Perilla oil squeezing process

Abstract

The invention discloses a perilla oil squeezing process which is characterized by comprising the following steps: cleaning, drying and peeling perilla seeds to obtain perilla seed kernels containing 13-17% of water, heating the perilla seed kernels to 95-105 DEG C, squeezing the perilla seed kernels by a double-screw oil press, winterizing crude oil obtained by squeezing, and physically filtering the crude oil to obtain the perilla oil. According to the method, the perilla oil is squeezed through the double-helix oil press, the oil yield can be increased on the premise that beneficial components and flavor substances of the perilla oil are reserved, the obtained perilla oil is low in acid value and light yellow in color and has natural faint scent, and commercially available refined perilla oil is deep in color and thicker in fragrance. The peroxide value and acid value of commercially available refined oil are obviously higher than those of the test grease.

Description

Technical Field

[0001] The invention relates to a perilla oil pressing process and belongs to the technical field of vegetable oil production. Background Art

[0002] Perilla is a herbaceous plant of the genus Perilla in the family Lamiaceae. It is one of the 60 earliest economic crops listed as both medicinal and edible. Perilla oil is extracted from mature seeds of Perilla. It is a highly unsaturated natural oil with an unsaturated fatty acid content of more than 90%, of which the α-linolenic acid content is as high as 45%-70%. In addition, Perilla oil is rich in linoleic acid, sterols, VE and other beneficial ingredients, does not contain cholesterol, erucic acid and other substances, and has good health value. The main reason why Perilla oil is called the "king of oils" is that its α-linolenic acid content is the highest known plant content, and it enjoys the reputation of "deep-sea fish oil on land". α-linolenic acid is a ω-3 polyunsaturated fatty acid, which is the basic substance of cell membranes and biological enzymes, the structural substance of the brain, and the core substance of life. It can be metabolized into DHA and EPA in the human body. DHA is present in large quantities in the cerebral cortex, retina and germ cells. It is a key nutrient that determines human intelligence and is called "brain gold". Reasonable supplementation of α-linolenic acid can promote the growth of brain cell nerve cells, improve memory, and increase the intelligence of infants by 20%-30%.

[0003] In the prior art, there are two main production routes for perilla oil. One is a high-temperature pre-pressing-extraction process, where the perilla seed is pressed at a temperature of about 120°C, and then the pre-pressed oil cake is extracted with an organic solvent, and the extracted crude oil is refined to obtain perilla oil; the other is low-temperature pressing of perilla seeds below 50°C, and the pressed crude oil is filtered to obtain perilla oil. The first method has a high oil yield, but high temperature will destroy the beneficial ingredients and flavor substances in perilla, and extraction requires an organic solvent, which does not conform to modern health concepts; the second low-temperature pressing can retain the beneficial ingredients and flavor substances in perilla, but the oil yield is low and the storage time is not long, so it is necessary to study a new perilla oil pressing process. Summary of the invention

[0004] The invention aims to provide a perilla oil pressing process, which can retain the beneficial components and flavor substances in the perilla and improve the oil yield.

[0005] The technical solution of the present invention is a perilla oil pressing process. After the perilla seeds are washed, dried and peeled, perilla kernels containing 13-17% of water are obtained. The perilla kernels are heated to 95-105° C. and pressed by a twin-screw oil press. The crude oil obtained by pressing is winterized and then physically filtered to obtain perilla oil.

[0006] The twin-screw oil press is pressed 2-4 times.

[0007] The twin-screw oil press was pressed 3 times.

[0008] The perilla seed kernel contains 14-16% water.

[0009] The perilla seed kernel contains 15% water.

[0010] The perilla seed kernels are heated to 97-103°C.

[0011] The perilla seed kernels are heated to 99-101°C.

[0012] Obtain perilla oil, add 0.03-0.05% of rosemary extract, 0.01-0.03% of tea polyphenols and 1-3% of VC by weight, and then preserve it.

