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Advances in extraction methods and refining processes of grape seed oil

 CO2 supercritical extraction for grape seed oil extraction

Abstract: The waste material in the wine production process is treated by washing and drying to separate the grape seed. The obtained grape seed is obtained by a pressing method, a solvent extraction method or a supercritical fluid extraction method, and the obtained crude oil is subjected to a refining process such as degumming, deacidification, water washing and drying, decolorization, deodorization and characteristic filtration to finally obtain a refined product oil. In this paper, the research progress of grape seed oil extraction method and refining process is reviewed.

China's annual use of fresh grapes for winemaking and other industries exceeds 100,000 tons, and there are 5,000 to 7,000 tons of by-product grape seed per year. The oil content of grape seed is about 14%~17%, and the content of linoleic acid is as high as 72%~76%. Grape seed oil also contains various fat-soluble vitamins, and the essential mineral elements such as potassium, copper, calcium and iron. Zinc, manganese, cobalt. Grape seed oil not only can prevent diseases, but also black hair, anti-aging, and longevity. In foreign countries, grape seed oil is mainly used as a high-grade nutrient oil for infants and the elderly, high-altitude workers, and advanced health oil for flight personnel. In China, the comprehensive utilization of grape seed is still in the primary development stage, and it is necessary to carry out the processing and utilization of grape seed oil.

1 Grape seed oil extraction method

1.1 Pressing method

Grapes are peeled and dried to obtain grape seeds (the raw materials are purchased in the winery, the raw materials contain a certain amount of impurities), after the impurities are removed, the crusher is broken, and then the softening pot is softened, and the softened moisture is controlled at 18%~ 20%, heated to 80 ° C, residence time of about 40 min, the billet, the thickness of the green sheet is 0.4 mm, the moisture is adjusted by the flat dryer, and the moisture of the grape seed in the leaching device is controlled to be less than 12%. The flat leaching device is used, the leaching time is about 1.5h, the solvent ratio is 1:1.2, the mixed oil is desolvated by the evaporator and the stripping tower to obtain the grape seed hair oil, and the seed mash is steamed off-line and then decomposed into the sputum.

The pressing method is simple, easy to realize industrial production, free from chemical pollution, and easy to separate; the disadvantage is that the grape seed core is hard, the oil yield is low, the residual oil in the cake residue is high, the impurity content is high, and the energy consumption is large, and the machine is easy to make The shaft breaks and a high temperature is formed inside during extrusion, which tends to decompose unsaturated fatty acids.

1.2 Solvent extraction method

After the grape seeds are dried, pulverized and conditioned, 10 g of grape seed powder is taken, placed in a homemade filter paper tube, the filter paper tube is placed in a Soxhlet extractor, and a 250 mL flask is connected to the extractor and poured from the upper portion of the extractor. The boiling range is 30~60 °C petroleum ether or n-hexane. When pouring, try to let the solvent directly enter the filter paper tube. The amount of solvent is about 2/3 of the volume of the flask. The mixture was condensed and refluxed, and the flask was heated in a water bath to start extraction. The heating temperature is set according to the boiling point of the solvent, generally not exceeding 65 ° C, to avoid the saponification value of the oil is too high, the extraction time is about 2 to 3 h, and the solution in the extractor is colorless and then extracted for 0.5 h. The solution was placed in a rotary evaporator concentrated solution to recover the solvent, and the heating temperature was the same as the extraction temperature to obtain a hair oil.

The foreign research institute adopts the superheated n-hexane extraction method, adopts Soxhlet extraction, the extraction temperature is 80 °C, and the extraction pressure is 8106 kPa. Although this method does not have a high solvent extraction rate, the extraction time is about 10 to 30 minutes, saving water and electricity.

The solvent extraction method has higher oil yield, more thorough extraction, solvent recovery, lower cost, simple operation and easy laboratory research. However, in the solvent recovery process, unsaturated fatty acid is easily decomposed, and the obtained oil saponification value is obtained. It is high, and there are solvent residues in the product. The solvent is extremely flammable and requires high operational safety. Due to the toxic or odor of the solvent, attention should be paid to ventilation and fire prevention to prevent leakage.

