A method for preserving semi-dried large yellow croaker product

Abstract

The present invention belongs to the technical field of aquatic product processing, and specifically relates to a preservation method for semi-dried large yellow croaker products. The present invention proposes a preservation method for semi-dried large yellow croaker products, which uses semi-dried large yellow croaker products as raw materials, places the semi-dried large yellow croaker products in a packaging container; places a number of fresh-keeping plant fiber absorbent papers at the bottom of the packaging container; and introduces a fresh-keeping gas conditioning system including hydrogen and carbon monoxide into the packaging container. The addition of hydrogen and carbon monoxide to the fresh-keeping gas conditioning system of the present invention can not only exert an antibacterial effect, but also produce a good passivation or activity inhibition effect on molds in dried aquatic products, as well as microbial metabolites-lipase and its analogs, thereby playing an unexpected protective role for large yellow croaker lipids.

Description

Technical Field

[0001] The invention belongs to the technical field of aquatic product processing, and particularly relates to a method for preserving semi-dried large yellow croaker products. Background Art

[0002] Semi-dry processing is an important form of aquatic product processing, which is more common in coastal and surrounding areas of my country. Semi-dried large yellow croaker and eel still have a high moisture content in the muscle (45-60%, w / w). It is difficult to effectively maintain product quality at room temperature or refrigerated storage because muscle lipids and proteins are easily oxidized, the moisture content and water activity are high, and microorganisms (mainly spoilage bacteria and molds) are easy to breed and contaminate. In actual consumption and storage, -18℃ freezing is often used. However, low-temperature freezing requires specific refrigeration equipment and needs to be thawed before consumption, which also brings certain inconveniences to consumers.

[0003] In view of the above problems, a method is developed that can control oxidative browning, be easy to store, and be easy to eat under conventional refrigerated conditions, achieve good preservation effects, and extend the shelf life of the product. The Chinese patent with patent number CN104247752B discloses "A method for preserving large yellow croaker using a natural preservative combined with modified atmosphere packaging", which provides a method for preserving large yellow croaker using a natural preservative combined with modified atmosphere packaging, which effectively extends the shelf life of the product. However, due to the complex operation steps and cumbersome production process of natural preservatives, it is not conducive to the application of actual industrial production. Carbon dioxide, nitrogen, and oxygen in modified atmosphere packaging are common traditional atmospheres used to control spoilage bacteria, and large yellow croaker is different from other fish species. The lipid content in large yellow croaker and dried products is high. Therefore, the traditional atmosphere combination is used to preserve large yellow croaker and dried products, which cannot effectively control species such as Acinetobacter, Psychrobacter, Cyclothrix, Lactobacillus, Shewanella, Wandering Coccus, and Aeromonas. Summary of the invention

[0004] In order to overcome the problems in the prior art that the preservatives for preserving large yellow croaker are difficult to prepare and the preservative atmosphere cannot effectively protect the lipids of large yellow croaker, the present invention proposes a preservative method for semi-dried large yellow croaker products, the preservative method uses the semi-dried large yellow croaker products as raw materials, the semi-dried large yellow croaker products are placed in a packaging container; a number of preservative plant fiber absorbent papers are placed at the bottom of the packaging container; and a preservative atmosphere system including hydrogen and carbon monoxide is introduced into the packaging container. The addition of hydrogen and carbon monoxide to the preservative atmosphere system of the present invention can not only exert an antibacterial effect, but also produce a good passivation or activity inhibition effect on molds in dried aquatic products, and microbial metabolites-lipase and its analogs, thereby playing an unexpected protective role on the lipids of large yellow croaker and extending the shelf life of the semi-dried large yellow croaker products.

[0005] The specific technical solution of the present invention is:

[0006] The invention provides a method for preserving semi-dried large yellow croaker products, comprising the following steps: placing the semi-dried large yellow croaker products in a packaging container; introducing a fresh-keeping atmosphere system into the packaging container; and the fresh-keeping atmosphere system comprises hydrogen and carbon monoxide.

[0007] Unlike other fish species, large yellow croaker and dried products have high lipid content, so during low-temperature storage, their microbial composition and changes are also different from other fish species. The specific main microorganisms in large yellow croaker and dried products include: Acinetobacter, Psychrobacter, Ringworm, Lactobacillus, Shewanella, Wandering Coccus, and Aeromonas, etc.; in addition, the lipase compounds generated by the metabolism of some microorganisms also hydrolyze, oxidize and degrade lipids. The addition of hydrogen and carbon monoxide to the fresh-keeping atmosphere conditioning system of the present invention can not only exert an antibacterial effect and inhibit all the above-mentioned bacterial genera, but also produce good passivation or activity inhibition effects on molds in dried aquatic products, as well as microbial metabolites-lipases and their analogs, so it has an unexpected protective effect on large yellow croaker lipids.

