Arda Serpen

Phenolic Compounds, Carotenoids, Anthocyanins, and Antioxidant Capacity of Colored Maize (Zea mays L.) Kernels

In this study, the contents of total phenolics, flavonoids, anthocyanins, β-carotene, and lutein as well as free, conjugated, and insoluble bound phenolic acids were determined in whole kernels of 10 different colored maize genotypes. In addition, the antioxidant activity was evaluated as radical scavenging activity with ABTS (2,2-azino-bis/3-ethil-benothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) reagents. Generally, considerable differences in phytochemical contents and antioxidant capacity were observed between the genotypes. The β-carotene and lutein contents ranged from 0 to 2.42 mg/kg d.m. and from 0 to 13.89 mg/kg d.m., respectively, whereas the total anthocyanin contents of anthocyanin-rich colored maize genotypes ranged from 2.50 to 696.07 mg CGE/kg d.m. (cyanidin 3-glucoside equivalent) with cyanidin 3-glucoside (Cy-3-Glu) as the most dominant form. The light blue ZPP-2 selfed maize genotype has a higher content of total phenolics, flavonoids, and ferulic acid as compared to other tested maize and the highest ABTS radical scavenging activity.

Equilibrium and kinetic studies on the adsorption of dark colored compounds from apple juice using adsorbent resin

Abstract The kinetics of adsorption of dark colored compounds on adsorbent resin were studied at different adsorbent resin concentrations (1, 2, 4, 8 g adsorbent resin per liter of apple juice) for the temperature range of 20–80 °C. For equilibrium adsorption curves; the Langmuir and Freundlich models were attempted and model parameters (Kad, Q0, Kf and n) were obtained for different temperatures. The adsorption data of dark colored compounds present in apple juice onto macro porous adsorbent resin fitted well both to Langmuir and Freundlich models. Heat of adsorption (ΔH) value of 10.567 kJ/mol indicated the endothermic nature of the adsorption process. A decrease of Gibbs free energy (ΔG) with increasing temperature also indicated the spontaneous nature of the process. The adsorption and desorption rate constants were determined separately by applying a geometric approach to the Langmuir model. The adsorption rate constants (ka) varied from 0.0093 to 0.1103 min −1 , and the desorption rate constants (kd) from 0.0050 to 0.0285 min −1 at different temperatures and adsorbent resin concentrations. The activation energy of adsorption (Ea) averaged as 21.2±4.2 kJ/mol, and that of desorption (Ed) as 10.1±3.3 kJ/mol.

Total antioxidant capacities of raw and cooked meats

This study investigated the total antioxidant capacity (TAC) of meats (beef, chicken, pork and fish) and its changes on thermal treatment. The QUENCHER procedure, which is performed directly on the solid material without extraction, was selected and proved to be particularly suitable for meat samples. The ABTS(+) scavenging capacity of raw meats ranged between 25.9±1.0 and 51.7±1.2 mmol Trolox Eq./kg. Raw chicken had the highest TAC followed by pork, beef and fish. Upon heating at 180°C, TAC of meats increased to an apparent maximum at 5 min followed by sudden decreases until 15 min, while the final stage of heating was characterized by slight increases. The modifications of TAC during cooking can be explained considering factors such as denaturation and exposure of reactive protein sites, degradation of endogenous antioxidants and the formation of Maillard reaction products having antioxidant properties.

Phytochemical quantification and total antioxidant capacities of emmer (Triticum dicoccon Schrank) and einkorn (Triticum monococcum L.) wheat landraces.

In this study, samples of 18 ancient wheat (12 emmer, 6 einkorn) and 2 bread wheat varieties grown in different regions of Turkey were examined for their total phenolics and flavonoids, phenolic acids, lutein, total yellow pigment, and total radical scavenging capacities against ABTS cation. Results showed that health beneficial phytochemicals and total antioxidant capacities were generally significantly different in emmer and einkorn wheat groups. Remarkably higher total antioxidant activity (18.31 +/- 1.31 micromol Trolox equiv/g), total phenolics (6.33 +/- 0.98 micromol gallic acid equiv/g), ferulic acid (662.95 +/- 61.07 microg/g), and flavonoids (1.61 +/- 0.34 micromol catechin equiv/g) content were detected in emmer wheat samples (n = 12), suggesting that they may have high potential for utilization as a novel grain, rich in natural antioxidants. In addition, quite high levels of lutein (7.33 +/- 2.43 microg/g) of einkorn samples (n = 6) hold the potential of developing high-lutein bakery products to considerably raise the dietary intake of carotenoids. These findings for ancient wheat varieties are considered to be very useful in breeding programs for selecting and breeding wheat varieties for higher concentration and better composition of health-beneficial phytochemicals.

