Preparation process of low-saturation margarine with ester exchange cottonseed oil as base oil

Abstract

The invention discloses a preparation process of low-saturation margarine with ester exchange cottonseed oil as base oil, and relates to the technical field of grease processing. Comprising the following steps: (1) heating and melting palm stearin, and adding cottonseed oil to obtain a binary mixture; (2) adding immobilized lipase Lipozyme TLIM into the binary mixture obtained in the step A, and carrying out ester exchange reaction in a vacuum state; (3) after the transesterification is finished, firstly separating out immobilized lipase TLIM, and then purifying the residual crude margarine butter base oil to prepare cottonseed oil-based margarine butter base oil; and (4) adding glyceryl monopalmitate, Span40 and glyceryl monostearate into the cottonseed oil-based margarine base oil to prepare an oil phase, taking purified water as a water phase, mixing and emulsifying the oil phase and the water phase, and cooling and kneading to obtain the low-fat margarine. The invention provides a preparation process of low-saturation margarine which takes cottonseed oil as a raw material, adopts an ester exchange technology, does not generate trans-fatty acid and has a taste close to that of natural butter.

Description

Technical Field

[0001] The invention belongs to the technical field of oil processing, and particularly relates to a process for preparing low-saturated margarine using ester-exchanged cottonseed oil as base oil. Background Art

[0002] As people's living standards continue to improve, the demand for cream in the biscuit and pastry making market is increasing. Margarine is a water-in-oil (W / O) emulsified food with a fat content of more than 80%. Fat is an important nutrient that provides energy to the human body and is divided into saturated fatty acids (SFAs) and unsaturated fatty acids (UFAs). Many studies have shown that excessive consumption of saturated fatty acids increases the risk of cardiovascular disease. The 2023 American Heart Association / American College of Cardiology Guidelines recommend that patients with chronic coronary heart disease limit their saturated fat intake to less than 6% of their total daily calories and replace it with unsaturated fats. Therefore, margarine rich in unsaturated fatty acids is an area worthy of in-depth research.

[0003] Currently, hydrogenation is widely used in oil modification due to its rapid crystallization and excellent plasticity. However, it produces a large amount of trans and saturated fatty acids, which are detrimental to human health and can increase the risk of cardiovascular disease. Transesterification has attracted considerable attention due to its mild reaction, ability to rearrange the fatty acids on the glycerol backbone, and the absence of trans fatty acids. With increasing awareness of nutritional health, the development of a new margarine with a low saturated fatty acid content has become of great practical significance.

[0004] Therefore, in order to solve the above technical problems, it is necessary to provide a new technical solution to solve this technical problem, especially a preparation process of low-saturated margarine using transesterified cottonseed oil as base oil. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the existing hydrogenated modified margarine technology easily produces trans fatty acids, and to provide a preparation process for low-saturated margarine using ester-exchanged cottonseed oil as base oil.

[0006] In order to achieve the above object, the present invention provides the following technical solution: a process for preparing low-saturated margarine using interesterified cottonseed oil as a base oil, comprising the following steps:

[0007] S1. The palm stearin was heated to 60-80 ° C and melted, and cottonseed oil was added, wherein the mass ratio of palm stearin to cottonseed oil was 8:2 to 4:6 to obtain a binary mixture;

[0008] S2 is added immobilized lipase Lipozyme TLIM, the immobilized lipase Lipozyme TLIM accounted for 4% to 8% of the total mass of the oil mixture, transesterification reaction under vacuum, transesterification reaction time 1 to 4h, the reaction temperature 50 to 60 ℃, to obtain a crude margarine base oil mixture;

[0009] S3. Immobilized lipase Lipozyme TLIM was separated from the crude margarine base oil mixture to obtain crude margarine base oil, and the remaining crude margarine base oil was purified to obtain cottonseed oil-based margarine base oil;

[0010] S4 was added to the cottonseed oil-based margarine base oil monopalmitic acid glyceryl, Span40, glyceryl monostearate to prepare the oil phase; purified water as the aqueous phase, and then the oil phase and the aqueous phase were mixed and emulsified, cooled, kneaded to obtain a low-fat margarine;

[0011] The added amount of the monopalmitic acid glycerol is 0.2% to 0.4% of the total mass of the margarine, the added amount of the Span40 is 0.2% to 0.4% of the total mass of the margarine, and the added amount of the monostearate glycerol is 0.4% to 0.6% of the total mass of the margarine.

