305,125 research outputs found
Analysing the water spectral pattern by near-infrared spectroscopy and chemometrics as a dynamic multidimensional biomarker in preservation: rice germ storage monitoring
No full textWater activity is an important phenomenon not yet explained in terms of water molecular structure. This paper aims to find the relationship between the water activity and water molecular structure of the rice germ, based on its spectral pattern which can be measured using non-destructive technology. Aquaphotomics near-infrared spectroscopy was used to study rice germ stored at different levels of water activity and atmosphere. The findings show that state of the rice germ is governed by the water activity upon storage, which is defined by the structure of water within germ matrix. The structure of water can be described solely by the absorbance spectral pattern at the following absorbance bands: proton hydrates, hydration shells and water vapor (1364, 1375 and 1382 nm), trapped water (1392 nm), free water (1410 nm), hydration water (1425 nm), adsorbed water (1455 nm), non-bonded hydroxyl (1436 nm) and bound water (1520 nm)
Qualitative pattern recognition in chemistry: Theoretical background and practical guidelines
No full textQualitative pattern recognition methods find important applications in the chemometric sector to extract structured information from complex experimental data. Two main strategies can be distinguished: unsupervised analysis, aimed at investigating on the presence of groupings within the samples analysed, and supervised analysis, aimed at predicting the class membership of new samples. Supervised qualitative methods are, in turn, divided in two families: discriminant and class-modelling methods. The first ones require at least two classes to be defined, while the second ones are suitable also for one-class classification. The features of each strategy, with a focus on advantages and limitations, are described and compared. New trends in the methods, as well as recent attempts to force discriminant methods to behave as class-modelling ones, and vice versa, are also critically presented
Pros and cons of image texture analysis on hyperspectral datacubes: the flour case-study
No full textNIR spectroscopy, an efficient tool for evaluating and enhancing the quality of extra virgin olive oil
No full textA NANOSPHERICAL DENDRIMERIC GALLATE ESTER FOR LONG TERM PRESERVATION OF ESSENTIAL OILS: AN INTEGRATED CHEMOMETRIC ASSISTED FT-IR STUDY
No full textEssential oils (EOs) are hydrophobic concentrated liquids from plants made of volatile chemical compounds. EOs are very popular in the food, cosmetic and pharmaceutical industry as aromas, fragrances and alternative therapeutic devices [1, 2]. EOs are susceptible to degradation reactions, especially of oxidative type, triggered by temperature, light and oxygen availability. A loss of quality and alterations of sensory and pharmacological properties may occur, causing the production of smelly or even harmful compounds, responsible for allergic reactions and skin irritation [3-5]. For preventing and delaying EOs’ spoilage, synthetic preservatives as 2,6-bis(1,1-dimetiletil)-4-metilphenol (BHT) or t-butil-4-hydrohyanisole (BHA) are commonly adopted; but, in addition to a limited efficiency due mainly to poor solubility in oils, they may cause health diseases [6]. Natural polyphenols as gallic acid (GA) are nowadays proposed as safer alternatives, but their efficiency is limited by their low compatibility with hydrophobic material again, or by the occurrence of probable side reactions with oils constituents. Recently, a hydrophobic and biodegradable GA-enriched dendrimer (GAD) (Fig. 1.a) characterised by a nanospherical morphology (Fig. 1.b) and endowed with a remarkable antioxidant activity was synthetized [7]. Further studies currently being completed, have shown that GAD, with respect to free GA, possesses also more efficient antibacterial properties against several antibiotics-resistant G+ strains, inhibits platelet aggregation and ROS accumulation thus representing an excellent alternative to conventional drugs to combat infections and thrombus formation [8]. In this study, based on integrated results obtained from the due investigations, GAD is advised also as an innovative and semi-synthetic preservative additive.
a)
b)
Figure 1. Intuitive representation of GA-enriched dendrimer (GAD) structure (a); SEM images of GAD spherical nanoparticles (b). Scale bars represent 300 nm.
In this regard, GAD proved a much more efficient preservative power than free GA and, unlike GA, it never acts as a pro-oxidant. Besides classic oxidation indexes, the desired information was obtained by FT-IR spectroscopy assisted by multivariate analysis (MVA). For further confirmation of the so obtained results, interpretations of FT-IR data by considering the area of some selected informative bands and iodometric titrations to determine the hydro peroxide value (PV) were also performed [9].
References
[1] Yamamoto S., SOFW J., 2008, 134, 8.
[2] Jiang Y., Wu N., Fu Y.-J., Wang W., Luo M., Zhao C.-J., Zu Y.-G., and Liu Y.-L., Environ. Toxicol. Pharmacol., 2011, 32, 63.
[3] Hagvall L., Skold M., Brared-Christensson J., Borje A., and Karlberg A.-T., Contact Dermatitis, 2008, 59, 143.
[4] Skold M., Hagvall L., and Karlberg A.-T., Contact Dermatitis, 2008, 58, 9.
[5] Brared-Christensson J., Matura M., Gruvberger B., Bruze M., and Karlberg A.-T., Contact Dermatitis, 2010, 62, 32.
[6] Hirose M., Takesada Y., Tanaka H., Tamano S., Kato T., and Shirai T., Carcinogenesis, 1998, 19, 207.
[7] Alfei S., Catena S., and Turrini F., Drug Deliv. Trans. Res., under review.
[8] Alfei S., Signorello M. A., Schito A., Catena S., and Turrini F., results not yet published
[9] Alfei S., Oliveri P., and Malegori C., New J. Chem., under review
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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