Crystallization of palm oil products

Chong, C.L. 2001. Crystallization of palm oil products. In, Crystallization and Solidification Properties of Lipids (N. Widlak, R. Hartel, S. Narine, eds.), pp. 110-119, AOCS Press, Champaign, IL. 

Palm oil production has increased significantly in the last 10 years and may soon exceed that of all other edible oils. Pahn oil is also the only p type whose crystal habit is not changed by interesterification. Interesterification has no effect on the oils in the p classification either however, randomization in the presence of another oil can moderate their p tendency (13). 

For the work reported here, the polymorphic forms of the crystals of all the palm oil products at the temperatures measured are either in the 3 or 3 form or a mixture of both. The 3 polymorphic crystal form is plate-like while the 3 crystal form is spherulitic with needle-like projections from the center of the crystal as can be seen from the electron microscope pictures published by van Putte and Bakker (12). Therefore it can be seen that for the P polymorph, although the final overall shape of the crystal assumes the shape of a sphere in three dimensions, the plates or leaves that form the crystal are thin. This shows that as far as the actual growing sites of the crystal are concerned, growth is in two and not in three dimensions. 

The transformation of crystals from the P to the P form takes place in the solids present in a fat. However, the rate of this transformation is greatly influenced by the amount of liquid oil in the fat. A suitable method to estimate the p stability of a fat is temperature cycling. An example is given in Table 9, where palm oil products were subjected to temperature cycling between 4 and 20°C. A cycle may take two or more days. The polymorphic forms can be measured at the end of each cycle. A product such as hydrogenated palm oil or palm olein will show no presence of P polymorphs after four cycles. Palm oil and palm stearin will... 

Palm midfraction (PMF), a fraction of palm oil whose melting points are between those of palm stearin and palm olein [77], has been employed for vegetable-fat-based creams as well in the production of cocoa butter equivalent fats (CBEs) used in chocolate [78]. The effects of additions of SOEs and PGEs on the crystallization of PMF in O/W emulsions were studied recently [79]. Figure 13a shows the isothermal crystallization behavior of PMF in oil-in-water emulsion at 10°C without (pure) and with the addition of 1 wt% S-170. It is obvious that the V values of the pure emulsion are always smaller than in emulsions with S-170... 

Fractionation of Palm Kernel Oil. As in palm oil, palm kernel oil can also be fractionated via the dry, detergent, and solvent processes (62). The principles applied are quite similar. The conditions of operation, however, are quite different because of the different triglyceride composition and crystallization behavior of palm kernel oil. In the dry fraction process, the separation of palm kernel olein from the palm kernel stearin is effected by hydraulic pressing under high pressure. In this case, the palm kernel stearin, which is an important material for production of lauric-basic cocoa butter substitute, is the premium product. Its yield ranges from 25 to 40% depending on the process used. 

Fractionation is designed to separate the various fractions based on differences in crystallizing temperatures. Often, the products of a single fractionation are not sufficiently fine tuned to produce some of the higher value specialty fats. Hence, the concept of double fractionation was introduced, with one of the phases (usually the olein) refractionated. This process is used quite frequently with palm oil. The products of the second fractionation are a super olein and a stearine used as tropical margarine base or a confectionery base. 

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