Effect of refining process on phenolic compounds and oxidation stabilities in oil-tea camellia seed oil

Abstract: 0This paper is aimed at studying the effect of refining processes on the quality of the camellia seed oil, and understanding the rule of phenols in camellia oil during refining. The camellia oil was sampled in local oil-tea camellia seed oil manufacturer, which was from 3 refining processes including squeezed oil refining process, leached oil refining process and squeezed oil's moderate refining process. The refining processes of squeezed oil included water washing, bleaching, deodorization, and dewaxing, the refining processes of leached oil included alkaline refining, water washing, bleaching, deodorization, and dewaxing, while the moderate refining processes of squeezed oil included degumming, alkaline refining, washing, and dewaxing. The total phenol content (TPC), phenolic compound (PC), oxidation resistance coefficient (AA) and oxidation induction time of these oil samples were detected. The results showed that, the TPC was higher in squeezed oil than that in leached oil, which were 103.06 and 48.52 μg/g, respectively. The TPC was declined by 88.9%, 86.7% and 63.81% after refining processes of squeezed oil, leached oil, and moderate refining processes of squeezed oil, respectively. The AA was declined by 88.3%, 93.51% and 83.25%, respectively in the 3 refining processes. Moderate refining process was better at the retention of TPC and AA in the study than traditional refining processes. The TPC and AA were 37.82 μg/g and 9.33% respectively in moderate refined oil, while 11.41 μg/g and 4.71% respectively in traditional refined oil. The same conclusion was got in the results of PC. There was only a small amount of cinnamic acid that was detected by high-performance liquid phase chromatography (HPLC) in the leached camellia oil after refining, while 3 PCs were detected in the squeezed oil after refining, which included benzoic acid, cinnamic acid and rutin, with the contents of 4.7, 1.58 and 0.22 μg/g, respectively. Nine PCs were detected in squeezed oil after moderate refining process, including tannic acid, chlorogenic acid, catechin, epicatechin, trans-cinnamic acid, rutin hydrate, coumarin, homovanillic acid, gallic acid and o-vanillic acid. The PCs with the highest content in squeezed oil after moderate refining process were tannic acid whose content was 4.57 μg/g and chlorogenic acid whose content was 3.26 μg/g. The oxidation stability of oils could be increased by refining processes. The oxidation induction time of oil before and after the moderate refining process was 8.56 and 11.66 h, respectively, with an increase of 26.63%, while the oxidation induction time of oil before and after the refining process was 8.14 and 10.42 h, respectively, with an increase of 21.83%. The conclusion is that moderate refining process is better at the retention of nutritional ingredients like PC, and the oil from moderate refining process will have higher oxidation stability. The results of the study provide the method of reserving nutrients in the oil-tea camellia seed oil, and the reference for the selection of refining processes and conditions for manufacturer. The correlation of single polyphenol and antioxidant stability of the oil will be studied in the future, and the determination of antioxidant activity will be improved in future research, too.