Free and conjugated polyamines and phenols in raw and alkaline-clarified sugarcane juices

Sugarcane juice contains a lot of sucrose associated with several monosaccharides, defined as low molecular mass carbohydrates (LMMC), as well as some polysaccharides and glycoproteins, which are defined as mid and high molecular mass carbohydrates (MMMC and HMMC, respectively). These three categories of carbohydrates can be separated by size-exclusion chromatography through Sephadex G-10 and Sephadex G-50 columns, but elution profiles change drastically after juice clarification performed by adjusting the pH value of the juice to 8.0. In addition, polyamines and some phenolics are currently associated with carbohydrate preparations, and the distribution pattern of these conjugates also changes after clarification. Polyamine levels generally decrease after juice clarification. Cadaverine is completely removed from the different carbohydrate preparations, whereas spermidine is the main polyamine occurring in association with sugarcane carbohydrates, as free or acid-soluble form in LMMC preparation or as acid-soluble and -insoluble forms in both MMMC and HMMC preparations. Polyamines, presumably spermidine, conjugate to p-hydroxybenzoic acid in LMMC, mostly to caffeic acid in MMMC, and to syringic acid in HMMC preparations. HMMC-associated polyamines appear in both acid-soluble and -insoluble fractions. Syringic acid also occurs in the LMMC preparation, but juice clarification changes it from acid-soluble to free form, and it coelutes with sucrose.