CN118765984A - A kind of oil gel and its preparation method and application - Google Patents

Abstract

The invention discloses an oleogel and a preparation method and application thereof, and belongs to the technical field of food processing. Dissolving red algae gum in water to obtain a water phase, dissolving dehydrated animal blood plasma in vegetable oil to obtain an oil phase, mixing the water phase with the oil phase, homogenizing to obtain a uniform emulsion, heating to obtain a soft solid, and drying and shearing to obtain the oil gel. The oil gel prepared by the invention has higher oil holding rate and lipid content, and good thermal stability, mechanical strength and structural stability; the volatile degradation of the essential oil can be effectively reduced after the perilla leaf essential oil is loaded, and meanwhile, the essential oil can play a role in inhibiting the oxidation of the lipid of the oil gel; when the animal fat is used in beef patties, the proportion of unsaturated fatty acid can be increased, the cooking property, the texture property and the flavor property can be improved, and the growth of microorganisms can be inhibited.

Description

A kind of oil gel and its preparation method and application

Technical Field

The invention belongs to the technical field of food processing, and in particular relates to an oil gel and a preparation method and application thereof.

Background Art

Plastic fats are widely used in the field of food processing, and they are mainly derived from animal fats and vegetable fats. Animal fats contain a large amount of saturated fatty acids and cholesterol, and excessive intake can pose risks to human health. Although vegetable fats have better processing properties than animal fats, they contain a large amount of unsaturated fatty acids and are easily affected by external factors, producing lipid oxidation products, which have a negative impact on food quality and sensory properties, leading to a decline in oil quality and a shortened shelf life.

Oleogel is a structured oil that forms a three-dimensional network structure through a gelling agent, converting liquid oil into a solid form, which can delay the oxidation of oils and fats to a certain extent, and can be used as a new type of healthy lipid to replace traditional plastic fats. In the process of oleogel formation, the gelling agent is a core component, and its internal structure has a significant effect on the texture and rheological properties of the oleogel. The gelling agents used in the prior art mainly include beeswax, candelilla wax, rice bran wax, monoglyceride, monostearate glyceryl, etc., but most wax-based oleogels will present a waxy texture and waxy flavor. At the same time, the oleogels in the prior art still have defects such as low oil retention, low lipid content, easy oxidation of lipids, poor thermal stability, mechanical strength, and structural stability, which limits its application in actual production and processing. Therefore, it is urgent to provide an oleogel with high oil retention, high lipid content, good thermal stability, mechanical strength, and good structural stability.

Summary of the invention

In view of this, the object of the present invention is to provide a method for preparing an oil gel, so that the prepared oil gel has high oil retention and lipid content, and good thermal stability, mechanical strength and structural stability.

Another object of the present invention is to provide a prepared oil gel, an oil gel loaded with perilla leaf essential oil, and a preparation method and application thereof.

In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

The present invention provides a method for preparing an oil gel, comprising the following steps:

Dissolving furcellaran in water to obtain an aqueous phase, dissolving dehydrated animal plasma in vegetable oil to obtain an oil phase, mixing the aqueous phase and the oil phase, homogenizing to obtain a uniform emulsion, heating to obtain a soft solid, dehydrating and drying, and shearing to obtain an oil gel;

The mass of the furcellaran is 0.2-0.4wt% of the mass of water; the mass of the dehydrated animal plasma is 2-10wt% of the mass of the vegetable oil; and the volume ratio of the water phase to the oil phase is 0.5-3:1.

Preferably, the method for preparing dehydrated animal plasma comprises the following steps:

Anticoagulant and saline are added to animal blood, mixed, centrifuged to obtain plasma, and the separated plasma is freeze-dried to obtain dehydrated animal plasma; the mass of the anticoagulant is 0.5-1.0wt% of the mass of the animal blood; the volume of the saline is 5-10% of the volume of the animal blood.

Preferably, the anticoagulant includes sodium citrate, sodium citrate, disodium edetate or potassium oxalate-sodium fluoride.

Preferably, the dehydrated animal plasma includes one or more of dehydrated buffalo plasma, dehydrated sheep plasma, dehydrated pig plasma, dehydrated duck plasma and dehydrated chicken plasma.

Preferably, the vegetable oil comprises one or more of pecan oil, soybean oil, linseed oil, sunflower seed oil, rapeseed oil, sesame oil, cottonseed oil, safflower seed oil and corn oil.

Preferably, the heating temperature is 70-90° C. and the heating time is 10-30 min.

The present invention also provides an oil gel prepared by any one of the preparation methods described above.

The invention also provides an oil gel loaded with perilla leaf essential oil. The oil gel is used as a carrier to load the perilla leaf essential oil to obtain the oil gel loaded with perilla leaf essential oil.

The present invention also provides a method for preparing an oil gel loaded with perilla leaf essential oil, comprising the following steps:

The method comprises dissolving red seaweed in water to obtain an aqueous phase, dissolving dehydrated animal plasma in vegetable oil to obtain an oil phase, dissolving perilla leaf essential oil in the oil phase, and fully mixing to obtain an oil phase loaded with perilla leaf essential oil. The aqueous phase and the oil phase loaded with perilla leaf essential oil are mixed in a volume ratio of 0.5 to 3:1, homogenized to obtain a uniform emulsion, heated to obtain a soft solid, and then dehydrated and dried and sheared to obtain an oil gel loaded with perilla leaf essential oil. The mass of the red seaweed is 0.2 to 0.4 wt% of the mass of water; the mass of the dehydrated animal plasma is 2 to 10 wt% of the mass of the vegetable oil; and the volume of the perilla leaf essential oil is 0.5 to 2% of the volume of the oil phase.

The present invention also provides an application of the oil gel or the oil gel loaded with perilla leaf essential oil in the preparation of food, medicine and cosmetics.

Beneficial effects of the present invention:

The present invention uses dehydrated animal plasma as a gelling agent, furcellaran as a thickener, and vegetable oil as an oil base material. The prepared oil gel (F-DG) has a higher oil retention rate and lipid content, and the oil droplets are smaller, more compact, and more evenly distributed in the network, and the sample has high brightness. The furcellaran makes the oil gel present a semi-crystalline state, and the gel molecules interact with each other through van der Waals forces. The addition of furcellaran enhances the thermal stability of the gel, and the prepared oil gel has high storage modulus and loss modulus, and the gel structure recovery stability is strong.

The present invention obtains an oleogel loaded with perilla leaf essential oil by loading perilla leaf essential oil. Encapsulating perilla leaf essential oil in the oleogel can effectively reduce the volatilization and degradation of the essential oil, and the essential oil can inhibit the lipid oxidation of the oleogel. Through in vitro digestion simulation, it is found that the three-dimensional network structure of the oleogel encapsulated oil and perilla leaf essential oil inhibits the digestion of lipids and reduces the release of lipids. The main release site of the essential oil is the small intestine, and the fatty acids in the digestive juice are mainly unsaturated fatty acids.

The present invention uses an oil gel (P-FDG) loaded with perilla leaf essential oil to replace animal fat and is applied to beef patties. The addition of P-FDG can reduce the lipid content and increase the protein content; it can also effectively reduce cooking loss, steaming loss, and thawing loss, and reduce the shrinkage of the patties; through the measurement of texture characteristics, it is found that when P-FDG replaces beef patties containing pig fat, the hardness, viscosity, adhesion and chewiness of the patties are improved; through the measurement of flavor and texture characteristics, it is found that the addition of P-FDG can increase the unique flavor of the patties without changing the taste, and can inhibit the growth of microorganisms.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the oil holding rate and lipid content of F-DG; A in the figure is the oil holding rate of F-DG, and B is the lipid content of F-DG;

Figure 2 shows the microstructure of oil gels with different FUR concentrations; confocal laser scanning microscopy imaging (200×) F-DG oil gel, oil stained green, FUR stained blue, scale bar = 20 μm;

Figure 3 shows the FTIR spectra of DFBP, FUR, JO and F-DG with different FUR concentrations;

FIG4 is an X-ray diffraction pattern of FUR, DFBP and F-DG with different FUR concentrations; A in the figure is FUR and DFBP, and B is F-DG with different FUR concentrations;

Figure 5 shows the thermal stability of FUR, DFBP, and F-DG with different FUR concentrations;

Figure 6 shows the frequency scanning curves of F-DG with different FUR concentrations;

Figure 7 shows the strain scanning curves of F-DG with different FUR concentrations;

Figure 8 shows the time scanning curves of F-DG with different FUR concentrations;

