Maria Stella Cosio

Evaluation of the antioxidant power of honey, propolis and royal jelly by amperometric flow injection analysis.

In this paper is described the applicability of a flow injection system, operating with an amperometric detector, for measurement in rapid and simple way the antioxidant power of honey, propolis and royal jelly. The proposed method evaluates the reducing power of selected antioxidant compounds and does not require the use of free radicals or oxidants. Twelve honey, 12 propolis and 4 royal jelly samples of different botanical and geographical origin were evaluated by the electrochemical method and the data were compared with those obtained by the DPPH assay. Since a good correlation was found (R(2)=0.92) the proposed electrochemical method can be successfully employed for the direct, rapid and simple monitoring of the antioxidant power of honeybee products. Furthermore, the total phenolic content of samples was determined by the Folin-Ciocalteau procedure and the characteristic antioxidant activities showed a good correlation with phenolics (R(2)=0.96 for propolis and 0.90 for honey).

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.

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.

Sensitive and selective magnetoimmunosensing platform for determination of the food allergen Ara h 1

A highly sensitive disposable amperometric immunosensor based on the use of magnetic beads (MBs) is described for determination of Ara h 1, the major peanut allergen, in only 2h. The approach uses a sandwich configuration involving selective capture and biotinylated detector antibodies and carboxylic acid-modified MBs (HOOC-MBs). The MBs bearing the immunoconjugates are captured by a magnet placed under the surface of a disposable screen-printed carbon electrode (SPCE) and the affinity reactions are monitored amperometrically at -0.20 V (vs a Ag pseudo-reference electrode) in the presence of hydroquinone (HQ) as electron transfer mediator and upon addition of H2O2 as the enzyme substrate. The developed immunosensor exhibits a wide range of linearity between 20.8 and 1000.0 ng mL(-1) Ara h 1, a detection limit of 6.3 ng mL(-1), a great selectivity, a good reproducibility with a RSD of 6.3% for six different immunosensors and a useful lifetime of 25 days. The usefulness of the immunosensor was demonstrated by determining Ara h 1 in different matrices (food extracts and saliva). The results correlated properly with those provided by a commercial ELISA method offering a reliable and promising analytical screening tool in the development of user-friendly devices for on-site determination of Ara h 1.

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.

Electronic Noses and Tongues

Electronic noses (e-noses) and electronic tongues (e-tongues) are sensor array devices that in combination with pattern-recognition systems can give useful information on the quality of food. Their basic principle is inspired by the neurophysiology of the senses of smell and taste. Subsequently, much time and effort are spent on methods that rapidly and automatically can estimate and measure these factors: e-noses and e-tongues offer an additional method. Analysis of multivariate data is also an essential part of these systems. This chapter examines the advances on electronic noses and tongues and their special applications to monitor food quality. In the first part, e-nose is presented and the different apparatus described in detail. In the second part, taste sensors are described in connection to batch and flow design. In the third part, the most common pattern-recognition techniques are briefly introduced. Recent applications of the e-noses and e-tongues in food and beverage are also reviewed.

Organic-phase enzyme biosensor for moisture determination in food products

A novel biosensing scheme for measuring the moisture content of food products is described. The strategy relies on a recently developed organic-phase water biosensor, involving the stimulation by water of the biocatalytic activity of the immobilized tyrosinase in the presence of catechol substrate. The dynamic properties of the water detector were exploited for rapid and reproducible flow injection assays of food products, such as butter, margarine and lyophilized products. The moisture contents found, correlate well with the values obtained by standard official methods. Such a development should facilitate rapid quality control testing in the food industry

Hexanal as biomarker for milk oxidative stress induced by copper ions

Milk flavor varies greatly due to oxidative stress during storage. Several studies have documented the use of volatile biomarkers for determining milk oxidation, but only a few have focused on the development of inline procedures enabling the monitoring of milk oxidative stress. In this work, oxidative stress was induced in pasteurized milk samples by spiking increasing concentrations of copper ions (from 0 to 32 mg·L-1). During storage (4°C), hexanal evolution was monitored by a proton transfer reaction mass spectrometer. The mass fragment m/z 83 was selected as a biomarker for hexanal determination. Its intensity evolved with a sigmoidal trend, showing a maximum rate proportional to the Cu2+ content in milk. The proposed approach is simple, fast (up to 120 sample/h), sensitive (8.8 μg·m-3 per μM hexanal in the sample), with low limit of detection (0.5 μM, determined as 3 times the standard deviation divided by the slope of a calibration line), precise (<6%), with good recovery (99-104%), and noninvasive. The method can be used for laboratory screening of milk susceptibility toward oxidation or for quality control in the processing line.

Development of Food Nanostructures by Electrospinning

In this chapter, a novel technique, named electrospinning, that is increasingly used to develop nano-fibers and nano-membranes that can be used in different areas such as filter media or food processing, is described. Particular attention was devoted to the material and processing parameters that are of paramount importance in developing useful nano-fiber materials. A number of important examples of application of this technology to the food and environmental sectors are reported.