[0012] Preferably, the heating temperature of palm stearin in step S1 is 70°C.

[0013] Preferably, in step S1, the mass ratio of cottonseed oil to palm stearin is 7:3.

[0014] Preferably, the amount of the immobilized enzyme used in step S2 is 6% of the total mass of the oil.

[0015] Preferably, the transesterification reaction time in step S2 is 2 hours and the reaction temperature is 55°C.

[0016] Preferably, the added amount of the monopalmitin glycerol is 0.25% of the total mass of the margarine, the added amount of the Span 40 is 0.25% of the total mass of the margarine, and the added amount of the monostearate glycerol is 0.5% of the total mass of the margarine.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention selects cottonseed oil (CSO) as raw material. Cottonseed oil is rich in a large amount of unsaturated fatty acid essential to the human body - linoleic acid. After the ester exchange process, the fatty acid saturation degree of the modified oil can be adjusted, and the crystal habit is β' type, with good oxidative stability and high nutritional value.

[0019] (2) The mixed oil obtained by the esterification reaction in step S2 of the present invention has a sliding melting point between 33 and 36° C., a saturated fatty acid content of less than 40%, a reduced content of highly saturated triglycerides, and a crystal form mainly of β' type, which meets the requirements of margarine base oil, and has good oxidative stability, a smooth SFC curve, finer grains, a reasonable triglyceride composition, and excellent reprocessing characteristics.

[0020] (3) The immobilized lipase Lipozyme TLIM in step S3 of the present invention is easy to separate from the product, has good reusability, and produces few reaction by-products, which effectively improves the safety of the reaction and reduces the cost.

[0021] (4) Margarine SFC produced in step S4 of the present invention 20℃ 10~18%, SFC 35℃ 1~4%, among which SFC 35℃ As low as 4%, with natural butter (SFC 35℃ The content of the margarine produced by the present invention is similar to that of margarine produced by conventional lipase transesterification reaction, and is much lower than that of margarine produced by conventional lipase transesterification reaction, and even lower than that of the product obtained by transesterification catalyzed by immobilized lipase TLIM in the existing mature technology. As a result, the margarine produced by the present invention can be almost completely melted in the mouth, producing a mouthfeel that is significantly better than that of margarine produced by existing technical means.

[0022] (5) The margarine prepared by the present invention has a saturated fatty acid content of 36.71% < 40%, no trans fatty acids, a low atherogenicity index (0.09) and a thrombogenicity index (1.13), a high saturated triglyceride content of 1.15 < 2%, and a β'-type crystal content of 59.49%, which is beneficial to human health; it has a wide plasticity range and low viscoelasticity, which is significantly higher than commercially available margarine; in vitro simulated digestion process analysis shows that the margarine prepared by the present invention has a smaller particle size, stronger emulsification ability, and a higher content of released free fatty acids (64.99%), making it easier for the human body to digest and absorb. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the specific operation process of the present invention.

[0024] Figure 2 3 and 4 are SMP and SFC diagrams of the present invention under different raw material ratios.

[0025] Figure 3 This is a diagram showing the appearance of margarine produced with different raw material ratios according to the present invention.

[0026] Figure 4 It is a diagram of the crystal form changes under different raw material ratios of the present invention.

[0027] Figure 5 It is a crystal content diagram under different raw material ratios of the present invention.

[0028] Figure 6 This is a graph of the sliding melting point and solid fat content before and after transesterification of the present invention.

[0029] Figure 7 It is a crystallization habit analysis diagram of the butter prepared by the present invention and commercially available butter.

[0030] Figure 8 The melting properties (A) and crystallization properties (B) of the butter prepared by the present invention and commercially available butter are analyzed.

