Survey of polychlorinated dibenzo-p-dioxins (PCDDs), Polychlorinated Dibenzo-p-furans (PCDFs), polychlorinated biphenyls (PCBs), and mineral components in Italian citrus cold-pressed essential oils

Investigation of PCDDs, PCDFs, PCBs, Al, As, Pb, Ba, Co, Cu, Cr, Fe, Mn, Cd, Ag, Sn, Zn, and Hg contents in 60 samples of cold-pressed essential oils produced in Calabria and Sicily in 2003-2005 was carried out. PCDDs, PCDFs, and PCBs were analyzed by HRGC-HRMS techniques using U.S. EPA 1613/94 and U.S. EPA 1668/A (1999) analytical methods. Mineral components were determined through GFAAS techniques; Hg content was determined by FI-M/H-AAS. The results of this study showed that essential oil contamination was due to a widespread pollution, typical background of rural areas, with relatively higher concentrations of PCDDs compared to PCDFs and little presence of PeCDF. Congeners OCDD, HpCDF, and OCDF were found at high concentrations. Regarding mineral components, mean values of Cr, Fe, and Ni were in agreement with data reported in the literature. Concentrations of As and Pb were below the maximum limits accepted by the current legislation. Finally, none of the samples analyzed were contaminated with Hg.     

Characterization of polyphenol oxidase and peroxidase and influence on browning of cold stored strawberry fruit

Polyphenol oxidase and peroxidase were extracted from two different varieties of strawberry fruit (Fragaria x ananassa D, cv. 'Elsanta' and Fragaria vesca L, cv. 'Madame Moutot') and characterized using reliable spectrophotometric methods. In all cases, the enzymes followed Michaelis-Menten kinetics, showing different values of peroxidase kinetics parameters between the two cultivars: Km = 50.68 +/- 2.42 mM ('Elsanta') and 18.18 +/- 8.79 mM ('Madame Moutot') mM and Vmax = 0.14 +/- 0.03 U/g ('Elsanta') and 0.05 +/- 0.01 U/g ('Madame Moutot'). The physiological pH of fruit at the red ripe stage negatively affected the expression of both oxidases, except polyphenol oxidase from 'Madame Moutot' that showed the highest residual activity (68% of the maximum). Peroxidase from both cultivars was much more thermolable as compared with PPO, losing over 60% of relative activity already after 60 min of incubation at 40 degrees C. The POD activation energy was much lower than the PPO activation energy (DeltaE = 97.5 and 57.8 kJ mol-1 for 'Elsanta' and 'Madame Moutot', respectively). Results obtained from d-glucose and d-fructose inhibition tests evidenced a decreasing course of PPO and POD activities from both cultivars as the sugar concentration in the assay medium increased. Changes in CIE L*, a*, b*, chroma, and hue angle values were taken as a browning index of the samples during storage at 4 degrees C. A decrease in L* was evident in both cultivars but more marked in 'Elsanta'. PPO and POD activities from cv. 'Elsanta' were very well-correlated with the parameter L* (r2=0.86 and 0.89, respectively) and hue angle (r2=0.85 and 0.93, respectively). According to these results, the browning of the fruit seemed to be in relation to both oxidase activities.     

Use of natural and modified cyclodextrins as inhibiting agents of peach juice enzymatic browning

Although cyclodextrins (CDs) have been successfully used as antibrowning agents in different fruit juices, no research has studied the effect of these compounds on enzymatic browning in peach juice. In this paper, the color of fresh peach juice was evaluated in the presence of two types of natural (alpha-CD and beta-CD) and a modified (maltosyl-beta-CD) CD, and the effectiveness of these compounds as browning inhibitors was determined using the color space CIELAB system. Moreover, to clarify the mechanism by which CDs inhibit peach juice enzymatic browning, the process was kinetically modeled in the absence and presence of CDs using a colorimetric method; the apparent complexation constants between the mixtures of diphenols present in peach juice and some types of CD were calculated. The results show that the highest affinity constant was presented by alpha-CD (Kc = 18.31 mM-1) followed by maltosyl-beta-CD (Kc = 11.17 mM-1), whereas beta-CD was incapable of inhibiting peach juice enzymatic browning. Keywords: Cyclodextrin; browning; peach; juice; color; polyphenol oxidase.     

