A palm-free low-trans coconut oil-based shortening and a method of making the same

Abstract

The present application relates to the field of oil processing and edible special oil preparation, and particularly relates to a palm-free low-trans coconut oil-based shortening and a preparation method thereof, aiming at solving the problems of narrow plasticity temperature range, coarse crystallization and high proportion of saturated fatty acid of the existing coconut oil-based shortening. The shortening is prepared from physical refining coconut oil, high-oleic sunflower oil, fully hydrogenated rapeseed oil, high-oleic safflower oil, fully hydrogenated soybean oil, through step-by-step lipase catalytic transesterification, high-melting-point solid-phase separation, complex seed auxiliary medium-chain fatty acid adaptive natural antioxidant compounding and quenching kneading forming process. The present application realizes gradient controllable optimization of triglyceride structure through step-by-step use of sn-1,3 specific lipase and non-specific lipase, and designs a ternary natural antioxidant system according to the characteristics of medium-chain saturated fatty acid in coconut oil.

Description

Technical Field

[0001] This invention relates to the field of oil processing and preparation of edible oils, specifically to a palm-free, low-trans-coconut oil-based shortening and its preparation method. Background Technology

[0002] Shortening is a commonly used plasticizing fat in the food industry, typically used to improve the shortening, spreadability, whipping properties, and texture of baked goods. Conventional vegetable shortenings often rely on palm oil, palm extracts, or hydrogenated oils to achieve suitable solid fat content profiles and processing plasticity. In recent years, the food industry has seen increased demand for shortenings that are palm-free, low in trans fatty acids, and have a lower proportion of saturated fatty acids. Coconut oil exhibits high solid fat characteristics near room temperature and can form semi-solid fats without hydrogenation. However, when coconut oil is used alone as the main structural fat, it is prone to problems such as concentrated melting range, narrow plastic temperature range, crystal coarsening under temperature fluctuations, and a high proportion of saturated fatty acids.

[0003] Existing technology, CN105454463A, discloses a non-palm shortening and its preparation method, aiming to prepare a low-trans-fatty acid non-palm shortening with palm oil shortening characteristics without using palm oil and palm kernel oil. This method uses non-palm fruit-derived vegetable oils and prepares shortening through hydrogenation, transesterification, and blending techniques. While this method addresses some non-palm substitute issues, it still uses hydrogenation as one of the process routes and does not propose stepwise lipase structure regulation, seed-assisted stepwise crystallization, or antioxidant adaptation schemes for the medium-chain saturated fatty acid system of coconut oil. CN104255953A discloses a method for preparing low trans fatty acid shortening, which involves mixing rice bran sesame fat, fully hydrogenated soybean oil, and coconut oil in a ratio of 41.6%–63.6%: 27.3%–41.6%: 9.1%–16.8%. This technique uses a single sn-1,3 specific lipase, has a low proportion of coconut oil, does not combine high-oleic acid liquid oil to reduce the proportion of saturated fatty acids, and does not use composite seed crystals to assist stepwise crystallization separation to control coarse crystal formation and plasticity temperature range.

