Breaking down castor seed oil content in two meaningful components

Seed oil content is the main quality attribute in castor seed ( Ricinus communis L.) for industrial purpose. As this characteristic has been traditionally measured as one single variable, this article proposes that castor seed oil content could be measured as two independent characteristic: the kernel oil content and the kernel percentage (i.e., the kernel weight in relation to the whole sample weight). The two separate components provide a more precise explanation on the factors influencing castor seed oil content. For instance, the kernel percentage is more influenced by the amount of residues (fruit husk, empty seeds, and contaminants), while the kernel oil content reflects the degree of seed filling and the varietal potential for storing oil. For demonstration, the two components were measured (a) in 14 castor genotypes and (b) in individual kernels sorted by weight. The kernel oil was extracted in Ankon XT15 using petroleum ether as solvent. The seed oil content was estimated from the product of kernel oil content and kernel percentage. Among varieties, the kernel oil content varied from 55.1% to 64.6%, the kernel percentage varied from 67.4% to 79.7%, and the seed oil content was estimated between 40.8% and 48.3%. The highest oil content was not found in the seed with the highest kernel oil content but with the highest kernel percentage. In the study with individual seeds, the kernel oil content was 16.8% in the lightest seeds (66 mg), it increased linearly to reach 64.8% in the seeds weighing 288 mg, and it remained stable in the seeds weighing between 323 and 476 mg (65.8% on average). This article discusses the advantages of measuring the kernel oil content and the kernel percentage separately. Kernel percentage can be a proxy for seed oil content, as it is easier to measure.