Diferentes estratégias de tratamento de amostras para avaliar a distribuição de fósforo em suco de laranja industrializado

Abstract

Assessment of phosphorus in fruit juices is of great interest due to its essentiality and nutritional properties. This study applied different sample treatment strategies to determine phosphorus fractions in industrialized orange juice. Firstly, total phosphorus (Ptotal) was determined from digestion and sample suspension exploring direct analysis by inductively coupled plasma optical emission spectrometry (ICP OES). Free phosphorus (Pfree) was determined through molybdenum blue spectrophotometric method and fractioning of this according to particle size was performed by analysis of filtered samples with 0.45 μm membrane. Phosphorus fractioning based on its charge was also performed by using two columns, the first a Sep-pack C18 cartridge (neutral) and the second packaged with ionic change resin Dowex 50WX8 (cationic). Determination of Ptotal showed that there was no significative difference between procedures, for 95%of confidence level. Pfree represented 30-90% of Ptotal with an inverse relation with respect to Ptotal concentration. Fractioning according to particles size evidenced the main fraction of Pfree in the samples after filtration and the high percentages of P in anionic fraction (from 91.2 to 95.9%) are related to free inorganic phosphate in equilibrium with its protonated forms. Thus, it was possible to assure nutritional potential of orange juice with respect of phosphorus content once it is in the available form of this element for the organism.