[0004] While existing technologies have reported on non-palm oil shortening or coconut oil-based shortening, most have failed to comprehensively address the aforementioned issues of plasticity, nutrition, and processing efficiency. Therefore, developing a coconut oil-based shortening that can simultaneously achieve a wide plasticity temperature range, optimize the saturated fatty acid profile, and efficiently produce a palm oil-free shortening is a pressing technical challenge in this field. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a palm-free, low-trans-coconut oil-based shortening and its preparation method. The preparation method includes: stepwise lipase-catalyzed transesterification, complex seed crystal-assisted high-melting-point solid-phase separation, compounding with medium-chain fatty acid-compatible natural antioxidants, and rapid cooling and kneading. A palm oil-free, low-trans-coconut oil-based shortening and its preparation method are disclosed below: S1: Take 15-25 parts by weight of physically refined coconut oil, 40-50 parts by weight of high-oleic sunflower seed oil, and 20-30 parts by weight of fully hydrogenated rapeseed oil, put them into a reaction vessel, heat to 60℃, stir and mix evenly, then dehydrate and degas for 30 minutes at 80℃ and vacuum degree -0.09MPa, so that the moisture content is reduced to below 0.05% by weight, add 4-6 parts by weight of immobilized lipase LipozymeTL IM, and carry out the first stage of transesterification to obtain the first stage transesterified oil; take 100 parts by weight of the first stage transesterified oil, add 8-12 parts by weight of high-oleic safflower seed oil and 8-10 parts by weight of fully hydrogenated soybean oil, stir and mix evenly, dehydrate and degas for 20 minutes at 80℃ and vacuum degree -0.09MPa, add 3-4 parts by weight of immobilized lipase Novozym 435, and carry out the second stage of enzyme-catalyzed transesterification to obtain the transesterified oil; S2: Take 1-2 parts of coconut oil stearin, 5-7 parts of high melting point monoglyceride, and 3-4 parts of sorbitan tristearate, melt them, stir at a constant temperature, and obtain a composite seed crystal with β′ type as the main crystal form. Crush the obtained composite β′ seed crystal to make its D90 particle size not higher than 50μm. S3: Heat the obtained transesterification oil to 68°C and hold for 20 minutes. Then cool it to 45°C at a rate of 2°C / min and keep it at 45°C for 2 hours. Centrifuge at 45°C to separate and remove the high-melting-point solid phase. The amount of high-melting-point solid phase removed is 10% of the mass of the transesterification oil. Collect the liquid phase to obtain the fractionated transesterification liquid oil. S4: The temperature of the transesterification liquid is maintained at 45℃. Add 2-4 parts of composite seed crystals and 0.05-0.08 parts of compound natural antioxidant composition. Stir at 100 rpm for 20 minutes after adding. Then, quickly cool and knead to form the shortening.

[0006] Further, the first stage of transesterification described in step S1 specifically involves purging with nitrogen for protection, stirring at a constant temperature of 55℃~65℃ for 2~4 hours, and after the reaction is completed, filtering out the lipase with a 200-mesh filter for recycling and repurposing, thus obtaining the first stage transesterified oil.

[0007] Furthermore, the second stage of enzyme-catalyzed transesterification described in step S1 specifically involves a constant temperature stirring reaction at 45℃~55℃ for 1~2 hours, followed by filtration of the lipase using a 200-mesh filter.

[0008] Furthermore, the melting described in step S2 specifically involves melting and mixing uniformly in a water bath at 75°C.

[0009] Furthermore, the isothermal stirring described in step S2 specifically involves rapidly cooling the molten mixture to 18°C ​​at a rate of 20°C / min, then heating it to 28°C at a rate of 3°C / min, and stirring at the isothermal temperature for 3 hours.

[0010] Furthermore, the centrifugation described in step S3 specifically involves a centrifugation speed of 4000–5000 r / min and a centrifugation time of 5–15 minutes.

[0011] Further, the antioxidant composition described in step S4 is specifically a mixture of rosemary extract, a natural mixed tocopherol mainly composed of γ-tocopherol and δ-tocopherol, and an oil-dispersible green tea extract in a mass ratio of 1:2:1.

[0012] Further, the rapid cooling and kneading molding described in step S4 specifically involves feeding the material into a scraper heat exchanger with a refrigerant temperature of -15℃ to 5℃ and an outlet material temperature of 8℃ to 18℃; then feeding it into a needle kneader with a kneading temperature of 16℃ to 26℃ and a kneading time of 1 to 8 minutes; and then maturing it at 20℃ to 26℃ for 12 to 72 hours.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses coconut oil as the core raw material and does not use palm oil or palm extract at all, thus avoiding the sustainability issues and post-hardening defects related to palm oil. Furthermore, it does not use hydrogenation process throughout the entire process and does not use any raw materials containing trans fatty acids, thus meeting the requirements for low trans fatty acids.