[0013] Obtain perilla oil, add 0.04% rosemary extract, 0.02% tea polyphenols and 2% VC by weight, and then preserve it.

[0014] Beneficial effect, perilla oil pressing temperature, moisture, and pressing times are important process parameters for pressing perilla seeds. The present invention adopts a double-screw oil press to press perilla oil, which can improve the oil yield while retaining the beneficial ingredients and flavor substances of perilla oil. The obtained perilla oil has a low acid value, light yellow color and natural fragrance, while the commercially available refined perilla oil is darker in color and has a stronger aroma. The peroxide value and acid value of commercially available refined oil are significantly higher than those of the oil tested in this experiment. All quality indicators of the perilla oil obtained under the optimal conditions of this experiment meet the requirements of Q / JLSJ 0001 S-2019 "Perilla Oil", and the sterol and squalene content contained are higher than those of commercially available refined perilla oil, indicating that the present process conditions can better retain the beneficial accompanying substances of perilla oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a comparison diagram of the effect of the pressing temperature on the residual oil rate of the perilla cake of the present invention; Figure 2 This is a comparison diagram of the effect of the pressing times on the residual oil rate of perilla cake of the present invention; Figure 3 This is a comparison diagram of the effect of moisture content on the residual oil rate of perilla cake of the present invention; Figure 4 This is a comparison diagram of the effect of tea polyphenols on the acid value of perilla oil of the present invention; Figure 5 This is a comparison diagram of the effect of tea polyphenols on the peroxide value of perilla oil of the present invention; Figure 6 This is a comparison diagram of the effect of rosemary on the peroxide value of perilla oil of the present invention; Figure 7 This is a comparison diagram of the effect of rosemary of the present invention on the acid value of perilla oil; Figure 8 This is a comparison diagram of the effect of VC on the peroxide value of perilla oil of the present invention; Fig. 9 This is a comparison diagram of the effect of VC on the acid value of perilla oil of the present invention; Fig.10 This is a comparison diagram of the effect of the composite antioxidant of the present invention on the peroxide value of perilla oil; Fig.11 This is a comparison chart of the effect of the composite antioxidant of the present invention on the acid value of perilla oil. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments, but they are not intended to limit the present invention in any way.

[0017] Embodiment 1 of the present invention: A perilla oil pressing process, after perilla seeds are washed, dried and peeled, perilla seed kernels containing 15% moisture are obtained, the perilla seed kernels are heated to 100° C., and pressed by a twin-screw oil press, the pressing is repeated 3 times, and the crude oil obtained by pressing is winterized and then physically filtered to obtain perilla oil.

[0018] Perilla oil is obtained, 0.04% rosemary extract, 0.02% tea polyphenols and 2% VC are added by weight, and then preserved to increase the shelf life.

[0019] Embodiment 2 of the present invention: A perilla oil pressing process, after the perilla seeds are washed, dried and peeled, a perilla seed kernel containing 14% of water is obtained, the perilla seed kernel is heated to 101° C., and pressed by a twin-screw oil press, the pressing is repeated twice, and the crude oil obtained by pressing is winterized and then physically filtered to obtain perilla oil.

[0020] Perilla oil is obtained, 0.03% rosemary extract, 0.01% tea polyphenols and 1.5% VC are added by weight, and then preserved to increase the shelf life.

[0021] Embodiment 3 of the present invention: A perilla oil pressing process, after the perilla seeds are washed, dried and peeled, a perilla seed kernel containing 16% of water is obtained, the perilla seed kernel is heated to 98°C, and pressed by a twin-screw oil press, the pressing is repeated 4 times, and the crude oil obtained by pressing is winterized and then physically filtered to obtain perilla oil.

[0022] Perilla oil is obtained, 0.05% rosemary extract, 0.03% tea polyphenols and 2.5% VC are added by weight, and then preserved to increase the shelf life.

[0023] Embodiment 4 of the present invention: A perilla oil pressing process, after the perilla seeds are washed, dried and peeled, a perilla seed kernel containing 13% of water is obtained, the perilla seed kernel is heated to 95°C, and pressed by a twin-screw oil press, the pressing is repeated 3 times, and the crude oil obtained by pressing is winterized and then physically filtered to obtain perilla oil.