FIG9 shows the DPPH scavenging rate and iron ion reducing ability of perilla leaf essential oil; in the figure, A is the DPPH scavenging rate, and B is the iron ion reducing ability;

FIG10 shows the degradation of PO in ungelled oil and P-FDG during storage under temperature and light conditions; A in the figure is 4°C, B is 25°C, C is 37°C, and D is UV;

Figure 11 shows the levels of primary oxidation POV and secondary oxidation MDA of lipid oxidation in oil gel; A in the figure is POV, and B is MDA;

Figure 12 shows the fatty acid release rate of oil during digestion;

Figure 13 shows the release rate of PO in gastric and intestinal fluids;

FIG14 shows the composition of fatty acids in the oil gel and pig fat digestive fluid; A in the figure is the oil gel, and B is the pig fat;

FIG15 shows the texture characteristics of beef patties; A in the figure shows the hardness, adhesion, and stickiness of the beef patties, and B shows the chewiness, elasticity, and cohesion of the beef patties;

FIG16 is a diagram showing the flavor characteristics of beef patties; FIG16 A is an electronic nose radar diagram of beef patties, and FIG16 B is a PCA analysis of the electronic nose data of beef patties, where PC1 and PC2 are the principal axes 1 and 2, respectively;

FIG. 17 shows the taste characteristics of beef patties; FIG. 17 A is an electronic tongue radar diagram of beef patties, and FIG. 17 B is a PCA analysis of electronic tongue data of beef patties;

FIG. 18 shows the changes in the total bacterial count (TVC) of beef patties during storage.

DETAILED DESCRIPTION

The present invention provides a method for preparing an oil gel, comprising the following steps:

Dissolving furcellaran in water to obtain an aqueous phase, dissolving dehydrated animal plasma in vegetable oil to obtain an oil phase, mixing the aqueous phase and the oil phase, homogenizing to obtain a uniform emulsion, heating to obtain a soft solid, dehydrating and drying, and shearing to obtain an oil gel;

The mass of the furcellaran is 0.2-0.4wt% of the mass of water; the mass of the dehydrated animal plasma is 2-10wt% of the mass of the vegetable oil; and the volume ratio of the water phase to the oil phase is 0.5-3:1.

In the present invention, as an embodiment, preferably, the mass of the furcellaran is 0.25-0.35wt% of the mass of water, and more preferably 0.3wt%. The present invention does not specifically limit the type of water, and can be conventionally selected according to actual needs, including distilled water, ultrapure water, double distilled water, triple distilled water, deionized water, etc. The furcellaran is dissolved in water under stirring, and there is no specific limitation on the stirring method, and manual stirring or mechanical stirring can be selected, and the mechanical stirring includes magnetic stirring; the temperature for dissolving the furcellaran is preferably 70-90°C, more preferably 75-85°C, and more preferably 80°C.

In the present invention, as an embodiment, preferably, the mass of the dehydrated animal plasma is 4-8wt% of the mass of the vegetable oil, and more preferably 6wt%. The present invention does not specifically limit the type of the dehydrated animal plasma, and can be conventionally selected according to actual needs, including one or more of dehydrated buffalo plasma, dehydrated sheep plasma, dehydrated pig plasma, dehydrated duck plasma and dehydrated chicken plasma. The dehydrated animal plasma can be purchased directly through commercial channels or prepared by itself. As an optional embodiment, the method for preparing dehydrated animal plasma includes the following steps: adding an anticoagulant and saline to animal blood, mixing, centrifuging, obtaining plasma, freeze-drying the separated plasma, and obtaining dehydrated animal plasma; the mass of the anticoagulant is 0.5-1.0wt% of the mass of the animal blood; the volume of the saline is 5-10% of the volume of the animal blood. The anticoagulant can be conventionally selected according to actual needs, including sodium citrate, sodium citrate, disodium ethylenediaminetetraacetate (EDTA) or potassium oxalate-sodium fluoride, etc.; the mass of the anticoagulant is preferably 0.7wt%; the volume of the saline is preferably 6%; preferably, the saline is a NaCl solution with a mass percentage of 1-5wt%, more preferably 1.5wt%; the mixing method can be conventionally selected according to actual needs, including stirring mixing or oscillating mixing, so that the anticoagulant, saline and animal blood are fully mixed. The centrifugal rate is 5000-10000rpm, preferably 8000rpm; the centrifugal time is 5-20min, preferably 10min; the centrifugal temperature is 2-5℃, preferably 4℃; the freeze-drying conditions are: freezing temperature -40--60℃, preferably -50℃; vacuum degree 0.05-0.2mbar, preferably 0.1mbar; time 36-60h, preferably 48h. In the present invention, there is no particular limitation on the type of the vegetable oil, which can be conventionally selected according to actual needs, including one or more of pecan oil, soybean oil, linseed oil, sunflower oil, rapeseed oil, sesame oil, cottonseed oil, safflower oil and corn oil. The dehydrated animal plasma is fully stirred to be completely dispersed in the vegetable oil to obtain an oil phase.

In the present invention, as an implementation method, the volume ratio of the aqueous phase to the oil phase is preferably 1 to 2:1, more preferably 1.5:1. After the aqueous phase and the oil phase are mixed, a uniform emulsion is obtained by homogenization, and the homogenization conditions are: 10000 to 15000 rpm, preferably 12000 rpm; the time is 1 to 5 min, preferably 3 min. After the emulsion is heated, the dehydrated animal plasma protein is denatured and the gelation process begins. The heating method can be conventionally selected according to actual needs, preferably water bath heating; the heating temperature is 70 to 90°C, preferably 75 to 85°C, more preferably 80°C; the time is 10 to 30 min, preferably 15 to 25 min, more preferably 20 min. After the emulsion is heated, a soft solid is obtained. The dehydration and drying method can be conventionally selected according to actual needs, such as vacuum freeze drying, vacuum drying, and electric heating blast drying. As an optional embodiment, the soft solid obtained after the emulsion is heated is then vacuum freeze dried, and the vacuum freezing conditions are: temperature -50 to -30°C, preferably -45°C; vacuum degree 0.1 to 1.0 mbar, preferably 0.1 mbar; time 36 to 60 hours, preferably 48 hours. After dehydration and drying, the oil gel is obtained by shearing. The shearing method can be selected as shearing with an electric stirrer, and the time is 30 to 50 seconds, preferably 40 seconds.

The present invention also provides an oil gel prepared by any one of the preparation methods described above.

The present invention uses dehydrated animal plasma as a gelling agent, furcellaran as a thickener, and vegetable oil as an oil base material to prepare an oil gel with furcellaran added. Through experiments such as oil holding rate, gel color difference analysis, gel texture analysis, thermodynamic properties, and rheological properties, it is verified that furcellaran can improve the oil holding rate and lipid content of the oil gel, make the oil droplets smaller, more compact, and more evenly distributed in the network, and the brightness of the sample is large. Furcellaran makes the oil gel present a semi-crystalline state, and the gel molecules interact with each other through van der Waals forces. The addition of furcellaran enhances the thermal stability of the gel, and the prepared oil gel has high storage modulus and loss modulus, and the gel structure recovery stability is strong.

The invention also provides an oil gel loaded with perilla leaf essential oil. The oil gel is used as a carrier to load the perilla leaf essential oil to obtain the oil gel loaded with perilla leaf essential oil.

In the present invention, the preparation method of the oil gel loaded with perilla leaf essential oil comprises the following steps: dissolving furcellaran in water to obtain an aqueous phase, dissolving dehydrated animal plasma in vegetable oil to obtain an oil phase, dissolving perilla leaf essential oil in the oil phase, fully mixing to obtain an oil phase loaded with perilla leaf essential oil, mixing the aqueous phase and the oil phase loaded with perilla leaf essential oil in a volume ratio of 0.5 to 3:1, homogenizing to obtain a uniform emulsion, heating to obtain a soft solid, dehydrating and drying, and shearing to obtain an oil gel loaded with perilla leaf essential oil; the mass of the furcellaran is 0.2 to 0.4 wt% of the mass of water; the mass of the dehydrated animal plasma is 2 to 10 wt% of the mass of the vegetable oil; and the volume of the perilla leaf essential oil is 0.5 to 2% of the volume of the oil phase.

