Specific screening for color precursors and colorants in beet and cane sugar liquors in relation to model colorants using spectrofluorometry evaluated by HPLC and multiway data analysis

A comparison was made of the fluorophores in beet thick juice and cane fina l evaporator syrup, which are comparable in the production of cane and beet sugar; that is, both represent the final stage of syrup concentration prio r to crystallization of sugar. To further elucidate the nature of the color components in cane and beet syrup, a series of model colorants was also pr epared, consisting of mildly alkaline-degraded fructose and glucose and two Maillard type colorants, glucose-glycine and glucose-lysine. Fluorescence excitation-emission landscapes resolved into individual fluorescent compone nts with PARAFAC modeling were used as a screening method for colorants, an d the method was validated with size exclusion chromatography using a diode array UV-vis detector. Fluorophores from the model colorants were mainly l ocated at visible wavelengths. An overall similarity in chromatograms and a bsorption spectra of the four model colorant samples indicated that the for mation of darker color was the distinguishing characteristic, rather than d ifferent reaction products. The fluorophores obtained from the beet and can e syrups consisted of color precursor amino acids in the W wavelength regio n. Tryptophan was found in both beet and cane syrups. Tyrosine as a fluorop hore was resolved in only beet syrup, reflecting the higher levels of amino acids in beet processing. In the visible wavelength region, cane syrup col orant fluorophores were situated at higher wavelengths than those of beet s yrup, indicating formation of darker colorants. A higher level of invert su gar in cane processing compared to beet processing was suggested as a possi ble explanation for the darker colorants.