Search

BACKGROUND Applications of chemical and enzymatic methods of esterification have been limited by low selectivity of chemical catalysts and low productivity and high cost of enzymes. The objective of this study was to produce eugenol esters with high productivity and selectivity using a microwave technique without adding any catalyst or solvent. Specific focus was given to reaction temperature and molar ratio to establish the kinetics and mechanism of eugenol auto‐catalytic acylation using microwave radiation. RESULTS: Reaction conversion was observed to increase in response to higher temperatures. The optimum molar ratio of eugenyl/acetic anhydride was 1:6, while the optimum molar ratio of eugenyl/butyric anhydride was 1:4.5. A high degree of selectivity (of over 97%) occurred under all conditions of the reaction. Based on modelling studies, it can be concluded that the intended reaction follows second‐order kinetics for both eugenyl acetate and eugenyl butyrate. Microwave heating at 70 °C led to an increase of rate constant by 3.71‐ and 3.83‐fold for eugenyl acetate and eugenyl butyrate, respectively, as compared to the conventional method. This was associated with a decrease in the activation energy (4.38% for eugenyl acetate and 3.11% for eugenyl butyrate) and an increase in the frequency factor (42.31% for eugenyl acetate and 49.84% for eugenyl butyrate) and entropy (4.71% for eugenyl acetate and 5.22% for eugenyl butyrate) as a result of using microwave radiation. CONCLUSIONS: The microwave technique can be considered as a green, low‐cost and quick process for auto‐catalytic production of eugenol esters. © 2020 Society of Chemical Industry (SCI) [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the antioxidant activity of different concentrations (250, 500 and 750 ppm) of Ocimum sanctum essential oil incorporated into soybean oil. The effect of O. sanctum essential oil at 250 ppm was similar to that of BHA on inhibiting oxidation in the soybean oil, but higher concentrations of essential oil (500 and 750 ppm) showed higher protection against oxidation in comparison with that of BHA. The influence of O. sanctum essential oil on stabilizing the soybean oil was more profound at 45 °C in comparison with 60 °C. In addition, the O. sanctum essential oil was significantly effective in protecting polyunsaturated fatty acids of soybean oil during storage at both temperatures of 45 and 60 °C. Generally, the O. sanctum essential oil can be introduced as a suitable natural antioxidant that can replace synthetic antioxidants. [ABSTRACT FROM AUTHOR]

Background and Objectives: Virgin olive oil is a vastly consumed product, with widespread appreciation for its good nutritional and health properties. However, oxidation can reduce its quality. The aim of this study was to investigate how the essential oil of Zataria multiflora (Shirazi thyme) can contribute to the prevention of virgin olive oil oxidation in comparison with the actions of α-tocopherol and BHT. Furthermore, the synergistic activities of citric acid with BHT, Z. multiflora essential oil, and α-tocopherol were investigated. Materials and Methods: Antioxidant activity of the essential oil was determined using radical scavenging capacity and reducing power assays. Virgin olive oil samples were stored at 60±1 °C in closed amber bottles for 16 days. Oxidation levels of samples were determined by measuring peroxide, anisidine, TOTOX, K232, K268 values, and chlorophyll and carotenoid contents of the samples during the storage period. Results: Z. multiflora essential oil exhibited a significant radical scavenging capacity and reducing power. Peroxide, anisidine, TOTOX, K232, and K268 values of samples containing Z. multiflora essential oil were significantly lower than those of the control group (without antioxidants). Z. multiflora essential oil reduced the oxidation of virgin olive oil to the same extent as BHT did. Z. multiflora essential oil was more effective than α-tocopherol. The synergistic activities between citric acid and the various compounds, i.e. BHT, Z. multiflora essential oil, and α-tocopherol were 2.42%, 4.74%, 1.28% respectively. Conclusions: In general, Z. multiflora essential oil can be considered as natural antioxidant for the stabilization of virgin olive oil against oxidation. [ABSTRACT FROM AUTHOR]

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, K232 and K268 values) of EOs were compared with those of BHT and β-carotene. As a result, the lowest peroxide value, p-anisidine value, K232 and K268 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 β-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 Applications VOO 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the antioxidant mechanism of action of fucoidan in sunflower oil and its oil-in-water emulsion. In addition, the effect of lecithin on the antioxidant mechanism of action of fucoidan in sunflower oil was investigated. In sunflower oil, fucoidan at 0.02 % (w/w) concentration showed the highest induction period (591.02 h), while in sunflower oil-in-water emulsion, fucoidan at 0.04 % (w/w) concentration showed the highest induction period (141.57 h). In addition, the induction period of sunflower oil samples containing fucoidan with lecithin was higher than those without lecithin. Evaluating the mechanism of action of fucoidan in sunflower oil and its oil-in-water emulsion indicated that fucoidan took part in the initiation chain's side reactions and the major termination reaction. The interfacial tensions of samples containing lecithin were significantly lower than those without lecithin. In addition, the reverse micelle size of samples containing lecithin was considerably lower than those without lecithin. Therefore, lecithin enhanced fucoidan's effectiveness by decreasing interfacial activity and increasing the capacity to incorporate lipid hydroperoxides within the structure of reverse micelles. The water produced during oxidation played an essential role in the antioxidant potency of fucoidan. Taken together, lecithin significantly enhanced the antioxidant activity of fucoidan by improving its interfacial activity in sunflower oil., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This research aimed to investigate and compare the effect of bath and horn ultrasound-assisted bleaching of sunflower oilon the degradation of tocopherols and sterols, production of volatile substances, and oxidation indices, including thiobarbituric acid (TBA) and peroxide value (PV) and with that of the industrial bleaching process. Ultrasonic bath and ultrasonic horn bleaching techniques reduced sunflower oil's total tocopherol and total sterol contents to a greater extent than conventional bleaching techniques. While bath and horn sonication operated theoretically equivalent power settings, power meter measurements demonstrated that the bath sonicator delivered significantly less power than the horn sonicator. Among the ultrasonic bleaching techniques, the ultrasonic bath at 400 W showed the lowest reduction in total tocopherols,sterols and volatile compounds compared to the ultrasonic horn technique at the same theoritical power. Moreover, Despite the 800 W bath sonicator having significantly higher nominal power than the 400 W horn sonicator, the horn sonicator was considerably more effective at degrading bioactive compounds. Higher degradation of bioactive compounds coincided with increasing patterns in primary and secondary oxidation indices and volatile compounds in horn compared to bath and industrial bleaching due to the direct effect of ultrasonic horn and free radical formations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)