Method for refining strong-flavor vegetable oil by using plasma activated water

Abstract

The invention discloses a method for refining strong-flavor vegetable oil by using plasma activated water. The method mainly comprises the following steps: adding 0.1-2.0% of plasma activated water into squeezed crude oil, stirring at the speed of 5-20 rpm / min for 15-30 minutes, and settling at the temperature of 4-35 DEG C for 10-48 hours; and carrying out centrifugal treatment on the settled grease to remove sediments, thereby obtaining the refined strong-flavor vegetable oil. According to the method, the strong-flavor vegetable oil is refined by adopting the plasma activated water, not only can impurities influencing the quality of the oil be quickly removed, but also more flavor substances and nutritional ingredients in the oil can be retained, the method is simple to operate and short in time consumption, no chemical reagent is adopted in the implementation process, and the method is suitable for industrial production. The method is an efficient and green strong-flavor vegetable oil refining method.

Description

Technical Field

[0001] The invention relates to the field of vegetable oil processing, in particular to a rich-flavor vegetable oil refining process. Background Art

[0002] Since there are some non-triglyceride components such as free fatty acids, phospholipids, waxes, and undesirable flavor substances in crude vegetable oils, the oils become hazy, have poor storage stability, and have a bad taste. Therefore, crude oils are often refined during edible oil processing to improve the quality of the oils. Different crude vegetable oils have different production processes, impurity contents, and requirements for the characteristics of finished oils. Different refining methods should be used for different oils. For example, crude soybean oil is often obtained by solvent leaching, and has a high phospholipid content. During the oil refining process, special attention should be paid to degumming and desolventizing. Sesame oil is favored by consumers for its unique aroma, and is often obtained by pressing and water substitution. During the refining process, special attention should be paid to the retention of flavor components.

[0003] Strong-flavored vegetable oils are popular with consumers for their rich aroma. In their refining process, water sedimentation, acidification, enzyme addition and other treatment methods are often used to remove colloidal impurities such as phospholipids, proteins, and sugars in crude oil. However, these technologies have long refining time, low efficiency, high cost, and pressure filtration, which leads to a large loss of flavor components, and the shelf life of the finished oil produced is low, which seriously restricts the development of strong-flavored oils. A Chinese patent application with publication number CN107245375B discloses a method for hydration degumming of rapeseed oil, which requires heating and maintaining the crude oil at 80-90°C, and adding 80-90°C salt water to the crude oil. During the degumming process, the oil temperature is too high, and the flavor compounds are lost more. Therefore, exploring a method for efficiently refining strong-flavored vegetable oils is of great significance to the development of the oil industry.

[0004] Cold plasma (CP) is a method of introducing electrical energy into gas at atmospheric pressure and ambient temperature to produce low-temperature, partially ionized gas rich in reactive oxygen species and reactive nitrogen species. Plasma-activated water (PAW) is a solution prepared by using a cold plasma system to generate plasma discharge on the water surface or directly in the water. Compared with traditional water-adding sedimentation, plasma-activated water can break the balance of ions inside the oil, thereby accelerating the sedimentation of impurities in the oil, and the sedimentation time is short and the temperature is low, which can retain more flavor components and nutrients in the oil. Summary of the invention

[0005] The invention provides a method for refining fragrant vegetable oil by using plasma activated water, thereby accelerating the sedimentation rate of crude oil and retaining more fragrance.

[0006] According to the technical solution of the present invention, the method for refining fragrant vegetable oil using plasma activated water comprises the following steps:

[0007] S1: adding plasma activated water to the aromatic plant crude oil, wherein the mass of the added plasma activated water is 0.1-2.0% of the oil, stirring at a speed of 5-20 rpm / min for 15-30 minutes and then stopping stirring;

[0008] S2: The crude oil added with plasma activated water is naturally precipitated at a temperature between 4°C and 35°C for 10-48 hours, and the precipitated oil is centrifuged to remove the sediment to obtain refined strong-flavor vegetable oil.

