Natural phenolic extracts from herbs and spices, namely Thyme (Thymus. Vulgairs), Marjoram (Origanum majorana) and Fennel (Foeniculum vulgare) were used as source of natural antioxidants to determine the stability refined, bleached and deodorized palm oil during deep of potato chip frying at 180° C for 12 hours .
Results of Total Phenolic Compounds (TPC) indicated that thyme extract have the highest total phenolic compounds represented 265.96 mg/g as Gallic acid in compare with marjoram and fennel extracts which were 194.08 and 52.25 mg/g as Gallic acid respectively.
HPLC results indicated that some major phenolic compounds were fractionated and identified namely Catechien, Caffien and some phenolic acids such as Ferrulic, P-Coumiric, Caffeic , Vanillic , Chlorogenic, Salsylic and Synergic acids.
Free Fatty Acid FFA% , peroxide value (PV) , P.Ansidine (p-A.V., Thiobarbituric acid (TBA), Iodine(IV) Values and Totox Number (TN) were determined. The statistical analysis of indicated a significant differences between untreated and treated palm oil during frying process up to 12 hours.
Results of chemical changes revealed that palm oil treated with thyme and marjoram were more stable than the other oil samples treated with fennel during deep fat frying at 180° C for 12 hours.
Also, significant changes in different chemical parameters were observed between control palm oil and treated oil with different phenolic extracts at the concentrates of 200 and 300 ppm during frying process.
So, Addition of Thyme and Marjoram phenolic extracts to palm oil improved the thermal stability and could extended the frying time in compare with Fennel phenolic extract.