[0008] Preferably, in the fresh-keeping atmosphere conditioning system, the volume fraction of hydrogen is 1.5-3.0%, and the volume fraction of carbon monoxide is 0.5-1.5%.

[0009] Previous studies have found that the addition of a small amount of hydrogen has a very good inhibitory effect on spoilage bacteria and molds. In addition, the addition of hydrogen also has the effects of inhibiting free radicals (antioxidation) and protecting polyunsaturated fatty acids from oxidation, which is especially suitable for fish products with high fat content. The introduction of a small amount of hydrogen into the fresh-keeping atmosphere system has a good preservation effect, while the hydrogen content is very low and does not affect the safety of the gas. When the proportion of hydrogen and carbon monoxide in the atmosphere is too low, it will cause the inability to effectively control all the microorganisms of the genera Acinetobacter, Psychrobacter, Cyclothrix, Lactobacillus, Shewanella, Wandering Coccus, and Aeromonas in large yellow croaker and dried products, and the purpose of protecting the lipids of large yellow croaker cannot be achieved; when the proportion of hydrogen in the atmosphere is too high, there will be a potential risk of explosion; when the proportion of carbon monoxide is too high, it will bring safety hazards to the health of consumers.

[0010] Preferably, the volume ratio of the hydrogen to the carbon monoxide is (2-3):1.

[0011] Based on experimental and theoretical research, the team of the present invention found that the ratio between hydrogen and carbon monoxide will also affect the above bacteria, thereby affecting the effect of protecting the lipids of large yellow croaker. When the volume ratio of hydrogen to carbon monoxide is too large, that is, when the hydrogen content is high, there is a potential explosion safety hazard; when the volume ratio of hydrogen to carbon monoxide is too small, it will make it difficult to better control all the above bacteria and microorganisms of the genera Acinetobacter, Psychrobacter, Cyclothrix, Lactobacillus, Shewanella, Wandering Coccus, and Aeromonas in large yellow croaker and dried products. When the volume ratio of hydrogen to carbon monoxide is between (2 to 3): 1, the gas conditioning system has a better effect of protecting the lipid stability of large yellow croaker and inhibiting the reproduction of microorganisms.

[0012] Preferably, a number of fresh-keeping plant fiber absorbent papers are placed at the bottom of the packaging container, and the preparation method of the fresh-keeping plant fiber absorbent papers comprises: adding litsea cubeba oil to the plant fiber absorbent papers to prepare the fresh-keeping plant fiber absorbent papers.

[0013] Preferably, the litsea cubeba oil is a litsea cubeba oil emulsified system; the preparation method of the litsea cubeba oil emulsified system comprises: preparing a litsea cubeba oil-water solution system, adding an emulsifier, and obtaining the litsea cubeba oil emulsified system.

[0014] The main active substances in Litsea cubeba oil include citral, limonene, methyl heptenone, coriander alcohol, geraniol, vanillin and camphene, etc. These active substances work synergistically with the fresh-keeping atmosphere to exert antibacterial and antioxidant effects. The active substances contained in Litsea cubeba oil are uniquely combined with plant fibers after emulsification, which can exert sustained-release and long-term antibacterial effects, and can also reduce the generation of volatile fishy smell of dried yellow croaker during storage.

[0015] Preferably, the plant fiber absorbent paper uses grass stem fibers as plant fiber raw materials.

[0016] Different plant fiber raw materials have different lignin, cellulose, and hemicellulose molecules and compositions. The team of the present invention has found based on experimental and theoretical studies that the main active substances in Litsea cubeba oil have different degrees of binding and sustained-release effects with other types of raw material molecules. The main active substances in Litsea cubeba oil, such as citral, limonene, methyl heptenone, vanillin, and camphene, are combined with cellulose, hemicellulose, and lignin molecules in the grass stem fiber plant fiber absorbent paper, and have good binding stability. Litsea cubeba oil and grass stem fiber plant fiber absorbent paper are combined in this way, so that the antibacterial substances in Litsea cubeba oil have long-lasting and sustained-release active effects, thereby achieving good antibacterial control effects and weakening the bad flavor of semi-dried large yellow croaker products. In addition, the use of fresh-keeping plant fiber absorbent paper to process semi-dried large yellow croaker products can also absorb the fishy substances produced during the refrigeration of semi-dried large yellow croaker products, which plays a positive role in maintaining the flavor of the product.

[0017] Preferably, the fresh-keeping atmosphere system further comprises carbon dioxide, nitrogen and oxygen; in the fresh-keeping atmosphere system, the volume fraction of carbon dioxide is 48-57%, the volume fraction of nitrogen is 25-30%, and the volume fraction of oxygen is 9.5-24%.

