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The aim of this study was to investigate the effects of Zataria multiflora Boiss. and Rosmarinus officinalis L. essential oils (EOs) on oxidative stability of virgin olive oil (VOO). Antioxidant activity indices (peroxide, p-anisidine, K 232 and K 268 values) of EOs were compared with those of BHT and b-carotene. As a result, the lowest peroxide value, p-anisidine value, K 232 and K 268 values were determined in samples containing BHT and Z. multiflora EO. The R. officinalis EO significantly reduced VOO oxidation with an induction period extension of 17.73%. Comparatively, BHT and Z. multiflora EO were more effective in reducing VOO oxidation, with an induction period extension of 63.72 and 48.90%, respectively. The b-carotene exhibited pro-oxidative effects toward primary and secondary oxidation products and reduced the induction period of VOO by 3.29%. It can be concluded that Z. multiflora and R. officinalis EOs can be used to extend the shelf life of VOO. PRACTICAL APPLICATIONSVOO is one of the few oils being consumed without any refining treatment. One of its most important quality problems is oxidative rancidity. Synthetic antioxidants such as BHA and BHT are used extensively to prevent oxidation. However, synthetic antioxidants are not permitted to be incorporated into olive oil. The current study investigated the effect of Zataria multiflora and Rosmarinus officinalis EOs as sources of natural antioxidants on the oxidation of VOO. The present results indicate that Z. multiflora and R. officinalis EOs can serve as natural antioxidants for improving the oxidative stability of VOO.

The objective of this study was to evaluate the effect of Bunium persicum and Rosmarinus officinalis essential oils on the oxidation of virgin olive oil during accelerated storage. The synergistic effect between citric acid and antioxidants of natural and synthetic types was investigated. The B. persicum and R. officinalis essential oils significantly retarded the oxidation of virgin olive oil. Their antioxidant capacity was comparable to butylatedhydroxytoluene and better than β-carotene. Here we show that when natural and synthetic antioxidants are combined with citric acid, they produce an extra antioxidant effect, hence the manifestation of synergy. Generally, the essential oils of B. persicum and R. officinalis can be applied to increase the oxidative stability of virgin olive oil.

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The objective of this research is to analyze the kinetic parameters of linseed oil by treating it with pomegranate peel and seeds at 353, 368, and 383 K using Rancimat. There are no significant differences (p < 0.05) between the oxidative stability indices of samples containing pomegranate peel and pomegranate seeds. In addition, the indices pertaining to the oxidative stability of linseed oil increase in value as the concentrations of pomegranate peel and seeds increase. Apart from the pomegranate peel at 0.1% and the quercetin, all other antioxidants are able to reduce the severity of temperature‐related parameters (i.e., temperature coefficient and Q10 values). In addition, these antioxidants are able to form an activated complex with lower levels of thermal energy (by reducing activation energy and enthalpy) but of more structured configuration (by reducing the frequency factor and entropy). A high correlation is found between the Gibbs free‐energy of activation and the oxidative stability index of samples. The most substantial increase in the Gibbs free‐energy of activation occurs by TBHQ, followed by gallic acid, quercetin, and pomegranate peel at 1%. Practical Applications: Linseed oil is characterized by its high amounts of essential polyunsaturated fatty acids (PUFAs). The high PUFA content of linseed oil contributes to its rapid oxidation. Pomegranate peel and seeds are valuable sources of natural antioxidants. Investigating the effect of pomegranate peel and seeds in reducing the dependence of linseed oil oxidation on temperature provides a range of valuable kinetic parameters. Nevertheless, this subject has received little attention so far. There are few published data regarding the effect of natural antioxidants on lipid oxidation by this approach. Accordingly, this study is designed to investigate the oxidation kinetics and mechanisms of linseed oil as manipulated by fruit peel and seeds of pomegranate. The results show that the fruit peel and seeds of pomegranate can improve the oxidative stability of linseed oil and reduce the severity of effects caused by undesirable temperatures that may increase the oxidation rate of linseed oil.