Study on modification methods of palm oil
With the development of oil industry, natural oil can not meet the needs of food industry. This requires that natural oils must undergo some means to improve their processing properties. The main modification methods of palm oil are extraction, hydrogenation and transesterification.
1. Palm oil fractionation
Oil fractionation methods commonly used in industry are: dry fractionation, surface active solvent fractionation, and solvent fractionation. Among them, dry fractionation is the simplest separation process. But the crystallization time of this method is as long as 24h, and production efficiency is lower in actual production. Tang Hongzhou and others improved the palm oil dry fractionation process, changing the palm oil crystallization process from continuous cooling regardless of time period to a staged crystallization method of rapid cooling, constant temperature, and slow cooling in several time periods. The improved process can shorten the crystallization time, reduce energy consumption, improve production efficiency, and help to maintain stable product quality. Guo Shaohai et al. pointed out that the crystallization temperature recovery phenomenon occurred in the palm oil dry fractionation process. The temperature recovery was caused by the high or low melting point of RBD palm oil, or the unsuitable crystallization curve. And according to different reasons of temperature recovery, corresponding solutions are put forward respectively.
2. Hydrogenation of palm oil
Hydrogenation is often used to convert liquid vegetable oils into semi-solid plastic fats. It can convert the natural vegetable oil resources with wide sources and low cost into necessary raw materials for chemical production, and obtain a variety of edible oil raw materials such as margarine, shortening and cocoa butter substitute of high quality. For example, CAI Yunsheng et al. saturated palm kernel soft fat (melting point is generally 24~30℃) through hydrogenation to obtain hydrogenated palm kernel oil with melting point of about 35℃, thus producing ice cream with better quality, which greatly changed the processing performance of palm oil.
3. Palm oil transesterification
Transesterification is a reaction in which an ester is mixed with another fatty acid, alcohol, self or other ester and accompanied by acyl exchange or molecular rearrangement to form a new ester. Palm oil and palm kernel oil are often modified by transesterification to make them suitable for various confectionery, margarine, cooking and frying oils. In the presence of methyloleic acid after fractionation, chemical transesterification can increase oleic acid content and improve the processing performance of palm oil. Transesterification technology has been widely used in the palm oil manufacturing of low trans margarine and shortening, cocoa butter substitute and coating industries. A good low trans margarine has been produced by enzymatic transesterification of soybean oil and palm oil. There is also a low trans margarine made from palm soft and palm hard by transesterification catalyzed by 1,3 specific lipases.
