Polymorphic stability of hydrogenated canola oil as affected by addition of palm oil

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Abstract
Palm oil was added to canola oil before and after hydrogenation and the effect of this addition on the polymorphic stability of the hydrogenated oils was investigated. Palm oil was added to canola oil at two levels to produce hydrogenated canola and palm oil blends containing 5 and 10% palm oil. The levels of palm oil added to hydrogenated canola oil were 5, 10 and 15%. Samples were subjected to temperature cycling between 5 and 20°C as well as storage at 5°C up to 56 days. X‐ray diffraction and polarized light microscopy were used to follow the changes of polymorphic form and crystal growth, respectively, during cycling and storage. Theβ‐crystal contents of the oils were quantified based on the relative density of the characteristic short spacings using a Soft Laser Scanning Densitometer. The delaying effect of palm oil on phase transition was observed using Differential Scanning Calorimetry. Palm oil showed no effect on the polymorphic stability of the temperature cycled selectively hydrogenated oil, however, it delayed the transition rate at a constant temperature of 5°C. Addition of palm oil at the 10% level before hydrogenation and the level after hydrogenation proved to be effective in delaying polymorphic instability of nonselectively hydrogenated canola oil. Theβ′ stabilization effect of palm oil on the polymorphic stability of hydrogenated canola oil is most likely due to a decrease of fatty acid chain length uniformity.

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