Extraction and quality analysis of volatile oils from onions by coupling pilot and laboratory equipment based on multi-rectification

Abstract

A technology based on multi-rectification coupling pilot and laboratory equipment was applied to prepare volatile oils from red or pink onions, which were cultivated in Shandong and Gansu province of China. In the present work, golden yellow, clear and sticky onion volatile oil with the yield of 0.033mL/kg was prepared by rectifying the distillates collected from the pilot device two times in the laboratory device. GC–MS analysis of the onion oils indicated that the content of dipropyl trisulfide was the highest and changed from 10% to 21% with onion types and cultivation areas. Various kinds of sulfides occupied 53–62.1% of the oils. And the content of the sulfide compounds in the dry substances of onions was 0.244–0.306g/kg. Red skin onion from Shandong province of China and red and pink skin onion from Jiuquan, Gansu province of China have the same components, only a minor discrepancy in relative content.