Effect of Nanofiltration Membrane on Volatile Components in Extraction Solution of Cymbopogon citratus

The effects of different pore sizes nanofiltration membrane on the volatile components and contents of Cymbopogon citratus extract were analyzed, which provided a technical reference for the preparation of natural flavors in Cymbopogon citratus. Five levels of nanofiltration membranes with different pore sizes of 10 kDa, 1 kDa, 500 Da, 300 Da, and 200 Da were used for fine separation of Cymbopogon citratus extract, and gas chromatography-mass spectrometry (GC-MS) was used to analyze the volatile components in the filtrates separated by five kinds of nanofiltration membranes with different pore sizes. The odor activity value (OAV) was calculated and the cluster analysis was carried out. The results showed that a total of 56 volatile components were detected in Cymbopogon citratus extract, and the aroma types of the filtrates separated by different nanofiltration membranes were basically similar. With the decrease of the nanofiltration membrane pore size, the relative content of hydrocarbons, acids and ketones in filtrate decreased, while the relative content of alcohols and aldehydes increased, and the total content of compounds decreased gradually. The content of the same volatile component decreases with the decrease of the pore size of the nanofiltration membrane. By OAV analysis, 18 compounds such as (+)-citronellal, geraniol and citronellol were found to be the key contributors to the characteristic flavor of Cymbopogon citratus extract. The results of sensory similarity evaluation showed that the aroma types of the filtrates separated by different nanofiltration membranes were basically similar and difficult to be distinguished. However, the smaller the pore size of the nanofiltration membrane was, the higher the sensory identification of the filtrate was, and the easier it was to be distinguished. Nanofiltration membrane could effectively reduce the complexity of the flavor substance system of Cymbopogon citratus extract. It was hoped that the research could provide technical support and theoretical reference for the development of stable and practical Cymbopogon citratus essence products.