CN-116399663-B - Extraction method and content inspection method of total phenols in rapeseed oil

Abstract

The invention discloses an extraction method of rapeseed oil total phenols and a content inspection method thereof, wherein the extraction method comprises the following steps of firstly, weighing rapeseed oil in a glass test tube, adding methanol, mixing by vortex oscillation, ultrasonic and freezing; transferring the upper liquid in the glass test tube to another clean test tube, blowing the glass test tube to dry in weak nitrogen in a metal bath, redissolving the residues in a methanol-water solution, uniformly mixing by vortex oscillation, and preserving for later use. According to the extraction method of the rapeseed oil total phenol, methanol is adopted for dissolution, ultrasonic auxiliary extraction is adopted, simultaneously, the rapeseed oil and the extracting solution are well separated by freezing, and an organic solvent extraction method and an ultrasonic auxiliary extraction method are combined, so that the extraction time is greatly saved, and the extracted rapeseed oil total phenol content is high. The invention is more suitable for measuring the total phenol content in the rapeseed oil after the standard substance (gallic acid) in the industry standard for measuring the total phenol content of the vegetable oil is replaced by canolol.

Inventors

• YAO YINGZHENG
• LIANG QIANG
• XIONG WEI
• XUAN PU
• ZHAO LING
• HU ZIHUI
• LI YAN
• XU XIA

Assignees

• 四川省农业科学院农产品加工研究所

Dates

Publication Date

20260505

Application Date

20230404

Claims (9)

1. 1. A method for testing the total phenol content of rapeseed oil, which is characterized by comprising the following steps: Step one, weighing rapeseed oil into a glass test tube, adding methanol, uniformly mixing by vortex oscillation, performing ultrasonic treatment, and freezing; Transferring the upper liquid in the glass test tube to another clean test tube, blowing the glass test tube to dry in weak nitrogen in a metal bath, redissolving residues in a methanol-water solution, and uniformly mixing by vortex oscillation to obtain a rapeseed oil total phenol extract; step three, respectively transferring canolol standard substance working solution, methanol-water solution and rapeseed oil total phenol extracting solution into a colorimetric tube; adding water, a Fu Lin Fen reagent and a sodium carbonate solution, carrying out vortex oscillation and mixing uniformly, and adding water to a fixed volume to a scale; Step five, carrying out water bath reaction, taking out, and cooling to room temperature; step six, measuring absorbance under the wavelength condition of 760-780 nm; Step seven, drawing a standard curve according to the absorbance of canolol standard working solutions and the canolol concentration of each canolol standard working solution; And step eight, quantitatively measuring the total phenol content in the rapeseed oil by using canolol as a correction standard according to the standard curve drawn in the step seven.
2. 2. The rapeseed oil total phenol content detection method according to claim 1 is characterized in that in the first step, vortex oscillation mixing time is 1-5 min, ultrasonic time is 10-30 min, freezing temperature is-90 to-8 ℃, and freezing time is 0.5-12 h.
3. 3. The method for testing the total phenol content of rapeseed oil according to claim 1, wherein in the second step, the metal bath temperature is 35-45 ℃, and the vortex oscillation mixing time is 0.5-1.5 min.
4. 4. The method for testing the total phenol content of rapeseed oil according to claim 1, wherein the dosage ratio of rapeseed oil, methanol and methanol-water solution is 0.5-1.5 g:5-15 ml:5-15 ml, and the volume concentration of methanol in the methanol-water solution is 30-100%.
5. 5. The method for testing the total phenol content of rapeseed oil according to claim 1, characterized in that in the first step, the concentration of canolol standard working solution is 200 μg/mL, 100 μg/mL, 50 μg/mL, 20 μg/mL, 10 μg/mL.
6. 6. The method for testing total phenol content of rapeseed oil according to claim 1, wherein in the second step, the vortex oscillation time is 0.5-1.5 min.
7. 7. The rapeseed oil total phenol content detection method according to claim 1 is characterized in that the volume ratio of canolol standard working solution/methanol-water solution/rapeseed oil total phenol extraction solution, fu Lin Fen reagent and sodium carbonate solution is 0.25-1.25 ml:0.5-1.5 ml:1-3 ml, and the mass concentration of the sodium carbonate solution is 7.5%.
8. 8. The method for testing the total phenol content of rapeseed oil according to claim 1, wherein in the third step, the water bath reaction temperature is 60-80 ℃ and the time is 20-40 min.
9. 9. The method for testing the total phenol content of rapeseed oil according to claim 1, wherein in the sixth step, the calculation formula of the total phenol content in rapeseed oil is as follows: Wherein X is the content of total phenols in the rapeseed oil, C is the concentration of canolol detected by a standard curve, D is the dilution multiple of the constant volume of the sample, D= 1;V is the re-dissolution volume of the dried extracting solution if the sample is not diluted, and m is the mass of the sample of the total phenols extracting solution of the rapeseed oil.