In the present invention, as an embodiment, preferably, the mass of the red seaweed gel is 0.25-0.35wt% of the mass of water, and more preferably 0.3wt%; preferably, the mass of the dehydrated animal plasma is 4-8wt% of the mass of the vegetable oil, and more preferably 6wt%. The type and source of the water, the type and source of the dehydrated animal plasma, and the preparation method of the water phase and the oil phase are the same as the above-mentioned oil gel preparation process. Preferably, the volume of the perilla leaf essential oil is 0.75-1.5% of the volume of the oil phase, and more preferably 1%. The perilla leaf essential oil is dissolved in the oil phase and fully mixed. The method of fully mixing can be conventionally selected according to actual needs, including manual stirring and mechanical stirring; magnetic stirring can be selected, the speed is 400-800rpm, preferably 600rpm; the time is 0.5-1.5h, preferably 1h. Preferably, the volume ratio of the water phase to the oil phase loaded with perilla leaf essential oil is 1-2:1, and more preferably 1.5:1. The process of mixing, homogenizing, heating, drying and shearing the water phase and the oil phase loaded with the perilla leaf essential oil is the same as the above-mentioned oil gel preparation process.

Perilla leaf essential oil (PO) is similar to cinnamon essential oil in aroma, has broad-spectrum antibacterial activity and high antioxidant activity, but PO essential oil is sensitive to light, heat, oxygen and other environments and is easy to decompose. Due to the particularity of the internal structure, oleogel not only encapsulates oil to enhance the oxidative stability of oil, but is also often used as a carrier of nutrients and/or lipophilic bioactive substances to improve the bioavailability of active substances in oil. The present invention uses the above-mentioned oleogel as a delivery carrier to load perilla leaf essential oil. The encapsulation of oleogel can improve the storage stability of perilla leaf essential oil, which is related to the binding effect of oleogel on liquid oil and physicochemical properties. Combined with the results of the oxidative stability analysis of oleogel during the same storage process, it can be inferred that oleogel can play a good protective role in the degradation of PO essential oil by limiting the migration of PO essential oil, physically blocking ultraviolet light, and inhibiting or delaying free radical-mediated oxidation reactions. At the same time, essential oil can play a role in inhibiting the oxidation of oleogel lipids. It was found through in vitro digestion simulation that the three-dimensional network structure of oleogel encapsulated oil and perilla leaf essential oil inhibited the digestion of lipids and reduced the release of lipids. The essential oil is released in the small intestine, and the fatty acids in the digestive juice are mainly unsaturated fatty acids, which can be used to replace animal fat to produce higher nutritional quality and healthier meat products.

The present invention also provides an application of the oil gel or the oil gel loaded with perilla leaf essential oil in the preparation of food, medicine and cosmetics.

In the present invention, as an implementation method, the oil gel or the oil gel loaded with perilla leaf essential oil can replace animal fat and be applied to food. The food includes meat, meat products, bakery products, spreads, and candy products; there is no special limitation on the type of the meat product, which can be selected according to actual needs, including sausages, hamburger patties, meat sauce, etc.

In the present invention, the oil gel or the oil gel loaded with perilla leaf essential oil has a structural configuration and quality characteristics similar to fat, and shows higher stability, more ideal fatty acid distribution, good texture and sensory properties, and can be used as a fat substitute to replace traditional animal fat or vegetable fat, avoiding various health risks caused by higher concentrations of saturated fatty acids and trans fatty acids. In addition, the strong antibacterial activity of perilla leaf essential oil against various bacterial pathogens can play a role in preservation and antiseptic treatment, and extend the shelf life of products. It has a wide range of application value in the fields of food, medicine, cosmetics, etc.

The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

In the following embodiments, unless otherwise specified, all of them are conventional methods.

Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

Example 1 Preparation of oil gel (F-DG) and effect verification

1.1 Preparation of oil gel (F-DG)

(1) Preparation of dehydrated plasma: Prepare a 1.5wt% NaCl solution. When collecting bovine blood, add 0.7wt% sodium citrate as an anticoagulant based on the weight of the bovine blood. At the same time, add 6% (v/v) NaCl solution based on the volume of the bovine blood and stir thoroughly. Use a centrifuge (6000rpm, 10min) to separate the blood into two parts: plasma and blood cells. The separated bovine plasma is freeze-dried (freezing temperature: -50°C, 48h; vacuum degree: 0.1mbar, vacuum freeze dryer), named dehydrated whole bovine plasma (DFBP), and stored at 4°C. The mass percentage of the components of dehydrated whole bovine plasma is: 78.42% protein, 1.17% lipid, 8.53% water, 7.65% ash, 4.23% carbohydrate.

(2) Preparation of oil gel: FUR was dissolved in distilled water at 80°C by magnetic stirring, and the mass of FUR was 0wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% and 0.5wt% of the mass of distilled water, respectively, to obtain water phases with different amounts of FUR added; DFBP was dissolved in pecan oil (JO), and the mass of DFBP was 6wt% of the mass of JO, and the mixture was fully stirred to completely disperse it in the vegetable oil to obtain an oil phase; the water phase and the oil phase were mixed at a volume ratio of 1.5:1, and homogenized at 12000rpm for 3min to obtain a uniform emulsion, and then heated in a water bath at 80°C for 20min to denature the dehydrated bovine plasma protein and start the gelation process to obtain a soft solid. The prepared soft solid was freeze-dried in vacuum, and the vacuum freezing conditions were: temperature -45°C, vacuum degree 0.1mbar, time 48h, and then sheared with an electric stirrer for 40s to obtain an oil gel (F-DG).

1.2 OBC and TLC determination

The prepared oil gel (F-DG) sample was weighed as M ₁ , placed in a centrifuge tube, and centrifuged at 8000 rpm for 15 min at 20°C. The solid sample after centrifugation was taken out and inverted on oil-absorbing paper for 30 min to completely absorb the free oil on the surface. The sample weight was recorded as M ₂ . The oil holding rate (OBC) was calculated according to the following formula:

The determination of lipid content (TLC) refers to GB/T 5009.6-2016 "Determination of crude fat in foods".

The results are shown in Figure 1. It can be seen from Figure 1 A that in the oil gel, compared with distilled water, the FUR content ranges from 0wt% to 0.5wt%, and the oil binding capacity of the oil gel is 70.18%, 72.44%, 92.40%, 94.75%, 85.54% and 83.37%, respectively, and the oil binding capacity of the oil gel is increased from 70.18% to 94.75%. When the FUR content reaches 0.3wt%, the binding force of the oil gel reaches the highest. This is because the dehydrated plasma protein has hydrophilic and hydrophobic ends, which can be fixed in the water phase and the oil phase respectively, and act as an emulsifier to stabilize the oil-water interface. Furphyrin (FUR) is a highly hydrophilic polysaccharide with high viscosity. It is often used as a thickener to assist plasma proteins in forming stable emulsions. Therefore, protein-polysaccharide complexes can be used as a new emulsifier for preparing emulsions to enhance the stability of oil-in-water systems. The experiment adopted the emulsion template method, added a certain amount of FUR, formed a protein-polysaccharide complex, removed the water in the system by high temperature denaturation and freeze drying, limited the formation of the network structure of the oil gel, and made the oil gel have more uniform and dense pores. Therefore, adding a certain amount of FUR to form a composite emulsifier can improve the oil holding capacity of the oil gel. However, too much FUR absorbs water in the water-oil system, resulting in a part of the oil being unable to emulsify with the water phase under high-speed average conditions to form a uniform emulsion system. As can be seen from Figure 1B, compared with distilled water, when the FUR content ranges from 0wt% to 0.5wt%, the lipid content is 77.82%, 79.04%, 85.14%, 89.68%, 83.20% and 79.42%, respectively. When the FUR addition amount is 0.3wt%, the lipid content (TLC) can reach a maximum value of 89.68%. When the FUR addition amount exceeds 0.3wt%, the total lipid content in the system decreases.

1.3 Color difference measurement

After the colorimeter was calibrated with a standard white plate, the oil gel (F-DG) sample was tested. When measuring different samples, the colorimeter lens was at the same height of the sample stage. Each test was repeated 3 times, and the L*, a*, and b* values of the samples were recorded.

Table 1 Effect of FUR addition on F-DG chromaticity

Note: (M±SD) Different letters indicate significant differences among the groups, P<0.05, the same below.

As can be seen from Table 1, the amount of FUR added has a significant effect on the color of the prepared F-DG (P<0.05). The addition of FUR can significantly increase the L* value of F-DG (P<0.05), among which 0.3wt% FUR has the highest L* value; the addition of FUR has little effect on the a* and b* values of F-DG. The above color change of F-DG may be related to the increase in the turbidity of the gel system by the addition of FUR and its own color, which is consistent with the color change of the apparent morphology of F-DG.

