Résumé
Non-isoprene components and especially lipids have been reported to be involved in some key properties of natural rubber. Unfortunately, these results are hardly comparable due to different extraction methods. This work aimed to optimize lipid extraction from natural rubber either in the liquid state (latex) or in the dry state (unsmoked sheets). Extraction of unsmoked sheets from the RRIM 600 clone was carried out with different combinations of organic solvents (chloroform/methanol and hexane/isopropanol mixes). Chloroform/methanol (2 : 1 vol/vol) was found to be the most suitable for lipid extraction from unsmoked sheet rubber. The lipid extraction yield was improved by increasing the exchange surfaces by grinding rubber under liquid nitrogen and extracting the ground rubber for 6 h at room temperature, leading to 1.82% lipid extraction yield (versus dry rubber). Concerning latex extraction, the problem of lipid entrapment in the coagulum from immediate coagulation of latex in the solvent was solved by preliminary two times dilution of latex, giving a 3.24% extract (versus dry rubber) containing a minimum quantity of contaminating polyisoprene. Concerning the nature of lipids, dilution increased mainly neutral lipid extraction, which may suggest that neutral lipids were those entrapped by coagulation.