[0018] Carbon dioxide, nitrogen and oxygen are the common traditional atmosphere control methods used to control spoilage bacteria. However, yellow croaker is different from other fish species in that its lipid content is high. Therefore, the use of traditional atmosphere control combination to preserve yellow croaker and its dried products will result in the inability to effectively control all the microorganisms of the genera Acinetobacter, Psychrobacter, Cyclothrix, Lactobacillus, Shewanella, Rovercoccus, and Aeromonas in yellow croaker and its dried products. Previous studies have found that hydrogen has a very good inhibitory effect on spoilage bacteria, molds, lipases and their analogs, especially under the synergistic conditions of nitrogen dioxide, nitrogen and oxygen, the effect of hydrogen on regulating microorganisms in semi-dried fish products is more obvious.

[0019] Preferably, the volume ratio of the semi-dried large yellow croaker product to the fresh-keeping atmosphere conditioning system is (0.5-3):1.

[0020] Preferably, the preparation method of the semi-dried large yellow croaker product comprises: splitting a whole yellow croaker in the middle to prepare large yellow croaker slices, marinating with NaCl, and then drying to obtain the semi-dried large yellow croaker product.

[0021] The initial moisture content in the product muscle is 45-60% and the water activity is 0.70-0.85. After drying processing, the moisture content and water activity in the semi-dried large yellow croaker fillet decrease, and the processing energy consumption is low and the time is short.

[0022] Preferably, the packaging container is a skin-fitting packaging box, and the fresh-keeping plant fiber absorbent paper is attached to the bottom of the skin-fitting packaging box.

[0023] The skin-friendly packaging box can ensure that the dried large yellow croaker product is stable and not prone to sliding, and the overall sensory experience of the product is good.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) Yellow croaker has less nutritional loss after drying, which can reduce the water content and water activity in the fish fillet, while keeping the water content as high as possible to increase the taste when eaten:

[0026] (2) Unlike other fish species, large yellow croaker and its dried products have a high lipid content. The addition of hydrogen can inhibit free radicals (antioxidant) and protect polyunsaturated fatty acids from oxidation. It is especially suitable for fish products with high fat content. In combination with nitrogen dioxide, nitrogen and oxygen, its role in regulating microorganisms in semi-dried fish products is more obvious.

[0027] (3) The addition of hydrogen and carbon monoxide to the fresh-keeping atmosphere conditioning system of the present invention not only has an antibacterial effect, but also has a good passivation or activity inhibition effect on molds in dried aquatic products, as well as microbial metabolites, namely lipase and its analogues. Therefore, it has an unexpected protective effect on the lipids of large yellow croaker, can prolong the shelf life, and meet the needs of the storage and consumption markets.

[0028] (4) Litsea cubeba oil contains one or more of the following: citral, limonene, methyl heptenone, coriander alcohol, geraniol, vanillin and camphene. These active substances work synergistically with the fresh-keeping atmosphere to exert antibacterial and antioxidant effects. The active substances contained in Litsea cubeba oil are emulsified and combined with plant fibers in a unique and stable manner, which can exert a sustained-release and long-lasting antibacterial effect. It can also reduce the generation of volatile fishy smell of dried yellow croaker during storage.

[0029] (5) The skin-tight packaging box can ensure that the dried large yellow croaker product is stable and not prone to sliding, and the overall sensory experience of the product is good. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to the embodiments, but is not intended to be limiting of the present invention.

[0031] Overall embodiment

[0032] A method for preserving semi-dried large yellow croaker products comprises the following steps: placing the semi-dried large yellow croaker products in a packaging container; introducing a fresh-keeping atmosphere system into the packaging container; and the fresh-keeping atmosphere system comprises hydrogen and carbon monoxide.

[0033] Preferably, in the fresh-keeping atmosphere conditioning system, the volume fraction of hydrogen is 1.5-3.0%, and the volume fraction of carbon monoxide is 0.5-1.5%.

[0034] Preferably, the volume ratio of the hydrogen to the carbon monoxide is (2-3):1.

[0035] Preferably, a number of fresh-keeping plant fiber absorbent papers are placed at the bottom of the packaging container, and the preparation method of the fresh-keeping plant fiber absorbent papers comprises: adding litsea cubeba oil to the plant fiber absorbent papers to prepare the fresh-keeping plant fiber absorbent papers.

[0036] Preferably, the litsea cubeba oil is a litsea cubeba oil emulsified system; the preparation method of the litsea cubeba oil emulsified system comprises: preparing a litsea cubeba oil-water solution system, adding an emulsifier, and obtaining the litsea cubeba oil emulsified system.

[0037] Preferably, the plant fiber absorbent paper uses grass stem fibers as plant fiber raw materials.