[0024] Perilla oil is obtained, 0.04% rosemary extract, 0.03% tea polyphenols and 2% VC are added by weight, and then preserved to increase the shelf life.

[0025] Embodiment 5 of the present invention: A perilla oil pressing process, after the perilla seeds are washed, dried and peeled, a perilla seed kernel containing 17% of water is obtained, the perilla seed kernel is heated to 105°C, and pressed by a twin-screw oil press, the pressing is repeated 3 times, and the crude oil obtained by pressing is winterized and then physically filtered to obtain perilla oil.

[0026] Perilla oil is obtained, 0.04% rosemary extract, 0.03% tea polyphenols and 2% VC are added by weight, and then preserved to increase the shelf life.

[0027] The applicant conducted relevant tests on the perilla oil pressing process as follows: Experimental materials: The seeds of perilla for processing were from the new oil-producing perilla variety Guisu No. 3 bred by Guizhou Oil Crops Research Institute; Oil press: Perilla oil cold pressing screw oil press: 6YL-125 type Yijiayi (Hubei) Machinery Equipment Group Co., Ltd.; Test methods 1 Single factor experiment on cold pressing of perilla oil Weigh 20 kg of perilla seeds accurately, control the moisture content to the required moisture content of the experiment, and place them in a sealed bag. According to the experimental requirements, select the moisture content of perilla (5%, 10%, 15%, 20%), set the pressing temperature (40 ℃, 60 ℃, 80 ℃, 100 ℃, 120 ℃), and the number of pressing times (1 time, 2 times, 3 times) for physical pressing to obtain perilla oil. The perilla oil was then centrifuged to remove the residue to obtain perilla crude oil, and the oil yield was calculated.

[0028] 2 Determination of oil yield and residual oil rate of perilla cake The above optimal process was used to extract and prepare perilla oil, and the differences in oil yields of perilla with different treatments were compared. Petroleum ether was used as solvent, and the residual oil rate in perilla cake was determined by Soxhlet extraction according to GB 5009.6-2016 National Food Safety Standard Determination of Fat in Food.

[0029] Residual oil rate in cake: X = (m0-m1) / m2 X is the fat content in the sample; m0 is the mass of the filter paper and fat after constant weight; m1 is the mass of the filter paper and fat; m2 is the mass of the sample Determination of 3 fatty acid composition (1) Sample pretreatment and preparation: Accurately weigh 0.1-1 g of the sample and transfer it to a 250 mL flat-bottom flask. Add about 100 mg of pyrogallic acid, a few zeolites, 2 mL of 95% ethanol and 4 mL of deionized water and mix well. (2) Acid hydrolysis: Add 5 mL of hydrochloric acid solution and mix well. Place the flask in a 70℃~80℃ water bath for hydrolysis for 40 min. Shake the flask every 10 min to mix the particles adhering to the wall of the flask into the solution. After the hydrolysis is completed, remove the flask and cool it to room temperature. (3) Fat extraction: Add 5 mL of 95% ethanol to the hydrolyzed sample and mix well. Transfer the hydrolyzate in the flask to a separatory funnel, rinse the flask and stopper with 25 mL of petroleum ether, add the rinse solution to the separatory funnel and cover it. Shake for 5 min and let it stand for 10 min. Collect the ether layer extract into a 250 mL flask. Repeat the above steps to extract the hydrolyzate 3 times. Finally, rinse the separatory funnel with a mixture of ether and petroleum ether and collect it in a 250 mL flask. Concentrate to dryness on a rotary evaporator. The residue is the fat extract (4) Saponification of fat and methylation of fatty acids: Add 4 mL of 2% sodium hydroxide methanol solution to the fat extract, connect a reflux condenser, and reflux on a water bath at 80℃±1℃ until the oil droplets disappear. Add 3.5 mL of 15% boron trifluoride methanol solution from the top of the reflux condenser and continue to reflux in a water bath at 80℃±1℃ for 2 min. Rinse the reflux condenser with a small amount of water. Stop heating, remove the flask from the water bath, and quickly cool to room temperature. Accurately add 7.5 mL of n-heptane, shake for 2 min, then add saturated sodium chloride aqueous solution, and let stand to separate. Pipette about 2.5 mL of the upper n-heptane extraction solution into a 25 mL test tube, add about 2 g of anhydrous sodium sulfate, shake for 1 min, let stand for 5 min, and pipette the upper solution into a sample bottle for determination. Add 3.5 mL of 15% boron trifluoride methanol solution from the top of the reflux condenser, and continue to reflux in a water bath at 80 ℃ ± 1 ℃ for 2 min. Rinse the reflux condenser with a small amount of water. Stop heating, remove the flask from the water bath, and quickly cool to room temperature. Accurately add 7.5 mL of n-heptane, shake for 2 min, then add saturated sodium chloride aqueous solution, and let stand for stratification. Pipette about 2.5 mL of the upper n-heptane extraction solution into a 25 mL test tube, add about 2 g of anhydrous sodium sulfate, shake for 1 min, let stand for 5 min, and pipette the upper solution into a sample bottle for determination.