Description

Extraction method and content inspection method of total phenols in rapeseed oil Technical Field The invention relates to a method for extracting polyphenol in vegetable oil and a method for detecting the content of the polyphenol, in particular to a method for extracting total phenol of rapeseed oil and a method for detecting the content of the total phenol. Background There are many extraction methods of rapeseed oil total phenols, and the main reported extraction methods are an organic solvent extraction method, an ultrasonic auxiliary extraction method, a solid phase extraction method and the like. The organic solvent extraction method has the advantages of simple process, low cost, high purity, low extraction rate and long time consumption, the ultrasonic-assisted extraction method has high extraction rate, the extract is not easy to damage, the purity of the product is not high, the solid phase extraction method has high sample recovery rate and good precision, and the solid phase extraction column is generally expensive. It was found that rapeseed oil total phenols are divided into phenolic acids and tannins, which in turn include free phenolic acids and bound phenolic acids. The free phenolic acid accounts for 6.5-9.0% of total phenols, mainly contains sinapic acid, 70-85% of total phenolic acid, and further contains a small amount of free p-salicylic acid, vanillic acid, gentisic acid, protocatechuic acid, syringic acid, p-coumaric acid, ferulic acid (cis and trans), caffeic acid, chlorogenic acid and the like. The bound phenolic acid comprises 80% of the total phenol, mainly sinapine (also known as sinapine choline ester), and is present in the rapeseed in an amount of about 0.4% to about 1.0%. The combined phenolic acids are alkaline hydrolyzed to produce small amounts of p-salicylic acid, vanillic acid, protocatechuic acid, syringic acid, p-coumaric acid, ferulic acid and caffeic acid. Thus, the polyphenols in cold pressed rapeseed oil and leached rapeseed oil are mainly sinapic acid, sinapine and sinapic acid glucoside and cinnamic acid derivatives. The heat treatment can be used for the hydrolytic decarboxylation of sinapic acid and sinapic acid to canolol (2, 6-dimethoxy-4-vinyl phenol), so that the hot mustard seed oil polyphenol is mainly canolol and a small amount of sinapic acid, sinapine and sinapic acid glucoside and cinnamic acid derivative. At present, the method mainly refers to Fu Lin Fenfa (Folin-Ciocalteu) in the standard LS/T6119-2017 for measuring the total phenol content of the vegetable oil in China, and takes gallic acid as a standard substance, wherein the detection principle is that under an alkaline condition, fu Lin Fen reagent oxidizes phenolic hydroxyl groups (-OH groups) in polyphenol and develops blue, and the degree of blue is in direct proportion to the number of phenolic groups. three-OH groups exist in the gallic acid molecular structure, while one-OH group exists in the rapeseed oil representative polyphenol canolol molecular structure, and the functional group structures and the quantity are inconsistent. The literature shows that the standard substances for measuring the total phenols of vegetable oils such as soybean oil, olive oil, camellia seed oil and the like are mostly gallic acid, while the standard substances for measuring the total phenols in rapeseeds or rapeseed oil are different, and are sinapic acid, caffeic acid, tannic acid and the like. Wherein sinapic acid is the most standard, and the results are expressed in terms of sinapic acid equivalent. However, no study or application using canolol as a standard was found. Disclosure of Invention In view of the fact that the existing industrial standard for measuring the total phenol content of vegetable oil is not suitable for measuring the total phenol content in rapeseed oil, the invention provides an extraction method and a content inspection method of the total phenol content in the rapeseed oil. The invention aims at realizing the following technical scheme: The extraction method of the rapeseed oil total phenol comprises the following steps: weighing 0.5-1.5 g of rapeseed oil into a glass test tube, adding 5-15 mL of methanol, swirling, uniformly mixing for 1-5 min, performing ultrasonic treatment for 10-30 min, and then putting into a refrigerator for freezing at the temperature of-90 to-8 ℃ for 0.5-12 h; Transferring the upper liquid in the glass test tube to another clean test tube, blowing the glass test tube to dry in a metal bath at 35-45 ℃ with weak nitrogen, redissolving residues in 5-15 mL and methanol-water solution (the volume concentration of methanol is 30-100%), carrying out vortex oscillation for 0.5-1.5 min, and uniformly mixing to obtain rapeseed oil total phenol extract, and storing at-18 ℃ for later use. A method for detecting total phenol content of rapeseed oil comprises the following steps: firstly, respectively transferring canolol standard substance working solution, metha