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Changes
in Free Fatty Acid of Oil samples at different frying Time and constant
Temperature

Spoilage of fat leads to the liberation of free fatty
acids from triglycerides. The amount of free fatty acid in a fat or oil is
indicative of its level of deterioration. Blending palm oil and shea butter at
a ratio of 1:1 affected the fatty acid composition and also change the
triacylglycerol composition of the oil sample. These factors can largely affect
the frying performance and chemical composition of the blend oil.

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As shown in Table 3, the initial free fatty acid for
Palm oil, Shea butter and blend 5.72 ± 0.05, 2.12 ± 0.01 and 3.28 ± 0.05
respectively. The free
fatty acid of the three oil samples significantly (P ?
0.05)
increased with frying time, though, blend shows no noticeable significant different throughout the
total frying time of 12hour with the change in free fatty acid ranges between
3.20 to 4.50%. The maximum percentage changes in free fatty acid
over the temperature range studied were 8.03% and 2.91% which was recorded by
palm oil and shea butter after 12hours of frying circle. Palm oil showed the
most noticeable free fatty acid changes that ranges between 5.72nto 8.03%. This
can be attributed to the polyunsaturated nature of the palm oil which made it
exhibit a greater degree of sensitivity to the moisture released by the fried
cheese. This is in agreement with the findings of Tiwari, Tiwari and Toliwal
(2014) who reported the increase
in Free fatty acid content of palm-sesame and their blend during 9 hours of
deep fat frying of chip. Also, agreed with the findings of Alireza et. al., (2010) who reported an
increase in the free fatty acid content of sesame-canola oil and their blend
during 15hours of deep fat frying sweep potatoes, also similar to the finding
of Sasikan Kupongsak and Wipawan
Kansuwan (2012) who
reported increase in the free fatty acid content of soybean-palm olein and
their blend during 12hours of French fries as a measure decomposition of
glycerides in the oil by lipase or other action and that decomposition is
accelerated by heating time and light.

This result is in contrast with the finding of Akinoso
R et. al., (2011) who reported decrease in free fatty
acid during oil extraction from orange seed with increase in roasting
temperature and duration. Blend shows no noticeable significant difference (P<0.05) throughout the total frying time of 12hour. This is due to slower hydrolytic degradation in the blends, possibly because of alteration of the triacylglycerol composition and reduction in polyunsaturated C18 fatty acids (Aladedunye FA 2015, and Tiwari M, 2014, Ogan M. 2016). Figure 1A shows the results of the kinetic study of the free fatty acid accumulation. It can be seen that free fatty acid concentration increased with time. This was also reflected by the increase in deterioration rate constant k with time, palm oil and blend recorded equal kinetic constant rate of 0.009min-1 while shea butter recorded the lowest value of 0.007min-1, this result shows palm oil and blend deteriorate faster than shea butter. The first-order kinetic model was adequate in describing the free fatty acid accumulation in palm oil, shea butter and blend. This is proven by the values of the regression coefficient R2. The activation energies Ea for the three oil samples were obtained from the non-linear regression of the Arrhenius equation (equation 8). The Ea (kJ/mol) values obtained were 21.85, 32.85 and 30.59 for palm oil, shea butter and blend, respectively. The Ea for palm oil was the most significantly low while shea butter and blend recorded highest Ea value of 32.85kJ/mol and 30.59kJ/mol. These results are in accordance with findings, that hydrolytic reactions that breaks the ester bonds of the TAG requires high activation energy (Laguerre M et al., 2007 Ogan M. 2016). Moisture attacks more readily the ester linkage of short and unsaturated fatty acids because they are more soluble in water than long and saturated fatty acids, releasing free fatty acid, glycerol, di- and mono-acylglycerols. Also, RCO with higher amounts of unsaturated C18 fatty acids is more amenable to hydrolysis (Laguerre M et al., 2007 Ogan M. 2016).

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