[0030] 4 Data analysis: Each group of experiments was repeated three times, and all data were expressed as SD ± mean value. P < 0.05 was considered statistically significant. All statistical analyses were performed using SPSS 21 software. Figure 1-3 .

[0031] Depend on Figure 1 It can be seen that with the increase of pressing temperature, the residual oil rate of perilla cake shows a trend of first decreasing, then decreasing, and then increasing. When the pressing temperature is 100℃, the residual oil rate of perilla cake is as low as 10.36%, which is significantly lower than the residual oil rate (meal) at 200℃ and 60℃. At 60℃, the residual oil rate of perilla cake is as high as 23.94%, which is significantly higher than the residual oil rate of other test groups. The residual oil rate of perilla cake is from high to low in the order of 60℃>200℃>80℃>40℃>100℃. Figure 2 It can be seen that the fatty acids in perilla seeds are mainly composed of four kinds of fats, which are pentadecanedioic acid (C15:1), palmitoleic acid, oleic acid, and α-linolenic acid in the order of peak appearance. The content of α-linolenic acid decreases with the increase of pressing temperature. The difference of α-linolenic acid between the treatments of 40℃, 60℃, 80℃, and 100℃ did not reach statistical significance, but they were all significantly higher than 200℃; the oleic acid content of 60℃ pressing was the highest at 22.25%, significantly higher than the other test groups, and the oleic acid content of 40℃ pressing was the lowest at 20.55%. The content of pentadecanoelic acid increases with the increase of pressing temperature. The content of pentadecanoelic acid in oils pressed at 80℃, 100℃ and 200℃ is significantly higher than that at 40℃ and 60℃. There is no significant difference in the content of palmitic acid among the treatments. It can be seen that the optimal temperature for pressing perilla oil is 100℃, at which the residual oil rate of perilla cake is the lowest, and the content of α-linolenic acid is not significantly different compared with 40℃, 60℃ and 80℃.

[0032] Depend on Figure 3 It can be seen that the residual oil rate of perilla cake decreases with the increase of pressing times. The residual oil rates of perilla cake after four pressings at 100°C are 19.59%, 11.98%, 10.36%, and 10.26%, respectively. The residual oil rates of perilla cake in the first three pressings are significantly reduced, and there is no significant difference between the residual oil rate of perilla cake in the fourth pressing and the third pressing. There is no significant difference in the fatty acid composition and content of perilla oil after four pressings. It can be seen that the residual oil rate of perilla cake decreases with the increase of pressing times, but there is no significant difference between the fourth pressing and the third pressing. Considering the labor and power costs, the optimal pressing times for perilla oil is three times. Under this condition, the quality of perilla oil fatty acids is not significantly affected, but the perilla oil yield is relatively large.

