A method for preparing high-content rtg-type fish oil using mackerel processing by-products
Patent Information
- Application Number
- PCT/IB2026/057314
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-07-15
- Publication Date
- 2026-10-01
Smart Images
Figure IB2026057314_01102026_PF_FP_ABST
Abstract
Description
[0001] DESCRIPTION
[0002] A METHOD FOR PREPARING HIGH-CONTENT rTG-TYPE FISH OIL USING MACKEREL PROCESSING BY-PRODUCTS TECHNICAL FIELD
[0003] The present invention relates to the technical field of high-value processing of aquatic by-products and preparation of functional fish oil, and specifically relates to a method for preparing high-content rTG-type fish oil using mackerel processing by-products.
[0004] BACKGROUND ART
[0005] The aquatic processing industry occupies an important position in the food industry system. Mackerel, as an economical marine fish with stable output and a relatively large fishing scale, continuously generates a large quantity of by-products such as fish heads, fish bones, fish skin, viscera, and fish belly trimmings during processing. At present, aquatic processing enterprises mostly sell such by-products at low prices or directly discard them, and only a small portion is used for simple fish meal processing. The unsaturated fatty acid resources contained in the by-products have not been fully explored and utilized, resulting in serious waste of high-quality lipid resources. Fish oil is a functional oil rich in polyunsaturated fatty acids, among which EPA and DHA have multiple physiological values such as regulating blood lipids and maintaining cardiovascular and cerebrovascular health. Market demand for fish oil products with high purity and high absorption efficiency continues to increase. Conventional fish oil raw materials are mostly whole-catch fish meat, resulting in relatively high raw-material procurement costs and production capacity that is easily restricted by fishery harvesting cycles. Compared with fatty acid ethyl ester fish oil, re-esterified triglyceride fish oil has significant advantages in human digestion and absorption, and is a mainstream development direction in the high-end functional fish oil market. Therefore, there is an urgent need in the industry for a complete processing process that relies on aquatic processingDESCRIPTION
[0006] waste and can stably prepare high-quality structured triglyceride fish oil.
[0007] Existing conventional processing methods for extracting fish oil from aquatic by-products mostly use high-temperature cooking and pressing. A high-temperature environment directly damages the molecular structure of unsaturated fatty acids, causes oil oxidation and deterioration, and results in finished products with excessive oxidation indicators. Large amounts of artificially synthesized antioxidants must be added to prolong the storage period, which poses food safety risks. A single-protease hydrolysis mode has low oil-release efficiency, and emulsification after enzymatic hydrolysis is severe. When crude fish oil is separated merely by standing for phase separation, the oil recovery rate is low and the crude fish oil has a high impurity content. Subsequent refining requires a large amount of acid and alkali reagents for decolorization and degumming, generating high-concentration saline organic wastewater and causing considerable environmental-treatment pressure. Traditional fish oil purification relies only on single distillation to enrich unsaturated fatty acids, and the enrichment effect is limited, making it difficult to meet the active-substance content standards required for high-end fish oil. Most processing processes can only produce fatty acid ethyl ester fish oil; if conversion into a triglyceride product is desired, chemical catalytic esterification is often used, which has harsh reaction conditions, many by-products, unrecoverable catalysts, high raw-material losses, and difficulty in controlling residual ethyl ester components in the finished product. In addition, the entire processing process lacks systematic oxygen-isolation protection, and the separate operations of each step have poor continuity, making it difficult to adapt to continuous, large-scale industrial production.
[0008] SUMMARY OF THE INVENTION
[0009] The purpose of the present invention is to remedy the deficiencies of the prior art by providing a method for preparing high-content rTG-type fish oilDESCRIPTION
[0010] using mackerel processing by-products. The method first uses low-temperature pretreatment together with a natural compound antioxidant to block oxidation, then relies on nitrogen-protected composite enzymatic hydrolysis to fully release oil, combines pH-salt synergistic demulsification with ceramic-membrane refining to purify crude fish oil, enriches unsaturated fatty acids after ethanolysis and two-stage molecular distillation, and then adopts immobilized lipase-catalyzed vacuum re-esterification, combined with short-path distillation for impurity removal and nitrogen sealing, to obtain the finished product. The whole process controls oxygen and temperature throughout, reduces the loss of unsaturated fatty acids, improves the oil extraction rate and product purity, allows the immobilized enzyme to be recovered to reduce production costs, and alleviates the environmental pressure of aquatic processing by resource utilization of waste.
[0011] To solve the above technical problems, the present invention provides the following technical solution: a method for preparing high-content rTG-type fish oil using mackerel processing by-products, the specific steps of which are as follows:
[0012] 51, taking mackerel processing by-products comprising fish heads, fish bones, fish skin, fish belly meat, and fish viscera, wherein the fish belly meat and fish viscera together account for 25%-55% of the total mass of the by-products, and the fish heads, fish bones, and fish skin together account for 45%-75%; washing at 0-8°C, draining, and mincing to 3-8 mm, adding a natural antioxidant compounded from mixed tocopherols and rosemary extract, and mixing uniformly;
[0013] 52, adding water to the pretreated raw materials to a material-liquid mass ratio of 1 :(1.0-1.4), replacing air with nitrogen, adding a composite protease compounded from neutral protease and papain, adjusting the pH to 6.8-7.2, conducting enzymatic hydrolysis at 46-50°C for 2-3 hours, and then heating to 78-82°C to inactivate the enzyme for 8-12 minutes;DESCRIPTION
[0014] 53, cooling the enzyme-inactivated hydrolysate to 48-52 °C, adding and dissolving food-grade sodium chloride, adjusting the pH to 5.3-5.6, standing for 20-35 minutes, centrifuging, and collecting an upper crude fish oil phase;
[0015] 54, subjecting the crude fish oil to cross-flow filtration through an inorganic ceramic membrane, collecting a clear permeate, and performing low-temperature vacuum dehydration to obtain refined mackerel fish oil;
[0016] 55, mixing the refined fish oil with anhydrous ethanol and a sodium ethoxide catalyst, and conducting an ethanolysis reaction under nitrogen protection; after the reaction is completed, adding water for washing, standing for phase separation, collecting an upper fatty acid ethyl ester phase, and removing residual ethanol and water under reduced pressure to obtain fish oil ethyl esters; enriching the fish oil ethyl esters by two-stage molecular distillation to obtain enriched ethyl esters;
[0017] 56, subjecting the enriched ethyl esters and food- grade glycerol to a re-esterification reaction under vacuum catalyzed by immobilized lipase, filtering to separate the immobilized lipase, conducting short-path distillation for impurity removal, and sealing for storage under high-purity nitrogen, thereby obtaining an rTG-type fish oil product.
