effect of sowing date on yield and physicochemical properties of medicinal castor bean plant oil (ricinus communis l.)

castor oil due to extraordinary physicochemical properties has numerous applications in pharmaceutical, chemical, hygienic, biodiesel and nowadays in food industries. during plant growth and development, as well as during postharvest and processing, different factors may affect caster oil properties. this study was conducted to evaluate oil content and physiochemical properties under different sowing dates under climatic conditions of tehran. the highest seed yield (1590.67 kg ha-1) and oil yield (774.43 kg ha-1) were obtained from 5th april sowing date, that had significant difference with other sowing dates. in analyzed samples oil content were (%34.45-49/97), moisture content (%0.97-2.12), refractive index (1.470-1.473), chlorophyll content (0.26-0.40 mg pheophytin/kg oil), acid value (0.28-0.62mg naoh/g oil), peroxide value (0 meq o2/kg oil), soponification value (165.62-181.34 mg koh/g oil) and iodine value (82.43-89.22 g i2/100 g oil). the results revealed significant differences for moisture and chlorophyll content, acid value (p 0.05) in samples for oil content, refractive index, iodine value and peroxide value. results of fatty acid analysis by gas chromatography (gc) showed that fatty acids composition of castor oil was influenced by sowing date, as ricinoleic acid (77.40-80.63%) was known the major oil fatty acid. nevertheless, the highest amount of oil with best quality was obtained from 5th april sowing date.