[0033] The composition analysis of perilla oil at different pressing temperatures is shown in Table 1: Table 1

[0034] The influence of different perilla water content on the residual rate of perilla cake and the quality of perilla oil is shown in Table Table 2

[0035] Moisture is another key factor affecting the residual oil and pressing quality of perilla cake. Under cold pressing conditions, the oil yield of perilla oil is low, and the cake generally needs to be pressed multiple times in production. As the number of pressings increases, the residual oil rate and moisture in the perilla cake decrease, and the bore may become stuck. Therefore, appropriate moisture should be added to the perilla seeds during pressing. Moisture can cause protein denaturation, improve oil droplet aggregation and destroy cell tissue structure to the greatest extent, making the oil easier to prepare. However, when too much moisture is added, the perilla cake may not be formed and the bore may become smooth. The effect of moisture content on the residual rate of perilla cake is shown in Table 4. As the moisture content increases, the residual oil in the perilla cake shows a trend of first decreasing and then increasing. When the moisture content of perilla seeds increases from 5% to 15%, the residual oil rate in the cake decreases from 17.89% to 10.54%; when the moisture content of perilla seeds is 20%, the residual oil in the cake rises sharply to 15.26%, and the perilla cake is not formed, resulting in blockage of the pressing chamber. From the perspective of fatty acid composition, when the moisture content of perilla seeds was 15%, the α-linolenic acid content and linoleic acid content in perilla oil reached the maximum value, which were 64.59% and 21.90% respectively, which were significantly higher than those of 5% and 20% moisture. Therefore, based on the changes in the residual oil rate and the content of each fatty acid component in perilla cake, the moisture content of 15% was finally selected for pressing.

[0036] The crude oil obtained under the process conditions of 100 degrees Celsius inlet material temperature, 15% moisture, and 3 pressings was winterized and then physically filtered using a plate and frame oil filter. The product quality indicators were compared with the physical and chemical properties of commercially available refined perilla oil. The perilla oil obtained under the optimal process conditions of this technology has a low acid value and a light yellow color; it has a natural perilla oil aroma, while the commercially available refined oil is slightly darker in color. There is no significant difference in the impurities of the two oils, both below the standard. The peroxide value of commercially available refined oil is significantly higher, indicating that the active substances in refined oil are more easily oxidized after being destroyed. Under the optimal conditions of this experiment, the squalene and sterol contents of perilla oil are higher than those of refined oil. The quality comparison of perilla oil with different processing technologies is shown in Table 3. This shows that the perilla oil obtained under this process condition can better retain the beneficial accompanying substances of perilla oil.

[0037] Table 3

[0038] The applicant further tested the storage stability of perilla oil and the effect of adding antioxidants on the antioxidant properties of perilla oil: 1 Experimental materials: Perilla seeds, from Guizhou Oil Research Institute, vitamin C, potassium citrate, grape seed extract, rosmarinic acid, L-theanine, sodium phytate, rosemary extract, grape seed extract, vitamin E, carotene, tea polyphenols, BHT, BHA, all of analytical grade, 2. Instruments and Equipment Agilent 7820A / 5975 gas chromatograph-mass spectrometer, Agilent Technologies (China) Co., Ltd.; SPX-70BⅢ Biochemical incubator, Tianjin Test Instrument Co., Ltd.; HH-2 digital display electronic constant temperature water bath, Changzhou Guohua Electric Co., Ltd.; glass burette 3 Test methods 3.1 Preparation of Perilla Oil Preparation of perilla oil according to the patented method 3.2 Accelerated oxidation of perilla oil Weigh a certain amount of perilla oil and place it in a container. Use the Schaal oven accelerated oxidation method to conduct an accelerated oxidation test. Set the temperature to (62±1)℃ for precise high-temperature continuous heating oxidation. Shake it every 24 hours and change its position in the constant temperature box at will. Weigh an appropriate amount of sample every 2 days to measure the oxidation value and peroxide value.