[0018] Further, in SI, the mass ratio of mixed tocopherols to rosemary extract in the natural antioxidant is 1 :(0.3-0.8), and the total addition amount accounts for 0.04%-0.08% of the mass of the by-products.
[0019] Further, in S2, the mass ratio of neutral protease to papain in the composite protease is 1 :(0.6-0.9), and the total addition amount accounts for 0.9%-1.4% of the mass of the by-products; the enzymatic hydrolysis reaction time is 2-3 hours, and the enzyme-inactivation holding time is 8-12 minutes.
[0020] Further, in S2, after nitrogen replacement, a slight positive pressure of 0.02-0.05 MPa is maintained in the reactor, and the oxygen content in the headspace of the reactor is reduced to not higher than 0.5%; during enzymatic hydrolysis, the stirring rate is 50-80 r / min.DESCRIPTION
[0021] Further, in S3, the addition amount of food-grade sodium chloride is 2.0%-3.0% of the total mass of the hydrolysate; the standing demulsification time is 20-35 minutes; the centrifugation speed is 3000-4000 r / min, and the centrifugation time is 10-15 minutes.
[0022] Further, in S4, the inorganic ceramic membrane is made of alumina and has a membrane pore size of 0.3-0.6 pm; the cross-flow filtration temperature is 30-38°C, the transmembrane pressure difference is 0.05-0.15 MPa, and circulating filtration is performed 2-3 times; the low-temperature vacuum dehydration temperature is 35-45°C, the vacuum degree is -0.08 MPa to -0.095 MPa, and dehydration is performed until the water content of the fish oil is <0.25%.
[0023] Further, in S5, the mass ratio of refined mackerel fish oil to anhydrous ethanol is 100: (35 -55), and the addition amount of the sodium ethoxide catalyst is 0.3%-0.8% of the mass of the refined fish oil; the ethanolysis reaction temperature is 42-52°C, and the reaction time is 1-2 hours.
[0024] Further, in S5, the fish oil ethyl esters obtained after the ethanolysis reaction have a total EPA+DHA content of 30%-50%; the two-stage molecular distillation enrichment uses wiped-film equipment and is protected by nitrogen throughout the process; the first-stage distillation temperature is 95-115°C, the second-stage distillation temperature is 120-145°C, the absolute system pressure is 0.1-5 Pa, and the single-stage material residence time is <60 seconds; the enriched ethyl esters obtained after the two-stage molecular distillation enrichment have a total EPA+DHA content of 68%-76%.
[0025] Further, in S6, the mass ratio of the enriched ethyl esters to food-grade glycerol is 100: (7- 10); the immobilized lipase is immobilized Candida antarctica lipase, and the addition amount is 4%-8% of the mass of the enriched ethyl esters; the re-esterification reaction temperature is 50-55°C, the absolute pressure of the system is 0.5-2 kPa, and the reaction time is 8-12DESCRIPTION
[0026] hours.
[0027] Further, in S6, the short-path distillation conditions are: a temperature of 90-135°C and an absolute system pressure of 0.5-10 Pa; the rTG-type fish oil product obtained after the short-path distillation meets the following indicators: a total EPA+DHA content of 65%-75%, a proportion of triglyceride-type lipids in the total oil of >80%, and a residual ethyl ester content of <15%.
[0028] Compared with the prior art, the method for preparing high-content rTG-type fish oil using mackerel processing by-products has the following beneficial effects:
[0029] First, the present invention completely utilizes various mackerel processing by-products as production raw materials, broadens the source of fish oil raw materials, reduces environmental pressure caused by direct discharge of aquatic processing waste, and realizes cyclic high-value utilization of aquatic processing resources. Low-temperature pretreatment with a compound natural antioxidant is combined with a nitrogen-based whole-process oxygen-isolation protection system to inhibit oxidative rancidity of oil throughout raw material treatment, enzymatic hydrolysis, esterification, and distillation, thereby greatly reducing the generation of peroxides, aldehydes, and other harmful substances during fish oil processing, without requiring a large amount of synthetic antioxidant additives, and improving the edible safety of the finished product. A composite protease synergistic mild enzymatic hydrolysis process can completely retain the structure of unsaturated fatty acids in fish oil compared with traditional high-temperature cooking oil extraction. In combination with pH-salt synergistic demulsification and ceramic-membrane cross-flow refining, it improves crude fish oil separation efficiency and clarity, simplifies subsequent refining steps, reduces excessive use of acids, alkalis, and organicDESCRIPTION
[0030] solvents, lowers production wastewater treatment costs, and takes both production economy and environmental protection into account.