[0014] (2) The stepwise transesterification of the present invention concentrates the triglyceride composition from the high melting point and low melting point ends to the middle melting point range, and the immobilized lipase can be reused, reducing production costs; the composite seed crystal-assisted crystallization and rapid cooling kneading together increase the proportion of β′ crystal form and inhibit crystal coarsening and oil separation during storage.

[0015] (3) This invention uses all plant-derived renewable raw materials, does not carry out hydrogenation reaction during the preparation process, and does not use partially hydrogenated oils; the fully hydrogenated vegetable oil used is a low trans stearin source, which is in line with the clean label and sustainable development trend. Attached Figure Description

[0016] Figure 1 This is a comparison chart of the oxidation stability test results for Experiment Example 1.

[0017] Figure 2 This is a comparison chart of the engineering verification results of Experiment Example 1.

[0018] Figure 3 This is a characterization diagram of the test in Experiment Example 2. Detailed Implementation

[0019] The following embodiments further explain and illustrate the technical solutions of the present invention. It is particularly noted that each specific embodiment is a specific interpretation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention. A palm-free, low-trans-coconut oil-based shortening and its preparation method, the detailed preparation steps of which are as follows: 1. Stepwise lipases catalyze transesterification Physically refined coconut oil provides a medium-chain saturated fatty acid backbone and unique mouth-melting properties; high-oleic sunflower oil is rich in oleic acid, used to reduce saturated fatty acid content and regulate crystallization behavior; fully hydrogenated rapeseed oil provides high-melting-point saturated fatty acids (mainly stearic acid), used to increase the solid content of oils; high-oleic safflower oil further supplements oleic acid and optimizes fatty acid composition; fully hydrogenated soybean oil provides additional stearic acid components and assists in crystal form regulation; sn-1 and sn-3 specific lipases catalyze acyl transfer at only the 1 and 3 positions of triglycerides, retaining the fatty acid composition at position 2. These lipases can be used to directionally introduce specific fatty acids to regulate melting behavior. Non-specific lipases, on the other hand, catalyze random rearrangement at all positions, which can be used to homogenize the triglyceride distribution in oils. Using these two types of enzymes stepwise allows for gradient optimization of the triglyceride molecular structure of the product.

[0020] 2. Preparation of composite seed crystals Take coconut oil stearin, high melting point monoglyceride and sorbitan tristearate, melt and mix them evenly in a water bath at 75℃, cool the molten mixture, then heat it up, stir and age it at a constant temperature to obtain a composite seed crystal with β′ type as the main crystal form, and pulverize the obtained composite β′ seed crystal to make its D90 particle size not higher than 50μm. The composite seed induces the oil to form a fine, uniform, and stable β′-type crystal network through the triple synergistic effect of the homologous crystal nucleus (coconut stearin), the β′-type crystal template (high melting point monoglyceride), and the interface regulator (sorbitan tristearate); and the stearic acid in the high melting point monoglyceride and sorbitan tristearate is from non-palm sources.

[0021] 3. High-melting-point solid-phase separation The obtained transesterification oil was heated to completely melt it and eliminate crystallization memory. Then it was kept at 45°C for 2 hours to enrich and crystallize the high-melting-point triglycerides. After the heat preservation was completed, it was centrifuged at 45°C to separate and remove the high-melting-point solid phase, and the liquid phase was collected to obtain the fractionated transesterification oil.

[0022] 4. Medium-chain fatty acid-compatible natural antioxidant compound and rapid cooling kneading type The temperature of the transesterification fluid is maintained at 45°C. A complex seed crystal and a compound natural antioxidant composition are added. This antioxidant composition consists of rosemary extract, a natural mixed tocopherol mainly composed of γ-tocopherol and δ-tocopherol, and an oil-dispersible green tea extract, which are pre-mixed evenly. Then, the mixture is rapidly cooled and kneaded to form the shortening.