[0031] Figure 9 Graph showing changes in particle size (A) and potential (B) during digestion of butter prepared according to the present invention and commercially available butter.

[0032] Figure 10 CLSM microstructure diagram of the butter prepared by the present invention and commercially available butter during digestion.

[0033] Figure 11 This is a comparison chart of the FFA release capacity of the butter prepared by the present invention and commercially available butter. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0037] Example 1: Figure 1 As shown, a process for preparing low-saturated margarine using interesterified cottonseed oil as a base oil comprises the following steps:

[0038] S1. Palm stearin was heated to 70 ° C and melted, and cottonseed oil was added, wherein the mass ratio of palm stearin to cottonseed oil was 7:3 to obtain a binary mixture;

[0039] S2 was added immobilized lipase Lipozyme TLIM, the immobilized lipase Lipozyme TLIM accounted for 4% of the total mass of the oil mixture, using a rotary evaporator under vacuum transesterification reaction, transesterification reaction time 2h, the reaction temperature 55 ℃, to obtain a crude margarine base oil mixture;

[0040] S3. Immobilized lipase Lipozyme TLIM was separated from the crude margarine base oil mixture to obtain crude margarine base oil, and the remaining crude margarine base oil was purified to obtain cottonseed oil-based margarine base oil;

[0041] S4 was added to the cottonseed oil-based margarine base oil monopalmitic acid glyceryl, span40, glyceryl monostearate to prepare the oil phase; purified water as the aqueous phase, and then the oil phase and the aqueous phase were mixed and emulsified, the two phases were fully emulsified for 20min, cooled, kneaded to obtain a low-fat margarine;

[0042] The added amount of the monopalmitic acid glycerol is 0.25% of the total mass of the margarine, the added amount of the span40 is 0.25% of the total mass of the margarine, and the added amount of the monostearate glycerol is 0.5% of the total mass of the margarine.

[0043] Example 2: A process for preparing low-saturated margarine using transesterified cottonseed oil as a base oil, comprising the following steps:

[0044] S1. Palm stearin was heated to 60 ° C and melted, and cottonseed oil was added, wherein the mass ratio of palm stearin to cottonseed oil was 8:2 to obtain a binary mixture;

[0045] S2 was added immobilized lipase Lipozyme TLIM, the immobilized lipase Lipozyme TLIM accounted for 4% of the total mass of the oil mixture, using a rotary evaporator under vacuum transesterification reaction, transesterification reaction time 1h, the reaction temperature 50 ℃, to obtain a crude margarine base oil mixture;

[0046] S3. Immobilized lipase Lipozyme TLIM was separated from the crude margarine base oil mixture to obtain crude margarine base oil, and the remaining crude margarine base oil was purified to obtain cottonseed oil-based margarine base oil;

[0047] S4 was added to the cottonseed oil-based margarine base oil monopalmitic acid glyceryl, span40, glyceryl monostearate to prepare the oil phase; purified water as the aqueous phase, and then the oil phase and the aqueous phase were mixed and emulsified, the two phases were fully emulsified for 20min, cooled, kneaded to obtain a low-fat margarine;

[0048] The added amount of the monopalmitic acid glycerol is 0.2% of the total mass of the margarine, the added amount of the span40 is 0.2% of the total mass of the margarine, and the added amount of the monostearate glycerol is 0.4% of the total mass of the margarine.

[0049] Example 3: A process for preparing low-saturated margarine using transesterified cottonseed oil as a base oil, comprising the following steps:

[0050] S1. Palm stearin was heated to 80 ° C and melted, and cottonseed oil was added, wherein the mass ratio of palm stearin to cottonseed oil was 4:6 to obtain a binary mixture;

[0051] S2 was added immobilized lipase Lipozyme TLIM, the immobilized lipase Lipozyme TLIM accounted for 8% of the total mass of the oil mixture, using a rotary evaporator under vacuum transesterification reaction, transesterification reaction time 4h, the reaction temperature 60 ℃, to obtain a crude margarine base oil mixture;

