Crosslinked Recombinant-Ara h 1 Catalyzed by Microbial Transglutaminase: Preparation, Structural Characterization and Allergic Assessment.
As the one of the major allergens in peanut, the allergenicity of Ara h 1 is influenced by its intrinsic structure, which can be modified by different processing. However, molecular information in this modification has not been clarified to date. Here, we detected the influence of microbial transglutaminase (MTG) catalyzed cross-linking on the recombinant peanut protein Ara h 1 (rAra h 1). Electrophoresis and spectroscopic methods were used to analysis the structural changes. The immunoreactivity alterations were characterized by enzyme linked immunosorbent assay (ELISA), immunoblotting and degranulation test. Structural features of cross-linked rAra h 1 varied at different reaction stages. Hydrogen bonds and disulfide bonds were the main molecular forces in polymers induced by heating and reducing. In MTG-catalyzed cross-linking, ε-(γ-glutamyl) lysine isopeptide bonds were formed, thus inducing a relatively stable structure in polymers. MTG catalyzed cross-linking could modestly but significantly reduce the immunoreactivity of rAra h 1. Decreased content of conserved secondary structures led to a loss of protection of linear epitopes. Besides, the reduced surface hydrophobic index and increased steric hindrance of rAra h 1 made it more difficult to bind with antibodies, thus hindering the subsequent allergic reaction.
Impact of Almond Variety on “Amaretti” Cookies as Assessed through Image Features Modeling, Physical Chemical Measures and Sensory Analyses.
In the present study, the influence of almond variety on color, chemical, physical and sensory characteristics of "amaretti" cookies during the shelf life, was assessed. Four varieties were chosen for the study, two of which were local (Cossu, Arrubia) and two widely cultivated (Tuono, Texas). Almonds have been characterized in the content of proteins, crude fat, amygdalin and fatty acids profile. The evolution of the characteristics during the shelf life hasbeen measured through image data modeling, texture, physical chemical and sensory analyses. Data were then treated with a multivariate approach performing a PCA. Image analysis and fitting on log normal and powerlaw functions highlighted the influence of the variety on the total area affected by surface breakages, and on the distribution of the cracking surfaces dimension classes. Texture parameters (crust hardness, thickness and work of deformation) were negatively correlated to moisture content. Sensory profile confirmed the differences in tactile features measured through instrumental texture, while slight to no differences were found in odor profile. Consumer test showed an higher acceptability for Arrubia, Texas and Tuono samples throughout the shelf life, while Cossu samples were less accepted. Overall, the choice of almond variety influences product features and liking of almond products, therefore it represents an important phase to direct the choice of both farmers and confectionery manufacturers.
Prediction of Walnut Deterioration Using Kernel Oxidative Stability.
Monitoring walnut oxidation is essential to control walnut quality during storage. An accelerated oxidation method for differentiating the oxidative stability index (OSI) of walnut kernels was examined and the effects of instrument operational parameters such as temperature and airflow were evaluated. Four cultivars, Chandler, Solano, Durham, and Howard were analyzed at 110, 120, and 130 °C with 15, 20, and 25 L h-1 airflow. Analysis using 110 °C with 25 L h-1 yielded the lowest coefficients of variance (4.4) than other operational parameters; analysis using the same temperature at lower airflow, 15 L h-1, yield the highest coefficient of variance (10.5). Kernel OSI values were independent of airflow, however, dependence of temperature coefficient and Q10 were demonstrated. The results from selected parameters were correlated with fat and moisture content, peroxide value, UV absorbances, oil oxidative stability, hexanal, and rancidity to establish the relationships between OSI values and quality changes during storage. Using 0.5 g of ground kernels, at 110 °C with 25 L h-1 airflow gave a lower coefficient of variance and higher correlation with kernel quality and oxidative markers comparing to other combinations of operating parameters.
Phage Displayed Domain Antibodies (dAb) for Detection of Allergenic Pistachio Proteins in Foods.