[0039] 3.3 Determination of perilla oil peroxide value and acid value The acid value of the sample is determined in accordance with GB 5009.229-2016 "National Food Safety Standard for Determination of Acid Value in Food". The peroxide value is determined in accordance with GB 5009.227-2016 "National Food Safety Standard for Determination of Peroxide Value in Food". 3.4 Determination of Perilla Oil Components Measure according to the previous test method 3.5 Effect of light on perilla oil Using the accelerated oxidation method, perilla oil was stored at 65 ℃ in fully transparent glass bottles, semi-transparent brown bottles and opaque boxes with covers. The acid value and peroxide value of the perilla oil were measured every day.

[0040] 3.6 Effect of temperature on perilla oil Perilla oil was stored at 0, 5, 25, 45 and 65℃ in the dark with a cover, mixed once a day, and the acid value and peroxide value were measured every 5 days.

[0041] 3.7 Effect of moisture content on storage stability of perilla oil The moisture content of the perilla oil sample was measured, ≤0.01%. The moisture content of the perilla oil was adjusted to 0.05%, 0.1%, 0.5%, 1%, and 2%, and the acid value and peroxide value of the perilla oil were measured every day under accelerated oxidation conditions at 65°C. 3.8 Effect of antioxidants on the antioxidant properties of perilla oil Perilla oil was placed in glass bottles, 50 g in each bottle, and VC (1%, 2%, 3%, 4%), rosemary extract (0.02%, 0.04%, 0.06%, 0.08%), and tea polyphenol extract (0.02%, 0.04%, 0.06%, 0.08%) were added respectively. A CK control group was set up at the same time. According to the shelf life coefficient formula, the oil was stored at 60℃ for 1 day, which is equivalent to being stored at room temperature (20℃) for 1 month. The peroxide value and acid value were measured on the 2nd, 4th, 6th, 8th, 10th, 12th, and 14th days respectively.

[0042] 3.9 Effect of composite antioxidants on the antioxidant activity of perilla oil On the basis of experiment 3.8, tea polyphenols, rosemary extract and VC were compounded, and perilla oil was subjected to accelerated oxidation test at 65°C, and its peroxide value and acid value were measured every 2 days.

[0043] 4 Statistical analysis Each experiment was performed in parallel for 3 times, and all data are expressed as SD ± mean, with P < 0.05 indicating statistical significance. All statistical analyses were performed using SPSS 21 software.

[0044] 5 Test results 5.1 High temperature has an adverse effect on perilla oil by promoting oxidation and deterioration, thereby affecting storage stability, while storage at low temperature has less impact. According to the test results, perilla oil can be stored below 25 ℃. Light can accelerate the increase of perilla oil acid value and peroxide value, which has a certain effect on storage stability. It should be stored away from light during storage. Moisture will accelerate the oxidation rate of oil and reduce the storage performance of oil. Moisture should be reduced as much as possible during oil processing.

[0045] 5.2 Effect of adding antioxidants on the antioxidant properties of perilla oil Three antioxidants, VC, rosemary extract and tea polyphenols, were selected for the experiment 5.3 Effect of tea polyphenols on the antioxidant activity of perilla oil Depend on Figure 4It can be seen that during the 7-day accelerated oxidation process, the addition of tea polyphenols had a significant effect on the peroxide value of perilla oil. The peroxide value of the group treated with tea polyphenols was significantly lower than that of the control group, and the longer the storage time, the greater the difference in peroxide value. During storage, as the concentration of tea polyphenols increased, the peroxide value showed a decreasing trend compared with the control. The peroxide value of CK (control group) reached 0.33g / 100g after 3 days of storage, exceeding the national standard of 0.25g / 100g. When 0.08% tea polyphenols was added, the peroxide value first increased and then decreased. The peroxide value on the 6th day was 0.25g / 100g, reaching the limit value of the national standard. Figure 5 It can be seen that the effect of tea polyphenols on the acid value of perilla oil is relatively small. On the 0th day of accelerated oxidation, the acid value of CK is 0.47 mg / g, and on the 7th day, the acid value is 0.72 mg / g. When 0.08% tea polyphenols are added, the acid value is 0.60 mg / g on the 7th day of accelerated oxidation, both of which are below the national standard of 3 mg / g. Based on the above experimental results, tea polyphenols can effectively enhance the antioxidant activity of perilla oil during storage. During the accelerated oxidation process, when the addition of tea polyphenols is 0.08%, the storage period can be effectively extended by 4 days. According to the Arrhenius empirical formula, 1 day in the oven is equivalent to the actual storage period of 1 month of perilla oil. Therefore, adding 0.08% tea polyphenols can increase the shelf life of perilla oil by 4 months.