1.3 Supercritical fluid extraction

Supercritical CO2 Extraction Machine

Unsaturated fatty acids are unstable and easily oxidatively decomposed. The extraction of grape seed oil with CO2 supercritical fluid has unique advantages. Extraction conditions: CO2 supercritical extraction device, moisture content of 5.0%, wet steaming time of 30 min, extraction pressure of 28 MPa, temperature of 33 ° C, gas velocity of 3.5 kg / h, extraction under this condition for 1.5 h, grape seed oil extraction rate Can be as high as 14%. The biggest advantage of supercritical fluid extraction is that it can be operated at low temperature, avoiding the oxidative decomposition of unsaturated fatty acids, and the solvent has no residue, CO2 is easy to obtain, and the energy consumption is low. Compared with the solvent extraction method, the solvent recovery and the refining process are omitted, thereby reducing the cost and easily achieving industrial production, and is a good method for preparing edible oil.

2 Grape seed oil refining process

Grape seed oil is degreased, deacidified, washed and dried, decolorized, filtered, deodorized, allowed to settle, and filtered to obtain refined oil.

Hydration degumming: using medium temperature hydration process, the oil temperature is 60~65°C, the water addition is 3.5 times of the phospholipid content in the oil, the water temperature is about 80°C, and the hot water is added within 15min. After the gums were clearly precipitated, the precipitate was allowed to stand for about 6 hours and then separated.

Alkali deacidification: The amount of alkali added should be determined according to the acid value of the hair oil. All lye should also be added within 15 minutes. The initial temperature of alkali refining is 30~35°C, and the final temperature is 60~70°C. After the soap particles were precipitated, they were allowed to stand for about 6 hours, and then the soap feet were separated.

Washing and drying: The oil temperature is adjusted to about 80 ° C, and water is added to the same temperature as the oil for washing. Wash 1~3 times, each time the water consumption is 10%~15% of the oil weight. After adding water, let it stand for about 1h and let off the waste water. After washing, the oil contains about 0.5% of water and is dried. Due to the high content of unsaturated fatty acids in grape seed oil, in order to avoid high temperature oxidation, dehydration should be vacuum dewatering, the vacuum dehydration temperature is 90~105 °C, and the vacuum degree is about 9 MPa.

Decolorization: The water after washing is pumped into the decolorizing pot to keep the absolute pressure in the pot below 8 kPa, and the oil is heated to above 80 °C to start dehydration until the mist in the pot disappears (the moisture content in the oil is less than 0.1%), indicating that the dehydration requirement is reached. When decolorizing, the oil temperature is raised to about 90 °C, and the activated clay is added, and the amount is 3% to 5% of the oil weight, and the mixture is mixed with the oil, and the decoloring time is 30 to 40 minutes. After the decolorization is completed, the oil is cooled to below 70 ° C, and then the vacuum is broken, and the oil is pumped out to separate the clay.

Deodorization: The decolorizing oil is sucked into the deodorizing pot. The absolute pressure in the pot is lower than 113 kPa, the temperature is 170~180 °C, the time is 3~8h, the oil is cooled to below 70 °C after deodorization, and the pump is filtered to be refined deodorizing oil.

Due to the waxy content in the grape seed hull, the grape seed also produces glycolipid during the fermentation process. These substances will not be removed during the above refining process. After 1 week of standing sedimentation, the filter is filtered by a special oil filter. After filtering, the grape seed oil is crystal clear and transparent, achieving the requirements of dewaxing and degreasing.

3 Conclusion

With the vigorous development of the wine industry, the scraps produced after brewing are concentrated due to seasonality, the production cycle is concentrated, and cannot be disposed of in time, but discarded as waste, which not only wastes resources but also pollutes the environment. If the fermented grape seeds can be rationally and comprehensively utilized, the seeds can be separated and further refined, tannins and cakes can be extracted or further used in food, medicine, chemical, cosmetics, feed and other industries. The pollution of the environment can turn waste into treasure and increase social and economic benefits.