Isabella Nicoletti

Chemical and biochemical change of healthy phenolic fractions in winegrape by means of postharvest dehydration.

Clusters of Aleatico winegrape were picked at 18 degrees Brix and placed at 10, 20, or 30 degrees C, 45% relative humidity (RH) and 1.5 m/s of air flow to dehydrate the berries up to 40% of loss of initial fresh weight. Sampling was done at 0, 10, 20, 30, and 40% weight loss (wl). Selected polyphenols and sugar content (expressed as SSC = soluble solids content) both measured on dry weight basis, polyphenol oxidase (PPO), and phenylpropanoid pathway gene expression were analyzed. Phenolic acids increased significantly at 20% wl at 20 degrees C, while at 10 degrees C the increase was lower. Stilbenes (trans-resveratrol and trans-piceid) and catechins rose more than double to 100 mg/kg and more than 3-fold to 135 mg/kg at 20 degrees C and 10% wl. At 10 degrees C the increase of these compounds was less, but higher than initial values. At 30 degrees C, except for a significant rise at 10% wl for catechins and stilbenes, all the rest of the compounds diminished. Anthocyanins increased at 10 and 20 degrees C, but decreased at 30 degrees C. PPO rapidly increased at 20 and 30 degrees C at 10% wl and then declined, while at 10 degrees C the activity lasted longer. Relative gene expression of phenylalanine ammonia lyase (PAL), stilbene synthase (STS), chalcone isomerase (CHI), dihydroflavonol reductase (DFR) were upregulated at 10 degrees C more than at 20 degrees C, at 20% wl, while at 30 degrees C the gene expression was downregulated.

Identification and Quantification of Phenolic Compounds in Grapes by HPLC-PDA-ESI-MS on a Semimicro Separation Scale

Reversed phase high performance liquid chromatography (RP-HPLC) on a semimicro separation scale was employed to develop a straightforward method for the simultaneous separation, identification, and quantification of phenolic compounds occurring in whole berries of Vitis vinifera, which comprise phenolic acids, flavonols, catechins, stilbenes, and anthocyanins. A C-18 narrow bore column of 150 x 2.0 mm I.D. and a semimicro photodiode array detector (PDA) cell of 2.5 microL, in conjunction with a mass spectrometry detector equipped with an electrospray ionization source (ESI-MS) to confirm peak identification, were employed. The C-18 narrow bore column was eluted by a multisegment gradient of increasing concentration of acetonitrile in water-formic acid solution that was optimized on the basis of the results of a study carried out to evaluate the influence of mobile phase composition and gradient shape on separation performance and detection sensitivity by ESI-MS. The identification of individual phenolic compounds was performed on the basis of their retention times and both UV-visible and mass spectra, acquired by a mass spectrometer (MS) equipped with an electrospray ionization (ESI) source, employed in conjunction with the PDA detector. Libraries comprising retention times, UV-visible, and mass spectra for major phenolic compounds expected in grape berries were made by subjecting solutions of each phenolic standard to the optimized RP-HPLC method. Quantification of individual compounds was performed by the external standard method using a six point regression graph of the UV-visible absorption data collected at the wavelength of maximum absorbance of each analyte determined by the PDA spectra. The RP-HPLC method was validated in terms of linearity of calibration graphs, limits of detection, limits of quantification, repeatability, and accuracy, which was evaluated by a recovery study. The developed method was successfully applied to identify the phenolic compounds occurring in the whole berries of nine red and one white grape of different varieties of Vitis vinifera, comprising some autochthonous varieties of south Italy such as Aglianico, Malvasia Nera, Uva di Troia, Negroamaro, Primitivo, and Susumaniello. Large differences in the content of phenolic compounds was found in the investigated grape varieties. As expected, only glycosilated flavonols were quantified, and the total amount of these compounds was higher in the whole berries of red grapes than in the white Moscato, where the most abundant phenolic compound was quercetin 3-O-glucoside. In almost all samples, the most and least abundant anthocyanins were malvidin 3-O-glucoside and cyanidin 3-O-glucoside, respectively, with the exception of Uva di Troia where the least abundant anthocyanin was delphinidin 3-O-glucoside.