[0052] S3. Immobilized lipase Lipozyme TLIM was separated from the crude margarine base oil mixture to obtain crude margarine base oil, and the remaining crude margarine base oil was purified to obtain cottonseed oil-based margarine base oil;

[0053] S4 was added to the cottonseed oil-based margarine base oil monopalmitic acid glyceryl, span40, glyceryl monostearate to prepare the oil phase; purified water as the aqueous phase, and then the oil phase and the aqueous phase were mixed and emulsified, the two phases were fully emulsified for 20min, cooled, kneaded to obtain a low-fat margarine;

[0054] The added amount of the monopalmitic acid glycerol is 0.4% of the total mass of the margarine, the added amount of the span40 is 0.4% of the total mass of the margarine, and the added amount of the monostearate glycerol is 0.6% of the total mass of the margarine.

[0055] Comparative Example: 1. Sliding melting point and solid fat content of base oils with different ratios

[0056] Based on the steps of Example 1, experiments were conducted by varying the mass ratio of palm stearin to cottonseed oil, with the mass ratios being 8:2, 7:3, 6:4, 5:5, and 4:6, respectively. The various parameters of Example 1 were tested to determine the optimal mass ratio.

[0057] 1. Sliding melting point and solid fat content of base oils with different ratios

[0058] The solid fat content (SFC) was determined by direct method according to GB / T 31743-2015 Animal and vegetable fats and oils - Determination of solid fat content by pulsed nuclear magnetic resonance; the slip melting point (SMP) was determined by GB / T 24892-2010 Animal and vegetable fats and oils - Determination of melting point (slip point) in an open capillary tube. The results are as follows: Figure 2 shown. Figure 2 (A) The SMP of base oils with different raw material ratios was analyzed, and it was found that with the increase of palm stearin ratio, the SMP gradually increased. This is because palm stearin contains a large amount of high-melting-point triglycerides. However, the experiment found that after transesterification, the SMP was significantly reduced, indicating that the samples that underwent enzymatic transesterification had better mouth melting and flavor release. The melting point range of margarine treated by enzymatic transesterification is 33.37℃ to 41.5℃. The base oil prepared at a ratio of 7:3 has a lower SMP (<37℃) and a better taste. Figure 2 (B) As can be seen, the isotherm curves of the transesterified samples are smooth, indicating good compatibility and, therefore, a more suitable base oil for margarine. As the temperature increases, the SFC content decreases dramatically. This is due to the rearrangement of fatty acids in triglycerides caused by the transesterification reaction, which reduces the proportion of high-melting-point triglycerides. This is consistent with the change in SMP. When the SFC of a fat exceeds 10% at 20°C, fat precipitation is prevented. The SFC at 35°C should be as low as possible; the lower the value, the better the meltability. As can be seen from the figure, the base oil prepared with an 8:2 ratio has an SFC of 8.44% at 35°C. Below 10% is prone to oil precipitation. As the proportion of palm stearin increases, the base oil becomes increasingly plastic. Base oils with ratios of 5:5 and 4:6 have a hard and brittle texture. In contrast, base oils prepared with ratios of 7:3 and 6:4 have good spreadability and an appropriate solid fat content.

[0059] 2. Appearance of base oils with different ratios

[0060] By observing the appearance image of oil and grease, we can intuitively judge its physical properties such as color and uniformity. These physical properties also reflect the state, stability and other properties of the oil and grease.

[0061] like Figure 2 As shown, all base oils are milky white and contain solid fats at room temperature. As the proportion of palm stearin increases, the base oils become increasingly plastic. The base oil with an 8:2 ratio exhibits some separation of liquid and solid fats at room temperature, with a small amount of oil separation. The base oils with 5:5 and 4:6 ratios exhibit a hard and brittle texture, as confirmed by SFC image analysis. This is directly related to their plastic fat content. In contrast, base oils with 7:3 and 6:4 ratios exhibit good compatibility, with moderate hardness and plastic fat content.

