Variability of Oil Content, Fatty Acid Composition and Karanjin Content in Pongamia pinnata and Its Relationship with Biodiesel Quality

Aims: To study the variability of oil content, fatty acid composition, karanjin and total carotene content in Pongamia pinnata (P. pinnata) and its relationship with biodiesel quality
Place and Duration of Study: Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand, from January 2011 to May 2013.
Methodology: The P. pinnata oil contents were extracted by Soxhlet apparatus and examined for fatty acid composition of the oil using gas chromatography (GC).The saponification number (SN) and iodine value (IV) were determined as described in ASTM D5558 and AOCS official method 1c-85.The cetane number (CN) of each of the FAMEs was estimated from SN and IV values. The karanjin content was determined using HPLC with UV-Vis detector. The total carotene content was determined using spectrophotometer.
Results: The variability of oil content was observed in 45 tree accessions of P. pinnata collected from three provinces in the southern of Thailand. The oil content was varied from 26.65 to 33.12 % (wt). Out of these, the fatty acid profiles of 20 accessions with varying seed oil content were examined. Large variations in the fatty acid content (% wt) were observed in stearic (C18), oleic (C18:1) and linoleic (C18:2) acid with values of 3.88-13.84 % (wt), 37.15-47.42 % (wt) and 16.61-22.23 % (wt), respectively. Less variation in the fatty acid content (% wt) was observed for palmitic (C16), linolenic (C18:3) and behenic (C20) acids with values of 12.82-17.63 % (wt), 0.00-5.88 % (wt) and 6.30-12.87 % (wt), respectively. The saponification number (SN), iodine value (IV) and cetane number (CN) of fatty acid methyl esters or biodiesel of oils varied from 196.81 to 207.69, 61.66 to 90.07 and 52.72 to 59.41, respectively. The fatty acid composition, IV and CN were used to predict the quality of fatty acid methyl esters. The fatty acid methyl esters of oil of P. Pinnata accessions RB3, RS11, RS15 (from Ranong), PK2(from Phungnga) and KB1 (from Krabi) were found to be the most promising (CN > 52.72) as biodiesel. Karanjin varying from 1.26 to 1.49 % (wt) was also found in these five selected samples. The low karanjin content enhances the quality of the biodiesel that support by purity of methyl ester obtained after transesterification.
Conclusion: All P. pinnata produced a high oil content greater than 30 % (wt), with CN>51 and IV<120, thus it meet the specific requirements of international biodiesel standards. The P. pinnata with low karanjin content can be ideal for biodiesel, too.