Pistachio nuts (Pistacia vera) have been consumed by past and present-day civilizations because of their organoleptic characteristics and potential health benefits. However, they can also produce moderate to severe IgE-mediated reactions in allergic individuals. In this work, we report the isolation of the first recombinant antibodies against pistachio nut, produced without animal immunization, to be used in immunoassays for detection of allergenic pistachio in food products. Several phage display biopanning strategies were evaluated to screen the human-based domain antibody library (dAb) in search for pistachio-specific probes. The clone producing the PVF4 phage-dAb was finally selected, and it does not cross-react with cashew despite the phylogenetic proximity with pistachio. Western blot and matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-TOF/TOF) analysis demonstrated that this clone recognised a unique band of ∼22 kDa related to the basic subunit of pistachio 11S globulin (allergen Pis v 2). The PVF4 phage-dAb allowed detection of pistachio in a food matrix with a limit of detection (LOD) of 3983 mg kg-1 in an indirect phage-enzyme-linked immunosorbent assay (ELISA). The ELISA method developed was used to assess applicability of the PVF4 phage-dAb for analysis of 77 commercial food products.
Effect of Different Method of Drying of Five Varieties Grapes (Vitis vinifera, L.) on the Bunch Stem on Physicochemical, Microbiological, and Sensory Quality.
The influence of the drying technique on certain quality attributes of dried grapes was analysed. Five varieties of grape were used in this study (Bezsemenné, Perlette, Vrboska, Beauty seedless, and Jakubské). All the varieties were dried using four methods: drying at 40 °C, combined drying (70, 65, and 60 °C), drying at 70 °C, and lyophilisation. The quality attributes such as total soluble solids, water activity, content of vitamin C, the colour parameters (L*, a*, b*), and microbiological (colony forming units, moulds, yeasts) and sensory (smoothness, gloss, colour, odour, chewability, juiciness, flavour, and overall impression) analysis were determined, depending on the method of drying. Lyophilised grapes from the Jakubské variety had the highest vitamin C content. They contained 0.58 mg of vitamin C per 100 g of dried grapes. However, no significant differences between varieties in vitamin C content were found. This confirmed concerns about the negative impact on the nutritional quality of dried grapes with increasing temperature. The lowest total count of microorganisms (CFU), moulds, and yeasts were determined after using highest drying temperature (70 °C). Higher CFU values were determined in lyophilised grapes, and then followed by grapes dried at 40 °C. Lyophilised grapes and grapes dried at 40 °C achieved the best sensory rating in general. The final product was intended to have a unique appearance while maintaining the evaluated quality parameters.
Physicochemical and Antioxidant Properties of Wheat Bread Enriched with Hazelnuts and Walnuts.
The aim of this study was to evaluate the effect of wheat bread enrichment using hazelnuts and walnuts (1%, 3%, 6%, 9%) on the nutritional value and selected physicochemical and antioxidant properties. The dough and bread yield, volume, specific volume and porosity were also determined. The crumb texture was analyzed by texture profile analysis (TPA) test using a texture meter. The color of the crumb was assessed in the CIE L*a*b* color space. Antioxidant properties were determined by the ABTS+ radical method. The contents of phenolic acids, flavonoids and total polyphenols were also determined. The test demonstrated that the enrichment of bread with nuts increased the level of minerals, protein, fiber and fat. Breads containing walnuts were characterized by the highest content of these nutrients. The bread with a 9% walnut content by the smallest volume (380 cm3) had lowest value of L*. The crumb of the enriched breads was characterized by greater hardness, gumminess and chewiness, the values of these parameters generally increasing in parallel to the nut content. Breads enriched with walnuts were characterized by a higher average total content of polyphenols (35.77 mg gallic acid equivalent (GAE)/100 g dry mass (DM)) compared to the breads enriched with walnuts (25.35 mg GAE/100 g DM).
Sesame, Pistachio, and Macadamia Nut: Development and Validation of New Allergenic Systems for Fast Real-Time PCR Application.
Food allergy is a worldwide health problem that concerns infants to adults. The main health risk for sensitised individuals is due to the presence of traces of allergens as the result of an accidental contamination during food processing. The labelling of allergens such as sesame, pistachio, and macadamia nut on food products is mandatory according to Regulation (EU) N. 1169/2011; therefore, the development of suitable and specific analytical methodologies is advisable. The aim of this study was to perform a multi-allergen real-time PCR system that works well in fast mode at the same annealing temperature and with the same thermal profile. The real-time PCR was developed designing new, specific, and efficient primer and probe systems for the 2S albumingene for sesame and pistachio and for the vicilin precursorgene for macadamia nut. These systems were subjected to a robust intra-laboratory qualitative validation process prior to their application, by DNA extraction and fast real-time PCR, on some real market samples to reproduce a potential allergen contamination along the food chain. The developed system results were specific and robust, with a sensible limit of detection (0.005% for sesame; 0.004% for pistachio; 0.006% for macadamia nut). The performance and the reliability of the target systems were confirmed on commercial food samples. This molecular approach could be used as a screening or as a support tool, in association with the other widespread monitoring techniques (such as ELISA).