[0023] Coconut oil is primarily composed of medium-chain saturated fatty acids, and its oxidation mechanism differs significantly from that of long-chain polyunsaturated oils. The arugula compounds in rosemary extract preferentially scavenge early-stage free radicals in medium-chain oils; mixed tocopherols can block the chain reaction of lipid peroxidation; and EGCG in oil-dispersed green tea extract can chelate metal ions and provide additional hydrogen atom donors. A specific ratio of these three components produces a significant synergistic effect; rapid cooling allows the oil to quickly pass through the crystallization zone, forming numerous fine crystal nuclei; high-speed kneading provides shear force, promoting a uniform and refined crystal network and preventing the formation of coarse crystals; subsequent low-temperature ripening further stabilizes the crystal network.

[0024] Example 1

[0025] Table 1 Raw Material Information Table

[0026] S1: Take 20 parts by weight of physically refined coconut oil, 45 parts by weight of high-oleic sunflower seed oil, and 25 parts by weight of fully hydrogenated rapeseed oil, put them into a reaction vessel, heat to 60℃, stir and mix evenly, then dehydrate and degas for 30 minutes at 80℃ and a vacuum of -0.09MPa, so that the moisture content is reduced to below 0.05% by weight. Add 5 parts of immobilized lipase Lipozyme TL IM, purge with nitrogen for protection, and stir and react at 60℃ for 3 hours. After the reaction, filter out the lipase through a 200-mesh filter for recycling and use, to obtain the first stage of transesterified oil; Take 100 parts of the first stage of transesterified oil, add 10 parts by weight of high-oleic safflower seed oil and 9 parts by weight of fully hydrogenated soybean oil, stir and mix evenly, dehydrate and degas for 20 minutes at 80℃ and a vacuum of -0.09MPa, and add 3.5 parts by weight of immobilized lipase Novozym 435, the second stage of enzyme-catalyzed transesterification was carried out. The reaction was carried out at 50°C with stirring for 1.5 hours. The lipase was filtered out through a 200-mesh filter to obtain transesterified oil. S2: Take 1.5 parts of coconut oil stearin, 6 parts of high melting point monoglyceride, and 3.5 parts of sorbitan tristearate, melt and mix them evenly in a 75°C water bath, rapidly cool the molten mixture to 18°C ​​at a rate of 20°C / min, then heat it to 28°C at a rate of 3°C / min, and age it at a constant temperature with stirring for 3 hours to obtain a composite seed crystal with β′ type as the main crystal form. Crush the obtained composite β′ seed crystal to make its D90 particle size not higher than 50μm. S3: The obtained transesterification oil is heated to 68°C and held for 20 minutes to completely melt it and eliminate crystallization memory. Then it is cooled to 45°C at a rate of 2°C / min and held at 45°C for 2 hours to enrich and crystallize the high-melting-point triglycerides. After the holding time is completed, it is centrifuged at 45°C at a speed of 4500 r / min for 10 minutes to separate and remove the high-melting-point solid phase. The amount of high-melting-point solid phase removed is 10% of the mass of the transesterification oil. The liquid phase is collected to obtain the fractionated transesterification liquid oil. S4: Maintain the temperature of the above-mentioned transesterification liquid oil at 45°C, add 3 parts of composite seed crystals and 0.06 parts of a compound natural antioxidant composition. This antioxidant composition is a pre-mixed mixture of rosemary extract, natural mixed tocopherols mainly composed of γ-tocopherol and δ-tocopherol, and oil-dispersible green tea extract in a mass ratio of 1:2:1. After adding, stir at 100 rpm for 20 minutes. Then, perform rapid cooling and kneading: send it into a scraper heat exchanger with a refrigerant temperature of -5°C and an outlet material temperature of 13°C. Then, send it into a needle kneader with a kneading temperature of 21°C and a kneading time of 4.5 minutes. Finally, mature at 23°C for 42 hours to obtain shortening.

