Cane juice during clarification is submitted to high temperature and high pH (in the juice + lime mixing tank). At these conditions:
- Enzymes are denaturated; PPO will cease its activity and formation of enzymatic browning colourants will cease.
- Anthocianins are degraded.
- Calcium hydroxide will neutralize organic acids and inorganic ions as phosphates and sulphates.
- Flavones present soluble and stable forms at high pH and, therefore will be not destroyed in this operation (Smith e Paton, 1985).
- Coulorants are formed: HADP and compounds resulting from reactions between phenols and amino compounds (Paton, 1992). Paton and Mc Cowage, 1987, report that HADP formation increase proportionally with invert sugars concentration and with pH increase. These authors also report that colour formation in synthetic solutions of clarified juice, at 15º brix, is due to HADP formation, even in presence of amino compounds. Melanoidins formation occurs preferentially at higher brix.
- Colurants are removed: A slight colour decrease is observed during clarification. Paton, 1992, observed a colour decrease of 13% (from 16200IU into 14100IU). N.H. Smith, reports a colour removal of 11% (colour = 10 a*420 at pH 7). Howeve colour removal in clarification must be is higher than this figures due to colourants formation.
- Reduction of high moelular weight compounds: According to Tu et al., 1977, in clarification there is a reduction of more than 50% of high molecular compounds. However, even after this reduction, contribution of high molecular compounds to clarified juice colour is 60% (Paton, 1992).
- Phenolic compounds behavior, during clarification, varies according to their chemical structure. Chlorogenic acid concentration increases in this operation. Paton, 1992, refers an increase from 60ppm into 160ppm, on juice solids. The same is observed to the cinnamic acids like caffeic, p-cumaric and ferulic acids (from 50ppm into 110ppm). These concentration increases can be due to the hydrolysis of esters bonds of these acids with polysaccharides as in case of CWP (cell wall polysaccharides). This hydrolysis happens due to high alkalinity conditions occurred during clarification. This phenolic acids release provokes an IV increase, from 4.6 into 6.9 (Paton, 1992).
Neutral phenolics suffer a 35% decrease, from 200ppm into 130ppm, on juice (Paton, 1992). Possibly these compounds are preferentially consumed in reactions between phenols and amino compounds, due to their neutral nature (Bento, 2003). Phenolic acids as are charged at clarification pH will not be consumed due to their anionic charge.
Bento L.S.M., 2003, PhD Thesis
Paton N.H., 1992, The origin of colour in raw sugar, Proc. Aust. S.S.C.T. Conf.,
Smith N.H., Inhibition of enzymatic browning in cane sugar processing, Int.
Sugar J., 259-263
Smith P., Paton N., 1985, Sugar cane flavonoids, Sug. Tech. Rev., 12, 117-142
Tu J.C., A. Kondo, E. Sloane, 1977, The role of high molecular weight colorants
in sugar color, Proc. of I.S.S.C.T. Conf., 1393-1400