[0062] 3. Triglyceride (TAG) composition of base oils with different ratios

[0063] The TAG composition of the samples was analyzed by ultra-high performance liquid chromatography (RP-HPLC) coupled with an evaporative light scattering detector (ELSD) according to the official AOCS method Ce5b-89.

[0064] Table 1 Analysis of triglyceride composition before and after transesterification

[0065]

[0066] As shown in Table 1, with the addition of palm stearin, the content of trisaturated triglycerides (S3) gradually increases, the content of triunsaturated triglycerides (U3) decreases, and the content of diunsaturated triglycerides gradually decreases. This is because palm stearin contains a large number of SFAs. During the transesterification process, its fatty acids rearrange with the UFAs of cottonseed oil, resulting in the formation of more TAGs. When the concentration of S3 triglycerides in plastic oils exceeds 2%, they will cause the final product to have an undesirable sandy texture. In this experiment, the S3 triglyceride content of the transesterified samples was below this critical value. This indicates that the transesterified samples are suitable for margarine production because their texture is not negatively affected by excessive crystallization of S3 triglycerides. Therefore, a lower S3 content helps produce a smooth margarine. A lower S3 content helps produce a smoother margarine. The S3 content of a 7:3 base oil is 1.15, lower than that of a 6:4 base oil (1.41). However, the combined content of disaturated and monounsaturated triglycerides (S2U) and monounsaturated and diunsaturated triglycerides (SU2) in the 6:4 base oil (80.21%) is higher than the combined content of S2U and SU2 in the 7:3 base oil (76.66%), resulting in better plasticity and meltability. Therefore, it is necessary to comprehensively evaluate the functional properties of plasticized fats using multiple indicators.

[0067] 4. Crystal composition of base oils in different proportions

[0068] XRD was used to detect the homogeneous polymorphism of oils with different raw material ratios after enzymatic transesterification reaction. Figure 4 As shown in the figure, the information obtained from the X-ray spectrum in the figure can be used to determine the crystalline structure of the oil. Figure 4 It can be seen that after transesterification, the oil and The nearby area shows a major short spacing, where The nearby peaks correspond to the β-crystal form of oil, 4.4, 4.2 and The nearby peaks correspond to the β' crystal form of the oil, indicating that the crystal forms of IB mainly include these two types.

[0069] In order to more intuitively analyze the change rules of the crystal forms of different transesterification products, the intensity of the short-spacing peaks in the oil diffraction patterns measured by XRD before and after transesterification was converted to calculate the relative content of the oil crystal form, thereby achieving quantitative analysis of the oil crystal form. The results are as follows: Figure 5 As shown in the figure, as the amount of cottonseed oil added decreases, the base oil's crystal form gradually shifts from β' to β-type. β'-type, due to its small and uniform crystals, delicate structure, and large contact surface, effectively encapsulates the liquid oil phase. This is why margarine phases are less likely to separate, resulting in excellent stability and casein properties. In contrast, β-type crystals are larger and more densely packed, with their size increasing over time, resulting in poorer ability to encapsulate liquid oil. Based on the β' crystal content, IBs obtained with ratios of 8:2 (65.04%), 7:3 (62.58%), and 6:4 (60.30%) contain over 60% β' crystals, while those obtained with ratios of 5:5 (55.65%) and 4:6 (48.45%) contain less β' crystals.

[0070] Through the above experimental research, it can be seen that the SFAs (36.71%) content, AI value (0.09) and TI value (1.13), and β' (62.58%) crystal form of the base oil in a ratio of 7:3 are all due to the base oil in other ratios. At this time, the S3 content (1.15) is <2%, and the performance is better. Therefore, the addition mass ratio of palm stearin to cottonseed oil is 7:3, which is the optimal addition ratio of this technical solution.

