Trace element food toxicology: An old and ever‐growing discipline

Food toxicology (FT) is an old science whose origins may go back to primitive humans. However, due to major environmental damage, daily market launches of new food products, and the analytical ability to detect ever smaller quantities of toxicants in foods, FT is also an ever‐growing science with an enormous task ahead. With respect to trace elements, current research trends can be encompassed under the headings of detection, control, and toxicological evaluation. Under the heading detection, quality, sensitivity, speed, automation, and specificity for each food type are the characteristics currently sought when developing new methodologies. Under control, there is a great need for constant monitoring, on an international level, of the levels of trace elements present in foods; and for development and application of new methodologies to guarantee product and process safety. Under toxicological evaluation, information about the bioavailability of trace elements and consequently studies of the chemical species present in foods have top priority. The work still outstanding in the study of trace element FT is immense, because it is necessary to achieve a profound understanding of the toxicological characteristics of food products in relation to trace elements; to give information to food manufacturers that they can use to adapt their production so that it meets the requirements of international legislation and demands for quality and innocuousness on the part of the market and consumers; and to develop standards regulating the maximum content of trace elements, according to the content of the various species.     

Fish protein hydrolysates from gold carp (Carassius auratus): I. A study of hydrolysis parameters using response surface methodology

The combined effects of pH, temperature (T), substrate/buffer ratio (S:B) and enzyme concentration (E) on protein recovery from gold carp (Carassius auratus) processing waste with Flavourzyme^® were characterised. The effect of hydrolysis parameters on the degree of hydrolysis (DH) was described through response surface analysis (RSA) and the model obtained was defined as follows: DH = ?316.30 + 7.1T + 44.5pH + 0.292S:B + 0.27E ? 0.048T² ? 2.407pH² ? 0.002S:B² ? 0.307TxpH ? 0.002S:BxE. All regression coefficients were significant (α = 0.05). The model showed a good fit with the experimental data, since the R² of 0.923 indicated that 92.3% of the variability within the range of values studied could be explained by the model. The mathematical model presented a plateau region with a maximum DH (>26.6%) at the following critical values: pH = 5.9, T = 53 °C, S:B = 14.7% and E = 80 LAPU (leucine aminopeptidase units) g^?1. Electrophoretic (SDS‐PAGE) patterns showed a progressive reduction in molecular weight of the peptidic fractions from 10 min of hydrolysis onwards. By controlling the enzymatic process, it was possible to predict the molecular weight of the peptides obtained, in turn affecting the functional and nutritional properties of the peptidic fractions. Copyright © 2004 Society of Chemical Industry     

Analysis of trace metal humic acid interactions using counterion condensation theory

Recent extensions of counterion condensation theory, originally developed for well-defined linear polyelectrolytes, enable us to analyze the interaction of trace metals with humic acid. In the present model, the heterogeneity of the macromolecule is taken into account as well as the chemical binding of the considered metal ions to the humic material. Experimentally, potentiometric titrations have been performed for humic acid in solution in the presence of different environmentally important (heavy) metals (Ca, Cd, Cu, Ni, and Pb) at various metal concentrations by titrating with potassium hydroxide without additional salt. From proton release data obtained for the initial point in the titration, it was estimated that the interaction of the different metals with the humic acid in terms of binding strength increased in the order Ca < Cd approximately = Ni < Pb approximately = Cu. These results were confirmed by model analysis. Experimentally obtained apparent dissociation constants were in good agreement for the humic acid systems containing Ca, Cd, and Ni at concentrations ranging from 0 up to 0.75 x 10(-3) mol L(-1) and polymer dissociation degree from about 0.1 up to approximately 0.8. Also for the Cu/humic acid and Pb/humic acid systems, the agreement between experimental data and calculated data was satisfactory atthe lowest metal concentrations over the complete titration curve. For elevated levels of Cu and Pb, the agreement between experimental data and theoretical calculations becomes less satisfactory at low degrees of dissociation of the humic acid. This distortion of the potentiometric curves is probably due to changes in the intrinsic pK of the functional groups due to metal binding. This complex process is not included in present polyelectrolytic models.     

Salt improves physical extraction of olive oil

The use of two concentrations of common salt (0.6 and 1.2%) as coadjuvant for the physical extraction of olive oil has been tested at a laboratory scale and compared with those tests which did not use a coadjuvant or used talc, the only coadjuvant that is allowed according to EC regulations, using the fruits of six different olive varieties (Olea europaea L. cvs. Arbequina, Hojiblanca, Lechín, Manzanilla, Picual, and Verdial). Common salt systematically allowed a higher oil yield than the controlled extraction without coadjuvants, with similar recovery rates to those values obtained when using the more expensive alternative of talc. Physico-chemical quality parameters of the virgin olive oils were not significantly affected by the use of this coadjuvant. However, the levels of oil stability, pigment content or intensity of bitterness were slightly increased. Salt addition seems to be a feasible alternative for the improvement of oil extraction. No appreciable advantages were observed when using the higher concentration of salt tested.     