[0009] Furthermore, in step S1, the pH of the plasma-activated water is 2.35-3.92, the oxidation-reduction potential is 398.73-561.66 mV, and the conductivity is 213.35-582.51 μS / cm; the raw materials of the rich-flavor plant crude oil include sesame, peanuts, sunflower seeds, and rapeseed.

[0010] The beneficial technical effects of the present invention are embodied in the following aspects:

[0011] (1) Compared with the traditional method, the method for refining fragrant vegetable oil using plasma activated water provided by the present invention can efficiently precipitate impurities in oils and fats, and the preparation of plasma activated water is safe, green and low-cost, which meets the development needs of the times and is suitable for industrial production.

[0012] (2) The method for refining strong-flavor vegetable oil using plasma activated water provided by the present invention can retain more aroma while removing impurities in the oil, and is suitable for refining strong-flavor oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Sensory evaluation of the rich-flavor vegetable oils of the comparative examples and the embodiments;

[0014] Figure 2 The aroma compound content of the strong-flavor plant oils in the comparative examples and embodiments. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0016] In the following examples and comparative examples, the detection methods and conditions are as follows:

[0017] (1) Determination of sediment content

[0018] Take the crude oil and acetone in a volume ratio of 1:1, vortex to mix thoroughly, and centrifuge to suck out the upper transparent oil. Add acetone to the lower sediment, repeat the above vortex, centrifuge and suck out the upper transparent oil twice to remove the residual oil in the lower sediment, and finally obtain the acetone-containing sediment. The sucked transparent oil is evaporated at 40°C to remove acetone to obtain pure oil.

[0019] The precipitate containing acetone was added to 20 mL of pure oil, and then dried in an oven at 105 °C for 2 h after rotary evaporation at 45 °C to completely remove the acetone. The standard sample with a concentration of 0.056 mg / g was obtained at a constant weight.

[0020] Add the standard sample to the pure oil and mix well to obtain a 0.01 g / mL standard solution to prepare vegetable oil containing precipitates with different concentration gradients. Pipette 1 mL into a 50 mL volumetric flask, dilute with acetone, pipette the above solution into a colorimetric bottle, calibrate to zero with the blank sample as the reference, measure the turbidity and draw a standard curve (y = 12980x-1.4236, R 2 =0.9985, x: sediment content, y: turbidity).

[0021] The sediment content in the refined vegetable oil treated under different conditions was determined. The specific steps were as follows: 1 mL of the oil sample to be tested was placed in a 50 mL volumetric flask, the volume was fixed with acetone, the turbidity was measured with a turbidity meter, and the sediment concentration in the refined vegetable oil was calculated by substituting the standard curve equation.

[0022] (2) Sensory evaluation

[0023] Ten trained evaluators (5 females and 5 males) were selected to evaluate the aroma characteristics of refined strong-flavor vegetable oils after different treatment conditions. Each of them had at least 3 years of experience in edible oil sensory evaluation. Informed consent was obtained from all sensory evaluators before the evaluation.

[0024] They were asked to rate the intensity of the aroma attributes of the refined strong-flavored vegetable oils on a 10-point scale ("0" is not perceptible and "10" is strongly perceptible). Each oil sample (10 mL) was poured into a 40 mL glass bottle, labeled with a random 3-digit number, and sealed with a plastic cap. The color of the glass bottle was brown so that any color difference between the samples could not be observed.

[0025] (3) Determination of aroma compound content (HS-SPME-GC-MS)

[0026] 3 g of refined aromatic vegetable oil and 4-nonanol (30 μL, 1 μg / μL) were placed in a 20 mL vial and sealed with a polytetrafluoroethylene septum. A divinylbenzene / carbonyl / polydimethylsiloxane (DVB / CAR / PDMS) fiber head (film thickness: 50 / 30 μm, length: 1 cm) was used. Before each extraction, the fiber was treated at 250 ° C for 60 minutes. The sample was balanced in a 60 ° C water bath for 20 minutes while being stirred by a magnetic stirrer (100 r / min). The SPME fiber was exposed to volatile absorption in the sample head space for 30 minutes, and then it was immediately inserted into the GC injection port (250 ° C) and desorbed for 3 minutes. Three parallel tests were performed for each sample.

