Recently, the evaluation of antioxidant properties using voltammetric techniques based on electrooxidation has attracted considerable attention. In this study, the antioxidant capacity, total phenolic compounds, and β-carotene content of orange-fleshed fruits and vegetables, including carrots, persimmons, and pumpkins, were evaluated by standard and electrochemical methods. The antioxidant capacity, evaluated by the ABTS and DPPH measurements, and the total phenolic compounds were determined spectrophotometrically. The results were expressed as Trolox equivalent antioxidant capacity (TEAC) and gallic acid, respectively. The β-carotene contents of the samples were determined by high-performance liquid chromatography (HPLC). Electrochemical measurements were performed with differential pulse voltammetry at a sensor formed by attaching single-walled carbon nanotubes onto the glassy carbon electrode surface. Trolox, gallic acid, and β-carotene were determined electrochemically with high sensitivity, repeatability, and low detection limits. Regression analysis was performed to correlate the results of the spectrophotometric assays and HPLC with those obtained electrochemically and satisfactory results were obtained.

This study aimed to investigate the effect of microencapsulation on the bioactive properties of clove essential oil (CEO). The CEO was microencapsulated into various wall materials, including maltodextrin (MD) and sodium caseinate (SC), and their combination with gum arabic (GA) and gelatin (G), through freeze-drying. The effects of wall material blend (MD-SC, MD-SC-GA, and MD-SC-G) on microencapsulation efficiency, morphology, in vitro release profile, antioxidant and antimicrobial properties were investigated. The MD-SC blend offered the best microencapsulation properties in terms of encapsulation efficiency (86.22%), ideal microcapsule shape, and maximum release rate (85.98%). Microencapsulation extended the radical scavenging time of the CEO. DPPH and ABTS scavenging activities of MD-SC microencapsulated CEO were 83.61% and 82.96% inhibition, while values were 76.37% and 80.03% inhibition for free CEO, respectively. Antimicrobial activities of microencapsulated and free CEO were investigated against eight microorganisms with in vitro (broth microdilution technique) and in-situ tests. Both free and CEO-loaded microcapsules were able to inhibit the growth of Gram-positive bacteria, except for Bacillus cereus, at the same concentration. Microencapsulated CEO exhibited weaker antimicrobial activity on Gram-negative bacteria than free CEO. The influence of the pH of fruit juices and components of milk on the antimicrobial activity of microencapsulated CEO was also evaluated. Microencapsulated CEO may have different antimicrobial effects depending on the pH and content of the food. This study showed that microencapsulation of CEO increased the application dose for antimicrobial effect in foods.

The determination of antioxidant capacity, total phenolics, and ascorbic acid using accurate, efficient, low cost, and rapid methods has great analytical importance. The antioxidant capacity, total phenolics, and ascorbic acid content of apricots, arugula, banana, cranberries, spinach, and strawberries were investigated with an electrochemical approach and examined for compatibility with conventional methods. The antioxidant activity was determined by ABTS and DPPH assays. The total phenolic content was determined by the Folin Ciocalteu method and ascorbic acid was quantified by high-performance liquid chromatography (HPLC). In order to perform sensitive and simultaneous electrochemical measurements, the surface of a glassy carbon electrode (GCE) was modified by electropolymerization with p-toluene sulfonic acid (TSA). The TSA/GCE modified sensor was used for the first time for the determination of antioxidant capacity and total phenolic content. The surface of the modified sensor was characterized by cyclic voltammetry and scanning electron microscopy. The TSA/GCE was linearly correlated with the differential pulse voltammetry (DPV) for Trolox and gallic acid in 0.1 M NaNO₃ and ascorbic acid in pH 7.4 phosphate buffer. Electrochemical methods offer a promising alternative for the determination of antioxidant capacity and total phenolic content due to their simplicity, rapid response, low cost, sensitivity, and reproducibility.

The compositional and antioxidant properties of cherry laurel (Prunus laurocerasus L.) fruit, which grow in two different locations (Trabzon and Rize) and altitudes, were investigated. The results were subjected to principal component analysis to better describe the relations between investigated properties and growing conditions. The results indicated that antioxidant activity, total phenolic content, citric acid, sugars and phenolic compounds were affected by location and altitude. While fruits of Trabzon province have higher composition content than those of Rize province, fruits collected at low altitudes in both regions were found to have superior properties. Total phenolic content in fruits from Trabzon and Rize provinces increased from 21.90 to 23.32 and from 16.84 to 18.91 mg gallic acid equivalent / 100 g dry weight (DW), β-carotene increased from 5.19 to 6.75 and from 4.16 to 5.61 mg / kg DW, and total sugar increased from 81.68 to 131.99 and from 86.44 to 99.58 mg / g DW when altitude decrease from 351 to 49 m and 316 to 14 m, respectively. Chlorogenic acid (1404.46-7358.63 mg / kg DW) and rutin hydrate (1491.05-2712.91 mg / kg DW) were major phenolic compounds in all samples.