[0038] Preferably, the fresh-keeping atmosphere system further comprises carbon dioxide, nitrogen and oxygen; in the fresh-keeping atmosphere system, the volume fraction of carbon dioxide is 48-57%, the volume fraction of nitrogen is 25-30%, and the volume fraction of oxygen is 9.5-24%.

[0039] Preferably, the volume ratio of the semi-dried large yellow croaker product to the fresh-keeping atmosphere conditioning system is (0.5-3):1.

[0040] Preferably, the preparation method of the semi-dried large yellow croaker product comprises: splitting a whole yellow croaker in the middle to prepare large yellow croaker slices, marinating with NaCl, and then drying to obtain the semi-dried large yellow croaker product.

[0041] Preferably, the packaging container is a skin-fitting packaging box, and the fresh-keeping plant fiber absorbent paper is attached to the bottom of the skin-fitting packaging box.

[0042] Example 1

[0043] A method for preserving semi-dried large yellow croaker products comprises the following steps:

[0044] (1) Preparation of semi-dried large yellow croaker fillets: A whole fish is cut in half, pre-treated, pickled in a 2.5% by volume NaCl solution, and then dried to obtain semi-dried large yellow croaker fillets.

[0045] (2) Preparation of fresh-keeping plant fiber absorbent paper A: First, a 0.36% lychee oil-water solution system was prepared, and after adding 0.20% Tween-50 (food grade) by volume, a high-speed vacuum shear emulsification method was used, maintaining 26000g for 30 minutes and a temperature of 65°C to prepare a lychee oil emulsified system. A small amount of the lychee oil emulsified system was sprayed on the surface of the grass stem fiber plant fiber absorbent paper by a spraying method, and then dried at 40°C overnight to prepare a fresh-keeping plant fiber absorbent paper A.

[0046] (3) Preparation of fresh-keeping atmosphere conditioning system A: Use a gas mixer to mix the gases in a volume ratio of (hydrogen: carbon dioxide: nitrogen: oxygen: carbon monoxide) = (3%: 50%: 30%: 15.5%: 1.5%) to form a mixed gas. All gases are food grade and have a gas purity of ≥ 99%.

[0047] (4) A rectangular skin-friendly packaging box is used to place the semi-dried large yellow croaker fillet in the packaging box containing the fresh-keeping atmosphere conditioning system A, and the volume ratio of the semi-dried large yellow croaker product to the injected gas is controlled to be 3:1. A sheet of plant fiber absorbent paper A prepared in step (2) is placed at the bottom of the packaging box.

[0048] (5) Storage: Place the sealed packaging box in a refrigerator at 0°C for refrigeration.

[0049] After storage for 30 days, the semi-dried large yellow croaker product preserved in the embodiment was sampled, and the total bacteria count, mold count, and fat oxidation degree (peroxide value) in the semi-dried large yellow croaker were measured, and the results are shown in Table 1. The color, smell and taste, and muscle elasticity of the large yellow croaker were used as the inspection items, and the semi-dried large yellow croaker product preserved in the embodiment was subjected to sensory evaluation, and the evaluation adopted a "five-point system", and each inspection item was respectively good, relatively good, average, relatively poor, and poor, and the scores were 5, 4, 3, 2, and 1, respectively. The assessors participating in the sensory evaluation consisted of 10 members of the sensory evaluation team of the School of Food and Pharmacy of Zhejiang Ocean University. The sensory evaluation standards are shown in Table 2, and the sensory evaluation results of the large yellow croaker after storage are shown in Table 3.

[0050] Example 2

[0051] A method for preserving semi-dried large yellow croaker products comprises the following steps:

[0052] (1) Preparation of semi-dried large yellow croaker fillets: A whole fish is cut in half, pre-treated, pickled in a 2.5% by volume NaCl solution, and then dried to obtain semi-dried large yellow croaker fillets.

[0053] (2) Preparation of fresh-keeping plant fiber absorbent paper A: First, a 0.36% lychee oil-water solution system was prepared, and after adding 0.20% Tween-50 (food grade) by volume, a high-speed vacuum shear emulsification method was used, maintaining 26000g for 30 minutes and a temperature of 65°C to prepare a lychee oil emulsified system. A small amount of the lychee oil emulsified system was sprayed on the surface of the grass stem fiber plant fiber absorbent paper by a spraying method, and then dried at 40°C overnight to prepare a fresh-keeping plant fiber absorbent paper A.

[0054] (3) Preparation of fresh-keeping atmosphere system B: Using a gas mixer, mix the gases in a volume ratio of (hydrogen: carbon dioxide: nitrogen: oxygen: carbon monoxide) = (1.5%: 48%: 25%: 25%: 0.5%) to form a mixed gas. The gases are all food grade and the gas purity is ≥ 99%.