[0031] Second, the present invention completes conversion of ordinary fish oil into high-purity structured triglyceride fish oil through a serial process comprising ethanolysis, two-stage molecular distillation enrichment, and enzymatic vacuum re-esterification. It effectively increases the total content of unsaturated fatty acids in the product and optimizes the molecular structure of the oil. Compared with ordinary ethyl ester fish oil, it better conforms to the human lipid absorption and metabolism pathway and improves the bioavailability of nutrients. Immobilized lipase is used to catalyze the esterification reaction, and the catalyst can be filtered, recovered, and reused, thereby reducing the continuing input cost of catalytic materials. Short-path distillation is used to remove residual ethyl esters and small-molecule impurities and precisely regulate the ratio of lipid components in the finished product. The whole low-pressure, low-temperature distillation process is combined with nitrogen-filled sealed storage, thereby avoiding damage to active unsaturated fatty acids caused by long-term high-temperature processing. The finished product has stronger stability and a longer storage period, and the entire process is suitable for scaled continuous production, with smooth connection between steps, no need for complex intermittent operations, and stable output of high-quality structured triglyceride fish oil products.
[0032] Other advantages, objectives, and features of the present invention will be set forth to some extent in the following description, and to some extent will be apparent to those skilled in the art based on examination and study of the following text, or may be learned from the practice of the present invention.
[0033] DESCRIPTION OF DRAWINGSDESCRIPTION
[0034] In order to more clearly explain the technical solutions in the embodiments of the present invention or in the prior art, the accompanying drawings required for describing the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention; those of ordinary skill in the art may also obtain other drawings based on these drawings without creative effort.
[0035] FIG. 1 is an overall process flowchart of preparing high-content rTG-type fish oil using mackerel processing by-products;
[0036] FIG. 2 is a flowchart of the nitrogen-protected composite enzymatic hydrolysis process for mackerel by-products;
[0037] FIG. 3 is a flowchart of the process of pH-salt synergistic demulsification of the hydrolysate and centrifugal extraction of crude fish oil.
[0038] DETAILED DESCRIPTION
[0039] To further explain the technical means and effects adopted by the present invention to achieve the intended purpose of the invention, the specific implementation, structure, features, and effects of the present invention are described in detail below with reference to the accompanying drawings and preferred embodiments.
[0040] Example 1 :
[0041] Twenty kilograms of mackerel processing by-products were weighed. The by-products comprised fish heads, fish bones, fish skin, fish belly meat, and fish viscera. The fish heads accounted for 25%, the fish bones for 18%, the fish skin for 12%, the fish belly meat for 25%, and the fish viscera for 20%; the fish belly meat and fish viscera together accounted for 45% of the total mass of the by-products, and the fish heads, fish bones, and fish skin together accounted for 55% of the total mass of the by-products. The specific steps are shown in FIG. 1.DESCRIPTION
[0042] The raw materials were washed with clean water at 4°C to remove blood and impurities from the surfaces. After washing, they were spread out and drained until no continuous water droplets fell, and were then fed into a mincing device and minced to a particle size of 3 mm to 8 mm.
[0043] A natural antioxidant was prepared, wherein the mass ratio of mixed tocopherols to rosemary extract was 1:0.5, and the total addition amount of the antioxidant was 0.06% of the total mass of the by-products. The antioxidant was uniformly sprinkled into the minced materials and continuously stirred and mixed uniformly.
[0044] Purified water was added to the mixed materials, the material-liquid mass ratio was controlled at 1 : 1.2, all materials were transferred into a sealed reactor, nitrogen was introduced to replace the air in the reactor, a slight positive pressure of 0.03 MPa was maintained in the reactor until the oxygen content in the headspace of the reactor was reduced to below 0.5%, as shown in FIG. 2.
[0045] A composite protease was prepared, wherein the mass ratio of neutral protease to papain was 1:0.8, and the total addition amount of the composite protease was 1.2% of the total mass of the by-products. The protease was added into the materials in the reactor, food-grade dilute hydrochloric acid and sodium bicarbonate were used to adjust the system pH to 7.0, a stirring device was started, the stirring rate was 60 r / min, and enzymatic hydrolysis was continuously carried out at 48°C for 2.5 h.
[0046] After the enzymatic hydrolysis process was completed, the temperature was raised to 80°C and maintained for 10 min to complete enzyme inactivation and terminate protease activity.DESCRIPTION
[0047] The enzyme-inactivated hydrolysate was cooled to 50°C, food-grade sodium chloride was weighed and added to the system, the sodium chloride addition amount was 2.5% of the total mass of the hydrolysate, stirring was continued until the sodium chloride was completely dissolved, the system pH was adjusted to 5.5, and standing was performed for 30 min to complete pH-salt synergistic demulsification, as shown in FIG. 3.
[0048] After demulsification was completed, the mixed liquid was fed into a tubular centrifuge, the rotational speed was set to 3500 r / min, and centrifugation was performed for 12 min. After phase separation, the upper crude fish oil phase was collected, and the lower protein-water phase and the intermediate solid residue were removed.
[0049] An inorganic ceramic membrane made of alumina and having a membrane pore size of 0.45 pm was selected. The crude fish oil was fed into a cross-flow filtration device, the filtration temperature was controlled at 35 °C, the transmembrane pressure difference was 0.10 MPa, circulating filtration was performed twice, and the clear fish oil permeate on the ceramic membrane side was collected.
[0050] The clear fish oil was transferred into a vacuum dehydration device, the dehydration temperature was set to 40°C, the vacuum degree was -0.09 MPa, and dehydration was continued until the water content of the fish oil was <0.25%, thereby obtaining low-oxidation mackerel fish oil. The intermediate product had a total EPA plus DHA content of 28.1%, a peroxide value of 2.3 meq 02 / kg, and a water content of 0.22%.
[0051] All of the low-oxidation mackerel fish oil was taken and mixed withDESCRIPTION
[0052] anhydrous ethanol at a mass ratio of 100:45. A sodium ethoxide catalyst was added, wherein the catalyst addition amount was 0.5% of the total mass of the refined fish oil. Nitrogen was introduced throughout the process to isolate oxygen, and an ethanolysis reaction was conducted at 48°C for 1.5 h.
