Fractionation of palm and palm kernel oils for designing high quality commodity and specialty fats

Abstract

Fractionation is the most important application of fat crystallization in edible oil processing. This process commonly consists of a controlled crystallization in bulk crystallizers followed by a separation of the liquid from the crystalline fraction, nowadays mostly carried out with membrane press filters. The motive for this process is evident: since nature endows each fat with a particular composition and distribution of the fatty acids on the glycerol, their use in specific applications is limited. Palm oil is the most fractionated oil worldwide; its potential for multi-step dry fractionation allows to generate various fractions with peculiar physicochemical properties used in many food formulations. The original booming of the dry fractionation process has helped palm oil to conquer a strong position on the commodity market in one single step. Other demands for special cuts drifted the industry towards a more sophisticated approach: high iodine value super and top olein with interesting cold resistances, high melting point super stearin (competing with fully hydrogenated products), hard palm mid fraction (for cocoa butter equivalents - CBE) or palm red fractions (high carotene and tocopherol/tocotrienol contents). A hybrid form of palm oil grows in Colombia and Ecuador: the high oleic palm oil has a higher oleic content than conventional palm oil. It can easily be fractionated as refined or semi-refined (red oil); the liquid fractions obtained have excellent cold resistance in one single fractionation step. Palm kernel oil has a very different triglyceride composition and its applications are quite different; it is known as a source of cocoa butter substitute (CBS) after fractionation and full hydrogenation of the stearin. The fractionation can be carried out in one or two steps, making it possible to produce three different CBS. Various technologies including continuous and static crystallization are being used to produce these specialty fats.