[0055] (4) A rectangular skin-packaging box is used to place the semi-dried large yellow croaker fillet in the packaging box containing the fresh-keeping atmosphere control system B, the volume ratio of the semi-dried large yellow croaker product to the injected gas is controlled to be 1:2, and a sheet of plant fiber absorbent paper A prepared in step (2) is placed at the bottom of the packaging box.

[0056] (5) Storage: Place the sealed packaging box in a refrigerator at 4°C.

[0057] After storage for 30 days, the semi-dried large yellow croaker product preserved in this embodiment was sampled, and the total bacteria count, mold count, and fat oxidation degree (peroxide value) in the semi-dried large yellow croaker were measured. The results are shown in Table 1; the semi-dried large yellow croaker product preserved in this embodiment was subjected to sensory evaluation, and the results are shown in Table 3.

[0058] Example 3

[0059] A method for preserving semi-dried large yellow croaker products comprises the following steps:

[0060] (1) Preparation of semi-dried large yellow croaker fillets: A whole fish is cut in half, pre-treated, pickled in a 2.5% by volume NaCl solution, and then dried to obtain semi-dried large yellow croaker fillets.

[0061] (2) Preparation of fresh-keeping plant fiber absorbent paper B: First, a litsea cubeba oil-water solution system with a volume fraction of 0.36% of litsea cubeba oil was prepared, and after adding 0.20% of Tween-50 (food grade) by volume, a high-speed vacuum shear emulsification method was used, maintaining 26000g for 30 minutes and a temperature of 65°C to prepare a litsea cubeba oil emulsified system. On the surface of the hemp plant fiber absorbent paper, a small amount of the litsea cubeba oil emulsified system was sprayed on the plant fiber absorbent paper by a spraying method, and then dried at 40°C overnight to prepare the fresh-keeping plant fiber absorbent paper B.

[0062] (3) Preparation of fresh-keeping atmosphere conditioning system A: Use a gas mixer to mix the gases in a volume ratio of (hydrogen: carbon dioxide: nitrogen: oxygen: carbon monoxide) = (3%: 50%: 30%: 15.5%: 1.5%) to form a mixed gas. All gases are food grade and have a gas purity of ≥ 99%.

[0063] (4) A rectangular skin-friendly packaging box is used to place the semi-dried large yellow croaker fillet in the packaging box containing the fresh-keeping atmosphere conditioning system A, and the weight of the semi-dried large yellow croaker and the volume of the filled gas are controlled to be 3:1. A sheet of plant fiber absorbent paper B prepared in step (2) is placed at the bottom of the packaging box.

[0064] (5) Storage: Place the sealed packaging box in a refrigerator at 0°C for refrigeration.

[0065] After storage for 30 days, the semi-dried large yellow croaker product preserved in this embodiment was sampled, and the total bacteria count, mold count, and fat oxidation degree (peroxide value) in the semi-dried large yellow croaker were measured. The results are shown in Table 1; the semi-dried large yellow croaker product preserved in this embodiment was subjected to sensory evaluation, and the results are shown in Table 3.

[0066] Comparative Example 1, the semi-dried large yellow croaker product in Example 3 has a poor preservation effect. Based on experimental and theoretical research, the present invention team found that the main active substances in Litsea cubeba oil, such as citral, limonene, methyl heptenone, vanillin and camphene, are combined with cellulose, hemicellulose and lignin molecules in the grass stem fiber plant fiber absorbent paper, and have good binding stability, so that the antibacterial substances in Litsea cubeba oil play a long-term, slow-release active role, thereby achieving a good antibacterial control effect, and weakening the bad flavor of the semi-dried large yellow croaker product. When other plant fibers are used as raw materials, it is difficult to achieve the long-term slow-release effect achieved by the special combination of Litsea cubeba oil emulsification system and the grass stem fiber plant fiber absorbent paper. The antibacterial substances in Litsea cubeba oil cannot play a long-term, slow-release active role, and also achieve a good antibacterial control effect, and the bad flavor of the semi-dried large yellow croaker product cannot be effectively weakened.

[0067] Example 4

[0068] A method for preserving semi-dried large yellow croaker products comprises the following steps:

[0069] (1) Preparation of semi-dried large yellow croaker fillets: A whole fish is cut in half, pre-treated, pickled in a 2.5% by volume NaCl solution, and then dried to obtain semi-dried large yellow croaker fillets.

[0070] (2) Preparation of fresh-keeping plant fiber absorbent paper C: First, a citronella essential oil-water solution system with a volume fraction of 0.36% citronella essential oil was prepared, and after adding 0.20% Tween-50 (food grade) by volume, a high-speed vacuum shear emulsification method was used, maintaining 26000g for 30 minutes and a temperature of 65°C to prepare a citronella essential oil emulsified system. On the surface of the grass stem fiber plant fiber absorbent paper, a small amount of the citronella essential oil emulsified system was sprayed onto the plant fiber absorbent paper by a spraying method, and then dried at 40°C overnight to prepare a fresh-keeping plant fiber absorbent paper C.

