Study On The Drying Kinetics And Bioactivity Of Chill Pepper(capsicum Annuum L.)

This study investigated the influence of infrared drying(IRD), hot air drying(HAD) and sun drying(SD) on drying characteristics and quality of dried red pepper, evaluated the degradation kinetics of main bioactive compounds in red pepper during process of both IRD and HAD, and further discussed the antioxidant activity and antibacterial activity of capsaicinoids. The purpose of current study was to provide a scientific evidence for the improvement of the drying efficiency and product’s quality of red pepper, for the control of bioactive substances during drying process and for the application of capsaicinoids which was one of the most important bioactive substances in red pepper. The main contents and conclusions could be summarized as follows:1. The drying kinetics of IRD, HAD and SD were studied, respectively. The results showed that the IRD technology significantly enchanced the drying efficient when compared with HAD and SD for the IRD shortened the drying time from 4800 min(via SD) and 780 min(via HAD, 70℃) to 510 min(70℃/1350 W /120mm), saving drying time by 34.6% compared with HAD(70℃). On the other hand, temperature was the most important factor affecting the moisture transfer during the process of IRD as well as HAD, whereas infrared radiation and distance between infrared emitters and samples surface showed no significant effect. Page model proved to be most suitable to describe the IRD and HAD processes of red pepper with R2 in the range of 0.9954~0.9989 and χ2 in the range of 0.0001~0.0005.2. The influence of drying methods on quality of dried red pepper was investigated. Results showed that IRD efficiently improved the quality of dried red pepper, and temperature was the most remarkable factor influencing the product quality whereas infrared radiation and distance between infrared emitters and samples surface showed no significant effect. The △E values of infrared dried and hot air dried red pepper were significantly high while the relatively high crispness values of 9~11 peaks were observed among the infrared dried samples. IRD was beneficial for the retention of capsaicinoids. The two drying technologies, IRD and HAD, showed no significant difference on total phenolic, carotenoids and antioxidant capacity of red pepper.3. The degradation kinetics of total phenolic, capsaicinoids and antioxidant capacity during the processes of both IRD and HAD were analysed. Results showed that the fractional conversion kinetic model proved to be suitable to fit the degradation processes. High temperature and infrared radiation(1350 W) accelerated the degradation rate of both total phenolic and capsaicinoids. The moisture content in red pepper was thought to be influential to the changes of total phenolic. In addition, the content of total phenolic exhibited significant correlation with antioxidant capacity of red pepper extract measured by DPPH, ABTS and FRAP, respectively(p<0.01).4. The antioxidant capacity and antibacterial activity of capsaicinoids were evaluated, respectively. Results indicated that both capsaicin and dihydrocapsaicin were antioxidative. On the other hand, both capsaicin and dihydrocapsaicin could inhibit the growth of microorganism and the inhibitory effect of them was equivalent with each other, stronger against bacteria than fungi.