1.4CLSM observation

The microstructure of the oil gel (F-DG) was observed by confocal laser scanning microscopy (CLSM) at 200× magnification. The oil gel was stained with an acetone solution containing 0.1 mg/mL Nile red, and the oil gel was stained with an aqueous solution containing 0.2 wt% fluorescent whitening agent. 15 mg of the stained oil gel was placed on a glass slide and covered with a glass cover slip. Nile red and fluorescent whitening agent were excited with 488 nm and 405 nm Ar lasers, respectively. Images were obtained and analyzed with LAXS software. The results are shown in Figure 2, and the fluorescent whitening agent and Nile red showed blue and green, respectively.

As can be seen in Figure 2, in the absence of FUR, the largest, aggregated and unevenly distributed oil droplets were observed throughout the system (0wt% F-DG). As the FUR concentration increased, the oil droplets became smaller, more compact and more evenly distributed in the network. When the added FUR content ratio was too high (0.3wt%), it caused matrix polymerization, thereby destroying the three-dimensional network structure of the oil gel. FUR is a non-surface active polysaccharide, which can act as a thickener, improve the adsorption capacity of plasma proteins, and prevent flocculation and aggregation of oil droplets. This process may lead to the formation of a gel network at the interface and improve the stability of the system. After removing water, the oil droplets were trapped in the matrix composed of FUR and DFBP, which acted as a barrier to minimize the interaction between oil droplets.

1.5 FTIR measurement

Each sample was analyzed using an FTIR spectrometer (Bruker Tensor 27) equipped with a universal ATR sampling accessory. All measurements were recorded at 4000 cm ^-1 and 500 cm ^-1 , 32 scans, a resolution of 4 cm ^-1 , and a temperature of 25°C. All spectra were subtracted from the background spectrum measured relative to the air background and analyzed by OMNIC (Thermo, v8.2). FUR, DFBP powder, JO were analyzed and compared with F-DG. The results are shown in Figure 3.

As can be seen from Figure 3, no new peaks are formed or disappear in the oil gel after adding FUR, and there is no chemical interaction between the oil gel components. The absorption bands of F-DG are related to the functional groups in FUR, DFBP and JO. The peak at 735 cm ^-1 is generated by the bending vibration of the alkyl chain (CH ₂ ) _n group, which is characterized as JO. The change in the absorption peak at 2867 cm ^-1 is attributed to the asymmetric stretching vibration of CH ₃ and CH ₂ groups in the oil, indicating that all oil gel systems have highly ordered and disordered acyl chains. The characteristic peak representing the triglyceride functional group can be observed at 1758 cm ^-1 (corresponding to the stretching vibration peak of C=O in the gel ester group). With the increase of FUR, the ester group absorption peak at 1758 cm ^-1 moves to a higher wave number, the vibration frequency of the ester group becomes larger, and the bonding strength increases, indicating that the strength of the oil gel further increases with the increase of its proportion. Oleogels can be formed based on molecular self-assembly or building blocks and are usually stabilized by non-covalent interactions such as hydrogen bonding, short-range van der Waals attractive interactions and π-π stacking. In this study, hydrogen bonds were compared with van der Waals forces, and the results showed that the latter dominated, although they are much weaker than hydrogen bonds, but the alkyl chains seem to be long enough to promote fairly strong interactions.

1.6 XRD determination

The structural characteristics of the oleogel, FUR and DFBP with different addition amounts of furcellaran were analyzed by X-ray diffractometer (XRD). A Cu target was used and the diffraction angle range of 5° to 40° (2θ) was scanned at a speed of 5°/min at room temperature. The results are shown in Figure 4.

As can be seen from Figure 4A, both FUR and DFBP present a semi-crystalline structure. For DFBP powder, two broad peaks were observed at 8.9° and 23.5°. For FUR, a broad peak was observed at 20.6°. This indicates that its crystal structure is weak and mixed with amorphous structure. As can be seen from Figure 4B, F-DG without FUR addition (0wt% F-DG) presents a single broad peak at about 20°, indicating a stronger crystal structure. Similarly, after adding FUR, the oil gel prepared from FUR and DFBP presents only one diffraction broad peak near 20°, which may be due to the interaction and rearrangement between protein and polysaccharide to form a crystalline region. With the increase of FUR concentration, in the polymer-based oil gel, the polysaccharide molecules tend to form aggregations by mutual entanglement during the drying process, producing a three-dimensional network structure, and the decrease in crystallinity may be due to its transformation from a crystalline to a microcrystalline state in the oil droplets. There is no obvious difference in the X-ray diffraction patterns of the oil gels with different FUR concentrations.

1.7DSC measurement

Thermal analysis was performed by differential calorimetry using DSC3 24 h after the oleogel preparation. 20-30 mg of oleogel samples with different amounts of furcellaran, FUR or DFBP were hermetically sealed in stainless steel pans, and an empty pan was used as a reference. Thermograms were recorded from 20°C to 100°C at a constant heating rate of 5°C/min under _N2 gas flow (20 mL/min). The results are shown in Figure 5.

As can be seen in Figure 5, for FUR and DFBP powders, no exothermic and endothermic changes were observed between 25 and 100 °C. For F-DG without FUR addition (0 wt% F-DG), an exothermic peak was observed at about 31.3 °C and an endothermic peak at 89.1 °C. However, the exothermic peak of the composite oil gel disappeared due to the interaction between FUR and DFBP, indicating that most of the highly polyunsaturated TAGs may not participate in the co-crystallization.

1.8 Rheological determination

Take an appropriate amount of oil gel and place it on the temperature-controlled base of the rheometer. The test temperature is 25°C, the gap is set to 1000μm, and the fixture is a 40mm flat plate. Study the relationship between the apparent viscosity and the shear rate: equilibrium time 500s, duration 2500s, shear rate 0.1~10s ^-1 . The critical strain value and linear viscoelastic region of F-DG oil gel were explored by strain scanning. Strain scanning program: frequency is 1.0Hz, strain range is 0.01%~100%. Frequency scanning program: strain is 0.1%, frequency is 0.1~100Hz. The viscosity recovery rate is calculated according to the following formula:

Where η ₉₀₀ is the viscosity value of the sample at 900 s, and η ₂₄₀₀ is the viscosity value of the sample at 2400 s.

(1) Frequency sweep

The frequency scanning curve of the oil gel sample under a strain of 0.1% is shown in Figure 6. It can be seen that the storage modulus (G') is greater than the loss modulus (G") at different concentrations, and all samples exhibit elastic behavior similar to that of a solid. In the range of 0.1 to 100 Hz, the G' value changes little with increasing frequency, showing low frequency dependence, indicating that the mechanical structure of the F-DG oil gel is stronger and more stable. With the addition of FUR, both G' and G" of the oil gel increase, indicating that the increase in the concentration of the complex will improve the mechanical strength and structural stability of the oil gel. In the high-frequency range (>10 Hz), the G' of the oil gel with 0.3 wt% and 0.4 wt% FUR shows independence from frequency, G' is greater than G" and the slope of G' is close to 0, which makes the oil gel exhibit a strong gel structure.

(2) Strain sweep

The strain scanning results are shown in Figure 7. The linear viscoelastic region (LVR) of the oil gel sample is in the strain range of 0.01% to 1%, and the maximum value of G' in the LVR can be used as an indicator of gel strength. The mechanical strength of F-DG increased after adding FUR, and the elastic modulus (G') of all samples was higher than the viscoelastic modulus (G"). The fact that G' is higher than G" in the LVR indicates that all F-DG are solid-like materials. When the strain is greater than 1%, the G' value of all F-DG begins to decrease and intersects with G". At this time, the gel structure of the F-DG sample is completely destroyed and changes from a solid to a fluid state.

(3) Time scan

The time scan curve of the oil gel is shown in Figure 8, which shows the thixotropy and structural recovery properties of the oil gel. The structural recovery performance of F-DG was evaluated by studying the viscosity change by alternating constant shear rates (0.1s ^-1 , 10s ^-1 and 0.1s ^-1 ). In general, the viscosity of all F-DG samples decreased over time. At the initial shear rate of 0.1s ^-1 , the viscosity of each sample showed a downward trend, showing shear thinning behavior. This may be due to the deagglomeration of oil droplets in the flow direction, and the tightly packed droplets return to a more random distribution, thereby reducing the flow resistance and causing a decrease in viscosity. The second cycle resulted in structural rupture, with a higher shear rate (10s ^-1 ) and a viscosity reduction of more than 50 times. This may be due to the rupture of the droplet agglomeration network under shear, resulting in a decrease in viscosity. In the third cycle, when the shear rate was restored to 0.1s ^-1 , the viscosity recovered. The apparent viscosity of the oil gel with FUR added slowly decreased with time and was higher than that of the oil gel without FUR added, indicating that the addition of FUR helps the oil gel to exhibit time-dependent behavior at a constant shear rate. Once the shear rate drops sharply from 10s ^-1 to 0.1s ^-1 , the apparent viscosity of the oil gel increases immediately, and the structure recovers 40-80% (Table 2).

