Influence of roasting on the physicochemical properties, chemical composition and antioxidant activities of peanut oil

Roasting before oil extraction improves qualities of vegetable oils. Herein, the physicochemical properties (color, conjugated dienes and trienes), chemical composition (carotenoids, phospholipids, Maillard reaction products, polycyclic aromatic hydrocarbons, 3-monochloropropane-1,2-diol esters, glycidyl fatty acid esters, and oxidized fatty acids), and antioxidant activities of oils extracted from unroasted peanut kernels and roasted ones in dry air (160 degrees C, 170 degrees C, 180 degrees C, and 190 degrees C for 10, 15, 20, 25, and 30 min at each temperature) were systematically investigated and compared. The results indicated that the a* value, carotenoids and antioxidant activities increased significantly (p < 0.05) while the L* and b* values decreased obviously (p < 0.05) with the increase of roasting temperature and time. Conjugated dienes and trienes, oxidized fatty acid, and phospholipids including phosphatidylcholine and phosphatidylethanolamine increased firstly and then decreased during roasting (p < 0.05). Maillard reaction products, polycyclic aromatic hydrocarbons increased significantly (p < 0.05) with roasting. However, roasting had no evident influence on the formation of 3-monochloropropane-1,2-diol esters and glycidyl fatty acid esters. The oils from roasted peanut kernels at 190 degrees C for 30 min had significantly higher oil quality and antioxidant activities.

Automated summary

Increasing roasting temperature and time significantly affect the physicochemical properties and chemical composition of vegetable oils, enhancing their antioxidant activities. Roasting also induces some thermal reactions and the formation of certain pollutants to a certain extent.