[0053] After the reaction was completed, purified water was added to the system for stirring and washing. After standing for phase separation, the upper fatty acid ethyl ester phase was collected, and residual ethanol and free water in the system were removed by reduced-pressure distillation to obtain fish oil ethyl esters. The fish oil ethyl esters had a total EPAplus DHA content of 39.2%.
[0054] The fish oil ethyl esters were fed into a wiped-film two-stage molecular distillation device, nitrogen protection was provided throughout the process, the absolute system pressure was 1 Pa, and the single-stage material residence time was 45 s.
[0055] The first-stage distillation temperature was 105°C, short-chain fatty acids and light-component impurities were removed, and the first-stage heavy-phase material was collected and fed into the second-stage molecular distillation. The second-stage distillation temperature was 132°C to separate long-chain saturated fatty acids, and enriched ethyl esters were finally obtained. The enriched ethyl esters had a total EPA plus DHA content of 72.8%, a peroxide value of 3.0 meq 02 / kg, and a water content of 0.08%.
[0056] The enriched ethyl esters and food-grade glycerol were weighed at a mass ratio of 100:8. Immobilized Candida antarctica lipase was added to the mixed system, and the lipase addition amount was 6% of the total mass of the enriched ethyl esters. The materials were transferred into a vacuum reactor, the absoluteDESCRIPTION
[0057] pressure of the system was controlled at 1.2 kPa, the temperature was 52°C, and the reaction was continuously stirred for 10 h, while the ethanol generated during the reaction was continuously removed under reduced pressure.
[0058] After the reaction was completed, the immobilized lipase was separated by filtration. The mixed oil was fed into a short-path distillation device, the distillation temperature was 115°C, the absolute system pressure was 3 Pa, and free fatty acids and residual ethyl esters in the system were removed.
[0059] After distillation was completed, high-purity nitrogen was introduced, and the product was sealed and stored away from light to obtain an rTG-type fish oil product.
[0060] Finished product testing indicators: total EPA plus DHA content, 70.6%; triglyceride-type lipids as a proportion of total oil, 83.2%; residual ethyl ester content, 8.8%; peroxide value, 3.2 meq 02 / kg; p-anisidine value, 8.6; TOTOX value, 15.0; acid value, 2.2 mg KOH / g; water content, 0.19%; turbidity, 4.8 NTU.
[0061] Example 2:
[0062] Twenty kilograms of mackerel processing by-products were used, with the mass proportions of the components being the same as in Example 1. The by-products were washed clean with low-temperature water at 6 °C, drained, and minced to a particle size range of 3 mm to 8 mm.
[0063] The natural antioxidant was prepared by compounding mixed tocopherols and rosemary extract at a ratio of 1:0.4, and the total addition amount of the antioxidant was 0.05% of the total mass of the by-products. The materials were fully stirred and mixed uniformly.
[0064] Water was added to adjust the material-liquid mass ratio to 1:1.2. NitrogenDESCRIPTION
[0065] was used to replace the air inside the reactor, a slight positive pressure of 0.02 MPa was maintained in the reactor, and the headspace oxygen content was below 0.5%.
[0066] The composite protease was compounded from neutral protease and papain at a mass ratio of 1:0.7, the total addition amount was 1.0% of the total mass of the raw materials, the system pH was adjusted to 6.9, the stirring rate was 50 r / min, and enzymatic hydrolysis was carried out at a constant temperature of 47°C for 3 h.
[0067] After enzymatic hydrolysis was completed, the temperature was raised to 78°C and maintained for 12 min to complete enzyme inactivation.
[0068] The hydrolysate was cooled to 48°C, food-grade sodium chloride in an amount of 2.2% of the total mass of the hydrolysate was added, the pH was adjusted to 5.6 after complete dissolution, and standing was performed for 20 min to complete demulsification.
[0069] The centrifuge speed was 3000 r / min, centrifugation was performed for 15 min, and the upper crude fish oil phase was collected.
[0070] A 0.3 pm alumina ceramic membrane was selected, the cross-flow filtration temperature was 30°C, the transmembrane pressure difference was 0.08 MPa, circulating filtration was performed 3 times, and clear fish oil was collected.
[0071] The vacuum dehydration temperature was 35°C, the vacuum degree was -0.08 MPa, and dehydration was performed until the water content was <0.25%, thereby obtaining low-oxidation mackerel fish oil.
[0072] The mass ratio of the refined fish oil to anhydrous ethanol was 100:40, the sodium ethoxide catalyst addition amount was 0.4%, and the ethanolysis reactionDESCRIPTION
[0073] was carried out at 42°C for 2 h.
[0074] Fish oil ethyl esters were obtained by water washing, phase separation, and ethanol removal, and the ethyl esters were fed into two-stage molecular distillation. The system pressure was 1 Pa, the material residence time was 50 s, the first-stage distillation temperature was 95°C, and the second-stage distillation temperature was 120°C, thereby obtaining enriched ethyl esters. The enriched ethyl esters had a total EPA plus DHA content of 70.9%, a peroxide value of 2.9 meq 02 / kg, and a water content of 0.09%.
[0075] The mass ratio of the enriched ethyl esters to glycerol was 100:7, the immobilized lipase addition amount was 5%, the reaction was carried out at 50°C and a system pressure of 0.5 kPa for 12 h, and the ethanol generated during the reaction was removed under reduced pressure.
[0076] The enzyme preparation was separated by filtration, short-path distillation was performed at 90°C and a system pressure of 5 Pa to remove impurities, and high-purity nitrogen sealing was performed to obtain the finished rTG fish oil.