[0027] Example 2

[0028] The preparation method is the same as in Example 1, but with the following differences: In step S1: Take 15 parts by weight of physically refined coconut oil, 40 parts by weight of high-oleic sunflower oil, and 20 parts by weight of fully hydrogenated rapeseed oil; add 4 parts by weight of immobilized lipase Lipozyme TL IM; add 8 parts by weight of high-oleic safflower oil, 8 parts by weight of fully hydrogenated soybean oil, and add 3 parts by weight of immobilized lipase Novozym 435.

[0029] In step S2: Take 1 part coconut oil stearin, 5 parts high melting point monoglyceride, and 3 parts sorbitan tristearate.

[0030] Example 3

[0031] The preparation method is the same as in Example 1, but with the following differences: In step S1: Take 25 parts by weight of physically refined coconut oil, 50 parts by weight of high-oleic sunflower oil, and 30 parts by weight of fully hydrogenated rapeseed oil; add 6 parts by weight of immobilized lipase Lipozyme TL IM; add 12 parts by weight of high-oleic safflower oil, 10 parts by weight of fully hydrogenated soybean oil, and add 4 parts by weight of immobilized lipase Novozym 435.

[0032] In step S2: Take 2 parts of coconut oil stearin, 7 parts of high melting point monoglyceride, and 4 parts of sorbitan tristearate.

[0033] Example 4

[0034] The preparation method is the same as in Example 1, but with the following differences: In step S4: Add 2 parts of composite seed crystals and 0.05 parts of compound natural antioxidant composition.

[0035] Example 5

[0036] The preparation method is the same as in Example 1, but with the following differences: In step S4: Add 4 parts of composite seed crystals and 0.08 parts of compound natural antioxidant composition.

[0037] Example 6

[0038] The preparation method is the same as in Example 1, but with the following differences: In step S1: the reaction is carried out at 55°C with constant stirring for 4 hours; the reaction is carried out at 45°C with constant stirring for 2 hours.

[0039] In step S3: the centrifugation speed is 4000 r / min and the centrifugation time is 15 minutes.

[0040] In step S4: the refrigerant temperature is -15℃, the outlet material temperature is 8℃; the kneading temperature is 16℃, the kneading time is 8 minutes; and then it is matured at 20℃ for 72 hours.

[0041] Example 7

[0042] The preparation method is the same as in Example 1, but with the following differences: In step S1: the reaction is carried out at 65°C with stirring for 2 hours; the reaction is carried out at 55°C with stirring for 1 hour.

[0043] In step S3: the centrifugation speed is 5000 r / min and the centrifugation time is 5 minutes.

[0044] In step S4: the refrigerant temperature is 5℃, the outlet material temperature is 18℃; the kneading temperature is 26℃, the kneading time is 1 minute; and then it is cured at 26℃ for 12 hours.

[0045] Comparative Example 1 The preparation method of Example 1 was followed, but without the addition of immobilized lipase Lipozyme TL IM; only a single enzymatic transesterification was performed. All other steps were the same.

[0046] Comparative Example 2 The preparation method of Example 1 is followed, but without the addition of composite seed crystals. All other steps are the same.

[0047] Comparative Example 3 The preparation method of Example 1 was followed, but without adding rosemary extract and oil-dispersible green tea extract; only natural mixed tocopherols were added, with the amounts remaining the same. All other steps were the same.

[0048] Comparative Example 4 The preparation method is the same as in Example 1, but without high-melting-point solid-phase separation. All other steps are the same.

