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1 Table IR absorption bands and possible assignment in the typical FT-IR spectrum of saffronBand (cm-1)*Assignment3365 3333 (broad) Stretching vibration of bonded and non-bonded O H groups2924 (m) and 2857 (m) Asymmetric CH2 , symmetric CH3 and CH2 stretching vibrations1745 1696 (sh) C=O stretching vibrations ( in the COOR groups of crocetin/ COOH groups of aminoacids)1659 1653 (s) =C H stretching vibrations ( in the RCH=CHR groups of crocetin)/amide I/O H bending vibrations in water1613 (m) C C skeletal vibrations1580 1578 (m) and 1545 1542 (sh) C O vibrations ( in the COOR groups of crocetin)/amide II/aromatic C=C stretching vibrations)1454 (w) C H bending (scissoring) (in CH3 groups)/aromatic C=C stretching vibrations1400 (w) and 1375 (w) OH bending vibrations, C O H in-plane bending vibrations, CH3 out-of-plane bending vibrations, CH2 wagging and twisting vibrations1317 (w), 1294 1292 (w), 1271 (w) and 1227 (s)C(O)

2 O stretching vibrations and OH in plane vibrations/amide III ( in aromatic ethers)1157 (sh) C O stretching vibrations ( in C O C glycosidic linkages of oligosaccharides or in triacylglycerols)1075 (s) C 1 H bending vibration in sugars1020 (sh) C 4 OH (typical for glucose residue of disaccharides)970 920 (sh) trans = C H out-of-plane bending780 700 (w) cis = C H out-of-plane bending* m: medium; s: strong; sh: shoulder; w: (ESI) TheRoyalSocietyofChemistry2016 Table results of PCA application on the transmittance FT-IR spectral data of Saffron samplesComponentEigen-valuePercent of VarianceCumulative percent of NaOOO NaAzorubineO3 SNaNNHONaSO3 Sunset yellowNNH3 COSCH3 SOOONaOOONaAllura redNO3 SNaNNNNaSO3 OHNaOOCT artrazineOHNO(NaSO3)XX=1,2,3 Quinoline-yellowNNOHS udan IIFigure (S1).

3 Chemical structure of food colorant1000200030004000050100 Wavenumber (cm-1)Transmittance1000200030000204060 Wavenumber (cm-1)Transmittance100020003000400005010 0 Wavenumber (cm-1)Transmittance100020003000400005010 0 Wavenumber (cm-1)Transmittance100020003000400005010 0 Wavenumber (cm-1)Transmittance100020003000400005010 0 Wavenumber (cm-1)Transmittance100020003000400005010 0 Wavenumber (cm-1)TransmittanceFigure (S2). (a) Saffron (b) Azorubine (c) Quinoline yellow (d) Allura red (e) Sudan (II) (f) Sunset yellow (g) Tartrazine(a)(b)(c)(e)(d)(f)(g)123456789 1011121314151617181920212223242526272829 3031323334353637383940414243444546474849 5051525354555657585960616263646566676869 7071727374757677787980818283848586878889 9091929394959697989910010110210310410510 6107108109110111112113114115116117118119 1201211221231241251261271281291301311321 3313413513613713813914014114214314414514 6147148149150151152153154155156157158159 1601611621631641651661671681691701711721 7317417517617717817918018118218318418518 6187188189190191192193194195196197198199 2002012022032042052062072082092102112122 1321421521621721821922022122222322422522 6227228229230231232233234235236237238239 2402412422432442452462472482492502512522 5325425525625725825926026126226326426526 6267268269270271272273274275276277278279 2802812822832842852862872882892902912922 9329429529629729829930030130230330430530 6307308309310311312313314315316317318319 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4 Distribution pattern of the wavenumbers from saffron data set obtained using 4-node Kohonen SOM for clustering of wavenumbers. The numbers from 1 1868 refer to the wavenumber transmittance data component 1 PLS component 2 AzorubineQuinolineAllura redSaffronSudan IISunset yellowTartraz