[0027] SPME extracts were injected into GC in a pulsed non-separation mode, and volatile compounds were separated in an HP-5MS capillary column (30m×0.25mm×0.25μm). The initial temperature of the column was 40℃, maintained for 3.5min, raised to 230℃ at a rate of 4℃ / min, maintained for 8min, and then raised to 250℃ at a rate of 10℃ / min, maintained for 10min. Full scan electron bombardment mode (70ev) was used, the scan speed was 2.0scan / s, the scan range was 33-500m / z, the injection port temperature was 250℃, the ion source temperature was 230℃, the transfer line temperature was 280℃, and the quadrupole temperature was 150℃.

[0028] Example 1

[0029] 1.0 g of plasma activated water was added to 1000.0 g of crude strong-flavor vegetable oil, stirred at 5 rpm / min for 30 min, allowed to settle at 4°C for 48 h, and centrifuged to remove the sediment to obtain refined strong-flavor vegetable oil. The refined strong-flavor vegetable oil was analyzed for sediment content, sensory and aroma compounds.

[0030] In the present embodiment, the content of acetone insoluble matter precipitated from the refined strong-flavor vegetable oil is 0.043 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 8.2, 6.7 and 6.1 respectively, and the total content of aroma compounds is 390.72±0.83 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 165.79±0.25 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 69.24±0.32 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 140.06±0.16 mg / kg.

[0031] Example 2

[0032] 5.0 g of plasma activated water was added to 1000.0 g of crude strong-flavor vegetable oil, stirred at 10 rpm / min for 20 min, and then allowed to settle at 15°C for 24 h. The sediment was removed by centrifugation to obtain refined strong-flavor vegetable oil. The refined strong-flavor vegetable oil was analyzed for sediment content, sensory and aroma compounds.

[0033] In the present embodiment, the content of acetone insoluble matter precipitated from the refined strong-flavor vegetable oil is 0.036 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 8.0, 6.5 and 6.0 respectively, and the total content of aroma compounds is 388.32±0.87 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 163.78±0.37 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 65.04±0.12 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 138.31±0.28 mg / kg.

[0034] Example 3

[0035] 10.0 g of plasma activated water was added to 1000.0 g of hot pressed sesame crude oil, stirred at 15 rpm / min for 20 min, and then allowed to settle at 25°C for 18 h. The sediment was removed by centrifugation to obtain refined strong-flavor vegetable oil. The sediment content, sensory and aroma compound analysis of the refined strong-flavor vegetable oil was performed.

[0036] In the present embodiment, the content of acetone insoluble matter precipitated from the refined strong-flavor vegetable oil is 0.033 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 7.8, 5.9 and 5.6 respectively, and the total content of aroma compounds is 380.78±0.77 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 156.39±0.11 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 60.75±0.32 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 130.11±0.23 mg / kg.

[0037] Example 4

[0038] 20.0 g of plasma activated water was added to 1000.0 g of hot pressed sesame crude oil, stirred at 20 rpm / min for 15 min, and then allowed to settle at 25°C for 18 h. The sediment was removed by centrifugation to obtain refined strong-flavor vegetable oil. The sediment content, sensory and aroma compound analysis of the refined strong-flavor vegetable oil was performed.

[0039] In the present embodiment, the content of acetone insoluble matter precipitated from the refined strong-flavor vegetable oil is 0.034 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 7.9, 6.0 and 5.7 respectively, and the total content of aroma compounds is 385.61±0.56 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 160.28±0.12 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 63.53±0.22 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 140.25±0.12 mg / kg.

[0040] Example 5

[0041] 5.0 g of plasma activated water was added to 1000.0 g of hot pressed sesame crude oil, stirred at 15 rpm / min for 20 min, and then allowed to settle at 35°C for 10 h. The sediment was removed by centrifugation to obtain refined strong-flavor vegetable oil. The sediment content, sensory and aroma compound analysis of the refined strong-flavor vegetable oil was performed.

