Thalia Tsiaka | National and Kapodistrian University of Athens (original) (raw)

Papers by Thalia Tsiaka

Research paper thumbnail of Development of a chemiluminescent method for the evaluation of total hydroperoxide content of edible oils

Food Research International, 2013

One of the most important quality indices of edible oils is the total hydroperoxide content expre... more One of the most important quality indices of edible oils is the total hydroperoxide content expressed as peroxide value (PV). Oils with high hydroperoxide content show a degree of oxidation and, hence, lower quality. For these reasons, the development of methods for the evaluation of this quality index of edible oils is required. The aim of the present work is to develop, a rapid, accurate, sensitive, simple and low cost chemiluminescence (CL) method for the determination of the total hydroperoxide content of different kinds of olive oils and other types of edible oils. The CL method proposed is based on the chemiluminescent reaction of alkaline luminol and the hydroperoxides of oil, catalyzed by Fe(III) using 1-propanol as the reaction solvent. Calibration curves of the CL intensity as a function of concentration of di-tert-butyl peroxide, used as an external peroxide standard, and of different types of edible oils were prepared. In all the cases the correlation coefficient (R) of the regression lines was satisfactory (R N 0.996). The precision of the method expressed in terms of repeatability and reproducibility was also satisfactory, as repeatability in terms of mean %RSD was 4.8% and reproducibility in terms of mean %RSD was 8%. The method was applied for the evaluation of total hydroperoxide content of olive oils, corn oils, sunflower oils, sesame oils and soybean oils, within the concentration range of 0.1-9.0%v/v and the obtained results were compared with those of the official method for peroxide value. Finally, the different types of olive oils and seed oils have been classified according to their estimated total hydroperoxide content.

Research paper thumbnail of Response surface methodology toward the optimization of high-energy carotenoid extraction from Aristeus antennatus shrimp

Analytica Chimica Acta, 2015

High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwa... more High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE. Response surface methodology (RSM) is used for the optimization of extraction methodologies, also being applied to optimize high energy techniques. Three independent variables, namely extraction time, ultrasound or microwave power and solvent/material ratio, were investigated for both methods by employing a 16-run three-level Box-Behnken design (BBD). Considering the extraction efficiency for carotenoids from Aristeus antennatus shrimp, the selected conditions for UAE were 5min, 600W and 10:1mLg(-1). Acetone was the solvent of choice for the extraction procedure. For MAE, the best experimental values were 7min, 30W and 20:1mLg(-1) using n-hexane:acetone:ethanol 2:1:1 (v/v/v) as extraction solvent. The determination of total carotenoid yield was carried out using the spectophotometric calibration curve (A=0.1646(±0.0061)C-0.005(±0.022), R(2)=0.996, n=3) of a standard mix solution of canthaxanthin, zeaxanthin and lutein at 452.1nm. Under the selected conditions, the yield of total carotenoids for UAE was 23.4(±2.3) and 6.73(±0.56)mg of carotenoids per 100g dry sample for the head and the body of shrimp, while for MAE was 23.92(±0.63) and 13.3(±1.1)mg of carotenoids per 100g dry sample, respectively. The recovery of both methods was calculated between 60 and 105%. The results indicate that high-energy extraction techniques are faster, less laborious, more repeatable and reproducible methods than the conventional approaches for the quantitative recovery of sensitive bioactive compounds. Moreover, the recovery of a high-added value group of bioactive molecules from natural sources, such as carotenoids, can constitute a profitable and valuable commercial alternative, as these compounds can be used as dietary supplements, food color enhancers and additives in animal feeds, functional foods, preservatives, pharmaceuticals and cosmetics.

Research paper thumbnail of Development of a chemiluminescent method for the evaluation of total hydroperoxide content of edible oils

Food Research International, 2013

One of the most important quality indices of edible oils is the total hydroperoxide content expre... more One of the most important quality indices of edible oils is the total hydroperoxide content expressed as peroxide value (PV). Oils with high hydroperoxide content show a degree of oxidation and, hence, lower quality. For these reasons, the development of methods for the evaluation of this quality index of edible oils is required. The aim of the present work is to develop, a rapid, accurate, sensitive, simple and low cost chemiluminescence (CL) method for the determination of the total hydroperoxide content of different kinds of olive oils and other types of edible oils. The CL method proposed is based on the chemiluminescent reaction of alkaline luminol and the hydroperoxides of oil, catalyzed by Fe(III) using 1-propanol as the reaction solvent. Calibration curves of the CL intensity as a function of concentration of di-tert-butyl peroxide, used as an external peroxide standard, and of different types of edible oils were prepared. In all the cases the correlation coefficient (R) of the regression lines was satisfactory (R N 0.996). The precision of the method expressed in terms of repeatability and reproducibility was also satisfactory, as repeatability in terms of mean %RSD was 4.8% and reproducibility in terms of mean %RSD was 8%. The method was applied for the evaluation of total hydroperoxide content of olive oils, corn oils, sunflower oils, sesame oils and soybean oils, within the concentration range of 0.1-9.0%v/v and the obtained results were compared with those of the official method for peroxide value. Finally, the different types of olive oils and seed oils have been classified according to their estimated total hydroperoxide content.

Research paper thumbnail of Response surface methodology toward the optimization of high-energy carotenoid extraction from Aristeus antennatus shrimp

Analytica Chimica Acta, 2015

High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwa... more High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE. Response surface methodology (RSM) is used for the optimization of extraction methodologies, also being applied to optimize high energy techniques. Three independent variables, namely extraction time, ultrasound or microwave power and solvent/material ratio, were investigated for both methods by employing a 16-run three-level Box-Behnken design (BBD). Considering the extraction efficiency for carotenoids from Aristeus antennatus shrimp, the selected conditions for UAE were 5min, 600W and 10:1mLg(-1). Acetone was the solvent of choice for the extraction procedure. For MAE, the best experimental values were 7min, 30W and 20:1mLg(-1) using n-hexane:acetone:ethanol 2:1:1 (v/v/v) as extraction solvent. The determination of total carotenoid yield was carried out using the spectophotometric calibration curve (A=0.1646(±0.0061)C-0.005(±0.022), R(2)=0.996, n=3) of a standard mix solution of canthaxanthin, zeaxanthin and lutein at 452.1nm. Under the selected conditions, the yield of total carotenoids for UAE was 23.4(±2.3) and 6.73(±0.56)mg of carotenoids per 100g dry sample for the head and the body of shrimp, while for MAE was 23.92(±0.63) and 13.3(±1.1)mg of carotenoids per 100g dry sample, respectively. The recovery of both methods was calculated between 60 and 105%. The results indicate that high-energy extraction techniques are faster, less laborious, more repeatable and reproducible methods than the conventional approaches for the quantitative recovery of sensitive bioactive compounds. Moreover, the recovery of a high-added value group of bioactive molecules from natural sources, such as carotenoids, can constitute a profitable and valuable commercial alternative, as these compounds can be used as dietary supplements, food color enhancers and additives in animal feeds, functional foods, preservatives, pharmaceuticals and cosmetics.