Rosemary plant (Rosmarinus officinalis L.), solvent extract and essential oil can be used to extend the usage life of hazelnut oil during deep frying

In this study, the effects of rosemary (Rosmarinus officinalis L.) plant (RP), its alcoholic extracts (REE and RME) and essential oil (REO) on the oxidative stability of hazelnut oil (HO) during deep frying were investigated. HOs containing rosemary additives had lower conjugated diene (CD) content, p-anisidine value (AV) and polar material content compared to control values. Additionally, changes in L*, a*, and b* color values and viscosity were lower than control values. RP (50 g/kg) caused the highest retention of alpha-tocopherol. At the end of the frying period, the induction periods (IPs) of HOs containing rosemary additives were between 9.43 and 35.01 min, much higher than the control IP (4.28 min). The ratios of C18:1/C16:0 and C18:2/C16:0 were 7.6 and 1.2, respectively, in HOs containing 50 g/kg RP, values which were higher than those of the control. The study indicated that HO containing 50 g/kg RP had the best frying performance. Rosemary additives had no adverse effects on sensory acceptability according to results of a sensorial analysis of French fries. The rosemary additives also had no significant effect in terms of texture and color of French fries (P>0.05). Consequently, this study shows that rosemary plant or extracts can be used to extend the usage life of hazelnut oil for frying.