[0077] Finished product testing indicators: total EPA plus DHA content, 68.9%; triglyceride proportion, 81.7%; residual ethyl esters, 10.6%; peroxide value, 3.5 meq 02 / kg; p-anisidine value, 9.4; TOTOX, 16.4; acid value, 2.4 mg KOH / g; water content, 0.22%; turbidity, 5.4 NTU.
[0078] Example 3 :
[0079] Twenty kilograms of mackerel processing by-products were weighed, with the component proportions being the same as in Example 1. The by-products were washed and drained at a low temperature of 5 °C, and minced to 3 mm to 8 mm particles.DESCRIPTION
[0080] Mixed tocopherols and rosemary extract were compounded at a mass ratio of 1:0.7 to prepare the antioxidant, the total addition amount was 0.07% of the mass of the raw materials, and the mixture was stirred uniformly.
[0081] Water was added to control the material-liquid mass ratio at 1 : 1.4, nitrogen was used to replace the air in the reactor, the slight positive pressure in the reactor was 0.05 MPa, and the headspace oxygen content was below 0.5%.
[0082] The composite protease was compounded from neutral protease and papain at a ratio of 1:0.9, the total addition amount was 1.4% of the mass of the raw materials, the pH was adjusted to 7.1, the stirring rate was 80 r / min, and enzymatic hydrolysis was carried out at 50°C for 2 h.
[0083] The temperature was raised to 82°C and held for 8 min to complete enzyme inactivation.
[0084] The hydrolysate was cooled to 52°C, food-grade sodium chloride in an amount of 2.8% of the total mass of the hydrolysate was added, the pH was adjusted to 5.4 after dissolution, and standing was performed for 35 min for demulsification.
[0085] Centrifugation was performed at 4000 r / min for 10 min, and the upper crude fish oil phase was collected.
[0086] A 0.6 pm alumina ceramic membrane was selected, the filtration temperature was 38°C, the transmembrane pressure difference was 0.12 MPa, and circulating filtration was performed twice.
[0087] Vacuum dehydration was performed at 45°C and a vacuum degree of -0.095 MPa until the water content was <0.25%, thereby obtaining low-oxidation mackerel fish oil.DESCRIPTION
[0088] The mass ratio of the refined fish oil to anhydrous ethanol was 100:50, the sodium ethoxide addition amount was 0.6%, and ethanolysis was carried out at 52°C for 1 h.
[0089] Fish oil ethyl esters were obtained by water washing and ethanol removal. The two-stage molecular distillation system pressure was 1 Pa, the material residence time was 40 s, the first-stage distillation temperature was 115°C, and the second-stage distillation temperature was 145°C. The enriched ethyl esters had a total EPA plus DHA content of 73.6%, a peroxide value of 3.2 meq 02 / kg, and a water content of 0.07%.
[0090] The mass ratio of the enriched ethyl esters to glycerol was 100:10, the immobilized lipase addition amount was 7%, the reaction was conducted at 55°C and a system pressure of 2 kPa for 8 h, and ethanol was continuously removed during the reaction.
[0091] The lipase was removed by filtration, short-path distillation was performed at 135°C and a system pressure of 10 Pa to remove residual ethyl esters and free fatty acids, and nitrogen sealing was performed to obtain the finished product.
[0092] Finished product testing indicators: total EPA plus DHA content, 71.4%; triglyceride proportion, 84.0%; residual ethyl esters, 7.9%; peroxide value, 3.6 meq 02 / kg; p-anisidine value, 9.8; TOTOX, 17.0; acid value, 2.5 mg KOH / g; water content, 0.24%; turbidity, 5.9 NTU.
[0093] Comparative Example 1 :
[0094] Twenty kilograms of mackerel processing by-products having completely the same components as in Example 1 were used. After washing with clean water at room temperature and draining, the by-products were directly fed into a cookingDESCRIPTION
[0095] device and cooked at a constant temperature of 95 °C for 20 min. After cooking, a screw press was used to press and separate oil, and after pressing, the crude oil was allowed to stand to remove solid residue.
[0096] No antioxidant was added to the pressed crude oil, and no nitrogen protection was performed. All subsequent operating parameters for pH-salt demulsification, ceramic membrane filtration, vacuum dehydration, ethanolysis, two-stage molecular distillation, lipase re-esterification, short-path distillation, and sealed storage were the same as in Example 1.
[0097] Finished product testing indicators: fish oil recovery rate, 78.1%; total EPA plus DHA content, 69.4%; triglyceride proportion, 82.5%; residual ethyl esters, 9.5%; peroxide value, 5.8 meq 02 / kg; p-anisidine value, 13.2; TOTOX, 24.8; acid value, 2.8 mg KOH / g; water content, 0.27%; turbidity, 7.6 NTU.
[0098] Comparative Example 2:
[0099] The operating parameters for low-temperature raw-material pretreatment, nitrogen composite enzymatic hydrolysis, and enzyme inactivation were all the same as in Example 1.
[0100] After enzyme inactivation was completed, the sodium chloride addition and pH adjustment operations were omitted. The hydrolysate was cooled to 50°C, allowed to stand directly for 30 min, and centrifuged at 3500 r / min for 12 min to collect the crude fish oil phase.
[0101] Ceramic membrane refining, ethanolysis, molecular distillation, enzymatic re-esterification, short-path distillation, and sealed storage were all carried out according to the parameters of Example 1.
[0102] Finished product testing indicators: fish oil recovery rate, 75.8%; total EPADESCRIPTION
[0103] plus DHA content, 68.7%; triglyceride proportion, 81.1%; residual ethyl esters, 11.8%; peroxide value, 4.2 meq 02 / kg; p-anisidine value, 10.7; TOTOX, 19.1; acid value, 2.6 mg KOH / g; water content, 0.31%; turbidity, 9.2 NTU.
