Characterisation of Ricinodendron heudelotii kernel oil composition and oxidation dynamics

Details

Supervisors

Yvan Larondelle

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

Ricinodendron heudelotii is a wild tree native to sub-Saharan Africa, which produces valuable kernels, known as “njansang” in Cameroon, rich in oil. R. heudelotii kernel oil (RHO) is characterised by a high content of conjugated linolenic acids (CLnAs), mainly in the form of α-eleostearic acid (α-ESA). CLnAs are conjugated polyunsaturated fatty acids with promising health benefits, in particular a strong anti-tumoral effect. In this respect, R. heudelotii kernels might be regarded as a novel source of CLnAs and exploited as a potential cancer preventive agent. However, the particular CLnA-rich composition of R. heudelotii kernels makes them extremely prone to oxidation. This sensitivity is not considered during the post-harvest treatments of R. heudelotii kernels, including the traditional dehulling process of the R. heudelotii seeds in Africa. This present work represents a first step in addressing the challenges of RHO oxidation and was divided into three main objectives. For the first objective, RHO has been characterised and compared between oxidised and non-oxidised RHO. R. heudelotii kernels were directly dehulled using an innovative nutcracker, which allowed to provide fresh, non-oxidised kernels and subsequently, nonoxidised RHO. The latter was compared with oxidised RHO obtained from market kernels. In oxidised RHO, the content of α-ESA was lower, while β-ESA and catalpic acid contents were higher than in fresh RHO. For the second objective, the oxidation dynamics and the stabilisation of RHO have been investigated in an accelerated ageing test at 30°C for 80 days. The experiment demonstrated that RHO was highly sensitive to oxidation due to its high content in CLnAs. This sensitivity was drastically reduced after the addition of green tea extract and Phytrox as natural antioxidants to RHO. For the last objective, the impact of the traditional processing of R. heudelotii seeds on RHO oxidation was assessed. This processing was reproduced and showed to have a strong impact on RHO oxidative status. Specifically, the drying step of the kernels under UV light was observed to be the most oxidising step of the traditional processing. As a short-term perspective, this step could be improved by drying the kernels in absence of light. Taken as a whole, the results obtained throughout this master’s thesis contribute to the body of knowledge on R. heudelotii, which is at present, still rudimentary and not rigorous. Improving this knowledge will add value to R. heudelotii, and lead to substantial improvements in the production chain, from domestication of the species to concrete applications in sub-Saharan Africa.