[0071] (3) Preparation of fresh-keeping atmosphere conditioning system A: Use a gas mixer to mix the gases in a volume ratio of (hydrogen: carbon dioxide: nitrogen: oxygen: carbon monoxide) = (3%: 50%: 30%: 15.5%: 1.5%) to form a mixed gas. All gases are food grade and have a gas purity of ≥ 99%.

[0072] (4) A rectangular skin-friendly packaging box is used to place the semi-dried large yellow croaker fillet in the packaging box containing the fresh-keeping atmosphere conditioning system A, and the weight of the semi-dried large yellow croaker and the volume of the filled gas are controlled to be 3:1. A sheet of plant fiber absorbent paper C prepared in step (2) is placed at the bottom of the packaging box.

[0073] (5) Storage: Place the sealed packaging box in a refrigerator at 0°C for refrigeration.

[0074] After storage for 30 days, the semi-dried large yellow croaker product preserved in this embodiment was sampled, and the total bacteria count, mold count, and fat oxidation degree (peroxide value) in the semi-dried large yellow croaker were measured. The results are shown in Table 1; the semi-dried large yellow croaker product preserved in this embodiment was subjected to sensory evaluation, and the results are shown in Table 3.

[0075] Compared with Example 1, the semi-dried large yellow croaker product in Example 4 has a poor preservation effect. Based on experimental and theoretical research, the present invention team found that the main active substances in Litsea cubeba oil include citral, limonene, methyl heptenone, cilantro, geraniol, vanillin and camphene, etc. These active substances work synergistically with the fresh-keeping atmosphere, and can play an antibacterial and antioxidant effect. At the same time, the active substances contained in Litsea cubeba oil are uniquely combined with plant fibers after emulsification, and can play a sustained-release and long-term antibacterial effect, and can also reduce the generation of volatile fishy smell of dried large yellow croaker during storage. When other types of plant essential oils are used, the antibacterial and antioxidant effects cannot be played, and the sustained-release and long-term antibacterial effects cannot be played on semi-dried large yellow croaker slices, so the generation of dried large yellow croaker fishy smell during storage cannot be reduced.

[0076] Example 5

[0077] A method for preserving semi-dried large yellow croaker products comprises the following steps:

[0078] (1) Preparation of semi-dried large yellow croaker fillets: A whole fish is cut in half, pre-treated, pickled in a 2.5% by volume NaCl solution, and then dried to obtain semi-dried large yellow croaker fillets.

[0079] (2) Preparation of fresh-keeping plant fiber absorbent paper A: First, a 0.36% lychee oil-water solution system was prepared, and after adding 0.20% Tween-50 (food grade) by volume, a high-speed vacuum shear emulsification method was used, maintaining 26000g for 30 minutes and a temperature of 65°C to prepare a lychee oil emulsified system. A small amount of the lychee oil emulsified system was sprayed on the surface of the grass stem fiber plant fiber absorbent paper by a spraying method, and then dried at 40°C overnight to prepare a fresh-keeping plant fiber absorbent paper A.

[0080] (3) Preparation of fresh-keeping atmosphere system C: Using a gas mixer, mix the gases in a volume ratio of (hydrogen: carbon dioxide: nitrogen: oxygen: carbon monoxide) = (2.25%: 50%: 30%: 15.5%: 2.25%) to form a mixed gas. The gases are all food grade and the gas purity is ≥ 99%.

[0081] (4) A rectangular skin-friendly packaging box is used to place the semi-dried large yellow croaker fillet in the packaging box containing the fresh-keeping atmosphere control system C, the volume ratio of the semi-dried large yellow croaker product to the injected gas is controlled to be 1:2, and a sheet of plant fiber absorbent paper A prepared in step (2) is placed at the bottom of the packaging box.

[0082] (5) Storage: Place the sealed packaging box in a refrigerator at 4°C.

[0083] After storage for 30 days, the semi-dried large yellow croaker product preserved in this embodiment was sampled, and the total bacteria count, mold count, and fat oxidation degree (peroxide value) in the semi-dried large yellow croaker were measured. The results are shown in Table 1; the semi-dried large yellow croaker product preserved in this embodiment was subjected to sensory evaluation, and the results are shown in Table 3.

[0084] Compared with Example 1, the semi-dried large yellow croaker product in Example 5 has a poor preservation effect. Based on experimental and theoretical research, the present invention team found that the ratio between hydrogen and carbon monoxide will also affect the above bacteria, thereby affecting the effect of protecting large yellow croaker lipids. When the volume ratio of hydrogen to carbon monoxide is between (2-3):1, the gas conditioning system has a better effect of protecting large yellow croaker lipid stability and inhibiting microbial reproduction. When the volume ratio of hydrogen to carbon monoxide is too small, mold, fat oxidation and hydrolysis, and some psychrophilic bacteria cannot be well inhibited, thereby affecting the effect of protecting large yellow croaker lipids.