[0049] Experimental Example 1 The samples prepared in Examples 1-5 and Comparative Example 1 were denoted as H1-H5 and C1, respectively, and their oxidation stability was tested and verified in engineering. Oxidative stability test: Peroxide value: Take 3.5g of sample, react with glacial acetic acid-isooctane mixed solvent, saturated KI in the dark, titrate with 0.01mol / L sodium thiosulfate, blank correction, and repeat in triplicate; p-anisidine value: Dissolve the sample in isooctane and make up to volume, measure the initial absorbance at 350nm, add p-anisidine reagent and react in the dark for 10min, then measure again at 350nm; TBARS: React the oil sample with the TBA / TCA system; heat at 95℃ for 30min; centrifuge after cooling; measure absorbance at 532nm; convert using the MDA standard curve; test results are as follows. Figure 1 As shown in the graph, the peroxide value of group H increased slowly over 90 days, while C1 increased significantly at an accelerated rate. The p-anisidine value and TBARS showed a consistent trend with the peroxide value, indicating that the compound antioxidant system not only delayed the formation of peroxides but also inhibited the accumulation of aldehydes and MDA-like secondary products.

[0050] Engineering Validation: SFC Curve: Samples were melted at 80℃ for 30 minutes; NMR tubes were loaded; measurements were taken after equilibration at -10, 0, 8, 17, 25, 33, 42, and 50℃; equilibration was performed for 30 minutes at each temperature point; Oil Yield: 30-50g of sample was stored at 35℃ or cyclically at 20 / 35℃; samples were taken at 0, 2, 4, 6, 8, 10, and 12 weeks; oil absorption using filter paper could be used; Oil Yield = Mass of Extracted Oil / Mass of Sample × 100%; Production Throughput: Refrigerant temperature, outlet material temperature, material pressure, needle kneader torque / current, and output were recorded; sampling interval was 1-10 seconds; test results are as follows. Figure 2 As shown in the graphs, the SFC of group H decreases continuously rather than sharply with increasing temperature, indicating that the system has a wide plasticity window. C1 shows a rapid decrease in SFC in the mid-to-high temperature region, indicating insufficient crystal network support. In the oil yield curves, H1-H4 maintain low oil yield over 12 weeks, while H5, as the boundary sample, shows slightly higher yield. C1 increases significantly, indicating that the defective control is more prone to liquid oil migration during temperature fluctuations or storage. Regarding production throughput, group H is approximately 440-500 kg / h, and C1 is approximately 325 kg / h, demonstrating that the complete process more easily forms a stable rheological state during continuous rapid cooling and kneading.

[0051] Experiment Example 2 Samples prepared in Examples 1, 3, 5, and 7, and Comparative Examples 1, 2, 3, and 4 were designated H1, H3, H5, H7, C1, C2, C3, and C4, respectively. 10 mg of each sample was placed on a glass slide and melted at 80°C to form a uniform oil film. 30 μm gaskets were used on both sides of the coverslip to control the thickness. The sample was cooled to 25°C at a rate of 5°C / min on a temperature-controlled hot stage and held for 30 min. A 200× POM microscopy scan was performed under crossed polarized light. The test results are as follows: Figure 3 As shown; The H1 micrograph should show a fine, continuous, and uniformly dispersed needle-like or fine-crystalline network, with a D50 of approximately 10-12 μm and a D90 of approximately 20-25 μm. C2, due to the lack of seed crystals, exhibits a wider crystal size distribution, with obvious coarse grains and aggregation. C4, due to the lack of separation of the high-melting-point solid phase, shows more coarse, high-melting-point crystals, and the grain size distribution shifts towards the larger size region. This demonstrates molecular structure regulation, β′ crystal form induction, microscopic network stability, and a wide plasticity window.

