Three newly formed pigments were detected and isolated from a 2-year-old Port wine through TSK Toyopearl HW-40(S) gel column chromatography and characterized by UV-visible spectrophotometry, NMR, and mass spectrometry (ESI/MS). (1)H NMR and (13)C NMR data for these pigments obtained using 1D and 2D NMR techniques (COSY, NOESY, gHSQC, and gHMBC) are reported for the first time. The structure of the pigments was found to correspond to the vinyl cycloadducts of malvidin 3-coumaroylglucoside bearing either a procyanidin dimer or a flavanol monomer ((+)-catechin or (-)-epicatechin). Additionally, conformational analysis was performed for one of these newly formed pigment using computer-assisted model building and molecular mechanics. A chemical nomenclature is proposed to unambiguously name this new family of anthocyanin-derived pigments.

An HPLC/DAD methodology for separating 13 phenolic compounds is described. This methodology is applied to the definition of qualitative and quantitative profiles of quince, pear, and apple purees and a blending of these purees. Two different extraction methods were needed for the complete definition of their profiles, one of them including an Amberlite XAD-2 cleaning step. The analysis of phenolics of each fruit puree profile and that of a blending seems to indicate that this methodology can be applied to the detection of apple and/or pear fraudulently added to quince puree. The presence of apple can be detected by phloretin 2‘-xylosylglucoside and phloretin 2‘-glucoside, while that of pear is detected by arbutin. In addition, 3-O-caffeoylquinic acid is present at a considerable relative amount (∼23.4%) in quince puree, while the sample of pear puree contains only 8.2%; this compound is absent in apple puree. Keywords: HPLC; phenolics; quince; purees; adulteration

The spectral characteristics and stability of three red wine pigments (pyranoMv-catechin, pyranoMv-epicatechin, and pyranoMv-dimer B3) toward pH variation and bisulfite bleaching, as well as their color stability and degradation during storage, have been studied. Unlike the absorbance spectra of most wine pigments, the intensity of which is more increased in more acidic conditions, oligomeric pyranoMv-flavanols have maximum absorbance at wine pH around 3.6, up to 30-50% higher than that in pH 1.0. This particular hyperchromic effect shown in mildly acidic solutions suggests the presence of intramolecular copigmentation in the molecule of pyranoanthocyanin-flavanols, giving rise to higher molar extinction coefficients around wine pH and contributing to the overall wine color. The most probable conformations were determined by computer-assisted model building and molecular mechanics. Besides exceptional stability toward pH variations, pyranoanthocyanin-flavanols were also shown to be entirely resistant to bleaching by sulfur dioxide. During a 6 month storage period, pyranoanthocyanin-flavanols were much more stable against degradation than the anthocyanin with the following order: pyranoMv-catechin > pyranoMv-dimer B3 > pyranoMv-epicatechin > carboxy-pyranoMv ≫ Mv. Kinetic decomposition monitored by high-performance liquid chromatography-diode array detection-mass spectrometry revealed the formation of a new pigment (pyranone-Mv structure) and the cleavage of the interflavanic linkage of procyanidin dimer in the solutions containing carboxy-pyranoMv and pyranoMv-dimer B3, respectively. Despite some degree of decline of these oligomeric pyranoanthocyanins, their color intensity was surprisingly enhanced, and their color stability greatly improved throughout the entire storage period, thus contributing significantly as long-lived orange-red pigments to the maintenance of aged wine color.

Maize is an important worldwide commodity susceptible to fungal contamination in the field, at harvest, and during storage. This work aimed to determine the occurrence of Fusarium spp. in maize grains produced in the Tagus Valley region of Portugal and the levels of related mycotoxins in the 2018 harvest and during their storage for six months in barrels, mimicking silos conditions. Continuous monitoring of temperature, CO2, and relative humidity levels were done, as well as the concentration of mycotoxins were evaluated and correlated with the presence of Fusarium spp. F. verticillioides was identified as the predominant Fusarium species. Zearalenone, deoxynivalenol and toxin T2 were not found at harvest and after storage. Maize grains showed some variability in the levels of fumonisins (Fum B1 and Fum B2). At the harvest, fumonisin B1 ranged from 1297 to 2037 µg/kg, and fumonisin B2 ranged from 411 to 618 µg/kg. Fumonisins showed a tendency to increase (20 to 40%) during six months of storage. Although a correlation between the levels of fumonisins and the monitoring parameters was not established, CO2 levels may be used to predict fungal activity during storage. The composition of the fungal population during storage may predict the incidence of mycotoxins.

No abstract

No abstract

Anthocyanins are responsible for an interesting variety of colors in flowers, red fruits, and plant-derived foodstuffs. Experimental evidence is presented supporting an unusual color change from red to blue during storage. It has been investigated as a function of temperature at constant pH (pH <2). The color properties of the vinylpyranoanthocyanin pigments, usually designated portisins, have been studied in this work using both experimental and theoretical techniques. The visible spectra obtained from the two approaches were in good agreement. This behavior was explained by a reversible physical-chemical change due to electronic and vibrational properties.

ABSTRACT:In this work, the partition method introduced by Melo and Ramos has been extended to enable the decomposition of the stabilization energies associated with molecular association processes into physical meaningful components (conformational rearrangement, nonbonding, bonding, and polarization plus charge transfer). This partition scheme, within a semiempirical formalism, enables a complete separability of the above-mentioned components. The molecular system has also been partitioned into perturbed and bulk regions, defined as flexible variable-size entities. This procedure enables one to evaluate the range of the perturbation originated by an association process. Several association processes (covalent and noncovalent) have been studied using this methodology. The results obtained enable us to conclude that the current decomposition scheme can be used for understanding the cohesive phenomena.