Insecticidal activity of Thymus pallescens de Noë and Cymbogon citratus essential oils against Sitophilus zeamais and Tribolium castaneum.

The thrust of the study was to determine the chemical composition of the essential oils extracted from Thymus pallescens de Noé and Cymbogon citratus Stapf. as well as to evaluate their efficacy in controlling Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) in either single or combined populations. Carvacrol (56.04%) and geraniol (20.86%) were identified as the major constituents of T. pallescens and C. citratus respectively. The tested essential oils showed pronounced insecticidal activity against the pest species in relation with the applied doses. T. pallescens EO had the highest efficacy and S. zeamais was found to be more susceptible to both individual and combined treatments. With reference to the contact and fumigation assessments, T. pallescens EO effectuated corrected mortality rates ranging from 42.5-100% to 25-100% in S. zeamais with corresponding lethal concentration (LC50) values of 17.7 µl/ml and 15µL/L air respectively. Whereas, the T. pallescens EO exhibited corrected mortality rates of 42.5-100% and 20-100% with corresponding LC50 values of 18.1 µl/ml and 15.5 µL/L air against T. castaneum in contact and fumigation assessments, respectively. The corrected mortality rates increased for both insect species when using combination treatments, with significant increases in the LC50 values, ranging from 8.59 to 49.9% for both pest species. Analysis of energy biomarkers in the treated insects indicate significantly increased protein and carbohydrate contents and decreased lipids levels. The study therefore demonstrated the bio-insecticidal toxicity of the EOs from T. pallescens and C. citratus against two important maize post-harvest pests, concurrently revealing significant positive and negative insecticidal activity gradients in relation to single or combined populations.

Exploitation of the Genetic Variability of Diverse Metric Traits of Durum Wheat (Triticum turgidum L. ssp. durum Desf.) Cultivars for Local Adaptation to Semi-Arid Regions of Algeria.

Abiotic stresses pose significant challenges to wheat farming, yet exploiting the genetic variability within germplasm collections offers an opportunity to effectively address these challenges. In this study, we investigated the genetic diversity of key agronomic traits among twenty durum wheat cultivars, with the intention to pinpoint those better suited to semi-arid conditions. Field trials were conducted at the ITGC-FDPS Institute, Setif, Algeria, during the winter season of 2021/22. A completely randomized design was used with three replicates. Statistical analyses revealed significant variation among the genotypes for most of the studied traits, with some cultivars exhibiting a superior performance in a stressful environment. Notably, traits like the number of grains per spike (NGS) and the grain yield (GY) displayed high genotypic coefficients of variation (CVg). Except for membrane thermostability (MT) and biological yield (BY), the majority of the assessed traits exhibited moderate-to-high heritability estimates. Genotypic and phenotypic correlation studies have confirmed the importance of many yield-related traits in the expression of GY. The harvest index (HI) underscored the highest genotypic direct effect on GY, followed closely by spike number (SN), serving as consistent pathways through which most of the measured traits indirectly influenced GY. The cluster analysis categorized the durum wheat cultivars into seven distinct clusters. The largest inter-cluster distance was observed between clusters G3 and G4 (D2 = 6145.86), reflecting maximum dissimilarity between the individuals of these clusters. Hybridizing divergent clusters may benefit future breeding programs aiming to develop potential durum wheat varieties through cross combinations. This study's findings contribute to sustainable agriculture efforts by facilitating the selection of genotypes with enhanced resilience and productivity, particularly for cultivation in challenging semi-arid regions.

Development of a portable spectrofluorimeter for measuring the microbial spoilage of minced beef.

