title: Direct and simultaneous quantification of tannin mean degree of polymerization and percentage of galloylation in grape seeds using diffuse reflectance fourier transform-infrared spectroscopy.
abstract: The direct and simultaneous quantitative determination of the mean degree of polymerization (mDP) and the degree of galloylation (%G) in grape seeds were quantified using diffuse reflectance infrared Fourier transform spectroscopy and partial least squares (PLS). The results were compared with those obtained using the conventional analysis employing phloroglucinolysis as pretreatment followed by high performance liquid chromatography-UV and mass spectrometry detection. Infrared spectra were recorded in solid state samples after freeze drying. The 2nd derivative of the 1832 to 1416 and 918 to 739 cm(-1) spectral regions for the quantification of mDP, the 2nd derivative of the 1813 to 607 cm(-1) spectral region for the degree of %G determination and PLS regression were used. The determination coefficients (R(2) ) of mDP and %G were 0.99 and 0.98, respectively. The corresponding values of the root-mean-square error of calibration were found 0.506 and 0.692, the root-mean-square error of cross validation 0.811 and 0.921, and the root-mean-square error of prediction 0.612 and 0.801. The proposed method in comparison with the conventional method is simpler, less time consuming, more economical, and requires reduced quantities of chemical reagents and fewer sample pretreatment steps. It could be a starting point for the design of more specific models according to the requirements of the wineries.
authors.affiliation: Dept. of Food Science & Human Nutrition, Agricultural Univ. of Athens, 75 Iera Odos, 11855, Athens, Greece.
authors.forename: Christos
authors.initials: C
authors.lastname: Pappas
authors.forename: Maria
authors.initials: M
authors.lastname: Kyraleou
authors.forename: Eleni
authors.initials: E
authors.lastname: Voskidi
authors.forename: Yorgos
authors.initials: Y
authors.lastname: Kotseridis
authors.forename: Petros A
authors.initials: PA
authors.lastname: Taranilis
authors.forename: Stamatina
authors.initials: S
authors.lastname: Kallithraka
mesh_terms: D000975:Antioxidants / Q000032:analysis; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005583:Fourier Analysis; D005707:Gallic Acid / Q000032:analysis*; D006801:Humans; D016018:Least-Squares Analysis; D010936:Plant Extracts / Q000032:analysis; D058105:Polymerization; D059808:Polyphenols / Q000032:analysis*; D012639:Seeds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013634:Tannins / Q000032:analysis*; D027843:Vitis / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D010936:Plant Extracts; D059808:Polyphenols; D013634:Tannins; D005707:Gallic Acid
keywords: diffuse reflectance Fourier transform spectroscopy; grape seeds; partial least squares; tannin degree of galloylation; tannin mean degree of polymerization