Table 2 Initial viscosity and viscosity recovery rate of oil gel

FUR (wt%) Initial viscosity (Pa·s) Viscosity recovery rate (%) 0 39103.90±14.2 ^c 27.09±0.21 ^f 0.1 315405.0±34.43 ^bc 51.11±0.89 ^c 0.2 1025020.0±46.44 ^bc 54.84±0.34 ^b 0.3 1327200.0±65.67 ^b 82.68±1.23 ^a 0.4 1775090.0±57.65 ^a 49.46±1.32 ^d 0.5 367276.0±76.75 ^bc 47.55±1.45 ^e

Different letters represent significant differences (P<0.05)

In summary, the gelation of pecan oil was achieved under the combined action of FUR and DFBP. For F-DG oil gel, the elastic structure dominated the stability of the gel network, which resulted in higher gel strength, shorter LVR length, and better thixotropic recovery. 0.3wt% F-DG showed higher apparent viscosity and gel network stabilization energy, strictly limited the molecular mobility of liquid oil, and was beneficial to the stability of the gel network. In contrast, the gel structure without FUR was the most unstable because it had the lowest gel strength, lowest apparent viscosity, and lowest stability.

Example 2 Preparation and effect verification of perilla leaf essential oil-loaded oil gel (P-FDG)

2.1 Determination of antioxidant activity of perilla leaf essential oil (PO)

(1) DPPH free radical scavenging activity

Prepare 0.05%, 0.1%, 1%, 5%, 10% (v/v) perilla leaf essential oil solutions with ethanol. Accurately weigh 0.0197 g of DPPH and dissolve it in anhydrous ethanol and dilute it to 10 mL with anhydrous ethanol. Dilute the DPPH solution with anhydrous ethanol when using it. The absorbance at 517 nm is 0.7±0.02. 50 μL of DPPH working solution was mixed with 50 μL of essential oil solution (sample) (volume ratio of 1:1), and the absorbance was measured at 517 nm after reacting at room temperature in the dark for 30 min, and the absorbance was recorded as A ₁ ; 50 μL of distilled water was mixed with 50 μL of essential oil solution (sample) (volume ratio of 1:1), and the absorbance was measured at 517 nm after reacting at room temperature in the dark for 30 min, and the absorbance was recorded as A ₂ ; 50 μL of DPPH working solution was mixed with 50 μL of anhydrous ethanol (volume ratio of 1:1), and the absorbance was measured at 517 nm after reacting at room temperature in the dark for 30 min, and the absorbance was recorded as A ₀ . The DPPH free radical elimination ability of polysaccharide was calculated according to the following formula.

(2) Iron ion reducing capacity

Prepare 5 mL of PO solution with concentrations of 0.05%, 0.1%, 1%, 5%, and 10% (v/v) with ethanol, add 5 mL of PBS buffer with a pH value of 7.2 and 5 mL of potassium ferricyanide solution with a concentration of 0.1%, keep warm at 50°C for 25 minutes, then add 5 mL of 10% trichloroacetic acid solution. Take 5 mL of the reaction solution, add 5 mL of distilled water and 1 mL of 0.1% ferric chloride solution, and let it stand for 10 minutes, and measure its absorbance at 700 nm.

The results are shown in Figure 9. It can be seen that increasing the PO concentration can significantly improve the antioxidant capacity and show strong free radical scavenging activity against DPPH (Figure 9A). In the concentration range of 0.05% to 10% PO, the corresponding DPPH free radical scavenging activities were 22.05%, 32.95%, 87.01%, 85.73% and 88.96%, respectively; 1%, 5% and 10% PO had the highest DPPH free radical scavenging activity, but there was no significant difference. With the increase of PO concentration, the reducing power also gradually increased (Figure 9B). Since no significant difference was observed between 1%, 5% and 10% PO (P>0.05), a lower concentration range of 0-2% PO was selected in this study. In addition, our preliminary test results fully show that the treatment method using a higher concentration of 5% to 10% PO is not appropriate, and high concentrations of PO may affect the sensory properties of the sample.

2.2 Preparation of perilla leaf essential oil-loaded oleogel (P-FDG)

FUR was placed in distilled water and heated in a water bath at 70°C, with the mass of FUR being 0.3wt% of the mass of distilled water, so that it was fully dissolved to obtain an aqueous phase. DFBP was dissolved in pecan oil (JO), with the mass of DFBP being 6wt% of the mass of JO, and was fully stirred to be completely dispersed in the vegetable oil to obtain an oil phase, and PO was dissolved in the oil phase, with the volume of PO being 1% (v/v) of the volume of the oil phase, and magnetic stirring (600rpm) was performed for 1h to obtain an oil phase loaded with perilla leaf essential oil. The aqueous phase and the oil phase loaded with perilla leaf essential oil were mixed in a volume ratio of 1.5:1, and the preparation process thereafter was the same as in Example 1 to obtain an oil gel (P-FDG) loaded with perilla leaf essential oil.

2.3P-FDG stability determination

(1) Thermal stability determination:

A 0.5 g oil gel sample loaded with perilla leaf essential oil was sealed and stored in a dark place at 4°C, 25°C, and 37°C. Ungelled pecan oil loaded with perilla leaf essential oil was used as a control. Samples were taken every 3 days to determine the residual content of perilla leaf essential oil in the oil gel sample.

PO content determination method: Weigh 0.1g of PO-loaded oil gel sample, add 5mL of chloroform-methanol organic solvent (2:1, v/v) to fully shake and extract essential oil, and measure the absorbance of the organic solvent after extraction at 318nm. The obtained standard curve equation is y=0.3092x+0.2807, ^R2 =0.9946. The retention rate of perilla leaf essential oil is expressed as a relative value in the form of _Co /C, where _Co is the essential oil content in the oil gel sample after storage for a period of time, and C is the initial essential oil content before storage.

(2) Photostability determination:

Take an oil gel sample loaded with perilla leaf essential oil, and use ungelled pecan oil loaded with perilla leaf essential oil as a control, store under ultraviolet light, control the temperature at 25°C, and measure the residual content of perilla leaf essential oil in the oil gel sample every 1 day.

The results are shown in Figure 10. In the thermal stability test (A-C in Figure 10), only 26.98% of the total PO in P-FDG was degraded after 15 days at 4°C. 57.59% of PO was retained in F-DG after storage for 15 days at 25°C. However, when PO was loaded in non-gelled JO, only 45.08% of PO was retained at 25°C. After storage for 15 days at 37°C, the retention rates of PO in F-DG and JO were 48.52% and 33.87%, respectively. As the temperature increased, the degradation amount of PO in all samples increased, indicating that high temperature can accelerate the degradation of PO. In the photostability test (D in Figure 10), the degradation rate of PO was slow at the beginning of UV light irradiation and increased significantly in the later stage. After the illumination ended, about 26.26% of PO remained in the ungelled oil. Under different storage temperatures and light conditions, PO degraded fastest in the ungelled oil phase, which indicates that the structure of the oil gel can provide better protection for the essential oil.

2.4 Lipid oxidative stability assay

JO, F-DG and P-FDG were accelerated oxidized at 37°C in a light-proof environment for 14 days, and samples taken at different time periods (0, 1, 3, 5, 7, and 14 days) were used to determine the content of lipid oxides.

(1) Determination of primary oxidation products - lipid hydroperoxides (POV)

Weigh 5±0.05g of sample into a 250mL conical flask, add 30mL of a mixed solution of acetic acid and chloroform in a volume ratio of 3:2, and mix thoroughly to dissolve the sample. Then, add 0.5mL of saturated KI solution, plug the bottle mouth, let it stand in the dark for 1min, take it out and shake it evenly, add 30mL of distilled water, and titrate with 0.01M sodium thiosulfate using starch indicator.

(2) Determination of the content of secondary oxidation product - malondialdehyde (MDA)

The malondialdehyde content during the accelerated oxidation of oils and fats was determined by the spectrophotometric method in accordance with GB 5009.181-2016 "Determination of malondialdehyde content in foods", wherein the calibration curve equation obtained was y=0.5716x+0.0513, R ² =0.9997.