Effectiveness of microsatellite DNA markers in checking the identity of protected designation of origin extra virgin olive oil

Collina di Brindisi is an Italian extra virgin olive oil that obtained the mark of protected designation of origin (PDO) according to EC Regulation 2081/92. The varietal requirements of the official production protocol of this oil foresee that this oil is prepared from cultivar Ogliarola (minimum 70%) and other Olea europaea L. cultivars that are diffused in the production area, accounting for a maximum of 30%. The aim of this work was to verify the effectiveness of microsatellite analysis in verifying the identity of Collina di Brindisi PDO olive oil. A preliminary assessment of product's quality by means of chemical analyses was also carried out. Microsatellite analysis clarified that the generic name Ogliarola, indicated in the technical sheet of this PDO oil, actually corresponded to the Ogliarola salentina cultivar. Furthermore, the obtained results showed that the examination of a limited number of DNA microsatellites enables the identification of the Ogliarola salentina cultivar in this PDO oil.     

D-amino acid formation in sterilized alkali-treated olives

The occurrence of d-amino acids in commercial ripe olives, a well-known sterilized alkali-treated product, was investigated by high-performance liquid chromatography (HPLC) with precolumn automatic derivatization. Absolute amounts of D-amino acids were in total 18.6-38.2 mg/100 g edible portion. The major D-amino acids were D-aspartic acid, D-glutamic acid, D-serine, and D-leucine. Furthermore, to evaluate the effects of sterilization time and olive pH on amino acid racemization, a simulated processing of green ripe olives was carried out. Serine (both free and bound form) was the most-racemized amino acid after heat treatment. Sterilization (15-35 min at 121 degrees C) increased the racemization values of both free and protein-bound amino acids, although in case of protein-bound phenylalanine the increase was not statistically significant. With an increase of pH from 8 to 10 units, the racemization values of all amino acids increased significantly, except for free forms of aspartic and glutamic acids. In general, the effects of the sterilization time and olive pH on total concentration (L + D enantiomers) of each amino acid were also significant.     

Phosphine resistance, respiration rate and fitness consequences in stored-product insects

Resistance to fumigants has been frequently reported in insect pests of stored products and is one of the obstacles in controlling these pests. The authors studied phosphine resistance and its physiological basis in adult insects of 12 populations of Tribolium castaneum (Herbst) (Tenebrionidae), ten populations of Rhyzopertha dominica (F.) (Bostrichidae) and eight populations of Oryzaephilus surinamensis L. (Silvanidae) from Brazil, and the possible existence of fitness costs associated with phosphine resistance in the absence of this fumigant. The bioassays for the detection of phosphine resistance followed the FAO standard method. The production of carbon dioxide and the instantaneous rate of population increase (r(i)) of each population of each species were correlated with their resistance ratios at the LC(50). The resistance ratio at LC(50) in T. castaneum ranged from 1.0- to 186.2-fold, in R. dominica from 2.0- to 71.0-fold and in O. surinamensis from 1.9- to 32.2-fold. Ten populations of T. castaneum, nine populations of R. dominica and seven populations of O. surinamensis were resistant to phosphine. In all three species there was significant association (P < 0.05) between respiration rate and phosphine resistance. The populations with lower carbon dioxide production showed a higher resistance ratio, suggesting that the lower respiration rate is the physiological basis of phosphine resistance by reducing the fumigant uptake in the resistant insects. Conversely, populations with higher r(i) showed lower resistance ratios, which could indicate a lower rate of reproduction of the resistant populations compared with susceptible populations. Thus, management strategies based on the interruption of phosphine fumigation may result in reestablishment of susceptibility, and shows good potential for more effective management of phosphine-resistant populations.     

The interspecific variation of plant traits in brassicas engenders stronger aphid suppression than the intraspecific variation of single plant trait

Journal of Pest Science - Increasing either inter- or intraspecific plant diversity has shown the potential to engender bottom-up and top-down effects upon herbivorous pests. Nonetheless, because...