Evaluation of a FTIR data pretreatment method for Principal Component Analysis applied to archaeological ceramics ☆

Published Date
March 2016, Vol.125:224–229, doi:10.1016/j.microc.2015.11.033

Title 
Evaluation of a FTIR data pretreatment method for Principal Component Analysis applied to archaeological ceramics ☆

• Author 

• Laura Medeghini ^a,1,
• Silvano Mignardi ^a
• Caterina De Vito ^a
• Aida Maria Conte ^b

• aDepartment of Earth Sciences, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
• bCNR – IGG – UOS Roma, c/o Department of Earth Sciences, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy

Received 14 July 2015. Revised 11 November 2015. Accepted 17 November 2015. Available online 1 December 2015.

Highlights

• •
  A new FTIR data pretreatment method for PCA is proposed.
• •
  Normalization of FTIR data between 0–1 and the second derivative were considered.
• •
  The proposed procedure has been applied to ancient ceramics.
• •
  The manipulation of experimental data and the influence on PCA are minimized.
• •
  The limited number of variables highlights the correspondence between bands and minerals.

Abstract

The aim of this work is to explore the potential of Fourier Transform Infrared (FTIR) spectroscopy and chemometric analysis as a tool to differentiate ceramics having different provenance. We propose a new spectral FTIR data pretreatment method for Principal Component Analysis (PCA) as the selection of a proper algorithm and its application could play an important role in minimizing the manipulation of data. We consider the data in the spectral region between 400 and 1500 cm^{− 1}, since this range takes into account the contribution of the fingerprints of inorganic compounds (below 1000 cm^{− 1}), and the carbonate absorption band at about 1400 cm^{− 1}. Normalization of FTIR data between 0 and 1 has been followed by the calculation of the second derivative, without the smoothing of data; thus resulting in minimizing the manipulation of experimental data and reducing the influence on PCA. The proposed procedure has been applied to ancient potteries from Khirbet al-Batrawy (Jordan), Motya (Trapani, Italy) and the Palatine Hill (Rome, Italy). A series of elaborations with PCA, step by step, is proposed to reduce the number of variables (from more than 1000 to ~ 200). This allowed the identification of the discriminating vibrational bands for each group obtained by PCA to explain the separation of samples on the basis of their mineralogical composition. The application of the statistical data processing proposed here allowed for the discrimination of different ceramic productions.

Keywords

• Archaeological pottery
• FTIR
• PCA
• Pretreatment method
• Provenance

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• ☆
  Selected papers presented at TECHNART 2015 Conference, Catania (Italy), April 27–30, 2015.

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http://www.sciencedirect.com/science/article/pii/S0026265X15003033

Determination of the thermo-mechanical properties in starch and starch/gluten systems at low moisture content – A comparison of DSC and TMA

Published Date
8 August 2014, Vol.108:1–9, doi:10.1016/j.carbpol.2014.02.049

Title 
Determination of the thermo-mechanical properties in starch and starch/gluten systems at low moisture content – A comparison of DSC and TMA

• Author 

• Stephen Homer ^,
• Michael Kelly 
• Li Day 

• CSIRO Animal, Food and Health Sciences, 671 Sneydes Road, Werribee, VIC 3030, Australia

Received 23 December 2013. Revised 13 February 2014. Accepted 15 February 2014. Available online 22 February 2014.

Highlights

• •
  Heating rate affects the temperature of transitions in starch as measured by DSC.
• •
  The optimum heating rate for starch T_g measurement by DSC was 5 °C/min.
• •
  T_g of starch changes upon ageing and is lowered by use of an initial heating scan.
• •
  Gluten plasticises starch and results in a lower T_g compared to starch alone.
• •
  TMA is a useful alternative to DSC for determining T_g in starch up to 80 °C.

Abstract

The impact of heating rate on the glass transition (T_g) and melting transitions observed by differential scanning calorimetry (DSC) on starch and a starch/gluten blend (80:20 ratio) at low moisture content was examined. The results were compared to those determined by thermo-mechanical analysis (TMA). Comparison with dynamic mechanical thermal analysis (DMTA) and phase transition analysis (PTA) is also discussed. Higher heating rates increased the determined T_g as well as the melting peak temperatures in both starch and the starch/gluten blend. A heating rate of 5 °C/min gave the most precise value of T_g while still being clearly observed above the baseline. T_g values determined from the first and second DSC scans were found to differ significantly and retrogradation of starch biopolymers may be responsible. T_gvalues of starch determined by TMA showed good agreement with DSC results where the T_g was below 80 °C. However, moisture loss led to inaccurate T_g determination for TMA analyses at temperatures above 80 °C.

Abbreviations

• DSC, differential scanning calorimetry
• TMA, thermo-mechanical analysis
• DMTA, dynamic mechanical thermal analysis
• PTA, phase transition analysis
• T_g, glass transition temperature
• T_r, relaxation temperature

Keywords

• Starch
• Gluten
• DSC
• TMA
• Glass transition
• Heating rate

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• ⁎ 
  Corresponding author. Tel.: +61 3 9731 3254; fax: +61 3 9731 3250.

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Infrared spectroscopy as a tool to characterise starch ordered structure—a joint FTIR–ATR, NMR, XRD and DSC study

Published Date
30 March 2016, Vol.139:35–42, doi:10.1016/j.carbpol.2015.11.066

Title 
Infrared spectroscopy as a tool to characterise starch ordered structure—a joint FTIR–ATR, NMR, XRD and DSC study

Author

Frederick J. Warren

Michael J. Gidley

Bernadine M. Flanagan ^,

• Centre for Nutrition and Food Sciences, ARC Centre of Excellence in Plant Cell Walls, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia

Received 12 October 2015. Revised 25 November 2015. Accepted 26 November 2015. Available online 2 December 2015.

Highlights

• •
  A larger sample set (61) of starches than has been used in previous studies.
• •
  Full structural characterisation using a range of techniques.
• •
  A non-linear, hydration dependent response occurs in the infrared spectrum.
• •
  Complex changes in the infrared spectra of starch with increasing structural order.

Abstract

Starch has a heterogeneous, semi-crystalline granular structure and the degree of ordered structure can affect its behaviour in foods and bioplastics. A range of methodologies are employed to study starch structure; differential scanning calorimetry, ¹³C nuclear magnetic resonance, X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). Despite the appeal of FTIR as a rapid, non-destructive methodology, there is currently no systematically defined quantitative relationship between FTIR spectral features and other starch structural measures. Here, we subject 61 starch samples to structural analysis, and systematically correlate FTIR spectra with other measures of starch structure. A hydration dependent peak position shift in the FTIR spectra of starch is observed, resulting from increased molecular order, but with complex, non-linear behaviour. We demonstrate that FTIR is a tool that can quantitatively probe short range interactions in starch structure. However, the assumptions of linear relationships between starch ordered structure and peak ratios are overly simplistic.

Graphical abstract

Keywords

• Starch
• Crystallinity
• Polymer structure
• FTIR–ATR
• NMR
• XRD

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• DOC (437K)

• ⁎ 
  Corresponding author. Tel.: +617 33653449.

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http://www.sciencedirect.com/science/article/pii/S014486171501156X