The results are shown in Figure 11. It can be seen that under accelerated storage conditions, the MDA value showed a similar trend to that of POV. There was no significant difference in the initial MDA value between F-DG and P-FDG oil gels. Subsequently, the MDA value of F-DG increased after 5 days, while the MDA value of P-FDG oil gel increased slightly. After 14 days, the degree of lipid oxidation between the experimental group and the control group was significantly different (P<0.05), and F-DG and P-FDG showed excellent oxidative stability during accelerated storage. The oxidative stability of F-DG is due to the fact that the network structure in the oil gel effectively blocks the contact between triglyceride molecules, thereby blocking the transfer of oxygen free radicals and inhibiting the production of oxidation reaction products. The reason why P-FDG has a better inhibitory effect on oxidation may be due to the antioxidant properties of PO itself.

2.5 In vitro digestion simulation test

(1) Construction of in vitro digestion model

1) Simulated gastric digestion: Prepare simulated gastric juice (SGF): dissolve 0.2 g NaCl, 6 mL HCl and 0.32 g pepsin in double distilled water, and make the solution up to 100 mL in a volumetric flask with double distilled water. After shaking, adjust the pH of the simulated gastric juice to 1.2 with 0.5 M HCl solution.

Simulated digestion process: 0.5 g of sample was dispersed in 50 mL of simulated digestive gastric juice. After mixing, the pH was adjusted to 2.5 with 0.5 M NaOH solution. Then, the mixture was digested at 37 °C in a shaker at 50 r/min. 5 mL of digestive fluid sample was taken out every 30 minutes.

2) Simulated intestinal digestion: The composition of the intestinal digestion solution is 50 mL phosphate buffer, 10 mg/mL bile salt, 150 mM NaCl and 10 mM CaCl _2. Pancreatic lipase (1.0 g) is added to 50 mL of the intestinal digestion solution and dissolved to obtain a simulated intestinal solution (SIF), and the pH is adjusted to 7.0. The sample (1.0 g) is added to 50 mL of the simulated intestinal solution and shaken at 150 r/min in an oscillator at 37±1°C. The fat decomposed sample is taken out every 30 min, and its pH is adjusted to 7.0 with 0.5 mol/L sodium hydroxide solution.

(2) Determination of FFA release rate during digestion

The amount of sodium hydroxide consumed during the above simulated intestinal digestion was recorded. The release rate of FFA was calculated according to the following formula.

where V _NaOH is the volume of NaOH consumed during lipolysis, C _NaOH is the concentration of NaOH, and _Moleogels is the mass of oleogels.

M _triglyceride is calculated from the average relative molecular weight of triglyceride by the above formula: wherein M _KOH is the molecular weight of KOH, and for walnut oil, the saponification value (SV) is 190 mg KOH/g.

The release law of fatty acids in the gelled oil gel system (F-DG) and the oil gel system loaded with PO (P-FDG) was studied with ungelled JO as the control group. The results are shown in Figure 12. The fatty acid release rates of the three samples all showed an upward trend. In the control group, fatty acids were released rapidly in the first 60 minutes, and then tended to be gentle, the fat decomposition reaction gradually balanced, and the final release rate reached 94.41%. In the experimental group, the fatty acids of the oil gel were released rapidly in the first 120 minutes, and then the rate slowed down, and the NaOH consumption rate slowed down. Compared with the control group, F-DG and P-FDG effectively delayed the digestion process. After 180 minutes, the FFA release rates of F-DG and P-FDG were 83.39% and 53.56%, respectively. In the ungelled JO, the fat was directly digested by pancreatic lipase, while the gelled oil system inhibited the digestion of lipids through the three-dimensional network structure and reduced the release of fatty acids. The effect of PO in inhibiting the release of fat fatty acids is mainly achieved through the interaction between its active ingredients and fats. The FFA released during digestion of all samples followed a similar pattern.

(3) PO release rate determination

During gastric and intestinal digestion, 5 mL samples were taken every 30 min and centrifuged at 12000 rpm for 10 min at 4 ° C to obtain the supernatant (micellar fraction). The micellar fraction (0.5 mL) was vortexed with 2 mL of chloroform and 1 mL of methanol, and then centrifuged at 12000 rpm for 5 min at 4 ° C. The supernatant was collected and the perilla leaf essential oil content was measured at 318 nm using a UV-visible spectrophotometer, and the PO release rate was calculated by the following formula.

Where P is the content of perilla leaf essential oil in the supernatant, and _P0 is the initial content of perilla leaf essential oil in the oil gel.

The results are shown in Figure 13. During gastric digestion, the release rate of PO was low, and as the digestion time progressed, the release rate only increased slightly, with the final release rate being 12.6%. This may be because the digestive enzymes in the gastric juice are proteases, which have less damage to the gel structure, and PO is bound to the gel structure. When P-FDG was incubated in simulated intestinal solution, lipids were rapidly hydrolyzed and PO was significantly released. The release rate of PO in P-FDG in SIF was higher than that in SGF, which may be due to the fact that pancreatic enzymes and bile salts reduced the protective ability of the oil gel. After digestion in the small intestine, the fat-soluble active substances dissolved in the hydrophobic phase are released from the matrix and dissolved in the mixed micelle phase. The increase in the release rate of essential oils in the small intestine may also be because the increase in the release of fatty acids helps to produce more micelle structures, while more hydrophobic PO is dissolved in the core of the micelles, thereby increasing the release rate of PO.

(4) Determination of fatty acid composition in digestive juice

Using pig fat as a reference, a comparative study was conducted through a simulated digestion process, and the fatty acid composition of P-FDG and the digestive fluid of pig fat after simulated digestion was determined respectively.

Remove 5 mL of digestion solution, select 10 mL of chloroform, add 20 mL of methane to the digestion solution and vortex for 2 minutes, then add 10 mL of chloroform, let it stand for 30 seconds, add 10 mL of distilled water, and let it stand. After 30 seconds, the lower chloroform layer is obtained, and the first extraction of fatty acids is completed. The upper water layer is drawn, and 0.2 mol/L HCl is added to adjust the pH to below 1.5 to acidify the water layer, and then the fatty acid extraction steps are repeated twice, and the chloroform layers obtained three times are combined and concentrated to obtain the fatty acid sample.

Methyl esterification: Weigh 100 mg of fatty acid sample, transfer to a 10 mL volumetric flask, add 1 mL of ether-n-hexane (2:1) solution, then add 1 mL of methanol solution containing 0.5 mol/L potassium hydroxide, shake well, let stand at room temperature for 30 min, add water to the scale, take the supernatant, and perform GC-MS analysis.

Gas chromatography conditions: Agilent 122-3832 capillary column (0.25 mm × 30 m × 0.25 μm), temperature program: 60 °C for 2 min, equilibration for 0.5 min, increase to 250 °C at 8 °C/min, hold for 10 min, carrier gas is nitrogen, flow rate is 1.0 mL/min, injection port temperature is 250 °C, split ratio is 50:1, injection volume is 0.5 μL.

Mass spectrometry conditions: electron bombardment ion source, electron energy 70 eV, solvent delay 2.6 min, ion source temperature 230 °C, quadrupole temperature 150 °C, mass scanning range (m/z) 35-450 °C amu.

The mass spectra of fatty acids were compared with the entries in the Nist11 library, and the relative content of each fatty acid was calculated using the peak area normalization method.

Table 3 Fatty acid content in oil gel and pig fat digestive fluid

The results are shown in Figure 14 and Table 3. It can be seen that the fatty acids in pig fat are mainly composed of palmitic acid (C16:0), oleic acid (C18:1) and stearic acid (C18:0), while the fatty acids in the digestive juice of P-FDG oil gel are mainly composed of oleic acid (C18:1), linoleic acid (C18:2) and α-linolenic acid (C18:3). Linoleic acid and α-linolenic acid are indispensable unsaturated fatty acids for the human body. They cannot be synthesized by the human body itself, so they must rely on food intake. As an important member of the ω-6 fatty acid series, linoleic acid participates in a variety of biochemical reactions in the body and can be used for energy supply or storage. It is essential to maintain normal physiological functions of the human body. As the mother of the ω-3 series of polyunsaturated fatty acids, α-linolenic acid can metabolize substances such as EPA and DHA in the body that are beneficial to cardiovascular health, anti-inflammatory, and anti-thrombotic, and have an important impact on human health.