The evaluation of meat spoilage is based on sensory and microbiological analyses. The disadvantages of sensory analyses are its reliance on highly trained panelists, a procedure which makes it costly and unattractive for routine analyses. Moreover, the classical microbiological analyses are lengthy, costly and destructive. In this study a portable fluorescence spectrometer was tested to quantify minced beef spoilage. This study was investigated on samples stored aerobically and under vacuum at 5 and 15 °C. Total viable counts (TVC), Pseudomonas, lactic acid bacteria, and yeast/molds counts were investigated with classical culture methods. Fluorescence spectra were recorded on the same samples using different excitation LEDs (280, 320, and 380 nm). PLS-R with leave-one-out cross validation was used to perform calibration and validation models. The PLS-R models presented good R²(CV) (0.50-0.99) and ratio of standard deviation (RPD(CV): 1.40-8.95) values after cross-validation. It could be concluded that portable spectrofluorimeters are promising devices to evaluate spoilage in minced beef.

Structural changes of milk components during acid-induced coagulation kinetics as studied by synchronous fluorescence and mid-infrared spectroscopy.

Dynamic oscillatory experiments and front-face synchronous fluorescence spectroscopy and mid-infrared (mid-IR) spectroscopy have been used to investigate structure evolution, at the macroscopic and molecular levels, during milk acidification kinetics. The studies were performed using skim milk, at two different temperatures (30 °C and 40 °C), to which was added glucono-δ-lactone (GDL) to generate different structural changes in casein micelles and gels. Synchronous fluorescence spectra were recorded in the 250-500 nm excitation wavelength range using an offset of 80 nm between the excitation and emission monochromators for each system during the 300 min acidification kinetics. The change in the fluorescence intensity at 281 nm reflects the pH-induced physicochemical changes of casein micelles and, in particular, structural changes in the micelles in the pH range 5.5-5.0. Regarding mid-infrared spectroscopy, the region located between 1700 and 1500 cm(-1), corresponding to the amide I and II bands, and the 1500-900 cm(-1) region, called the fingerprint region, were considered for the characterization of milk coagulation kinetics. Changes in the absorbance at 1063 cm(-1) as a function of pH for kinetics recorded at 30 °C and 40 °C reflected pH-induced phosphate dissolution in the pH range 5.5-5.0. Compared to rheometry, which reveals microstructure changes only in the gel state, spectroscopic methods make it possible to monitor molecular structure changes in micelles throughout the acidification processes.

Effects of added minerals (calcium, phosphate, and citrate) on the molecular structure of skim milk as investigated by mid-infrared and synchronous fluorescence spectroscopies coupled with chemometrics.

Minerals play an important role in the structure and stability of casein micelles: minerals and caseins in milk are in dynamic equilibrium. Front-face synchronous fluorescence and mid-infrared spectra in combination with multivariate statistical analysis have been used to investigate, at a molecular level, the effects of added minerals (calcium, phosphate, or citrate) on mineral equilibria and casein micelle structure. Synchronous fluorescence spectra were recorded in the 250-500 nm excitation wavelength range using an offset of 80 nm between the excitation and emission monochromators for skim-milk samples fortified with 0, 3, 6, and 9 mM of calcium, phosphate, or citrate at 30 degrees C and 4 degrees C. Regarding midinfrared spectroscopy, the region located between 1700-1500 cm(-1), corresponding to the amide I and II bands, and the 1500-900 cm(-1) region, called the fingerprint region, were considered for the characterization of the fortified skim-milk samples at the two considered temperatures. Principal component analysis (PCA) was applied to the collections of fluorescence and infrared spectral data of the two systems to optimize their description. The results show that the phenomena induced by the addition of phosphate were different from the ones observed following the addition of calcium or citrate, a calcium-chelating agent. Finally, common components and specific weights analysis was applied to infrared spectra and fluorescence data collected on fortified skim-milk samples. This analysis enabled the relationship between the different data tables to be established.

Synchronous front-face fluorescence spectroscopy coupled with parallel factors (PARAFAC) analysis to study the effects of cooking time on meat.