[0104] Comparative Example 3 :
[0105] The steps of low-temperature pretreatment, nitrogen composite enzymatic hydrolysis, enzyme inactivation, pH-salt synergistic demulsification, and centrifugal separation of crude fish oil were completely the same as in Example 1.
[0106] The crude fish oil obtained by centrifugation was directly fed into a vacuum dehydration device, the alumina ceramic membrane cross-flow filtration process was omitted, and the vacuum dehydration parameters were the same as in Example 1.
[0107] The ethanolysis, two-stage molecular distillation, enzymatic re-esterification, and short-path distillation processes were the same as in Example 1.
[0108] Finished product testing indicators: fish oil recovery rate, 82.4%; total EPA plus DHA content, 69.8%; triglyceride proportion, 80.6%; residual ethyl esters, 12.7%; peroxide value, 4.6 meq 02 / kg; p-anisidine value, 11.9; TOTOX, 21.1; acid value, 2.8 mg KOH / g; water content, 0.33%; turbidity, 14.8 NTU.
[0109] Comparative Example 4:
[0110] Raw-material pretreatment, nitrogen enzymatic hydrolysis, pH-salt demulsification, ceramic membrane filtration, vacuum dehydration, ethanolysis, and two-stage molecular distillation were all carried out according to the process of Example 1 to obtain enriched ethyl esters.
[0111] The enriched ethyl esters were not mixed with glycerol and immobilized lipase for a re-esterification reaction, but were directly subjected to short-pathDESCRIPTION
[0112] distillation to remove light-component impurities and then sealed and stored under nitrogen, thereby obtaining an ethyl ester-type fish oil product.
[0113] Finished product testing indicators: fish oil recovery rate, 84.1%; total EPA plus DHA content, 72.8%; triglyceride-type lipid proportion, 9.4%; residual ethyl ester content, 86.5%; peroxide value, 3.4 meq 02 / kg; p-anisidine value, 9.1; TOTOX, 15.9; acid value, 2.6 mg KOH / g; water content, 0.21%; turbidity, 5.1 NTU.
[0114] Comparative Example 5 :
[0115] The low-temperature pretreatment, nitrogen composite enzymatic hydrolysis, and enzyme-inactivation processes were completely the same as in Example 1.
[0116] After the enzyme-inactivated liquid was cooled to 50°C, food-grade sodium chloride was not added, and only dilute hydrochloric acid was used to adjust the system pH to 5.5. Standing for demulsification was performed for 30 min, and centrifugation was performed at 3500 r / min for 12 min to collect crude fish oil.
[0117] Ceramic membrane refining, ethanolysis, molecular distillation, re-esterification, and short-path distillation all used the parameters of Example 1.
[0118] The water content of the crude fish oil phase was 0.63%. Finished product testing indicators: fish oil recovery rate, 79.4%; finished product water content, 0.28%; turbidity, 8.7 NTU; peroxide value, 3.7 meq 02 / kg.
[0119] Comparative Example 6:
[0120] The raw-material pretreatment, nitrogen-protected composite enzymatic hydrolysis, and enzyme-inactivation steps were the same as in Example 1.
[0121] The enzyme-inactivated liquid was cooled to 50°C, sodium chloride in an amount of 2.5% of the total mass of the hydrolysate was added and completelyDESCRIPTION
[0122] dissolved, the system pH was not adjusted, and the mixture was directly allowed to stand for 30 min and then centrifuged to collect the crude fish oil phase.
[0123] The subsequent ceramic membrane filtration, ethanolysis, molecular distillation, enzymatic re-esterification, and distillation / sealed storage operations were completely the same as in Example 1.
[0124] The water content of the crude fish oil phase was 0.69%. Finished product testing indicators: fish oil recovery rate, 78.7%; finished product water content, 0.30%; turbidity, 10.1 NTU; peroxide value, 3.9 meq 02 / kg.
[0125] Performance Testing:
[0126] The fish oil recovery rate was calculated as the ratio of the actual mass of the obtained low-oxidation mackerel fish oil to the total extractable oil mass of the same batch of raw materials; the peroxide value was determined by an iodometric method; the acid value was determined by acid-base titration; the EPA and DHA contents were determined by gas chromatography; the proportion of triglyceride-type lipids and the residual ethyl ester content were determined by high-performance liquid chromatography; the water content was determined by a moisture determination method; turbidity was determined with a turbidity meter; the p-anisidine value was determined according to an oil oxidation evaluation method; and the TOTOX value was calculated as 2 x peroxide value + p-anisidine value.
[0127] TABLE 1 SHOWS MAIN INDICATOR DATA OF INTERMEDIATE PRODUCTS DURING THE PROCESS.
[0128] INTERME TOTAL PEROXIDE WATE DIATE EPA+DHA VALUE / (meq R DESCRIPTION
[0129]
[0130] PRODUCT CONTENT / O2 / kg) CONTDESCRIPTION
[0131] O / / o ENT /
[0132] O / / o
[0133] Obtained by low-temperature enzymatic hydrolysis, Low-oxidati
[0134] 0.16-0. demulsification, on mackerel 26.8-29.5 2.1-2.6
[0135] 22 ceramic membrane fish oil
[0136] coalescence clarification, and vacuum dehydration Obtained by ethanolysis Enriched conversion and 70.9-73.6 2.8-3.2 <0.10
[0137] ethyl esters two-stage molecular distillation enrichment Obtained by immobilized lipase rTG-type 0.19-0.
[0138] 68.9-71.4 3.2-3.6 re-esterification and fish oil 24
[0139] short-path distillation to
[0140]
[0141] remove residues TABLE 2 SHOWS COMPARATIVE PERFORMANCE TESTING DATA OF THE EXAMPLES AND COMPARATIVE EXAMPLES 1 TO 4.