[0085] Example 6

[0086] A method for preserving semi-dried large yellow croaker products comprises the following steps:

[0087] (1) Preparation of semi-dried large yellow croaker fillets: A whole fish is cut in half, pre-treated, pickled in a 2.5% by volume NaCl solution, and then dried to obtain semi-dried large yellow croaker fillets.

[0088] (2) Preparation of fresh-keeping plant fiber absorbent paper A: First, a 0.36% lychee oil-water solution system was prepared, and after adding 0.20% Tween-50 (food grade) by volume, a high-speed vacuum shear emulsification method was used, maintaining 26000g for 30 minutes and a temperature of 65°C to prepare a lychee oil emulsified system. A small amount of the lychee oil emulsified system was sprayed on the surface of the grass stem fiber plant fiber absorbent paper by a spraying method, and then dried at 40°C overnight to prepare a fresh-keeping plant fiber absorbent paper A.

[0089] (3) Preparation of fresh-keeping atmosphere conditioning system E: Use a gas mixer to mix the gases in a volume ratio of (hydrogen: carbon dioxide: nitrogen: oxygen: carbon monoxide) = (1%: 53%: 30%: 15.7%: 0.3%) to form a mixed gas. All gases are food grade and have a gas purity of ≥ 99%.

[0090] (4) A rectangular skin-friendly packaging box is used to place the semi-dried large yellow croaker fillet in the packaging box containing the fresh-keeping atmosphere control system E, and the weight of the semi-dried large yellow croaker and the volume of the filled gas are controlled to be 3:1. A sheet of plant fiber absorbent paper A prepared in step (2) is placed at the bottom of the packaging box.

[0091] (5) Storage: Place the sealed packaging box in a refrigerator at 0°C for refrigeration.

[0092] After storage for 30 days, the semi-dried large yellow croaker product preserved in this embodiment was sampled, and the total bacteria count, mold count, and fat oxidation degree (peroxide value) in the semi-dried large yellow croaker were measured. The results are shown in Table 1; the semi-dried large yellow croaker product preserved in this embodiment was subjected to sensory evaluation, and the results are shown in Table 3.

[0093] Compared with Example 2, the preservation effect of the semi-dried large yellow croaker product in Example 6 is poor. Based on experimental and theoretical research, the present invention team found that hydrogen has a very good inhibitory effect on spoilage bacteria, molds, lipases and their analogs, especially under the synergistic conditions of nitrogen dioxide, nitrogen and oxygen, the effect of hydrogen on regulating microorganisms in semi-dried fish products is more obvious; large yellow croaker is different from other fish species, and the lipid content in large yellow croaker and dried products is high. Therefore, for the preservation of large yellow croaker and dried products, it is necessary to use a gas conditioning combination containing hydrogen and carbon monoxide to effectively control species such as Acinetobacter, Psychrobacter, Ringworm, Lactobacillus, Shewanella, Wandering Coccus, and Aeromonas. Preferably, in the fresh-keeping gas conditioning system, the volume fraction of hydrogen is 1.5-3.0%, and the volume fraction of carbon monoxide is 0.5-1.5%. When the proportion of hydrogen and carbon monoxide in the controlled atmosphere is too low, it will be difficult to effectively control all species of microorganisms such as Acinetobacter, Psychrophilic Bacillus, Cyclotrichol, Lactobacillus, Shewanella, Rhizococcus, and Aeromonas in large yellow croaker and dried products, thereby failing to achieve the purpose of protecting the lipids of large yellow croaker and exerting an antibacterial effect.

[0094] Comparative Example 1

[0095] A method for preserving semi-dried large yellow croaker products comprises the following steps:

[0096] (1) Preparation of semi-dried large yellow croaker fillets: A whole fish is cut in half, pre-treated, pickled in a 2.5% by volume NaCl solution, and then dried to obtain semi-dried large yellow croaker fillets.

[0097] (2) Preparation of fresh-keeping plant fiber absorbent paper A: First, a 0.36% lychee oil-water solution system was prepared, and after adding 0.20% Tween-50 (food grade) by volume, a high-speed vacuum shear emulsification method was used, maintaining 26000g for 30 minutes and a temperature of 65°C to prepare a lychee oil emulsified system. A small amount of the lychee oil emulsified system was sprayed on the surface of the grass stem fiber plant fiber absorbent paper by a spraying method, and then dried at 40°C overnight to prepare a fresh-keeping plant fiber absorbent paper A.