In this study, the potential of synchronous front-face fluorescence coupled with chemometrics has been investigated for the analysis of cooked meat. Bovine meat samples (thin slices of 5 cm diameter) taken from Longissimus dorsi muscle were cooked at 237 degrees C for 0, 1, 2, 5, 7, and 10 min under control conditions. Synchronous front-face fluorescence spectra were collected on meat samples in the excitation wavelength range of 250 to 550 nm using offsets (Delta lambda) of 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, and 160 nm between excitation and emission wavelengths. The synchronous fluorescence landscape containing 360 spectra was analyzed using PARAFAC. The best PARAFAC model presented 2 components since core consistency values for the first 2 components were 100% and the explained variance was 67.98%. The loading profiles of 1st and 2nd components had an optimal Delta lambda of 70 and 40 nm, respectively, allowing to determine the excitation (exc.) and emission (em.) maxima wavelengths of 1st (fluorescence band at about exc.: 340 to 400/em.: 410 to 470 nm, and peak at exc.: 468/em.: 538 nm) and 2nd (exc.: 294 nm/em.: 334 nm) components. As the loading profile of the 1st component of PARAFAC was assigned to Maillard-reaction products formed during cooking, the profile of the 2nd component corresponded with the fluorescence characteristics of tryptophan residues in proteins. Loadings and scores of the PARAFAC model developed from the synchronous fluorescence spectra enabled to get information regarding the changes occurring in meat fluorophores during cooking of meat at 237 degrees C from 0 to 10 min.

Fluorescence spectroscopy as a promising tool for a polyphasic approach to pseudomonad taxonomy.

Fluorescence spectroscopy is an emerging tool for the analysis of biomolecules from complex matrices. We explored the potentialities of the method for the pseudomonad taxonomic purpose at the genus and species level. Emission spectra of three intrinsic fluorophores (namely, NADH, tryptophan, and the complex of aromatic amino acids and nucleic acid) were collected from whole bacterial cells. Their comparisons were performed through principal component analysis and factorial discriminant analysis. Reference strains from the Xanthomonas, Stenotrophomonas, Burkholderia, and Pseudomonas genera were well separated, with sensitivity and selectivity higher than 90%. At the species level, P. lundensis, P. taetrolens, P. fragi, P. chlororaphis, and P. stutzeri were also well separated, in a distant group, from P. putida, P. pseudoalcaligenes, and P. fluorescens. These results are in agreement with the generally admitted rRNA and DNA bacterial homology grouping but they also provide additional information about strain relatedness. In the case of environmental isolates, the method allows good discrimination, even for strains for which ambiguity still remained after PCR and API 20NE identification. Rapid, easy to perform, and low cost, fluorescence spectroscopy provides substantial information on cell components. Statistical analysis of collected data allows in-depth comparison of strains. Our results strongly support the view that fluorescence spectroscopy fingerprinting can be used as a powerful tool in a polyphasic approach to pseudomonad taxonomy.

Effects of mild heating and acidification on the molecular structure of milk components as investigated by synchronous front-face fluorescence spectroscopy coupled with parallel factor analysis.

This paper reports the potential of synchronous front-face fluorescence spectroscopy in the characterization at the molecular level of milk changes during mild heating from 4 to 50 degrees C and acidification in the pH range of 6.8 to 5.1. Synchronous fluorescence spectra were collected in the 250-550 nm excitation wavelength range using offsets of 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, and 240 nm between excitation and emission monochromators. The potential of parallel factor (PARAFAC) analysis in the decomposition of the whole synchronous fluorescence data set into the contribution of each of the fluorescent compounds present in milk has been investigated for heating and acidification data sets. Models were fitted from 1 to 7 components. Considering the core consistency values, PARAFAC models with three components have been considered. The first three components explained 94.43% and 94.13% of the total variance for heating and acidification data sets, respectively. The loading profiles of the first and second components derived from PARAFAC analysis performed on heating and acidification data sets corresponded quite well with the characteristics of tryptophan and vitamin A fluorescence spectra, respectively. The third component corresponded to the riboflavin fluorescence spectrum. Considering the heating experiment, the profile of the concentration mode for the second component showed large variations according to the temperature, which were assigned to the melting of triglycerides between 4 and 50 degrees C. For the acidification experiment, drastic changes in the concentration modes of the three components were observed for pH below 5.6, in agreement with structural changes in casein micelles.