Abstract
In the frame of African artisanal small-scale extraction of palm oil, the effects of post-harvest storage time and freezing of palm fruits on the extraction yield and quality of crude palm oil (CPO) were studied at laboratory scale using a process mimicking artisanal extraction. The extraction yield and free fatty acid (FFA) content of CPO increased with the length of fruit storage time at room temperature and freezing. FFA, total fatty acid and triacylglycerol profiles indicated a lack of specificity of the lipases at work. During post-harvest storage, the carotenoid content of CPO decreased slightly, tocopherols and tocotrienols (tocols) remained steady, while lipid oxidation remained at a very low level. For frozen fruits, carotene and tocol contents decreased sharply as a function of storage time, thought remaining quite high, but decreasing amounts of secondary oxidation products were detected. The FFA content and lipid oxidation level were highly correlated, indicating a pro-oxidant effect of FFAs. To conclude, three days of storage prior to artisanal extraction seemed the best trade-off between extraction yield and CPO quality. Combined storage at room temperature and freezing of palm fruits led to a large range of FFA contents in CPO. Optimization of the FFA contents of artisanal CPOs in line with local consumer’s demand calls for an assessment of their functional properties and sensory perception of foods formulated with CPOs.
Highlights
Palm oil is extracted from the mesocarp of the oil palm fruit (Elaeis guineensis Jacq.)
The following variables were assessed throughout the present study: extraction yield and free fatty acid (FFA) content for samples for crude palm oil (CPO) from sets 1 and 2, composition of the FFA fraction, total fatty acid composition, triacylglycerol composition, tocopherol and tocotrienol composition and contents, carotene content, peroxide value, anisidine value and TOTOX for the CPOs from set 2 (Fig. 1)
As the fruits used for the second set of experiments were stored for 4 months in a frozen state, ice crystal growth during frozen storage could have caused further damage to the palm fruit cells and further enhanced the differences in extraction yields recorded between frozen and unfrozen fruits
Summary
Palm oil is extracted from the mesocarp of the oil palm fruit (Elaeis guineensis Jacq.). The FFA content is involved in the typical sensory properties of CPOs and CPO consumer preferences, as long as it is not too high (Cheyns et al, 2006; Poku, 2002) They have FFA contents higher than requested by international standards, artisanal crude palm oils are in line with local consumer standards for many recipes. It would be relevant to guarantee the nutritional quality and safety of CPOs containing high levels of FFA, but which meets consumer’s expectations This will mean being able to produce in the laboratory palm oils with a wide range of FFAs to further test their functionalities and acceptability for consumers. The incidence of post-harvest treatments on the activity and specificity of lipases was investigated
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