[0046] 5.4 Effect of rosemary extract on the antioxidant activity of perilla oil Depend on Figure 6 It can be seen that during the accelerated oxidation process, adding rosemary extract can significantly reduce the peroxide value of perilla oil, and the longer the storage time, the greater the difference in peroxide value, with the largest reduction being 0.04%. On the third day of accelerated oxidation, the peroxide value of each treatment exceeded or approached the national standard of 0.25g / 100g. On the seventh day of accelerated oxidation, the peroxide value of CK was 0.9g / 100g, and the peroxide value of adding 0.04% rosemary extract on the seventh day of accelerated oxidation was 0.62g / 100g, which was significantly lower than CK. Figure 7 It can be seen that rosemary extract has a relatively large effect on the acid value of perilla oil. The acid value of CK increases during the accelerated oxidation process, and the addition of rosemary extract shows a trend of first increasing and then decreasing. On the 0th day, the acid value of CK was 0.47 mg / g, and on the 7th day, the acid value was 0.72 mg / g. When 0.04% rosemary extract was added and the acid value was accelerated on the 7th day of oxidation, it was 0.55 mg / g, both of which were below the national standard of 3 mg / g. Based on the above experimental results, rosemary extract can effectively reduce the peroxide value of perilla oil during the storage of perilla oil, but it has no significant increase in the shelf life of perilla oil.

[0047] 5.5 Effect of VC on the antioxidant activity of perilla oil Depend on Figure 8It can be seen that during the accelerated oxidation process, the addition of VC can significantly reduce the peroxide value of perilla oil, and the longer the storage time, the greater the difference in peroxide value. The greater the decrease in peroxide value with the increase in VC concentration during storage. However, the peroxide value of CK reached the national standard of 0.25g / 100g on the 3rd day. On the 7th day of accelerated oxidation, the peroxide value of CK was 1.0g / 100g, and the peroxide value of 3% VC on the 7th day of accelerated oxidation was 0.79g / 100g, which was significantly lower than CK. Fig. 9 It can be seen that VC has a greater impact on the acid value of perilla oil. The acid value of CK increases during the accelerated oxidation process, and the acid value of perilla oil with the addition of VC shows a relatively stable trend. On the 0th day, the acid value of CK was 0.47 mg / g, and the acid value on the 7th day was 0.72 mg / g. After adding 3% VC and accelerating oxidation on the 7th day, the acid value was 0.53 mg / g, both of which are below the national standard of 3 mg / g. Based on the above experimental results, VC can effectively reduce the peroxide value of perilla oil during storage, but it has no significant increase in the shelf life of perilla oil.

