Currently, pressing process for oil extraction is a popular extraction method on the market. Compared with other oil extraction method, it has the advantages of simple process, less equipment, strong adaptability to different oil-bearing crops, flexible production, good quality of oil, light color, pure flavor, etc. Pressing oil extraction extracts oil through the external force generated by the screw press.
Oil extraction of oil press can be divided into hot pressing and cold pressing. What is the difference between them?
In hot pressing, oil plants generally need to be cleaning and crushing before being heated in high temperature processing to produce a series of changes in the internal structure of oil plants: to destroy the oil cell, promote protein denaturation, reduce oil viscosity and make them suitable for pressing and to increase the yield of oil. However, crude oil produced through high temperature processing of oil plants has darker color and higher acid value. Thus, the crude oil must be refined to become edible. Meanwhile, bioactive substances (vitamin E, sterols, carotenoid, etc.) in the oil plants are lost seriously in high temperature oil extraction, resulting in a waste of resources. Hot pressing screw oil press need to be used in general hot rolling.
Cold pressing oil extraction refers to the pressing method that oil plants before pressing are not heated or kept in low temperature state before being fed into the oil press. Cold pressing is generally in the temperature of less than 60℃. Cold pressed oil retains the natural flavor and color of oil plants, complete preserves the physiological active substances with lower protein denaturation degree and conducive to the comprehensive utilization of protein. Raw materials of cold pressed oil must be carefully selected, otherwise it will affect the quality of cold pressed oil. Generally speaking, the smoke point of cold pressed oil is low and the moisture content is not stable, which is not conducive to long-term storage.
Difference of hot pressed oil and cold pressed oil
Hot pressed oil has pure and fragrant flavor, especially for oil plants with rich oil content like peanut and sesame, the oil produced is more fragrant after hot pressing. The disadvantage is that there would be overflow and foam when cooking hot pressed oil without any treatment. The problem could be solved after filtering and refining by centrifugal oil filter.
Cold pressed oil has light color and smell, it keeps the original flavor of oil plants, green and environmental protection. Especially suitable for pressing organic plants and economic crops with high added value, such as olive, walnut, grape seed, linseed oil and other oil crops.
No matter hot pressing process or cold pressing process, users should choose the proper pressing process according to their own consumer groups.