[0052] Experimental Example 3 The comprehensive properties of the shortenings prepared in Examples 1-7 and Comparative Examples 1-4 were determined. (1) Comprehensive performance test Trans fatty acid content test: Referencing standard GB 5009.257-2016 "National Food Safety Standard - Determination of Trans Fatty Acids in Food", gas chromatography was used for determination. Animal and vegetable oil samples underwent transesterification with methanol under alkaline conditions to generate fatty acid methyl esters, which were separated on a strongly polar stationary phase capillary column and determined using a gas chromatograph equipped with a flame ionization detector. Saturated fatty acid content test: Referencing standard GB / T 17377-2008 "Gas Chromatographic Analysis of Fatty Acid Methyl Esters in Animal and Vegetable Oils", the sample was subjected to gas chromatography analysis after methylation treatment, and the results were calculated. Solid fat content test: Each sample was completely melted at 80℃ for 30 minutes to eliminate crystallization memory. Then, the temperature was adjusted according to the program of 0℃, 10℃, 20℃, 25℃, 30℃ and 35℃. The SFC was determined by pulse nuclear magnetic resonance. The test results at 20℃, 30℃ and 35℃ are recorded below. Peroxide value test: Referring to the standard GB 5009.227-2023 "National Food Safety Standard - Determination of Peroxide Value in Food", the oil sample was dissolved in a mixed solvent of glacial acetic acid and isooctane, and potassium iodide solution was added to react. The precipitated free iodine was titrated with sodium thiosulfate standard solution. The peroxide value after 12 days of accelerated treatment at 60℃ was calculated based on the consumption. At the same time, the limit requirement of peroxide value ≤0.25g / 100g (approximately 9.85mmol / kg) in GB 2716-2018 "National Food Safety Standard - Vegetable Oils" was used as the judgment basis. The specific test comparison results are shown in Table 2: Table 2 Comparison of comprehensive performance test results between Examples 1-7 and Comparative Examples 1-4

[0053] (2) Baking application test Application tests were conducted using the following cookie recipe: 100 parts low-gluten flour, 35 parts powdered sugar, 45 parts shortening, 12 parts whole egg liquid, and 0.5 parts salt. The shortening was warmed to 22℃ for 2 hours and then whipped. The other ingredients were then added and mixed to form the cookie mixture, which was then baked at 180℃ for 12 minutes. The cookie hardness, expansion ratio, and crumblyness score were measured; the test results are shown in Table 3.

[0054] The comparison results above show that Comparative Example 1, using only the non-specific lipase Novozym 435 for one-step transesterification, had a SFC of only 6.7% at 35℃, and suffered severe loss of plasticity at higher temperatures. This is because although one-step transesterification achieves random rearrangement of fatty acids at all positions, the triglyceride molecular structure is not optimized enough. The sn-1 and sn-3 positions did not undergo the directional introduction of stearic acid for regulation, leading to rapid melting of the solid components during heating. Comparative Example 2 did not add composite seed crystals, resulting in extremely uneven crystal size distribution and a noticeable grainy and gritty texture in the product. Comparative Example 3 only added natural mixed tocopherols as antioxidants, without adding rosemary extract or oil-dispersible green tea extract. Although the initial peroxide value and acid value of this sample were normal, after 12 days of accelerated oxidation at 60℃, the peroxide value increased sharply, failing to meet the requirements for oxidative stability during normal shelf life. This is because coconut oil is mainly composed of medium-chain saturated fatty acids, and its oxidation mechanism differs from that of long-chain polyunsaturated oils. While mixed tocopherols can terminate lipid peroxidation chain reactions by providing hydrogen atoms, they have a weak ability to scavenge early-stage free radicals in medium-chain lipids and lack metal ion chelation ability. Comparative Example 4, without high-melting-point solid-phase separation, suffered from severe crystal coarsening and crystal form transformation problems, resulting in poor baking test results.