[0048] 5.6 Effect of composite antioxidants on the antioxidant activity of perilla oil Depend on Fig.10 , 11 It can be seen that the peroxide value and acid value of the perilla oil in each treatment showed an increasing trend in general during the accelerated oxidation process. The addition of composite antioxidants can significantly enhance the antioxidant properties of perilla oil, and its effect is better than that of a single antioxidant. During the 16-day accelerated oxidation process, the peroxide value of CK reached 0.24g / 100g on the 8th day of storage, which is close to the national standard of 0.25g / 100g. Each composite antioxidant has a significant effect on the peroxide value of perilla oil. The peroxide value of perilla oil with the addition of 4% vc + 0.02% rosemary extract + 0.02% tea polyphenols and 0.04% tea polyphenols + 2% VC + 0.02% rosemary extract first increased, then decreased, and then increased again, while the peroxide value of perilla oil with the addition of 0.04% rosemary extract + 0.02% tea polyphenols + 2% VC first increased and then decreased, and did not increase during the 16th day of accelerated oxidation, and did not exceed the national standard of 0.25g / 100g on the 16th day. Fig.11It can be seen that during the accelerated oxidation process, the acid value of perilla oil increased with the oxidation time. At the 16th day of accelerated oxidation, the acid value of CK was 1.2 mg / g. The acid value of adding composite antioxidants was maintained at a low level. The acid value was the lowest when 0.04% rosemary extract + 0.02% tea polyphenols + 2% VC was added. At the 16th day of accelerated oxidation, the acid value was still maintained at a low level of 0.01 mg / g, which was below the national standard of 3 mg / g. Based on the test results of peroxide value and acid value, composite antioxidants can significantly enhance the antioxidant properties of perilla oil. According to the Arrhenius empirical formula, 1 day in the oven is equivalent to the actual storage period of 1 month of perilla oil. Therefore, adding 0.04% rosemary extract + 0.02% tea polyphenols + 2% VC mixed antioxidants can increase the shelf life of perilla oil by 8 months.

[0049] 5.7 Experimental Summary As the storage time of oil increases, the acid value and peroxide value of perilla oil will increase. Temperature, light, air and moisture content will accelerate the oxidation of perilla oil, causing the fat to become rancid faster and the acid value to increase, while the peroxide value basically shows a trend of first increasing, then decreasing and then increasing. Therefore, perilla oil should be kept at low temperature, away from light and low moisture conditions during storage to extend the storage period.

[0050] Tea polyphenols have a significant effect on enhancing the antioxidant activity of perilla oil. In the process of accelerated oxidation, when the amount of tea polyphenols added is greater than 0.08%, the antioxidant activity of perilla oil is significantly enhanced, and the antioxidant activity increases with the increase of the added concentration; the single addition of VC has no obvious effect on the antioxidant activity of perilla oil. The composite antioxidant composed of tea polyphenols, rosemary extract and VC has a significant effect on the antioxidant activity of perilla oil, and the antioxidant effect is significantly higher than that of a single antioxidant; the composite addition formula of 0.04% rosemary extract + 0.02% tea polyphenols + 2% VC has the best antioxidant effect, which can increase the theoretical shelf life of perilla oil by 8 months.

Claims

1. A perilla oil pressing process, characterized in that: After the perilla seeds are washed, dried and peeled, perilla kernels containing 13-17% of water are obtained. The perilla kernels are heated to 95-105° C. and pressed by a twin-screw oil press. The crude oil obtained by pressing is winterized and then physically filtered to obtain perilla oil.

2. The perilla oil pressing process according to claim 1, characterized in that: The twin-screw oil press is pressed 2-4 times.

3. The perilla oil pressing process according to claim 3, characterized in that: The twin-screw oil press was pressed 3 times.

4. The perilla oil pressing process according to claim 1, characterized in that: The perilla seed kernel contains 14-16% water.

5. The perilla oil pressing process according to claim 4, characterized in that: The perilla seed kernel contains 15% water.

6. The perilla oil pressing process according to claim 1, characterized in that: The perilla seed kernels are heated to 97-103°C.

7. The perilla oil pressing process according to claim 6, characterized in that: The perilla seed kernels are heated to 99-101°C.

8. The perilla oil pressing process according to claim 1, characterized in that: Obtain perilla oil, add 0.03-0.05% of rosemary extract, 0.01-0.03% of tea polyphenols and 1-3% of VC by weight, and then preserve it.

9. The perilla oil pressing process according to claim 8, characterized in that: Obtain perilla oil, add 0.04% rosemary extract, 0.02% tea polyphenols and 2% VC by weight, and then preserve it.

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