Biologically Active Compounds in Selected Organic and Conventionally Produced Dried Fruits.
A growing demand for organic foods is driven by consumers' perception that they are more nutritious. However, while there is a number of scientific studies showing some superior qualities of organically grown fruit and vegetables, including, i.e., higher content of phenolics, some vitamins and antioxidant activity, scientific research looking into the quality of processed organic products is very limited. At the same time the consumption of processed, convenient foods, with a long shelf-life, is rapidly increasing all over the world. Among the processed fruit-based products, dried fruits are recognized by consumers as one of the best snacks, highly nutritious and containing a large amount of fibre. In the presented experiment, four types of organic and conventionally produced dried fruits were examined: Apricots, apple rings, cranberries, and prunes. The concentrations of polyphenols (in all products) and carotenoids (in apricots) were measured using high performance liquid chromatography (HPLC). The study confirms that dry fruits can be undoubtedly considered as a rich source of polyphenols, however, a large variation in the concentrations of these compounds among different brands of products was also pointed: 219.03 ± 3.90-296.96 ± 2.86 mg 100 g-1 in dried apricots, 95.24 ± 15.12-627.71 ± 48.64 mg 100 g-1 in dried apple rings, 14.64 ± 0.43-203.09 ± 7.96 mg 100 g-1 in dried cranberries, and 134.65 ± 12.27-422.44 ± 9.00 mg 100 g-1 in prunes. Carotenoids concentrations in dried apricots ranged from 2.72 ± 0.31 to 17.49 ± 0.17 µg g-1. Among the tested dried fruits, only in the case of apricots organic products were characterized by the higher contents of phenolics and carotenoids compared to the conventional brands. In the case of other products there was either no consistent significant production system effect, or the concentrations of the analyzed phenolic compounds were higher in conventional products.
Non-Targeted Detection of Adulterants in Almond Powder Using Spectroscopic Techniques Combined with Chemometrics.
Methods that combine targeted techniques and chemometrics for analyzing food authenticity can only facilitate the detection of predefined or known adulterants, while unknown adulterants cannot be detected using such methods. Therefore, the non-targeted detection of adulterants in food products is currently in great demand. In this study, FT-IR and FT-NIR spectroscopic techniques were used in combination with non-targeted chemometric approaches, such as one-class partial least squares (OCPLS) and data-driven soft independent modeling of class analogy (DD-SIMCA), to detect adulterants in almond powder adulterated with apricot and peanut powders. The reflectance spectra of 100 pure almond powder samples from two different varieties (50 each) were collected to develop a calibration model based on each spectroscopic technique; each model was then evaluated for four independent sets of two varieties of almond powder samples adulterated with different concentrations of apricot and peanut powders. Classification using both techniques was highly sensitive, the OCPLS approach yielded 90-100% accuracy in different varieties of samples with both spectroscopic techniques, and the DD-SIMCA approach achieved the highest accuracy of 100% when used in combination with FT-IR in all validation sets. Moreover, DD-SIMCA, combined with FT-NIR, achieved a detection accuracy between 91% and 100% for the different validation sets and the misclassified samples belong to the 5% and 7% adulteration sets. These results suggest that spectroscopic techniques, combined with one-class classifiers, can be used effectively in the high-throughput screening of potential adulterants in almond powder.
Interaction of Monocyte-Derived Dendritic Cells with Ara h 2 from Raw and Roasted Peanuts.
Ara h 2 is a relevant peanut allergen linked to severe allergic reactions. The interaction of Ara h 2 with components of the sensitization phase of food allergy (e.g., dendritic cells) has not been investigated, and could be key to understanding the allergenic potential of this allergen. In this study, we aimed to analyze such interactions and the possible mechanism involved. Ara h 2 was purified from two forms of peanut, raw and roasted, and labeled with a fluorescent dye. Human monocyte-derived dendritic cells (MDDCs) were obtained, and experiments of Ara h 2 internalization by MDDCs were carried out. The role of the mannose receptor in the internalization of Ara h 2 from raw and roasted peanuts was also investigated. Results showed that Ara h 2 internalization by MDDCs was both time and dose dependent. Mannose receptors in MDDCs had a greater implication in the internalization of Ara h 2 from roasted peanuts. However, this receptor was also important in the internalization of Ara h 2 from raw peanuts, as opposed to other allergens such as raw Ara h 3.