Walnut Oil Refining Processing

The process for refining walnut oil is as follows: crude walnut oil, filtration, degumming, deacidification, decolorization, vacuum deodorization, low-temperature dewaxing, and refined walnut oil.

Impurity removal is a physical method used to remove mechanical impurities from the walnut oil, ensuring its clarity. Centrifugation or filtration methods are commonly used.

Degumming is a process that uses a combination of chemical and physical methods to remove phospholipids from walnut oil. Phospholipids have the property of being soluble in water but insoluble in oil. The degumming process involves hydrating the gums with water and then using the difference in density between oil and water to remove the gums.

Deacidification is the process of removing free fatty acids from the oil. There are two commonly used methods: physical and chemical. The physical method involves vacuum distillation at a certain temperature to evaporate the free fatty acids from the oil. The chemical method involves adding a certain amount of alkali to the oil, causing a reaction between the alkali and the free fatty acids, which separates the free fatty acids from the oil.

Decolorization is the process of removing pigments from the oil using physical adsorption methods such as activated carbon or diatomaceous earth.

Deodorization refers to the removal of non-triglyceride components from the oil, such as ketones, aldehydes, hydrocarbons, and oxidation products of unsaturated fatty acids. Deodorization is achieved by creating a certain vacuum level and utilizing the difference in volatility between triglycerides and volatile odor substances. Water vapor passes through the oil containing odor components, creating a vapor-liquid interface. The water vapor becomes saturated with the volatile odor components and escapes according to their partial pressures, thereby achieving deodorization.

Dewaxing is the process of crystallizing waxes at low temperatures and separating them from the oil. Methods such as filtration and centrifugation are used to remove the waxes. Drying is done to remove moisture from the oil. Vacuum drying is used to avoid damage to the nutritional elements of the oil caused by high temperatures.