Variations in Oil Content and Fatty Acid Composition in the US Castor Bean Germplasm.

As a potential feedstock for biodiesel production, the oil content and fatty acid composition of castor bean seeds may become considering factors for determining the price and quality of biodiesel. Forty-eight castor bean and two soybean accessions were selected from the US germplasm collection and planted in two trials for the experiment. From newly harvested seeds, the oil content was quantified by a cold pressing (CP) method as well as nuclear magnetic resonance (NMR), and the fatty acid composition was analyzed by gas chromatography. The cold press can be used as a quick and preliminary method for screening oil content of castor bean germplasm, but it provides a relatively lower value than NMR. In comparison, castor bean seeds contain a significant higher amount of oil (50.3%) than soybean seeds (23.28%) based on NMR analysis. Significant variation in the oil content (45.35% - 54.89%) was also detected by NMR among castor bean accessions. Castor bean seeds mainly contain ricinoleic acid (86.8%) and much lower amounts of linoleic acid (5.70%), oleic acid (4.05%), palmitic acid (1.25%), and linolenic acid (0.55%) than soybean seeds (49.17% linoleic, 28.89% oleic, 11.26% palmitic, and 6.26% linolenic). Significant variation in ricinoleic acid (83.41%-88.94%), linoleic acid (4.56%-7.33%), and oleic acid (2.62%-6.00%) was detected among castor bean accessions. Significant negative correlations of the ricinoleic acid with other four major fatty acids were detected. Our results indicate that a higher oil content and better fatty acid composition of castor bean seeds when compared to soybean seeds make castor bean a suitable feedstock for biodiesel production. But some practical problems (seed ricin content and harvest problems) need to be resolved before large-scale production can occur.