<Emphasis Type="Italic">Listeria</Emphasis> Inactivation by the Combination of High Hydrostatic Pressure and Lactocin AL705 on Cured-Cooked Pork Loin Slices

The effect of the bacteriocin lactocin AL705 in combination with high hydrostatic pressure (HHP) on the inactivation of Listeria innocua 7, a nonpathogenic indicator for Listeria monocytogenes, deliberately inoculated (ca. 6.4 log CFU/g) onto the surface of ready-to-eat (RTE) sliced cured-cooked pork loin, was evaluated. Nontreated pork slices (control) and treatments subjected to lactocin AL705 (105 AU/ml) and/or HHP (400 or 600 MPa) were prepared. L. innocua 7 was monitored at days 1, 20, and 40 of storage at 4 °C. The results showed a complete inhibition of L. innocua 7 after the combined treatment with lactocin AL705 and 600 MPa and no regrowing of cells up to 40-day storage. The treatment at 600 MPa alone was not enough to avoid regrowth of L. innocua. Ultrastructural cell damage was observed at the cytoplasm and cell membrane/wall levels with all treatments; however, complete cell lysis was observed only with the combined treatment. HHP in combination with lactocin AL705 provided a wider margin of safety as post-processing listericidal treatment of RTE cured-cooked meat products.     

Transport implications resulting from internal redistribution of arsenic and iron within constructed soil aggregates

Soils are an aggregate-based structured media that have a multitude of pore domains resulting in varying degrees of advective and diffusive solute and gas transport. Consequently, a spectrum of biogeochemical processes may function at the aggregate scale that collectively, and coupled with solute transport, determine element cycling in soils and sediments. To explore how the physical structure impacts biogeochemical processes influencing the fate and transport of As, we examined temporal changes in speciation and distribution of As and Fe within constructed aggregates through experimental measurement and reactive transport simulations. Spherical aggregates were made with As(V)-bearing ferrihydrite-coated sand inoculated with Shewanella sp. ANA-3; aerated solute flow around the aggregate was then induced. Despite the aerated aggregate exterior, where As(V) and ferrihydrite persist as the dominant species, anoxia develops within the aggregate interior. As a result, As and Fe redox gradients emerge, and the proportion of As(III) and magnetite increases toward the aggregate interior. Arsenic(III) and Fe(II) produced in the interior migrate toward the aggregated exterior and result in coaccumulation of As and Fe(III) proximal to preferential flow paths as a consequence of oxygenic precipitation. The oxidized rind of aggregates thus serves as a barrier to As release into advecting pore-water, but also leads to be a buildup of this hazardous element at preferential flow boundaries that could be released upon shifting geochemical conditions.     

Inkjet Printed Negative Supercapacitors: Synthesis of Polyaniline‐Based Inks,Doping Agent Effect,and Advanced Electronic Devices Applications

Low frequency negative supercapacitors and high frequency negative capacitors are realized developing a polyaniline (PANI) based ink for piezoelectric inkjet printers, water based. PANI is synthesized by oxidation polymerization starting from the aniline dimer, thus avoiding the use of a toxic/mutagen substance such as aniline. In order to work in aqueous phase, the reverse addition of the dimer in the oxidative solution is made. The chlorinated emeraldine salt of PANI is produced and emeraldine base is prepared by dedoping. Two different doped PANI solutions are produced by solubilization of the emeraldine salt in dimethylsulphoxide and addition of respectively trifluorosulfonic acid and camporsulfonic acid, and then used as inks for the fabrication of inkjet‐printed tracks of different geometries. The properties of inkjet‐printed devices are characterized both in DC and AC regimes, showing very good performances under specific measurement conditions in terms of conductivity, as well as extremely interesting phenomena whose origin is still under debate, such as low frequency negative supercapacitance, high frequency negative capacitance and negative resistance. The realization of the highest negative supercapacitance realized so far, of –2.3 mF @ 30 Hz, corresponding to a specific mass capacity of –799 F g^?1, is reported.     

Post‐Deposition Activation of Latent Hydrogen‐Bonding: A New Paradigm for Enhancing the Performances of Bulk Heterojunction Solar Cells

Small conjugated molecules (SM) are gaining momentum as an alternative to semiconducting polymers for the production of solution‐processed bulk heterojunction (BHJ) solar cells. The major issue with SM‐BHJs is the low carrier mobility due to the scarce control on the phase‐segregation process and consequent lack of preferential percolative pathways for electrons and holes to the extraction electrodes. Here, a new paradigm for fine tuning the phase‐segregation in SM‐BHJs, based on the post‐deposition exploitation of latent hydrogen bonding in binary mixtures of PCBM with suitably functionalized electron donor molecules, is demonstrated. The strategy consist in the chemical protection of the H‐bond forming sites of the donor species with a thermo‐labile functionality whose controlled thermal cleavage leads to the formation of stable, crystalline, phase‐separated molecular aggregates. This approach allows the fine tuning of the nanoscale film connectivity and thereby to simultaneously optimize the generation of geminate carriers at the donor–acceptor interfaces and the extraction of free charges via ordered phase‐separated domains. As a result, the PV efficiency undergoes an over twenty‐fold increase with respect to control devices. This strategy, demonstrated here with mixtures of diketopyrrolopyrrole derivatives with PCBM can be extended to other molecular systems for achieving highly efficient SM‐BHJ solar cells.