New electroanalytical method for the determination of trans-anethole in spices and sweets.

A completely new method for the determination of trans-anethole (TAN) based on the anodic oxidation of this flavouring substance in pure acetonitrile using differential-pulse voltammetry has been developed. A nonaqueous carbon paste electrode bulk-modified with solid sodium dodecyl sulphate of 40 % (w/w) content was chosen as optimum. To propose TAN electrode reaction mechanism, its electrochemical behaviour was investigated at glassy carbon electrode in nonaqueous media. At optimum working conditions, the current response could be calibrated within a linear range 2-200 µmolL-1 TAN, a coefficient of determination of 0.9971, a sensitivity of 0.1122µALµmol-1, and a detection limit of 0.7 µmolL-1. A satisfactory precision (relative standard deviation of 4 %) has been achieved. The validation performed by analysis of spices and sweets provided comparable results with reference reverse-phase HPLC with spectrophotometric detection, thus confirming the practical use of the developed voltammetric method in food analysis.

The Effect of Vibratory Grinding Time on Moisture Sorption, Particle Size Distribution, and Phenolic Bioaccessibility of Carob Powder.

Carob pod powder, an excellent source of health-promoting substances, has found its use in a wide range of food products. Grinding conditions affect the physical and chemical properties of the powder, but their influence on the bioaccessibility of phenolic compounds in carob pod powder has not yet been determined. The carob pods were ground for 30-180 s in a vibratory grinder. The median values (D50) of particle size decreased after 60 s of grinding (87.9 µm), then increased to 135.1 µm. Lightness showed a negative correlation with D50 and aw, while the values of redness and yellowness decreased with the reduction in particle size and water activity. The smaller the value of D50, the higher the equilibrium moisture content of carob powder. Phenolic acids (vanillic, ferulic, cinnamic) and flavonoids (luteolin, naringenin, apigenin) were found in all samples of carob powder. The grinding time influenced their content in carob powder, with maximum values at 180 s. Similar observations were made when assessing antioxidant capacity. The in vitro digestion process only improved the bioaccessibility of catechin content in all samples. However, the bioaccessibility of the phenolic compounds and the total phenolic and flavonoid contents decreased with the increase in grinding time. Our findings revealed that the grinding of carob pods for 180 s improved the extractability of phenolics; however, their bioaccessibility was reduced. It is sufficient to ground the carob pod for 30 s, ensuring good availability of nutraceuticals and lower energy cost for grinding.

Bioaccessibility of phenolics from carob (Ceratonia siliqua L.) pod powder prepared by cryogenic and vibratory grinding.

Carob pod powder prepared by cryogenic (CG) and vibratory grinding for 4 min (VG-4) and 8 min (VG-8) was evaluated for its antioxidant properties, and phenolic content. The bioaccessibility of phenolics was determined after the oral, gastric, and intestinal digestion phases in vitro. CG carob powder had a higher total phenolic content (6.46 mg gallic acid/g) and antioxidant capacities in terms of DPPH (15.60 mg Trolox/g) and ABTS (28.58 mg Trolox/g) assays. Quercitrin (44.54-64.68 µg/g) and cinnamic acid (27.48-31.40 µg/g) were the most abundant phenolics in all carob powder samples determined by liquid chromatography. The bioaccessibility of only ferulic acid (108%) had increased after digestion of the CG carob powder. Vibratory grinding (VG-4 and VG-8) improved the bioaccessibility of cinnamic acid (86-87%), vanillic acid (87-95%), quercitrin (33-34%), and naringenin (19-22%). A better bioaccessibility of phenolic constituents was observed for vibratory ground carob powder.

Flow Injection Amperometric Evaluation of Trolox Equivalent Antioxidant Capacity of Chocolates with Different Cocoa Content at a Boron-Doped Diamond Electrode.

RESEARCH BACKGROUND: The objective of this paper is to introduce an instrumentally simple analytical tool for determination of cocoa solid content in chocolates. This electroanalytical method is based on amperometric oxidation of all present antioxidants in chocolates at boron-doped diamond electrode (BDDE) that is integrated in a flow injection analysis (FIA) wall-jet electrode system. EXPERIMENTAL APPROACH: As part of optimisation, thirteen commonly occurring antioxidants were investigated using cyclic voltammetry at the BDDE in 0.1 mol/L phosphate buffer with different methanol (MeOH) content. Working parameters, such as MeOH volume fraction, flow rate and detection potential, were optimised. Principally, the height of the oxidation peak (current response) representing the oxidation of the sum of antioxidants (total antioxidant content; TAC) was expressed as Trolox equivalents. RESULTS AND CONCLUSIONS: For analytical purpose, a linear range from 5 to 100 mg/L described by regression equation and characterised by high correlation coefficient R2=0.9994 was achieved. Obtained high positive correlation between the determined values of Trolox equivalent antioxidant capacity (TEAC) and cocoa mass fractions characterised by correlation coefficient of 0.9187 for eight randomly selected samples (one white, two milk, and five dark chocolates) confirmed that cocoa solids represent the main source of antioxidants (reducing agents). NOVELTY AND SCIENTIFIC CONTRIBUTION: The research demonstrates that TEAC values could be considered as an additional marker of cocoa content in the chocolate analysis to the commonly used theobromine (authenticity of food products). The developed FIA could therefore serve as simple analytical tool in the food quality control.

Rapid monitoring of fungicide fenhexamid residues in selected berries and wine grapes by square-wave voltammetry at carbon-based electrodes.

A completely new electroanalytical method for the determination of fenhexamid (FNX) residues in fruit samples has been developed. This method is based on anodic oxidation of fungicide in Britton-Robinson buffer (pH 4) containing 10% (v/v) methanol using square-wave voltammetry when five different carbon-based electrodes were tested. An electrochemical behaviour of FNX was studied on a glassy carbon electrode using cyclic voltammetry, while glassy carbon paste electrode was selected for analytical purposes. Linear range for FNX from 3.96 to 49.50 µmol L-1 characterized by coefficient of determination of 0.9964, sensitivity of 0.176 µA L µmol-1, and detection limit of 1.32 µmol L-1 were calculated. Results acquired from analyses of blueberries and wine grapes were compared to those obtained by a reference chromatographic method, and a satisfactory agreement has been reached. Finally, it seems that the present voltammetric approach could find its application in food quality control as screening assay.