Studies in palm oil crystallization

Abstract

The melting and crystallization behaviors of palm oil were examined by nuclear magnetic resonance, differential scanning calorimetry, and plasticity measurements and were correlated with composition and chemical characteristics• Fractionation into high melting and low melting components is adversely affected by increase in free fatty acids (FFA), diglyceride content, and degree of oxidation, and hence, for an oil that is to be fractionated, both hydrolysis and oxidation should be kept to a minimum. Palm oil with very low FFA content, obtained from ripe, unbruised fruit, contains substantially more diglycerides than would be expected from the level of FFA present• Liquid and solid palm oil fractions manufactured in the producing countries showed large variation in characteristics, due in part to the use of various fractionation processes. The characteristics used to define the quality of palm oil are also applicable to its fractions. X-ray diffraction has shown that each state corresponds to a definite packing order of "short spacing" (i.e., distance between hydrocarbon chains lying contiguously to each other) and "long spacing" (i.e., width of successive layers of contiguously packed molecules). The latter depends on the chain length of the molecule but also on the angle of tilt between a hydrocarbon chain and the boundary plane of the molecular layer (5,6). The melting and solidification of fats is also governed by the degree of intersolubility of the glycerides, which is linked to the pattern of imbrication of the triglyceride chains in the crystal. The most common configurations are of patterns usually called "double chain" and "triple chain":

Differential scanning calorimetry: A potential tool for discrimination of olive oil commercial categories

“…A more ordered crystal structure may be hypothesized for olive oil samples (EvOo, Oo and ROo) due to a more uniform chemical composition (higher TUTAG, especially OOO content) as compared to olive-pomace oils that resulted in a narrower range of transition, as previously observed [9,14]. The lower crystallization enthalpy of EvOo with respect to the other olive oils, may have been influenced by lipid oxidation products (higher values of both POV and PAV) and free fatty acids (higher acidity values), as these molecules have been reported to be adsorbed into the crystal lattices of TAG, forming mixed crystals [25] that may have required lower enthalpy to undergo phase transition.…”

“…DAG were found to influence (accelerating or delaying) TAG crystallization in vegetable oils (palm and coconut) and in fats [26,27] and to shift crystallization onset temperature toward higher temperature in EvOo samples with DAG contents comparable to those found in olive-pomace oils in this study [9]. DAG were also reported to be adsorbed into crystal lattices of TAG, hindering their crystallization process [25]. The elevated DAG content, together with the high content of lipid oxidized molecules (PAV, Table 1), may also explain the larger transition range exhibited by both Po and RPo.…”

Impacts of Bleaching and Packed Column Steam Refining on Cocoa Butter Properties

“…In this context, it should be mentioned that Jacobsberg and Oh [26] have reported a similar tendency in palm oil, claiming this is due to the formation of a eutectic mixture of TAG and FFA.…”

Palm oil refining

“…Jacobsberg and Oh [2] reported a total diacyglycerol (DAG) concentration in crude palm oils ranging from 5.3 to 7.7%. They also noticed no correlation between FFA, MAG and DAG contents: DAG found in crude palm oil is probably a residual by-product of the biosynthesis of the TAG.…”