Color software

CIE (Commission Internationale de l’Eclairage) L*, a* and b* color coordinates were measured [57 ,58 ]. Visible spectra were recorded at 400–700 nm transmittance using a spectrophotometer Lambda 35 UV⁄Vis (PerkinElmer) equipped with the RSA-PE-20 Integrating Sphere accessory assembly (Labsphere, North Sutton, NH, USA). UV WinLab Software was used to record the spectra (version 2.85.04, PerkinElmer Inc.) and CIE L*a*b* color coordinates were calculated for the CIE illuminant D65 and 10° standard observed conditions, using Color software (version 3.00, 2001, PerkinElmer Inc.). Samples transmittance was measured using a 1 mm quartz cuvette.

The CIE (Commission Internationale de l’Eclairage) L*, a* and b* color coordinates of the oenotannin solutions were measured according to OIV [34 ]. Visible spectra were recorded in transmittance at 400–700 nm using a 10 mm path length quartz cell and the Lambda 35 UV-Visible spectrophotometer (Perkin Elmer Inc., Shelton, CT, USA) equipped with the RSA-PE-20 Integrating Sphere accessory assembly (Labsphere, North Sutton, NH, USA). UV WinLab software was used to record the spectra (version 2.85.04, Perkin Elmer Inc., Shelton, CT, USA), and CIELab color coordinates were calculated for the CIE illuminant D65 and 10° standard observed conditions using Color software (version 3.00, 2001, Perkin Elmer Inc., Shelton, CT, USA). Color differences between the oenotannin solutions were determined using the ΔE value of the CIELab diagram, according to the following equation: $$\Delta E=\sqrt{{\left({\Delta L}^{*}\right)}^2+{\left({\Delta a}^{*}\right)}^2+{\left({\Delta b}^{*}\right)}^2}$$
When ΔE ≥ 3, the differences between oenotannin solutions are perceivable by the human eye [35 (link)].