Effects of extrusion, infrared and microwave processing on Maillard reaction products and phenolic compounds in soybean

BACKGROUND The Maillard reaction indicators furosine, hydroxymethylfurfural (HMF), acrylamide and color were determined to evaluate heat effects induced during extrusion, infrared and microwave heating of soybean. In addition, the present paper aimed to study changes in the phenolic compounds, as well as in the overall antioxidant properties of different soybean products in relation to heating at 45-140 °C during the processes. RESULTS Soybean proteins were highly sensible to Maillard reaction and furosine was rapidly formed under slight heating conditions during extrusion and infrared heating. Microwave heating at lower temperatures for a longer time yielded lower acrylamide levels in the final soybean products, as a result of its partial degradation. However, during infrared heating, acrylamide formation greatly increased with decreasing moisture content. After a short time of extrusion and infrared heating at 140 °C and microwave heating at 135 °C for 5 min, concentrations of HMF increased to 11.34, 26.21 and 34.97 µg g(-1), respectively. CONCLUSION The heating conditions caused formation of acrylamide, HMF and furosine in high concentration. The results indicate that the complex structure of soybeans provides protection of phenolic compounds from thermal degradation, and that Maillard reaction products improved the antioxidant properties of heat-treated soybean.

Nutritional and functional characteristics of seven grades of black tea produced in Turkey.

Seven grades of black tea [high-quality black tea (grades 1-3) and low-quality black tea (grades 4-7)], processed by ÇAYKUR Tea Processing Plant (Rize, Turkey), were examined for their proximate composition, dietary fiber, minerals, and water-soluble vitamins as well as total phenolic content, various antioxidant assays, phenolics (flavanols, alkoloids, condensed phenolics, and phenolic acids), chlorophylls, and carotenoids. Some variations, albeit to different extents, were observed (p < 0.05) among these parameters in seven grades of black tea. With respect to proximate composition, dietary fiber was the predominant compound (ranging from 49.68 to 54.31 g/100 g), followed by protein, carbohydrate, and, to a lesser extent, ash, moisture, and fat. Thirteen minerals, four water-soluble vitamins, six flavanols, two alkoloids, three condensed phenolics, one phenolic acid, two chlorophylls, and two carotenoids were identified in the seven grades of black tea. Total phenol content ranged from 7.52 to 8.29 g of gallic acid equivalents (GAE)/100 g, being lowest in grade 6 and highest in grade 1. With regard to antioxidant activities, a large variation in oxygen radical absorbance capacity (ORAC) values was observed among all grades of black tea (ranging from 777 μmol of trolox equivalents (TE)/g in grade 7 to 1210 μmol of TE/g in grade 3). The present work suggests that high- and low-quality black teas should not be distinguished on the basis of their nutritional and functional characteristics. The combination of nutritional compounds together with functional characteristics renders combination effects that provide the characteristic quality of each grade of black tea.

A Practical Spectrophotometric Approach for the Determination of Lipoxygenase Activity of Durum Wheat

ABSTRACTIn this study, a practical spectrophotometric approach was used to determine the hydroperoxidation activity of durum wheat lipoxygenase (LOX). As stated in the related literature, the buffered linoleic acid solution used as the reaction medium is not optically clear enough at neutral and lower pH values due to its limited solubility. In our study, the optical clarity was obtained by the formation of sodium-salt of unreacted linoleic acid just before absorbance measurement. The durum wheat LOX was characterized in terms of pH and temperature optima as well as kinetic parameters. The maximum linoleic acid hydroperoxidation activities were determined at pH 5.0 and 6.5 and at 40°C This result can be considered as evidence for the presence of at least two LOX isoforms with respective optima at pH 5.0 and 6.5 in the crude durum wheat extract. The Michaelis constant (Km) and maximum hydroperoxidation) activity rate (Vmax) of durum wheat LOX for linoleic acid were estimated) to be 0.131 ± 0.019 mM and 42....