Separation of alditols of interest in food products by high-performance anion-exchange chromatography with pulsed amperometric detection

High-performance anion-exchange chromatography (HPAEC)-pulsed amperometric detection (PAD) employing a CarboPac MA 1 column was investigated with respect to mobile phase composition, linear response characteristics, repeatability, reproducibility and sensitivity with different alditols used as sugar substitutes in food and confectionery products. The energy-reduced bulk sweeteners isomalt and maltitol were well resolved in less than 25 min by isocratic elution with 600 mM sodium hydroxide solution. HPAEC-PAD was also successfully applied to the determination of alditols in sugar-free products and a low-calorie sweetener containing sorbitol, mannitol and fructose at different levels.

Maillard reaction in milk-based foods : Nutritional consequences

Chemical reactions occurring during industrial treatments or storage foods can lead to the formation of epsilon-deoxyketosyl compounds, the Amadori products. Food protein value can be adversely affected by these reactions, and in particular lysine, an essential amino acid having on its side chain a free amino group, can be converted to nonbioavailable N-substituted lysine or blocked lysine. by acid hydrolysis of epsilon-deoxyketosyl compounds, furosine is formed. In this paper furosine prepared from milk-based commercial products has been evaluated by use of a recently developed HPLC method using a microbore column and phosphate buffer as the mobile phase at controlled temperature. Furosine levels have been used, together with protein, total amino acids, and lysine content, as an estimate of protein quality of a few different products such as cooked-cream dessert, yogurt mousse, white chocolate, milk chocolate, milk chocolate with a soft nougat and caramel center, milk chocolate with a whipped white center, chocolate spread, part-skim milk tablets, milk-based dietetic meals, and baby foods. The protein content of the analyzed products ranged from 34.3 gxkg(-1) (milk nougat) to 188.4 g x kg(-1) (milk tablets). The Maillard reaction caused a loss in available lysine that varied from 2.5% (cooked cream) to 36.2% (condensed milk). The contribution to the lysine average daily requirement is heavily affected by this reaction and varied from 13% (milk tablets and soft nougat) to 61% (dietetic meal). Variable results were also obtained for the other essential amino acids.

Identification and Quantification of Soluble Free, Soluble Conjugated, and Insoluble Bound Phenolic Acids in Durum Wheat (Triticum turgidum L. var. durum) and Derived Products by RP-HPLC on a Semimicro Separation Scale

A straightforward semimicro separation scale RP-HPLC method was developed for the identification and quantification of phenolic acids (PAs) occurring as soluble free, soluble conjugated, and insoluble bound compounds, which were independently extracted from wholemeal of durum wheat and from its derived products coarse bran, semolina, and dried pasta. A narrow bore column and a semimicro photodiode array detector (PDA) cell, in conjunction with a single quadrupole mass spectrometer, equipped with an electrospray ionization source (ESI-MS), were employed. The method was validated in terms of linearity of calibration graphs, limits of detection, limits of quantification, repeatability, and accuracy, which was evaluated by a recovery study. In each sample (wholemeal, coarse bran, semolina, and dried pasta), the total amounts of the three different forms of PAs were in the order bound > conjugated > free, with bound PAs accounting for 61.0-83.6% of the total PAs. Ferulic acid was the most abundant PA in both soluble free and insoluble bound forms, whereas sinapic acid predominated in the conjugated ones. The highest PA content, calculated as the sum of total PAs quantified in the three forms, was found in coarse bran, followed by wholemeal, semolina, and dried pasta.

Co-electroosmotic capillary electrophoresis of basic proteins with 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids as non-covalent coating agents of the fused-silica capillary and additives of the electrolyte solution

