Shelf Life Extension and Quality Improvement of Cucumber Slices Impregnated in Infusions of Edible Herbs

Abstract

Development of functional food through their enrichment with herbal extracts is gaining much attention from the food industry. The present study evaluates the benefits, such as the oxidative stability and quality retention, of the enrichment of cucumber (Cucumis sativus) with natural phenolic compounds through immersion into a variety of herbal infusions. After a preliminary experiment with gallic acid solutions, the beneficial effect of hypotonic solutions was observed and the optimal process conditions were defined. The second step of the study involved the immersion of cucumber in the herbal infusions for 2.5?h at 70?°C. The total phenolic content (TPC), antiradical and antioxidant activity of osmo-treated slices were determined to evaluate the extent of bioactive compounds’ impregnation. During the immersion, TPC, antioxidant and antiradical activity significantly increased irrespective of the type of the herbal infusion. The TPC varied greatly, ranging from 1.41 to 781.14?mg GAE/kg of cucumber. The highest total phenolics were found in cucumber treated with Origanum vulgare infusion, followed by Jasminum officinale and Mentha spicata infusions. The aforementioned osmo-treated slices were also highly appreciated by the sensory panel; therefore, for those best performing herbal infusions, the third phase of this work involved the study of quality degradation under subsequent storage of the osmo-treated slices vs. the untreated ones. The results regarding color, texture, and visual assessment demonstrated the superior quality retention of the osmo-treated samples that exhibited a shelf life extension ranging from two- to almost four-fold compared to the untreated tissue.     

New horizons in mouse immunoinformatics: reliable in silico prediction of mouse class I histocompatibility major complex peptide binding affinity

Quantitative structure-activity relationship (QSAR) analysis is a main cornerstone of modern informatic disciplines. Predictive computational models, based on QSAR technology, of peptide-major histocompatibility complex (MHC) binding affinity have now become a vital component of modern day computational immunovaccinology. Historically, such approaches have been built around semi-qualitative, classification methods, but these are now giving way to quantitative regression methods. The additive method, an established immunoinformatics technique for the quantitative prediction of peptide-protein affinity, was used here to identify the sequence dependence of peptide binding specificity for three mouse class I MHC alleles: H2-D(b), H2-K(b) and H2-K(k). As we show, in terms of reliability the resulting models represent a significant advance on existing methods. They can be used for the accurate prediction of T-cell epitopes and are freely available online ( http://www.jenner.ac.uk/MHCPred).     

Nitrate as an Oxidant in the Cathode Chamber of a Microbial Fuel Cell for Both Power Generation and Nutrient Removal Purposes

Nitrate ions were used as the oxidant in the cathode chamber of a microbial fuel cell (MFC) to generate electricity from organic compounds with simultaneous nitrate removal. The MFC using nitrate as oxidant could generate a voltage of 111 mV (1,000 Ω) with a plain carbon cathode. The maximum power density achieved was 7.2 mW m⁻² with a 470 Ω resistor. Nitrate was reduced from an initial concentration of 49 to 25 mg (NO₃⁻−N) L⁻¹ during 42-day operation. The daily removal rate was 0.57 mg (NO₃⁻–N) L⁻¹ day⁻¹ with a voltage generation of 96 mV. In the presence of Pt catalyst dispersed on cathode, the cell voltage was significantly increased up to 450 mV and the power density was 117.7 mW m⁻², which was 16 times higher than the value without Pt catalyst. Significant nitrate removal was also observed with a daily removal rate of 2 mg (NO₃⁻–N) L⁻¹ day⁻¹, which was 3.5 times higher compared with the operation without catalyst. Nitrate was reduced to nitrite and ammonia in the liquid phase at a ratio of 0.6% and 51.8% of the total nitrate amount. These results suggest that nitrate can be successfully used as an oxidant for power generation without aeration and also nitrate removal from water in MFC. However, control of the process would be needed to reduce nitrate to only nitrogen gas, and avoid further reduction to ammonia.     

Toward prediction of class II mouse major histocompatibility complex peptide binding affinity: in silico bioinformatic evaluation using partial least squares, a robust multivariate statistical technique

The accurate identification of T-cell epitopes remains a principal goal of bioinformatics within immunology. As the immunogenicity of peptide epitopes is dependent on their binding to major histocompatibility complex (MHC) molecules, the prediction of binding affinity is a prerequisite to the reliable prediction of epitopes. The iterative self-consistent (ISC) partial-least-squares (PLS)-based additive method is a recently developed bioinformatic approach for predicting class II peptide-MHC binding affinity. The ISC-PLS method overcomes many of the conceptual difficulties inherent in the prediction of class II peptide-MHC affinity, such as the binding of a mixed population of peptide lengths due to the open-ended class II binding site. The method has applications in both the accurate prediction of class II epitopes and the manipulation of affinity for heteroclitic and competitor peptides. The method is applied here to six class II mouse alleles (I-Ab, I-Ad, I-Ak, I-As, I-Ed, and I-Ek) and included peptides up to 25 amino acids in length. A series of regression equations highlighting the quantitative contributions of individual amino acids at each peptide position was established. The initial model for each allele exhibited only moderate predictivity. Once the set of selected peptide subsequences had converged, the final models exhibited a satisfactory predictive power. Convergence was reached between the 4th and 17th iterations, and the leave-one-out cross-validation statistical terms--q2, SEP, and NC--ranged between 0.732 and 0.925, 0.418 and 0.816, and 1 and 6, respectively. The non-cross-validated statistical terms r2 and SEE ranged between 0.98 and 0.995 and 0.089 and 0.180, respectively. The peptides used in this study are available from the AntiJen database (http://www.jenner.ac.uk/AntiJen). The PLS method is available commercially in the SYBYL molecular modeling software package. The resulting models, which can be used for accurate T-cell epitope prediction, will be made freely available online (http://www.jenner.ac.uk/MHCPred).     

NMR spectroscopy and MALDI-TOF MS characterisation of end-functionalised PVP oligomers prepared with different esters as chain transfer agents

Ester-functionalised poly(1-vinylpyrrolidin-2-one) (PVP) oligomers obtained by radical polymerisation in methyl propionate, diethyl malonate and diethyl 2-methylmalonate were characterised by NMR spectroscopy, and MALDI-TOF mass spectrometry. The chain-transfer constants were determined as 5.54 x 10(-4), 1.22 x 10(-3) and 1.70 x 10(-2), respectively, by measuring the variation of the number-average molecular weight on conversion. These values were compared with those of methyl isobutyrate (1.65 x 10(-3)) and ethyl lactate (1.03 x 10(-2)), which had been previously determined. A clear dependence was found on the reactivity of the mobile hydrogen atoms alpha with the ester group. All of the macromolecules carried a single ester function. Therefore, the re-initiation step by the CTA-derived radicals overwhelmingly prevailed over initiation by the primary radicals.     

Mechanochemical Desymmetrization of Unbiased Bis- and Tris-alkynes to Access 3,5-Isoxazoles-Alkyne Adducts and Unsymmetrical Bis-3,5-isoxazoles**

A mechanochemical desymmetrization of symmetrical bis- and tris-alkynes by a controlled 1,3-dipolar cycloaddition reaction using nitrile oxide dipoles (NOs). This operationally simple protocol allows access to 3,5-isoxazole-alkyne adducts from easily prepared or commercially available symmetrical bis- and tris-alkynes in moderate to excellent yields. In addition, we have highlighted the synthetic utility of 3,5-isoxazole-alkyne by developing a route to access, for the first time, β-ketoenamine-alkyne derivatives, and unsymmetrical bis-3,5-isoxazoles.