Optimization of Thyme Volatiles Retention by Refined Corn Oil Using Response Surface Methodology

Response surface methodology was used to optimize thyme volatiles retention by refined corn oil. The effects of two parameters namely mixing time and thyme flowers quantity, on volatiles retention in corn oil, were studied. Essential oil (EO) composition of thyme flowers and flavoured oil volatile compounds were analyzed by GC-MS. The fitted mathematical model allowed us to plot response surfaces as well as isoresponse curves and to determine optimal retention conditions. Thyme flowers EO was dominated by phenol fraction (67.30 %). Monoterpene hydrocarbons attained 28.23 % and carvacrol was the main component constituting 67 % of thyme EO followed by -terpinene (7.83 %) and p-cymene (5.88 %). Thus, three responses were studied: terpinene, p-cymene and carvacrol retention by refined corn oil. Flavoured oil major volatiles were p-cymene (0.060 0.341 mg/ml), -thujene (0.042 0.306 mg/ml) and -terpinene (0.011 0.202 mg/ml). The carvacrol was one of the minor volatile compounds of the flavoured oil ranging from 0.001 mg/ml to 0, 020 mg/ml. Results clearly indicated that flowers quantity was the main factor influencing the -terpinene, p-cymene and carvacrol retention by refined corn oil. The selected optimal conditions were: Flowers quantity 5 g and mixing time 25 min. In these optimal conditions -terpinene, p-cymene and carvacrol yields can reach about 0.202 mg/ml, 0.341 mg/ml and 0.020 mg/ml, respectively. Oil enriched with thyme volatiles may have more biological activities and increased oxidative stability then refined one.