[0071] 2. Analysis of experimental results

[0072] 1. Slip melting point and solid fat content before and after transesterification

[0073] The SFC was determined by pulsed nuclear magnetic resonance (pNMR) according to AOCS official method Cd16b-93. The SMP of oils and fats was determined by open capillary method according to GB / T 24892-2010. Figure 6 As shown, PS, PB, and IB refer to palm stearin, physically mixed base oil, and enzymatic interesterified base oil, respectively. Palm stearin, rich in saturated fatty acids, has a high solid fat content. When the temperature rises from 5°C to 30°C, the solid fat content of IB decreases sharply compared to PB. This is due to the transesterification reaction, which rearranges the fatty acids within triglycerides and reduces the proportion of high-melting-point triglycerides. At 35°C, the SFC of PB is 9.02%, exceeding 5%, while that of IB is 0.98%, indicating good palatability. The SMP of the PB sample is 45.27°C, while that of the IB sample is 35.25°C, indicating that the interesterified samples have better melting properties and better flavor release.

[0074] 2. Determine the crystal composition before and after transesterification

[0075] X-ray diffraction was used to analyze the crystal composition before and after transesterification

[0076] Table 2 Crystal composition analysis before and after transesterification

[0077]

[0078] As shown in Table 2, the esterification reaction promotes crystallization in the oil and facilitates the transformation of the β-crystal structure in the oil to the β' crystal structure. Compared to the pre-esterification sample, the post-esterification sample has a higher β' content, which is the most ideal crystal form for margarine. This allows the formation of a fine crystal network capable of binding a large amount of liquid oil, which improves stability, gas storage capacity, and structural properties.

[0079] 3. Determine the triglyceride (TAG) composition before and after transesterification

[0080] The TAG composition of the samples was analyzed by ultra-high performance liquid chromatography (RP-HPLC) coupled with an evaporative light scattering detector (ELSD) according to the official AOCS method Ce5b-89.

[0081] Table 3 Analysis of triglyceride composition before and after transesterification

[0082]

[0083]

[0084] As shown in Table 3, palm stearin contains a significantly higher content of S3 triglycerides (62.42%). In contrast, cottonseed oil has a higher content of U3 triglycerides, which is related to the degree of saturation of its fatty acids. As can be seen from the table, the transesterification reaction increases the content of S2U and SU2 triglycerides, promoting the formation of more β' crystals; it also reduces the levels of S3 and U3 triglycerides, favoring the formation of smaller crystals. In the present invention, the S3 triglyceride content of the esterified sample was 1.15%, which greatly reduced the likelihood of grittiness. This indicates that the esterified sample is suitable for margarine production because its texture is not negatively affected by excessive crystallization of S3 triglycerides.

[0085] 3. Comparison of margarine of the present invention with butter sold on the market

[0086] The commercially available butters are Dumi Fresh Margarine and Becel Margarine. In the figure below, IB-M is a margarine prepared using the process of the present invention; CB-1 and CB-2 are commercially available butters for comparison.

[0087] 1. Crystallization Habit Analysis

[0088] like Figure 7As shown in the figure, the relative content of β' crystal form of IB-M is 60.3% and 59.49%, respectively, which is higher than the relative content of β' crystal form of commercial margarine (50.39% and 50.04%), with finer crystal particles and better mouth melting properties.

[0089] 2. Crystallization and melting characteristics analysis

[0090] like Figure 8 As shown, a comparison of IB-M, CB-1, and CB-2 revealed that the high-melting-point melting peaks of these three samples were broad, indicating enhanced plasticity. Their small peak areas can help reduce the brittleness of the oil during melting. The strong correlation between the total enthalpy and its freshness during melting further demonstrates the success of the prepared IB-M. A comparison of IB-M, CB-1, and CB-2 revealed that the peak area of high-freezing-point triglycerides gradually decreased and the peak shape slightly broadened during the cooling process, thereby enhancing their plasticity. This demonstrates that the prepared IB-M has certain advantages in the preparation of margarine.

[0091] 3. Digestive Performance Analysis

[0092] An in vitro digestion model was used to study the digestion and absorption of IB-M in the human body, and a comparative analysis was conducted with commercially available margarine (CB). The digestion patterns of margarine in the human body were preliminarily studied based on the changes in average particle size, zeta potential and microstructure at each digestion stage.