[0042] In the present embodiment, the content of acetone insoluble matter precipitated from the refined strong-flavor vegetable oil is 0.036 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 8.6, 6.6 and 6.1 respectively, and the total content of aroma compounds is 475.28±0.56 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 180.23±0.22 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 101.25±0.10 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 145.25±0.12 mg / kg.

[0043] Example 6

[0044] 5.0 g of plasma activated water was added to 1000.0 g of hot pressed sesame crude oil, stirred at 15 rpm / min for 20 min, and then allowed to settle at 25°C for 18 h. The sediment was removed by centrifugation to obtain refined strong-flavor vegetable oil. The sediment content, sensory and aroma compound analysis of the refined strong-flavor vegetable oil was performed.

[0045] In the present embodiment, the content of acetone insoluble matter precipitated from the refined strong-flavor vegetable oil is 0.033 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 8.8, 6.9 and 6.2 respectively, and the total content of aroma compounds is 480.95±0.59 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 185.03±0.12 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 116.15±0.16 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 146.32±0.12 mg / kg.

[0046] Comparative Example 1

[0047] 5.0 g of distilled water was added to 1000.0 g of hot-pressed crude sesame oil, and the mixture was stirred at 10 rpm / min for 20 min, and then allowed to settle at 35°C for 5 days. The sediment content, sensory and aroma compound analysis of the rich-flavor vegetable oil after sedimentation was performed.

[0048] In this comparative example, the content of acetone insoluble matter precipitated from the strong-flavor vegetable oil is 0.060 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 8.0, 6.1 and 5.7 respectively, and the total content of aroma compounds is 311.28±0.67 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 105.11±0.12 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 60.15±0.16 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 121.30±0.10 mg / kg.

[0049] Comparative Example 2

[0050] 10.0 g of distilled water was added to 1000.0 g of hot-pressed crude sesame oil, and the mixture was stirred at 20 rpm / min for 30 min, and then allowed to settle at 4°C for 15 days. The sediment content, sensory and aroma compound analysis of the rich-flavor vegetable oil after sedimentation were performed.

[0051] In this comparative example, the content of acetone insoluble matter precipitated from the strong-flavor vegetable oil is 0.064 mg / g, and the sesame oil after precipitation has a strong flavor of roasted sesame, caramel and smoky flavors, with sensory scores of 7.6, 5.3 and 5.0 respectively, and the total content of aroma compounds is 297.18±0.76 mg / kg, of which the content of nitrogen-containing heterocyclic compounds that mainly contribute to the roasted sesame flavor is 93.15±0.22 mg / kg, the content of oxygen-containing heterocyclic compounds that mainly contribute to the caramel flavor is 61.25±0.13 mg / kg, and the content of phenolic compounds that mainly contribute to the smoky flavor is 91.32±0.12 mg / kg.

[0052] The results of the above examples 1-6 and comparative examples 1-2 are analyzed and sorted out. The specific results are shown in Tables 1 and Figure 1-2 .

[0053] Table 1 Acetone insoluble matter content of the precipitated strong-flavor vegetable oil of comparative examples and embodiments (mg / g)

[0054] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 0.060 0.064 0.043 0.036 0.033 0.034 0.036 0.033

Claims

1. A method for refining fragrant vegetable oil using plasma activated water, characterized in that: The following steps are involved: S1: adding plasma activated water to the aromatic vegetable crude oil, wherein the mass of the added plasma activated water is 0.1-2.0% of the oil, stirring at a speed of 5-20 rpm / min for 15-30 minutes and then stopping stirring; S2: The crude oil added with plasma activated water is naturally precipitated at a temperature between 4°C and 35°C for 10-48 hours, and the precipitated oil is centrifuged to remove the sediment to obtain refined strong-flavor vegetable oil.

2. The method for activating water-flavored vegetable oil using plasma according to claim 1, characterized in that: The pH of the plasma-activated water in step S1 is 2.35-3.92, the redox potential is 398.73-561.66 mV, and the conductivity is 213.35-582.51 μS / cm.

3. The method for activating water-flavored vegetable oil using plasma according to claim 1, characterized in that: The raw materials for strong-flavor vegetable crude oil include sesame, peanuts, sunflower seeds and rapeseed.

Images