Example 3 Application of P-FDG in beef patties

3.1 Beef Patties Production

Table 4 Beef Patty Recipe

raw material Mass/g raw material Mass/g raw material Mass/g raw material Mass/g Lean beef 70 MSG 0.2 Sodium tripolyphosphate 0.3 Onion powder 0.3 Fat 30 Nutmeg powder 0.08 Liquor 2.0 Black pepper 0.3 salt 1.5 Ice water mixture 20 Ginger powder 0.15 Corn starch 10 White sugar 1.0

Preparation of beef patties: Prepare beef patties according to the formula in Table 4. Remove visible fat and connective tissue from lean beef, mince the processed lean beef with a meat grinder, add the minced beef to a chopper, add salt, phosphate and some ice water to chop and extract salt-soluble protein to obtain minced beef. Fat is composed of pig fat and P-FDG, and the content is shown in Table 5. Crush the pig fat with a meat grinder, emulsify the minced pig fat with ice water, and mix it evenly with P-FDG to obtain minced fat. Mix the minced beef, minced fat, the remaining seasonings and the remaining ice water, and chop and mix for use to obtain a minced beef mixture. Put the minced beef mixture into a mold and store it in a freezer at -20°C. Each patty is about 100g (80mm in diameter and 15mm in height).

Table 5 Beef patties with different contents of perilla leaf essential oil loaded oil gel (P-FDG)

M1 M2 M3 Control group Pig fat(g) 20 10 0 30 P-FDG(g) 10 20 30 0

3.2 Determination of basic components

Determination of moisture: The direct drying method in GB/T 5009.3-2016 "Determination of moisture in food" was used. Determination of protein content: The Kjeldahl nitrogen method in GB/T 5009.5-20016 "Determination of protein in food" was used. Determination of crude fat content: The fat extraction method in GB/T 5009.6-20016 "Determination of crude fat in food" was used to determine the crude fat content in beef patties. Determination of ash: GB 5009.4-2016 National Food Safety Standard "Determination of ash in food" was used. The results are shown in Table 6.

Table 6 Effect of P-FDG content on the composition of beef patties

Element Control group M1 M2 M3 Crude fat (%) 16.07±0.42a 15.32±0.53a 13.35±0.52b 11.39±0.04c protein(%) 11.18±0.18c 12.42±0.09b 13.04±0.01a 13.36±0.30a Moisture (%) 51.98±1.40a 50.27±1.72a 48.98±1.30a 49.54±2.54a Ash content (%) 1.05±0.03a 1.09±0.03a 1.13±0.02a 1.11±0.02a

It can be seen that the content of protein and crude fat in the M2 and M3 groups was significantly different from that in the control group (P < 0.05). The addition of P-FDG oil gel increased the protein content in the beef patties, reduced the lipid content, and had little effect on the moisture and ash content of the beef patties. Among them, the protein content of the beef patties increased by 0.32% to 2.18%. This is because the oil gel contains a certain amount of protein emulsifier, so the protein content increases with the increase in the amount of oil gel added; the lipid content decreased by 0.75% to 4.68%. The use of gelled vegetable oil to replace animal fat can reduce the intake of saturated fatty acids and increase the proportion of unsaturated fatty acids. Therefore, the P-FDG oil gel of the present invention can effectively increase the protein content and reduce the lipid content, thereby producing a healthier, nutritious and low-fat meat patty product.

3.3 Chromaticity measurement

The color of the surface of the beef patty sample was measured using a handheld colorimeter under standard daylight light source D65 and a standard viewing angle of 10°. The colorimeter was calibrated with a standard white porcelain plate before measurement. The L*, a*, and b* values were measured at different locations on the surface of the patty. Each sample was randomly measured 3 times in parallel at different locations, and the average value was taken. The results are shown in Table 7.

Table 7 Effect of the amount of P-FDG added on the chromaticity of beef patties

Chroma Control group M1 M2 M3 L* 53.87±0.57a 50.6±1.32b 48.7±0.9c 45.73±0.67d a* 6.3±0.1b 6.53±0.15b 6.6±0.35b 7.73±0.15a b* 16.3±0.2ab 14.2±2.17b 18.17±0.47a 17.27±0.35a

The L*, a* and b* values reflect the brightness, redness and yellowness of the beef patties, respectively. From the results in Table 7, it can be seen that the amount of P-FDG oil gel added has a significant effect on the L* value (P<0.05). Since P-FDG is light yellow and pig fat is white, the increase in a* value may be related to the increase in oil gel content and the decrease in pig fat content. For the experimental group, there was no significant difference in the effect of the amount of oil gel replacement on the brightness and yellowness of the beef patties.

3.4 Determination of cooking characteristics

(1) Cooking loss

The raw beef patties prepared in Experiment 3.1 were placed in a refrigerator and frozen at -20°C for 12 hours. The frozen beef patties were thawed at 4°C for 12 hours. They were heated in a steamer at 100°C for 10 minutes. The mass of the samples before and after steaming was accurately weighed. The cooking loss was calculated according to the following formula:

Cooking loss (%) = [(mass before cooking – mass after cooking) / mass before cooking] × 100

(2) Thawing loss

Take out the frozen beef patties and weigh them as m ₁ . Thaw them at room temperature for 4 hours. Use filter paper to absorb the juice on the surface. Weigh the mass of the thawed sample and record it as m ₂ . Calculate the thawing loss rate of the patties according to the following formula:

Wherein, m ₁ : the mass of meat patties before thawing, g; m ₂ : the mass of meat patties after thawing, g.

(3) Frying shrinkage

The frozen beef patties were thawed at 4°C for 12 hours. They were fried in soybean oil at 110°C for 5 minutes. The radius (r ₁ ) and thickness (h ₁ ) of the patties before cooking, the radius (r ₂ ) and thickness (h ₂ ) of the patties after cooking, the surface areas S ₁ and S ₂ of the patties before and after cooking were measured, and the frying shrinkage was calculated according to the following formula:

Table 8 Effect of P-FDG addition on the cooking characteristics of beef patties

Cooking properties Control group M1 M2 M3 Cooking loss (%) 21.39±1.38a 19.10±1.70ab 18.94±0.88ab 17.11±1.05b Thawing loss (%) 4.26±0.26a 3.25±0.09b 3.31±0.31b 3.49±0.25b Surface shrinkage (%) 23.57±0.55a 20.13±0.81b 19.67±0.61b 19.33±0.45b Thickness shrinkage (%) 11.33±0.53a 8.00±0.55b 5.67±0.68c 4.67±0.58d

In meat products, cooking loss can represent the product's ability to bind water and fat, and thawing loss is an important indicator for evaluating the quality of frozen products. The combination of the two can describe the changes in product juice to a certain extent, and can be used as an objective indicator to characterize the juiciness of meat patties. The results are shown in Table 8. It can be seen that with the increase in the amount of P-FDG oil gel, the thawing rate loss of meat patties decreased by 2.29% to 4.28%, the surface shrinkage rate decreased by 3.44% to 4.24%, and the thickness shrinkage rate decreased by 3.33% to 6.66%, which was significantly different from the control group (P<0.05). These indicators can represent their ability to retain juice to a certain extent. Due to its solid or semi-solid structure, the oil gel can better contact the surface of the food, forming a protective film, effectively locking the moisture inside the food, and reducing the loss of water during cooking.

3.5 Determination of texture characteristics

The beef patties after frozen storage were thawed at 4℃ for 12h, heated in a steamer at 100℃ for 10min, and the cooked patties were cut into ^1cm3 cubes and compressed to 50% of the original height with a cylindrical aluminum probe with a diameter of 36mm, and moved at a constant speed of 5mm/s. The speeds before and after the test were 2mm/s and 5mm/s respectively. The data are expressed in hardness (N), elasticity (mm), cohesion, gelatinity (N) and chewiness (N.mm). The results are shown in Figure 15.

Total texture analysis (TPA) is an important indicator for evaluating the pulverization effect and acceptability of meat products, which is mainly manifested in hardness, elasticity, adhesiveness, chewiness and cohesion. As can be seen from Figure 15, after adding P-FDG oil gel, the hardness, chewiness and adhesion of the meat patty changed. Its hardness, chewiness and adhesion first decreased, then increased and then decreased. Among them, when the addition amount of P-FDG oil gel was 20% (M2), the maximum hardness was 154.68N, and the chewiness reached 29.71 at this time, which was significantly different from the control group (P<0.05). The higher hardness and chewiness of the meat patty in the experimental group may be due to the fact that at this ratio, the oil gel can be closely combined with the minced meat and evenly distributed in the meat patty to form a stable structure, which enables the meat patty to maintain a certain hardness and viscosity when subjected to external force, thereby enhancing the chewiness.