[0142] COMPA COMPA COMPA COMPA EXA EXA EXA RATIVE RATIVE RATIVE RATIVE ITEM MPL MPL MPL EXAMP EXAMP EXAMP EXAMP
[0143] E 1 E 2 E 3
[0144] LE 1 LE 2 LE 3 LE 4 Comb Comb Comb
[0145] No
[0146] ined ined ined
[0147] Cooking No ceramic
[0148] proces proces proces No and pH-salt membran Process s of s of s of enzymati pressing synergisti e
[0149] differenc the the the c
[0150] oil c coalescen
[0151] e presen presen presen re-esterifi extractio demulsifi ce
[0152] t t t cation n cation clarificati
[0153] invent invent invent
[0154] on
[0155] ion ion ion
[0156]
[0157] Fish oil 84.6 83.2 82.7 78.1 75.8 82.4 84.1DESCRIPTION
[0158] recovery
[0159] rate / %
[0160] Finished
[0161] rTG rTG rTG Ethyl product rTG type rTG type rTG type
[0162] type type type ester type form
[0163] Total
[0164] EPA+D
[0165] HA 70.6 68.9 71.4 69.4 68.7 69.8 72.8 content /
[0166] %
[0167] Triglycer
[0168] ide-type
[0169] lipid 83.2 81.7 84.0 82.5 81.1 80.6 9.4 proporti
[0170] on / %
[0171] Residual
[0172] ethyl
[0173] ester 8.8 10.6 7.9 9.5 11.8 12.7 86.5 content /
[0174] %
[0175] Peroxide
[0176] value / (m
[0177] 3.2 3.5 3.6 5.8 4.2 4.6 3.4 eq
[0178] 02 / kg)
[0179] p-Anisid
[0180] 8.6 9.4 9.8 13.2 10.7 11.9 9.1 ine value
[0181] TOTOX
[0182] 15.0 16.4 17.0 24.8 19.1 21.1 15.9 value
[0183] Acid
[0184] value / (m
[0185] 2.2 2.4 2.5 2.8 2.6 2.8 2.6 g
[0186] KOH / g)
[0187] Water
[0188] content / 0.19 0.22 0.24 0.27 0.31 0.33 0.21 %
[0189]
[0190] Turbidit 4.8 5.4 5.9 7.6 9.2 14.8 5.1DESCRIPTION
[0191]
[0192] y / NTU
[0193] TABLE 3 SHOWS COMPARATIVE TEST DATA FOR DIFFERENT DEMULSIFICATION MODES.
[0194] COMPARATIVE COMPARATIVE ITEM EXAMPLE 1
[0195] EXAMPLE 5 EXAMPLE 6 pH adjustment + Only addition of Demulsification Only pH
[0196] 2.5% sodium 2.5% sodium mode adjustment to 5.5
[0197] chloride chloride
[0198] Fish oil recovery
[0199] 84.6 79.4 78.7
[0200] rate / %
[0201] Water content of
[0202] crude fish oil 0.42 0.63 0.69
[0203] phase / %
[0204] Finished product
[0205] 0.19 0.28 0.30
[0206] water content / %
[0207] Turbidity / NTU 4.8 8.7 10.1
[0208] Peroxide
[0209] 3.2 3.7 3.9
[0210]
[0211] value / (meq 02 / kg)
[0212] Experimental Conclusions:
[0213] The complete process of Examples 1 to 3 includes all steps of low-temperature nitrogen-protected composite enzymatic hydrolysis, pH-salt synergistic demulsification, ceramic membrane coalescence clarification, ethanolysis conversion, two-stage molecular distillation enrichment, and immobilized lipase re-esterification. The fish oil recovery rate ranges from 82.7% to 84.6%; the total EPA plus DHA content of the finished product ranges from 68.9% to 71.4%; the triglyceride-type lipid proportion ranges from 81.7% to 84.0%; the residual ethyl ester content ranges from 7.9% to 10.6%; the peroxide value ranges from 3.2 to 3.6 meq 02 / kg; the p-anisidine value ranges from 8.6 toDESCRIPTION
[0214] 9.8; the TOTOX value ranges from 15.0 to 17.0; the acid value ranges from 2.2 to 2.5 mg KOH / g; and the water content ranges from 0.19% to 0.24%.
[0215] Compared with the cooking-and-pressing oil extraction process of Comparative Example 1, the low-temperature nitrogen composite enzymatic hydrolysis of the present invention can significantly reduce the peroxide value, p-anisidine value, and TOTOX value of the oil when the subsequent enrichment and re-esterification parameters remain unchanged, thereby effectively inhibiting oxidation of polyunsaturated fatty acids.
[0216] Compared with Comparative Example 2 in which the pH-salt synergistic demulsification process was omitted, the synergistic demulsification mode of simultaneous pH adjustment and sodium chloride addition can improve oil recovery efficiency, reduce the water content of the finished product, and improve the oil separation effect.
[0217] Compared with Comparative Example 3 in which the ceramic membrane coalescence clarification process was omitted, alumina ceramic membrane cross-flow filtration can remove raw-material protein colloids and fine suspended solids, reduce turbidity and residual water in the finished product, and reduce the interference of impurities with subsequent distillation and re-esterification reactions.
[0218] Compared with Comparative Example 4 in which the immobilized lipase re-esterification process was omitted, after the enzyme-catalyzed re-esterification reaction, the high-content ethyl ester raw material can be converted into rTG-type fish oil mainly composed of triglycerides, thereby meeting product-indicator requirements for edible fish oil having absorption advantages. The product notDESCRIPTION
[0219] subjected to re-esterification is mostly in the ethyl ester structure and does not comply with the standard for high-rTG fish oil.
[0220] Compared with the single demulsification modes of Comparative Examples 5 and 6, merely adjusting pH or merely adding sodium chloride cannot achieve efficient demulsification; the fish oil recovery rate decreases, the crude fish oil entrains a large amount of water, and the turbidity, water content, and peroxide value of the final product are significantly deteriorated. This proves that the synergistic effect of pH adjustment and sodium chloride compounding is a key condition for ensuring efficient oil-water separation.