The paper reports the results of a study carried out to evaluate the use of three 1‐alkyl‐3‐methylimidazolium‐based ionic liquids as non‐covalent coating agents for bare fused‐silica capillaries and additives of the electrolyte solutions (BGE) for CE of basic proteins in the co‐EOF separation mode. The three ionic liquids are differentiated from each other by the length of the alkyl group on the imidazolium cation, consisting of either an ethyl, butyl or octyl substituent, whereas tetrafluoroborate is the common anionic component of the ionic liquids. Coating the capillary with the ionic liquid resulted in improved peak shape and protein separation, while the EOF was maintained cathodic. This indicates that each ionic liquid is effective at masking the protein interaction sites on the inner surface of the capillary, also when its adsorption onto the capillary wall has not completely neutralized all the negative charges arising from the ionization of the silanol groups and the ionic liquid is not incorporated into the BGE employed for separation. Using the coated capillaries with BGE containing the ionic liquid employed for the coating, at concentration low enough to maintaining the EOF cathodic, both peak shape and protein separation varied to different extents, based on the particular ionic liquid used and its concentration. Fast and efficient separation of the model basic protein mixture in co‐electroosmotic CE is obtained with the 1‐butyl‐3‐methylimidazolium tetrafluoroborate coated capillary and 100 mM acetate buffer (pH 4.0) containing 4.4 mM 1‐butyl‐3‐methylimidazolium tetrafluoroborate as the BGE.

Influence of electrolyte composition on the electroosmotic flow and electrophoretic mobility of proteins and peptides.

The influence of electrolyte composition on the electroosmotic flow and peptide/protein migration behavior in capillary zone electrophoresis, either with bare fused-silica or polyacrylamide-coated capillaries, has been investigated. The examined electrolyte solutions consist of buffers tailored for controlling the protonic equilibrium over a wide pH range and effective at masking the active adsorption sites of the capillaries for proteins and peptides. Such buffers are composed of the aliphatic oligoamine triethylentetramine (TETA), in combination with either a monoprotic or a polyprotic acid. The drastic variations in the electroosmotic flow and the inhibition of untoward interactions of basic proteins with the capillary wall observed over a wide pH range were associated with the specific adsorption of TETA ions at the interface between the capillary wall and the electrolyte solution. Modifications of the migration behavior of basic proteins and closely related peptides observed using different buffer anions, such as perchlorate, phosphate and citrate, in combination with TETA may be the result of selective interactions of these counter-ions with the analytes.

High-performance thin-layer chromatography on amino-bonded silica gel: application to barbiturates and steroids

Abstract The retention of some barbiturates and steroids on amino-bonded silica gel pre-coated plates was examined by employing high-performance thin-layer chromatography and compared with that on silica gel pre-coated plates, with respect to the pure organic solvent used as the eluents. Aqueous and non-aqueous binary mixtures were also tested as eluents. The retentions on the two types of plates were generally different. For the pure organic solvents, the relative solvent strengh on NH 2 -modified plates did not follow an order resembling that reported for other polar supports, such as alumina. The subdivision of the solvents in several classes, postulated for silica support, may explain some differences in chromatographic behaviour with respect to the eluent and to the compounds examined.

Effects of Genotype and Environment on Phenolic Acids Content and Total Antioxidant Capacity in Durum Wheat

ABSTRACT In cereals, phenolic acid (PA) content and total antioxidant capacity (TAC) may have a wide range of variability, probably because of several factors influencing the occurrence of grain antioxidants, which include genotype, environment, and their possible interactions. However, only a few studies have investigated the influence of these factors on durum wheat. In the present study, we investigated the impact of the genetic and environmental factors on the profile and content of PAs occurring as soluble free, soluble conjugated, and insoluble bound compounds, as well as on the TAC level, in three genotypes of durum wheat grown in three different Italian agroclimatic areas during two crop years. The results show that genotype, environment, and crop year have highly significant effects on TAC levels and on PA contents. In particular, TAC and free PAs are most influenced by year, whereas conjugated and bound PAs are most influenced by environment × year and genotype, respectively. Therefore, it is ev...

Identification and dosage of 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde in beverages by reversed phase chromatography with a microbore column

Abstract This paper reports the results of a study performed to develop a rapid and straightforward chromatographic method for the identification and dosage of 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde (FA), which are recognized indices of deteriorative changes in commercially processed food. The method employs a Supelco microbore reversed phase column (300 × 1.0 mm I.D.), eluted isocratically with a 94:6 (v/v) water/acetonitrile mixture at flow rate of 60 μL/min. Sample is detected at 280 nm in a micro flow cell of 300 nl. Peak purity and identification is assessed by comparing the UV spectra monitored at two points through the chromatographic peak in continuous flow mode in the range from 200 to 400 nm. This method is successfully applied to the identification and quantitative determination of HMF and FA in alcoholic and non-alcoholic beverages by an internal standard method without any sample pretreatment.