3.6 Flavor characteristics determination

Weigh 2.0g of each sample, chop it into pieces and put it into a 10mL headspace injection bottle for measurement. The headspace temperature is 50℃, the incubation time is 300s, the carrier gas flow rate is 150mL/s, the injection volume is 500μL, the data collection time is 120s, and the delayed data collection is 180s. Each group is measured 10 times, and the stable results of 3 times are retained. The characteristics of the electronic nose PEN3 sensor are shown in Table 9. The test results are shown in Figures 16-17.

Table 9 Sensitive substances of PEN3 electronic nose sensor

serial number sensor Sensitive substances serial number sensor Sensitive substances S1 W1C Aromatic compounds S6 W1S Alkanes S2 W5S Nitrogen oxides S7 W1W Sulfur compounds S3 W3C Ammonia aromatic molecules S8 W2S Detect alcohols and some aromatic compounds S4 W6S Hydride S9 W2W Aromatic compounds Sulfur organic compounds S5 W5C Olefins, aromatics, polar molecules S10 W3S Alkanes and aliphatics

As can be seen from A in Figure 16, there is a high similarity in aroma between the M1, M2 and M3 samples. After cooking, the beef patties in the control group contain higher nitrogen oxides, sulfides and organic compounds of aromatic sulfur compounds. This is because the Maillard reaction and protein degradation promote the production of heterocyclic and aromatic polymers. Sulfur-containing compounds are also an important component of meat flavor. Cysteine is degraded to produce hydrogen sulfide and acetaldehyde, and hydrogen sulfide reacts with furanone to produce meat flavor substances. The response values of the experimental group to W1S, W1W and W2W decreased, and the response value of W5S increased, that is, the content of nitrogen oxides in the beef patties increased after adding P-FDG oil gel, and the content of organic compounds of alkanes, sulfur compounds, and aromatic sulfur compounds decreased. This may be because the perilla leaf essential oil in the oil gel triggered an oxidation reaction during high-temperature heating, reducing the levels of alkanes and sulfides. Perilla leaf essential oil contains a variety of components, such as monoterpenes, monoterpene alcohols, aldehydes, monoterpene aldehydes, etc., which combine or transform with nitrogen sources in beef at high temperatures to form nitrogen oxides, and increase with the increase of P-FDG oil gel content.

As can be seen from Figure 16B, PC1 and PC2 represent 73.7% and 24.8% of the total variance, respectively, and the cumulative variance contribution of the two principal components is 98.2%, indicating that replacing pig fat with P-FDG oil gel has a significant difference in the flavor of beef patties. Therefore, P-FDG oil gel can be used in meat products to give food a unique flavor.

3.7 Taste characteristics determination

A certain amount of beef sample was placed in a food processor, and pure water was added in a ratio of 1:6 to homogenize. After filtering, the filtrate was used for the TS-5000z taste analysis system test. The reference solution used in the test is composed of potassium chloride and tartaric acid. Tasteless represents the output (tasteless point) of the reference solution, that is, the tasteless point of sour taste is -13, and the tasteless point of salty taste is -6. Based on this, when the taste value of the sample is lower than Tasteless, it means that the sample has no taste, otherwise it has. The results are shown in Figure 17.

As can be seen from Figure 17A, since the saltiness value of the sample is 0 after dilution, the main taste indicators of beef patties are umami, bitterness, astringency, aftertaste A and aftertaste B. Among them, the bitterness value of the M3 group is the largest. Since the P-FDG oil gel is loaded with 1% perilla leaf essential oil, perilla aldehyde is an important compound in perilla leaf essential oil, which has a strong aroma and a certain bitterness. At high temperatures, perilla aldehyde becomes more active, resulting in a more obvious bitterness. The sourness values of the beef patty samples in the four groups are all below the tasteless point, and the bitterness value and astringency value are close.

As can be seen from Figure 17B, the cumulative contribution rate of the first and second principal components is 80.7%, so the first and second principal components can characterize the characteristics of the overall data to a certain extent. From the PCA diagram of the electronic tongue, it is found that the distribution areas of the four types of beef patties are all concentrated in the central area, and the taste of the four types of beef patties cannot be distinguished, indicating that the difference in taste of the four samples is small.

3.8 Determination of total colony count

The total colony count of beef patties during storage was determined according to the method in GB 4789.2-2022 "National Food Safety Standard Food Microbiology Test Colony Count Determination". The results are shown in Figure 18.

Microorganisms are the main factor causing meat spoilage. It is generally believed that the total colony count below 10 ⁴ CFU/g is fresh meat, 10 ⁴ to 10 ⁶ CFU/g is sub-fresh meat, and 10 ⁶ CFU/g is spoiled meat. As shown in Figure 18, with the extension of storage time, the number of microorganisms in the meat pie continues to increase, and the total colony count shows an upward trend. Within 1 to 3 weeks of storage, the total colony counts of the three groups of meat pie, M1, M2, and M3, increased. Compared with the control group, each concentration treatment group can significantly inhibit the growth of microorganisms (P<0.05), and as the amount of P-FDG in the meat pie increases, the antibacterial effect increases. After 21 days of storage, the meat pie is close to the end of storage, and after 28 days, the meat pie in the test group has completely deteriorated. The present invention can inhibit the growth of microorganisms by loading PO to prepare oil gel instead of animal fat, thereby achieving the effect of extending the shelf life.

The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims (10)

1. A method for preparing an oil gel, characterized in that it comprises the following steps: Dissolving furcellaran in water to obtain an aqueous phase, dissolving dehydrated animal plasma in vegetable oil to obtain an oil phase, mixing the aqueous phase and the oil phase, homogenizing to obtain a uniform emulsion, heating to obtain a soft solid, dehydrating and drying, and shearing to obtain an oil gel; The mass of the furcellaran is 0.2-0.4wt% of the mass of water; the mass of the dehydrated animal plasma is 2-10wt% of the mass of the vegetable oil; and the volume ratio of the water phase to the oil phase is 0.5-3:1. 2. The preparation method according to claim 1, characterized in that the dehydrated animal plasma preparation method comprises the following steps: Anticoagulant and saline are added to animal blood, mixed, centrifuged to obtain plasma, and the separated plasma is freeze-dried to obtain dehydrated animal plasma; the mass of the anticoagulant is 0.5-1.0wt% of the mass of the animal blood; the volume of the saline is 5-10% of the volume of the animal blood. 3. The preparation method according to claim 2, characterized in that the anticoagulant comprises sodium citrate, sodium citrate, disodium edetate or potassium oxalate-sodium fluoride. 4. The preparation method according to claim 1 is characterized in that the dehydrated animal plasma comprises one or more of dehydrated buffalo plasma, dehydrated sheep plasma, dehydrated pig plasma, dehydrated duck plasma and dehydrated chicken plasma. 5. The preparation method according to claim 1, characterized in that the vegetable oil comprises one or more of pecan oil, soybean oil, linseed oil, sunflower seed oil, rapeseed oil, sesame oil, cottonseed oil, safflower seed oil and corn oil. 6. The preparation method according to claim 1, characterized in that the heating temperature is 70-90°C and the time is 10-30 minutes. 7. The oil gel prepared by the preparation method according to any one of claims 1 to 6. 8. An oil gel loaded with perilla leaf essential oil, characterized in that the oil gel according to claim 7 is used as a carrier to load the perilla leaf essential oil to obtain the oil gel loaded with perilla leaf essential oil. 9. The method for preparing the oil gel loaded with perilla leaf essential oil according to claim 8, characterized in that it comprises the following steps: The method comprises dissolving red seaweed in water to obtain an aqueous phase, dissolving dehydrated animal plasma in vegetable oil to obtain an oil phase, dissolving perilla leaf essential oil in the oil phase, and fully mixing to obtain an oil phase loaded with perilla leaf essential oil. The aqueous phase and the oil phase loaded with perilla leaf essential oil are mixed in a volume ratio of 0.5 to 3:1, homogenized to obtain a uniform emulsion, heated to obtain a soft solid, and then dehydrated and dried and sheared to obtain an oil gel loaded with perilla leaf essential oil. The mass of the red seaweed is 0.2 to 0.4 wt% of the mass of water; the mass of the dehydrated animal plasma is 2 to 10 wt% of the mass of the vegetable oil; and the volume of the perilla leaf essential oil is 0.5 to 2% of the volume of the oil phase. 10. Use of the oil gel according to claim 7 or the oil gel loaded with perilla leaf essential oil according to claim 8 in the preparation of food, medicine and cosmetics.