[0221] All experimental data prove that the complete continuous process combination defined by the present invention can stably use mackerel processing by-products as raw materials to prepare high-content rTG-type fish oil having excellent indicators.
[0222] The above description is merely the preferred embodiments of the present invention and is not intended to limit the present invention in any form. Although the present invention has been disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications or changes to equivalent embodiments by using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. Any simple modifications, equivalent changes, and amendments made to the above embodiments according to the technical essence of the present invention without departing from the contents of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. CLAIMS1. A method for preparing high-content rTG-type fish oil using mackerel processing by-products, characterized in that the method comprises the following specific steps:51, taking mackerel processing by-products comprising fish heads, fish bones, fish skin, fish belly meat, and fish viscera, wherein the fish belly meat and fish viscera together account for 25%-55% of the total mass of the by-products, and the fish heads, fish bones, and fish skin together account for 45%-75%; washing at 0-8°C, draining, and mincing to 3-8 mm, adding a natural antioxidant compounded from mixed tocopherols and rosemary extract, and mixing uniformly;52, adding water to the pretreated raw materials to a material-liquid mass ratio of l:(1.0-1.4), replacing air with nitrogen, adding a composite protease compounded from neutral protease and papain, adjusting the pH to 6.8-7.2, conducting enzymatic hydrolysis at 46-50°C for 2-3 hours, and then heating to 78-82°C to inactivate the enzyme for 8-12 minutes;53, cooling the enzyme-inactivated hydrolysate to 48-52°C, adding and dissolving food-grade sodium chloride, adjusting the pH to 5.3-5.6, standing for 20-35 minutes, centrifuging, and collecting an upper crude fish oil phase;54, subjecting the crude fish oil to cross-flow filtration through an inorganic ceramic membrane, collecting a clear permeate, and performing low-temperature vacuum dehydration to obtain refined mackerel fish oil;55, mixing the refined fish oil with anhydrous ethanol and a sodium ethoxide catalyst, and conducting an ethanolysis reaction under nitrogen protection; after the reaction is completed, adding water for washing, standing for phase separation, collecting an upper fatty acid ethyl ester phase, and removing residual ethanol and water under reduced pressure to obtain fish oil ethyl esters; enriching the fish oil ethyl esters by two-stage molecular distillation to obtain enriched ethyl esters;56, subjecting the enriched ethyl esters and food- grade glycerol to aCLAIMSre-esterification reaction under vacuum catalyzed by immobilized lipase, filtering to separate the immobilized lipase, conducting short-path distillation for impurity removal, and sealing for storage under high-purity nitrogen, thereby obtaining an rTG-type fish oil product.
2. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in SI, the mass ratio of mixed tocopherols to rosemary extract in the natural antioxidant is l:(0.3-0.8), and the total addition amount accounts for 0.04%-0.08% of the mass of the by-products.
3. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S2, the mass ratio of neutral protease to papain in the composite protease is l:(0.6-0.9), and the total addition amount accounts for 0.9%-1.4% of the mass of the by-products; the enzymatic hydrolysis reaction time is 2-3 hours, and the enzyme-inactivation holding time is 8-12 minutes.
4. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S2, after nitrogen replacement, a slight positive pressure of 0.02-0.05 MPa is maintained in the reactor, and the oxygen content in the headspace of the reactor is reduced to not higher than 0.5%; during enzymatic hydrolysis, the stirring rate is 50-80 r / min.
5. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S3, the addition amount of food-grade sodium chloride is 2.0%-3.0% of the total mass of the hydrolysate; the standing demulsification time is 20-35 minutes; the centrifugation speed is 3000-4000 r / min, and the centrifugation time is 10-15 minutes.
6. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S4, theCLAIMSinorganic ceramic membrane is made of alumina and has a membrane pore size of 0.3-0.6 pm; the cross-flow filtration temperature is 30-38°C, the transmembrane pressure difference is 0.05-0.15 MPa, and circulating filtration is performed 2-3 times; the low-temperature vacuum dehydration temperature is 35-45°C, the vacuum degree is -0.08 MPa to -0.095 MPa, and dehydration is performed until the water content of the fish oil is <0.25%.
7. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S5, the mass ratio of refined mackerel fish oil to anhydrous ethanol is 100:(35-55), and the addition amount of the sodium ethoxide catalyst is 0.3%-0.8% of the mass of the refined fish oil; the ethanolysis reaction temperature is 42-52°C, and the reaction time is 1-2 hours.
8. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S5, the fish oil ethyl esters obtained after the ethanolysis reaction have a total EPA+DHA content of 30%-50%; the two-stage molecular distillation enrichment uses wiped-film equipment and is protected by nitrogen throughout the process; the first-stage distillation temperature is 95-115°C, the second-stage distillation temperature is 120-145°C, the absolute system pressure is 0.1-5 Pa, and the single-stage material residence time is <60 seconds; the enriched ethyl esters obtained after the two-stage molecular distillation enrichment have a total EPA+DHA content of 68%-76%.
9. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S6, the mass ratio of the enriched ethyl esters to food-grade glycerol is 100: (7- 10); the immobilized lipase is immobilized Candida antarctica lipase, and the addition amount is 4%-8% of the mass of the enriched ethyl esters; the re-esterification reaction temperature is 50-55°C, the absolute pressure of the system is 0.5-2 kPa, and the reaction time is 8-12 hours.CLAIMS10. The method for preparing high-content rTG-type fish oil using mackerel processing by-products according to claim 1, characterized in that, in S6, the short-path distillation conditions are: a temperature of 90-135°C and an absolute system pressure of 0.5-10 Pa.