[0093] (1) Particle size, surface potential and micromorphology analysis

[0094] like Figure 9 As shown in Figure A, the initial particle size of margarine is CB-2 > CB-1 > IB-M, indicating that under the same reaction conditions, different types of butter have different emulsifying abilities. Butter contains over 80% fat. Studies have shown that the length of the fatty acid chain is negatively correlated with the emulsifying ability of the fat, while its saturation is significantly positively correlated with the emulsifying ability of the fat. Existing research shows that CB-2 and CB-1 contain large amounts of SFAs, while IB-M is richer in UFAs. Therefore, when the reaction conditions are consistent, IB-M has superior emulsifying ability and a smaller emulsion particle size (p < 0.05). Studies have shown that the initial particle size of the emulsion system affects the digestibility of lipids. For the same fat, a smaller initial particle size results in a higher digestibility, but this does not affect the final digestibility.

[0095] (2) Analysis of each digestion stage

[0096] from Figure 10 The CLSM microstructure shown in the figure shows that all fat globules are evenly dispersed in the water phase. Figure 9From the Zeta potential of Figure B, it can be seen that the initial emulsion surfaces of the three butters are in a neutral pH environment. The original emulsion surfaces of the three butters have a large amount of negative charges, among which IB-M has the most negative charge, with a value of -42.4 mV, and the charge intensity is significantly higher than that of CB-1 and CB-2 (p<0.05), indicating that IB-M has a strong electrostatic repulsion and can inhibit the aggregation and flocculation between fat globules, which is related to its high proportion of unsaturated fatty acids.

[0097] After oral digestion, the average particle size of all emulsions increased significantly (p < 0.05), which is due to the bridging or flocculation of mucin in the mouth, leading to the aggregation of lipid droplets. In addition, the increase in the particle size of small-sized IB-M lipid droplets may be due to their higher content of needle-shaped β′, which is more likely to cause emulsion instability and more likely to cause collisions and aggregation during mixing, further increasing their particle size. Zeta potential also shows that in the mouth, although the negative charge of the emulsion decreases slightly, it still maintains a strong negative charge. These negative charges are evenly dispersed in the emulsion, which is also due to the strong repulsive force between fat globules. The electrostatic shielding effect of mineral ions in simulated saliva will lead to a reduction in charge in the mouth. CLSM images show that all emulsions are relatively evenly dispersed throughout the system during digestion, and only a small amount of oil aggregation occurs.

[0098] After gastric digestion, the average particle size of all emulsions increased significantly (p < 0.05), and the potential of the digestive fluid decreased rapidly, almost reaching a neutral state. Combined with the CLSM images, large fat globules were observed in the gastric digestive fluid of all three butters. This is closely related to the low pH and high ionic strength of the gastric fluid, as well as the hydrolytic action of pepsin. These factors weaken the electrostatic repulsion between fat globules, reducing their stability and thus inducing lipid droplet aggregation. Furthermore, the hydrolysis caused by pepsin ruptures the interfacial membrane, exposing the fat crystals, which further leads to microagglomeration of lipid droplets and loss of emulsion stability. Smaller crystals may provide better surface coverage. The study found that all samples exhibited significant aggregation in the stomach, with particle size increasing significantly from the initial stage.

[0099] After passing through the small intestine, the average particle size of all emulsions decreased significantly (p<0.05), with significant differences between the three emulsions (p<0.05). This phenomenon may be due to the displacement of reactive anionic species such as phospholipids and bile salts contained in the intestinal fluid. After the addition of pancreatic lipase, it binds to the oil droplets, replacing components such as proteins and bile salts on the droplet surface, decomposing triglycerides. Large oil droplets are gradually hydrolyzed into various highly negatively charged substances such as free fatty acids, resulting in a smaller average particle size. This change can also be seen in the CLSM images.

[0100] The positive / negative charge of the digestive system is significantly correlated with stability. In the experiment, all three butters exhibited high stability during the initial digestion phase. However, during gastric digestion, the emulsion's stability decreased significantly, and the droplets tended to aggregate. After entering the intestine, the emulsion's stability recovered somewhat. This is consistent with the observations from the CLSM images.

