARS).

Volatile basic nitrogen (TVB-N) was measured according to the semi-trace nitrogen determination method of GB 5009.228-2016 national food safety Standard for volatile basic nitrogen determination. During storage, the protein is decomposed by the action of the enzyme and bacteria in the muscle to generate volatile ammonia and alkaline nitrogen-containing substances such as amines. Such materials are volatile, with higher levels indicating more amino acid damage. According to the regulation in NY/T842-2012 "Green food Fish": the content of the seawater fish volatile basic nitrogen is less than or equal to 15mg/100 g. As can be seen from FIG. 4, the TVB-N of salmon refrigerated in a normal refrigerator at 4 ℃ exceeds 15mg/100g on days 4 to 6, and the average value on day 15 is 26.375mg/100 g.

The total number of colonies is determined according to GB4789.2-2016 (national food safety Standard for food microbiology test) for total number of colonies. The colony count is a very effective parameter for evaluating the quality and shelf life of meat products. According to the international food microbiology commission regulations: international Commission on Microbiological specificities for Foods (ICMSF) (1986). Sampling planes for fish and shells. microorganisms in Foods 2. Sampling for Microbiological analysis: primary and specific applications, the total number of colonies of fresh fish must be ≤ 6lg CFU/g. As can be seen from FIG. 5, the total number of colonies of salmon refrigerated in a 4 ℃ common refrigerator was more than 6lg CFU/g on days 5 to 6, and the average value on day 15 was 8.658lg CFU/g.

Reference to juice loss, eni, o.,T.,&t. (1982) Minced fish production from capelin (Mallotus villosus) -a new method for typing, skinning and removal of fat from small fat fish species journal of Food Science 47(2) p.347-349,354. The juice loss is one of the indexes for measuring the water holding capacity of meat. The juice loss of meat stored at 4 ℃ is continuously increasing. As can be seen from the attached figure 6, the average value of the 15 th day juice loss of salmon refrigerated in a common refrigerator at 4 ℃ is 4.875%

Thiobabituric acid (TBARS) assay reference Siu G M, Draper H H.A SURVEY OF THE MALONALDEHYDEDYDE CONTENT OF RETAIL MEATS AND FISH [ J ]. Journal OF Food, 2010,43(4): 1147-. TBARS is widely used for determining the degree of oxidative rancidity of lipid substances in foods, particularly the degree of oxidative rancidity of fat in meat and aquatic products. The total thiobarbituric acid of the salmon is in a rising trend, and as can be seen from the attached figure 7, the average value of the thiobarbituric acid of the salmon refrigerated in a common refrigerator at 4 ℃ on day 15 is 2.476 mg/kg.

Through comprehensive analysis of volatile basic nitrogen (TVB-N), total bacterial count, juice loss and thiobarbituric acid (TBARS), the freshness date of the salmon refrigerated in a common refrigerator at 4 ℃ is 4-5 days.

Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.