The purpose of this paper was to evaluate the quality of bee honey from different sources: beekeeper, local market and organic honey. Sensory analysis was performed and the water content, pH, acidity, protein content and total metal content (Cu, Cr, Mn, Co, Ni, Pb, Cd, Fe) were determined. The sensory analysis was carried out by a group of untrained panelists for quality assessment of honey. The metal content was determined by graphite atomic absorption spectrometry (GTAAS). Mineralization was carried out in a microwave digestion system, in a high-pressure polytetrafluoroethylene (PTFE) vessel, using a standard acid-digestion protocol. The results regarding the physico-chemical parameters showed that the honey samples were in accordance with the quality regulations for honey as a commercial product. The concentration of metals in the investigated honey samples varied in the order Cu > Cr > Pb > Fe > Ni > Mn > Co > Cd, the values being within the limits established by the EU Commission (No. 1881/2006). The variations observed in the evaluated parameters can be caused by the difference in plant species from which the honey comes, the harvesting period and the level of environmental pollutants. The Pearson correlations between the physico-chemical parameters and the metals indicate that water content (w_c) is strongly negatively correlated with Cd and Ni, while pH is strongly positively correlated with Mn and Fe. Moreover, EC is strongly negatively correlated with Ni and Fe, and the Brix degrees are strongly positively correlated with Cd and Ni. Statistically significant positive correlation was found between Brix–Cd, Ni–Cd and Cu–Cr and a statistically significant negative correlation was detected between w_c and Cd.

A simple, fast and sensitive high-performance liquid chromatography/electrospray ionization-mass spectrometry method is described and validated in terms of linearity, accuracy/recovery and reproducibility, as well as limit of detection for the determination of ascorbic acid from grape (Vitis vinifera L.) samples from Murfatlar vineyard. Good linearity (correlation factor > 0.9970) was achieved in the concentration range 0.5–15 μg mL⁻¹ for AA in acetic acid 0.1% solution. The obtained RSD values (below 5%) indicated excellent repeatability of the proposed method. The limit of detection was 0.32 μg mL⁻¹ while the recovery ranged between 96.86 and 102.41%. The advantages of the method are: small amounts of sample and solvents, short analysis time and minimum steps for sample preparation.

Vitamin C or ascorbic acid is a basic nutrient, a highly effective antioxidant, widely used as food additive. Therefore, quality control in food industry demands ascorbic acid determination methods. The purpose of this study was to determine vitamin C in natural orange juices by spectrometric and voltammetric methods. Another goal was to determine the kinetic and thermodynamics activation parameters for ascorbic acid degradation in orange juices over time and at different temperatures. It was observed that during storage, ascorbic acid concentrations in orange juices were gradually decreased with time at a rate depending on storage temperature and type of orange juice. The reaction order was determined through integrated graphical analysis where the dependences of ln c_t/c₀ as a function of time reveals the high values for R², indicating that the kinetics of the degradation of AA follows first order reaction at both studied temperatures. For studied samples the loss of ascorbic acid was varied between 4.33% and 9.13%. Enthalpy variation (ΔH) and entropy variation (ΔS) of activation process were obtained from the Eyring–Polany model based on transition state theory. The values of activation energy ranged between 7289.24 kJmol⁻¹ and 15689.54 kJmol⁻¹.

The objective of the present work was to adapt the Prussian Blue reaction for the determination of ascorbic acid. The procedure was successfully applied for the determination of ascorbic acid in red and white grapes (Vitis vinifera L.) just previous ingathering. In the present work was used the red and white grapes from Murfatlar vineyard: Mamaia, Cabernet Sauvignon, Merlot, Pinot Noir, Chardonnay, Sauvignon, Muscat Ottonel and Riesling Italian. The results were situated in the range of 0.67 - 1.79 mg vitamin C/100g product for red grapes and respectively 0.50 - 1.49 mg vitamin C/100g for white grapes.