[0098] (3) Preparation of fresh-keeping atmosphere conditioning system X: Using a gas mixer, mix the gases in a volume ratio of (carbon dioxide: nitrogen: oxygen) = (49%: 25.5%: 25.5%) to form a mixed gas. The gases are all food grade and have a purity of ≥99%.

[0099] (4) A rectangular skin-friendly packaging box is used to place the semi-dried large yellow croaker fillet in the packaging box containing the fresh-keeping atmosphere conditioning system X, and the weight of the semi-dried large yellow croaker and the volume of the filled gas are controlled to be 1:2. A sheet of plant fiber absorbent paper A prepared in step (2) is placed at the bottom of the packaging box.

[0100] (5) Storage: Store the sealed packaging in a refrigerator at 4°C.

[0101] After storage for 30 days, the semi-dried large yellow croaker product preserved in this embodiment was sampled, and the total bacteria count, mold count, and fat oxidation degree (peroxide value) in the semi-dried large yellow croaker were measured. The results are shown in Table 1; the semi-dried large yellow croaker product preserved in this embodiment was subjected to sensory evaluation, and the results are shown in Table 3.

[0102] Comparative Example 2, the preservation effect of the semi-dried large yellow croaker slices in this example is poor. Based on experimental and theoretical research, the present invention team found that hydrogen has a very good inhibitory effect on putrefactive bacteria, molds, lipases and their analogs, especially under the synergistic conditions of nitrogen dioxide, nitrogen and oxygen, the effect of hydrogen on regulating microorganisms in semi-dried fish products is more obvious. Carbon dioxide, nitrogen and oxygen are common traditional atmospheres for controlling putrefactive bacteria, and large yellow croaker is different from other fish species. The lipid content in large yellow croaker and dried products is high. Therefore, the use of traditional atmosphere combinations for preservation of large yellow croaker and dried products will result in the inability to effectively control all bacterial microorganisms of the genera Acinetobacter, Psychrobacter, Cyclothrix, Lactobacillus, Shewanella, Wandering Coccus, and Aeromonas in large yellow croaker and dried products.

[0103] Table 1 Analysis results of physical and chemical properties of semi-dried large yellow croaker products (stored at 0℃ for 30 days)

[0104]

[0105] Table 2 Sensory evaluation scoring criteria for semi-dried large yellow croaker products

[0106]

[0107] Table 3 Sensory evaluation results of semi-dried large yellow croaker products (stored at 0°C for 30 days)

[0108] Case Color Smell and taste Muscle elasticity Example 1 4.63±0.16 4.56±0.13 4.76±0.11 Example 2 4.57±0.13 4.51±0.15 4.79±0.15 Example 3 3.23±0.12 3.04±0.14 3.23±0.12 Example 4 3.12±0.10 2.99±0.09 3.31±0.13 Example 5 2.89±0.11 2.87±0.10 2.76±0.09 Example 6 2.98±0.07 2.87±0.09 3.11±0.13 Comparative Example 1 2.03±0.10 1.98±0.09 2.23±0.08

[0109] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0110] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preserving semi-dried large yellow croaker products, characterized in that: The following steps are involved: A number of fresh-keeping plant fiber absorbent papers are placed at the bottom of a packaging container, a semi-dried large yellow croaker product is placed in the packaging container, and a fresh-keeping atmosphere system is introduced into the packaging container; the fresh-keeping plant fiber absorbent paper is prepared by adding a litsea cubeba oil emulsified system to the plant fiber absorbent paper; the raw material of the plant fiber absorbent paper is grass stem fiber, and the fresh-keeping atmosphere system includes 0.5-1.5% carbon monoxide, 1.5-3.0% hydrogen, 48-57% carbon dioxide, 25-30% nitrogen and 9.5-24% oxygen by volume fraction; the volume ratio of hydrogen to carbon monoxide is 2-3:1, and the volume ratio of the semi-dried large yellow croaker product to the fresh-keeping atmosphere system is 0.5-3:

1.

2. The preservation method according to claim 1, characterized in that: The preparation method of the litsea cubeba oil emulsified system comprises: preparing a litsea cubeba oil-water solution system, and then adding an emulsifier into the litsea cubeba oil-water solution system for emulsification to obtain the litsea cubeba oil emulsified system.

3. The preservation method according to claim 1, characterized in that: The preparation method of the semi-dried large yellow croaker product comprises: splitting a whole yellow croaker in the middle to prepare large yellow croaker slices, and then salting and drying the slices to prepare the semi-dried large yellow croaker product.

4. The preservation method according to claim 3, characterized in that: The pickling adopts NaCl.

5. The preservation method according to claim 1, characterized in that: The packaging container is a skin packaging box.

6. The preservation method according to claim 5, characterized in that: The skin packaging box is rectangular.

7. The preservation method according to claim 5, characterized in that: The fresh-keeping plant fiber absorbent paper is attached to the bottom of the skin packaging box.

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