Air-steam explosion enhancing the extraction efficiency of chlorogenic acid from leaves of Eucommia ulmoides Oliver

In order to achieve the desirable extraction yield of thermosensitive chlorogenic acid, a novel air-steam explosion with low temperature was developed to pretreat Eucommia ulmoides leaves in this study. The correlation of temperature and different partial pressure of air was investigated, and the pretreatment performance was evaluated by the extraction efficiency and antioxidant capacity of chlorogenic acid. Results showed that the pretreatment temperature obviously decreased with the increase of air partial pressure. Mixed with 0.4 MPa of air partial pressure, the temperature of gas mixture was 26.69% lower than that without air (0.8 MPa of steam). After pretreatment for 120 s, the yield, extraction rate, and OH− and O2− scavenging ratios of chlorogenic acid from air-steam exploded sample were 2.83%, 0.182 min−1, 31.10% and 95.85%, respectively, which were 62.0%, 423.0%, 94.6% and 9.5% higher than those from raw sample. Additionally, the equilibrium time of chlorogenic acid extraction decreased from 120 min to 15 min. The reason for these results were that the fibrous networks and the cell walls of the leaves were destroyed after air-steam explosion pretreatment, which improved the solute-solvent accessibility and the internal mass transfer in extraction process. Therefore, air-steam explosion was an efficient pretreatment to enhance the extraction performance of chlorogenic acid from E. ulmoides leaves.