Abstract

SOROL, Natalia; ZOSSI, Silvia; RUIZ, Marcelo  and  SASKA, Michael. Validation and application of the colorimetric method of phosphates in sugarcane and sweet sorghum juice. Rev. ind. agric. Tucumán [online]. 2019, vol.96, n.1, pp.25-33. ISSN 1851-3018.

Phosphate in sugar cane and sweet sorghum comes in inorganic (soluble and insoluble) and organic forms. Soluble inorganic phosphates are an important factor in clarification of sugar cane and sweet sorghum juices as they enter chemical reactions with added calcium ions, forming insoluble phosphates that are very effective in removing from the juice cane colloids, colorants and other species. The frequently recommended levels for good clarification are about 300 mg P2O5/L in the incoming juice. The results from several years of testing at EEAOC indicate high variability, with levels ranging mostly from 100 to 700 mg P2O5/L. The high variability makes the frequent analysis for soluble phosphates important for monitoring and control of the clarification process in the sugar factories. The frequently used colorimetric method was reviewed and validated. A simplification of the filtration procedure that makes the analysis more time-efficient was introduced and validated. The analysis time was reduced by 60%. The limit of detection and quantification of the method were found to be 4 and 10 mg P2O5/L, respectively. The average P2O5 recovery was found to be about 99% within the working range 10 - 1000 mg P2O5/L. The levels of insoluble phosphates were found below the detection limit in a set of samples of mixed juice and good quality clarified juice from sugar cane and sweet sorghum. The method´s expanded uncertainty was 7,9%.

Keywords : Sugarcane juice; phosphates; validation; clarification.

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