Saverio Mannino

A New Method for the Evaluation of the ‘Antioxidant Power’ of Wines

Phenols present in wines are responsible for its antioxidant properties. Traditionally the antioxidant power of wines has been measured using in vitro tests principally based on the inhibition of human LDL oxidation and also using the ORAC assay with different reactive species. This work describes a new method to evaluate the antioxidant power of several red and white wines based on a FIA system with electrochemical detection. It represents a significant improvement over other previously reported methods since it is based on the chemical structure of polyphenols and does not require the use of reactive species.

Nanofibrous membrane based tyrosinase-biosensor for the detection of phenolic compounds.

A tyrosinase-modified electrode is described to be used as amperometric biosensor for the detection of phenolic compounds in food. The enzyme has been immobilized by drop-coating on a glassy carbon electrode covered by a polyamidic nanofibrous membrane prepared by electrospinning. With respect to others, the selectivity of the designed tyrosinase-biosensor resulted modified by the presence of the nanostructured coating which seems to affect the permeability of phenols as a function of the pH of the solution and of their dissociation constants. The biosensor exhibits a response time of 16 s, a detection limit of 0.05 microM, and a linearity up to 100 microM (slope: -304 nA microM(-1); intercept: -191 nA, r(2)=0.996, n=19). Among others, it can be successfully used for monitoring in real time the release kinetics of phenols encapsulated in polymeric microcapsules.

Organic-Phase Enzyme Electrode for the Determination of Phenols in Olive Oils

Abstract A rapid procedure for determining phenols in olive oils, based on an organic-phase enzyme electrode, is described. Direct assays are performed in chloroform solutions which support the tyrosinase activity. This class (phenol)-specific enzyme strongly adheres to the surface of the graphite transducer. The resulting wall-jet detector offers effective flow injection operation, with a detection limit of 4×10−7 M (0.8 ng) phenol and sample frequency of 60 h−1. Applicability to olive-oil samples of different origins is illustrated.

Amperometric detection of carbohydrates and thiols by using a glassy carbon electrode coated with Co oxide/multi-wall carbon nanotubes catalytic system.

A glassy carbon electrode coated with cobalt oxide/multi-wall carbon nanotubes (MWCNT) system was used for the detection of carbohydrates and thiols. The modification of the glassy carbon electrode increased the anodic current response of these organic compounds and decreased their overvoltage. The amperometric responses were extremely stable with no loss of sensitivity over many days of storage. Such attractive performance characteristics indicate great promise for using this new catalytic system for monitoring in fast and simple way compounds of great interest for food industry, biotechnology and clinical diagnostics.

Optical nanoprobes based on gold nanoparticles for sugar sensing

A novel optical nanoprobe for sugar sensing is reported. The assay used an electrospun polyamide mesh containing Au salts. The reaction of carbohydrates with these Au salts in alkaline media generates gold nanoparticles (AuNPs) at room temperature without the need for Au seeds. The optical properties of the resulting AuNPs relate to the total reducing sugar content of the samples analysed. The development of such inexpensive disposable optical nanoprobes could find applications in a host of industrial, biomedical and clinical fields.

Silicone-grease-based immobilisation method for the preparation of enzyme electrodes.

An approach to the construction of amperometric biosensors based on the incorporation of an enzyme in silicone grease and using the grease to fill micropores on a graphite surface is described. The enzyme-grease electrode concept, illustrated with the enzyme tyrosinase, offers a very simple, rapid and inexpensive approach to the fabrication of enzyme electrodes. The tyrosinase electrode responds very rapidly to dynamic changes in the concentration of phenolic compounds. A response time (t95%) as low as 5 s has been determined. With flow injection, 120 samples per hour can be processed with a relative standard deviation of 2.4%. The electrode remains active for about 12 d. The detection limit for dopamine is 6 x 10(-6) M. This method of biosensor construction should be applicable to other enzyme-substrate systems.

Encapsulation of volatiles in nanofibrous polysaccharide membranes for humidity-triggered release

A single-step electrospinning process will be applied to a blend of edible carbohydrate polymers (pullulan and β-cyclodextrin) to encapsulate bioactive aroma compounds and allow a humidity-triggered release. The encapsulation is rapid and efficient and the final product is an active nanofibrous membrane that can be directly used for food or active packaging applications. The membrane hosts small and homogeneously dispersed crystals of cyclodextrin-aroma complexes which are formed during the electrospinning. With this type of structure, the release of aroma compound is negligible at ambient conditions (23 °C and 55% UR) even at high temperature (up to 230 °C), and it occurs beyond a given relative humidity threshold (90%), useful for food packaging applications. The mass fraction of free aroma released is directly related to the water activity of the system, namely, φ=aW(n)/(aW(n)+Kapp) explaining the observed key role played by the relative humidity on the release of the aroma compounds.

Application of adsorptive stripping voltammetry to the speciation and determination of iron(III) and total iron in wines

An analytical procedure for the determination of iron(III) and total iron in wines based on adsorptive stripping voltammetry is described. Iron(III) was determined by using Solochrome Violet Red as chelating agent while catechol was used for the determination of the total iron content. Each chelate was adsorbed on the hanging mercury electrode and the reduction current of the accumulated chelate was measured. The results obtained from the application of this procedure to wine samples are discussed.

Determination of Peroxide Value in Vegetable Oils by an Organic-Phase Enzyme Electrode

Abstract An organic-phase biosensor is used for measuring the peroxide value in vegetable oils. Rapid flow injection monitoring of the peroxide value is accomplished by injecting the untreated oil sample directly into a chloroform carrier solution which transports it to the downstream horseradish-peroxidase (HRP) based flow detector. The Eastman AQ polymer is used for entrapping the HRP onto the detector surface. The new scheme offers convenient monitoring of low level peroxide values and high selectivity (accrued from the biospecificity of HRP towards peroxide species and from the low operating potential). The biosensor results are consistent with those obtained by the official iodometric method. Such development should facilitate quality control testing of oil products.

Polymer Composites Containing Gated Mesoporous Materials for On-Command Controlled Release

Polyamidic nanofibrous membranes containing gated silica mesoporous particles, acting as carriers, are described as novel hybrid composite materials for encapsulation and on-command delivery of garlic extracts. The carrier system consists of MCM-41 solids functionalized in the outer surface, with linear polyamines (solid P1) and with hydrolyzed starch (solid P2), both acting as molecular gates. Those particles were adsorbed on electospun nylon-6 nanofibrous membranes yielding to composite materials M1 and M2. FE-SEM analysis confirmed the presence of particles incorporated on the nylon nanofibers. The release of the entrapped molecules (garlic extract) from the P1, P2, M1, and M2 materials was evaluated using cyclic voltammetry measurements. Electrochemical studies showed that at acidic pH P1 and M1 were unable to release their entrapped cargo (closed gate), whereas at neutral pH both materials release their loading (open gate). Dealing with P2 and M2 materials, in the absence of pancreatin a negligible release is observed (closed gate), whereas in the presence of enzyme the load is freely to diffuse to the solution. These newly developed composite nanomaterials, provide a homogeneous easy-to-handle system with controlled delivery and bioactive-protective features, having potential applications on pharmacology, medical and engineering fields.