Claims

1. A method for preparing a palm-free, low-trans-coconut oil-based shortening, characterized in that, The specific steps include the following: S1: Take 15-25 parts by weight of physically refined coconut oil, 40-50 parts by weight of high-oleic sunflower seed oil, and 20-30 parts by weight of fully hydrogenated rapeseed oil, put them into a reaction vessel, heat to 60℃, stir and mix evenly, then dehydrate and degas for 30 minutes at 80℃ and vacuum degree -0.09MPa, so that the moisture content is reduced to below 0.05% by weight, add 4-6 parts of sn-1,3 specific lipase, and carry out the first stage of transesterification to obtain the first stage transesterified oil; take 100 parts of the first stage transesterified oil, add 8-12 parts by weight of high-oleic safflower seed oil and 8-10 parts by weight of fully hydrogenated soybean oil, stir and mix evenly, dehydrate and degas for 20 minutes at 80℃ and vacuum degree -0.09MPa, add 3-4 parts by weight of non-specific lipase, and carry out the second stage of enzyme-catalyzed transesterification to obtain the transesterified oil; S2: Take coconut oil stearin, high melting point monoglyceride, and sorbitan tristearate, melt them, and stir at a constant temperature to obtain a composite seed crystal with β′ type as the main crystal form; S3: Heat the obtained transesterification oil to 68°C and hold for 20 minutes. Then cool it to 45°C at a rate of 2°C / min and keep it at 45°C for 2 hours. Centrifuge at 45°C to separate and remove the high-melting-point solid phase. The amount of high-melting-point solid phase removed is 10% of the mass of the transesterification oil. Collect the liquid phase to obtain the fractionated transesterification liquid oil. S4: The temperature of the transesterification liquid is maintained at 45℃. Add 2-4 parts of composite seed crystals and 0.05-0.08 parts of compound natural antioxidant composition. Stir at 100 rpm for 20 minutes after adding. Then, quickly cool and knead to form the shortening.

2. The method for preparing a palm-free, low-trans-coconut oil-based shortening according to claim 1, characterized in that, The first stage of transesterification described in step S1 involves purging with nitrogen for protection and stirring at a constant temperature of 55℃~65℃ for 2~4 hours. After the reaction is completed, the lipase is filtered out using a 200-mesh filter and recycled for later use, thus obtaining the first stage transesterified oil.

3. The method for preparing a palm-free, low-trans-coconut oil-based shortening according to claim 1, characterized in that, The second stage of enzyme-catalyzed transesterification described in step S1 involves stirring the reaction at a constant temperature of 45℃ to 55℃ for 1 to 2 hours, and then filtering out the lipase using a 200-mesh filter.

4. The method for preparing a palm-free, low-trans-coconut oil-based shortening according to claim 1, characterized in that, The melting process described in step S2 specifically involves melting and mixing the materials evenly in a water bath at 75°C.

5. The method for preparing a palm-free, low-trans-coconut oil-based shortening according to claim 1, characterized in that, The isothermal stirring in step S2 specifically involves rapidly cooling the molten mixture to 18°C ​​at a rate of 20°C / min, then heating it to 28°C at a rate of 3°C / min, and stirring at the isothermal temperature for 3 hours.

6. The method for preparing a palm-free, low-trans-coconut oil-based shortening according to claim 1, characterized in that, The centrifugation described in step S3 specifically involves a centrifugation speed of 4000–5000 r / min and a centrifugation time of 5–15 minutes.

7. The method for preparing a palm-free, low-trans-coconut oil-based shortening according to claim 1, characterized in that, The antioxidant composition described in step S4 is specifically a mixture of rosemary extract, natural mixed tocopherols mainly composed of γ-tocopherol and δ-tocopherol, and oil-dispersible green tea extract in a mass ratio of 1:2:

1.

8. The method for preparing a palm-free, low-trans-coconut oil-based shortening according to claim 1, characterized in that, The rapid cooling and kneading molding process described in step S4 specifically involves feeding the material into a scraper-type heat exchanger with a refrigerant temperature of -15℃ to 5℃ and an outlet material temperature of 8℃ to 18℃; then feeding it into a needle kneader with a kneading temperature of 16℃ to 26℃ and a kneading time of 1 to 8 minutes; and finally maturing it at 20℃ to 26℃ for 12 to 72 hours.

9. The shortening prepared by the method for preparing a palm-free, low-trans-coconut oil-based shortening according to any one of claims 1-8, characterized in that, Its trans fatty acid content does not exceed 0.18%, and its saturated fatty acid content does not exceed 38.8%.

10. A palm-free, low-trans-coconut oil-based shortening according to claim 9, characterized in that, The shortening is used in baked goods, confectionery, or frozen desserts.

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