Spectrophotometric analyses of chlorophyll and single carotenoids during fruit development of tomato (Solanum lycopersicum L.) by means of iterative multiple linear regression analysis.

When using spectrophotometric transmittance readings of fruit extracts, the analysis of single carotenoids is difficult because of coinciding absorption bands of the various carotenoids and chlorophylls present in the solution. Aimed at the separate analyses of pigments, an iteratively applied linear regression was developed based on spectral profiles of pigment standards. The iterative approach was validated by dilution series of pigments and compared with commonly applied equation systems. High coefficients of determination and low measuring uncertainties were found for chlorophyll a and b (R(2) > or = 0.99, root mean square error RMSE < or = 10%). Carotenoids were separately analyzed with R(2) = 0.99, R(2) = 0.96, and R(2) = 0.98 for lycopene, beta-carotene, and lutein, respectively. The approach based on the spectral profiles provided low measuring uncertainties even if lutein was additionally present in the solutions, which was not possible with common data analyses. Subjecting tomato tissues (Solanum lycopersicum L.) to the iterative approach, contents of in vivo measured pigments were calculated with R(2) = 0.82, R(2) = 0.84, R(2) = 0.67, and R(2) = 0.03 for chlorophyll a and b, lycopene, and beta-carotene, respectively.