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FTIR Spectroscopy in Combination with Chemometrics for the Estimation of Grape Pomace Geographical Origin
1 , 1, 2 , 3 , 1 , * 1
1  Laboratory of Chemistry, Department of Food Science and Human Nutrition, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Attica, Greece
2  Department of Food Science and Technology, University of West Attica, Ag. Spyridonos str, Egaleo,
3  Department of Food Science and Technology, Ionian University, Terma Leoforou Vergoti, GR28100 Argostoli, Cephalonia, Greece
Academic Editor: Arun Bhunia (registering DOI)

Grape is one of the world’s largest fruit crops and grape pomace is one of wastes generated by wine-making processes. According to Greek Ministry of Rural Development and Food in 2017, Greek Ionian islands produced 1,179.25 tons of grapes for wine making and 175.12 tons of them were grape pomace. Protected Designation of Origin of Cephalonia Robola wine and other traditional grape varieties are of particular interest. Fourier-transformed infrared spectroscopy (FTIR) in combination with chemometric analysis is among one promising analytical method for determining the approach geographical origin of them. In this study, FTIR spectra of 31 grape pomace samples from three geographical regions, Cephalonia (n=13), Zakynthos (n=9) and Corfu (n=9), were obtained in triplicates, using a Nicolet 6700 FTIR in the Diffuse Reflectance (DRIFTS) mode with DTGS detector. Collection and processing of spectral data was carried out using OMNIC ver. 7.3. Stepwise discriminant analysis was performed using the spectral region 1900-600 cm-1 in SPSS software ver. 25.0. The equivalence between the groups was checked with Box’s M test (p >0.001). Results showed that five steps were formed. The percentage of samples that were classified correctly was 90.3% while with the method of cross-validation was 87.1%. The Wilks λ values for the two discriminant functions had p <0.05, indicating a good discriminant power of the model. Eigenvalues suggest that the first discriminant function was more discriminating with high canonical correlation (0.846) which explained 84.6% of the total variance. Results showed that FTIR spectroscopy combined with chemometrics techniques can be used for the differentiation of grape pomace geographical origin.

Keywords: Grape pomace; Robola; FTIR; chemometrics; wastes