Clarification - Cane Juice

By Bento, Luis San Miguel
Posted on 2006-11-30    Last edited on 2009-09-23

Juice clarification is made by adding calcium hydroxide with heating to the mixed juice. This juice is filtered by passing it through static screens, before heating.

Calcium hydroxide will neutralize organic acids and inorganic ions as phosphates and sulphates. The pH rise with simultaneous heating will provokes enzymes denaturation. PPO will cease its activity and there is no more formation of enzymatic browning colourants. Also, in this stage anthocianins will be decomposed. Flavones present soluble and stable forms at high pH and, therefore will be not destroyed in this operation (Smith e Paton, 1985).

The precipitate formed in clarification is decanted in clarifiers. Phosphoric acid can be added to juice, if this component does not exist in sufficient quantity, in cane. A flocculant is added to the juice to enhance insoluble precipitation. Mud formed in clarifier, are removed from the bottom and are filtered in rotative vacuum filters, to recover sucrose. Swwet waters formed are returned to clarified juice.

A slight colour decrease is observed during clarification. Paton, 1992, observed a colour decrease of 13% (from 16200IU into 14100IU).  However, as there is HADP colourants formation, and resulting from reaction between phenols and amino compounds (Paton, 1992), colour removal in clarification must be is higher.
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.

Clarificatin scheme

According to Tu et al., 1977, in clarification there is a reduction of more than 50% of high molecular compounds, but the percentage of low molecular compounds is maintained the same. 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 ISP. 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. Phenolic acids as are charged at clarification pH will not be consumed due to their anionic charge.

In some countries carbonatation is used to clarify cane mixed juices. In R.P. of China 20% of cane sugar factories use this system.


Paton N.H., 1992, The origin of colour in raw sugar, Proc. Aust. S.S.C.T. Conf. 8-17
Paton N.H., Mc Cowage, 1987, Colour forming mechanisms during mill processing, Proc. Aust. S.S.C.T.
Simth P., N.H. Paton, 1985, Sugar cane flavonoids, Sugar Tech. Rev., 12, 117-142
Tu J.C., A. Kondo, E. Sloane, 1977, The role of high and low molecular weight colorants in sugar color,
Proc. of I.S.S.C.T. Conf., Manufact., 1393-1400

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