Factors that influence saponification reaction in annatto (Bixa orellana L.) carotenoids

This research aimed to evaluate the effect of different KOH concentrations (0.6%, 1%, 2%, 3%, 4% and 5%) and extraction temperature (25 degrees C, 50 degrees C, 60 degrees C and 70 degrees C) on the progress of saponification reaction in annatto pigments. The progress of the reaction was monitored by quantification of bixin and norbixin using high performance liquid chromatography (HPLC). The highest alkali concentration made possible the maximum conversion of bixin into norbixin (KOH 5% - bixin: 0.44 g.100g(-1), norbixin: 1.43 g.100g(-1)) and using the lowest concentration, saponification didn't take place (KOH 0.6% - bixin: 2.00 g.100g(-1), norbixin: not detected). The elevation of extraction temperature was associated to a decrease of bixin content and to an increase of norbixin content (T-70 degrees C-bixin: 0.01 g.100g(-1), norbixin: 2.34 g.100g(-1); T-25 degrees C-bixin: 1.04 g.100g(-1), norbixin: 0.78 g.100g(-1)). Therefore, for the extraction of bixin is recommended to use alkaline solutions in low concentrations. To obtain the hydrossoluble pigment, higher concentrations are suggested, and they could be associated to heating.