[0101] In summary, by comparing the droplet sizes of the three butters at different digestion stages, it can be found that the margarine (IB-M) prepared by the preparation process of the present invention has stronger emulsification ability (p < 0.05), higher stability (p < 0.05), smaller droplet size (p < 0.05), and a larger contact area with lipase, thus being easier to be digested and absorbed by the human body.

[0102] 4. FFA Release Analysis

[0103] Depend on Figure 11 As shown, the amount of FFA released gradually increased with prolonged digestion time. FFA release was rapid during the first 20 minutes of intestinal digestion, with IB-M, CB-1, and CB-2 contributing 57.91%, 39.33%, and 46.78% of the free fatty acids, respectively. Between 20 and 120 minutes of small intestinal digestion, the hydrolysis rates of the three ingredients decreased significantly. This is due to the accumulation of hydrolysis products, such as MAG or FFA, at the interface of lipid droplets, limiting the contact between lipase and oil droplets. However, the total amount of FFA released by IB-M was significantly higher than that released by CB-1 and CB-2 (p < 0.05). This may be related to the degree of unsaturation and crystal morphology of the three ingredients. Polyunsaturated fatty acids have a higher gastrointestinal digestibility than SFAs, and higher unsaturation is associated with higher oil digestibility. Larger fat crystals present greater steric hindrance, thus hindering the adsorption of the trypsin / colipase complex. β-crystals, with tightly connected triangular unit cells, are the densest crystalline form and are more resistant to trypsin hydrolysis. After 2 h in the intestinal stage, the release of FFA decreased by 64.99%, 54.22% and 57.14% in IB-M, CB-1 and CB-2, respectively.

[0104] The above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention. The scope of patent protection of the present invention should be defined by the claims.

Claims

1. A process for preparing low-saturated margarine using transesterified cottonseed oil as base oil, characterized in that: The following steps are involved: S1. The palm stearin was heated to 60-80 ° C and melted, and cottonseed oil was added, wherein the mass ratio of palm stearin to cottonseed oil was 8:2 to 4:6 to obtain a binary mixture; S2 is added immobilized lipase Lipozyme TLIM, the immobilized lipase Lipozyme TLIM accounted for 4% to 8% of the total mass of the oil mixture, transesterification reaction under vacuum, transesterification reaction time 1 to 4h, the reaction temperature 50 to 60 ℃, to obtain a crude margarine base oil mixture; S3. Immobilized lipase Lipozyme TLIM was separated from the crude margarine base oil mixture to obtain crude margarine base oil, and the remaining crude margarine base oil was purified to obtain cottonseed oil-based margarine base oil; S4 was added to the cottonseed oil-based margarine base oil monopalmitic acid glyceryl, Span40, glyceryl monostearate to prepare the oil phase; purified water as the aqueous phase, and then the oil phase and the aqueous phase were mixed and emulsified, cooled, kneaded to obtain a low-fat margarine; The added amount of the monopalmitic acid glycerol is 0.2% to 0.4% of the total mass of the margarine, the added amount of the Span40 is 0.2% to 0.4% of the total mass of the margarine, and the added amount of the monostearate glycerol is 0.4% to 0.6% of the total mass of the margarine.

2. The process according to claim 1, wherein: The heating temperature of palm stearin in step S1 is 70°C.

3. The process according to claim 1, wherein: In step S1, the mass ratio of cottonseed oil to palm stearin is 7:

3.

4. The process according to claim 1, wherein: The amount of the immobilized enzyme used in step S2 is 4% of the total mass of the oil.

5. The process according to claim 1, wherein: The transesterification reaction time in step S2 is 2 hours, and the reaction temperature is 55°C.

6. The process according to claim 1, wherein: The added amount of the monopalmitic acid glycerol is 0.25% of the total mass of the margarine, the added amount of the Span40 is 0.25% of the total mass of the margarine, and the added amount of the monostearate glycerol is 0.5% of the total mass of the margarine.

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