Browsing by Author "Pavlovic, Suzana"

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    Adsorption of starch, amylose, amylopectin and glucose monomer and their effect on the flotation of hematite and quartz.
    (2003) Pavlovic, Suzana; Brandão, Paulo Roberto Gomes
    The depressant effect of corn starch, its polysaccharide components (amylose and amylopectin), the monomer glucose and the dimer maltose were studied on hematite and quartz, by means of infrared spectrometry, adsorption isotherms determination and microflotation tests. All the carbohydrates tested have been effective in maintaining hematite hydrophilic, including glucose and maltose; as for quartz, only a flocculation action (mainly by amylopectin) had a mild effect in decreasing its floatability by the amine collector. FTIR studies confirmed that the carbohydrates adsorbed intensively onto hematite and the spectra of the adsorbed polymers and monomer were very similar, even though the non-adsorbed monomer spectrum was markedly different. The common adsorption mechanism indicated is a surface reaction involving the iron ion.
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    Maillard reaction during the processing of "Doce de Leite".
    (1994) Pavlovic, Suzana; Santos, Rinaldo Cardoso dos; Glória, Maria Beatriz Abreu
    ‘Doce de leite’, a dairy product widely consumed in Brazil as a dessert or cake filling, is obtained from the heat treatment of milk and sucrose. On heating, the Maillard reaction occurs with the formation of desirable browncoloured products with a characteristic and pleasant flavour. However, the reaction can also lead to changes in nutritive value. In order to follow chemically the extension of the Maillard reaction and its effect on the nutritive value of ‘doce de leite’ its commercial processing was followed. Increases in the level of free 5-hydroxymethylfurfural and in absorption at 420 nm by pigments attached to the protein were observed. The amino acid analysis showed a significant decrease in lysine levels (33%) as well as in arginine (11%) and histidine (10%). There was also a reduction in available lysine levels, as measured by the fluorodinitrobenzene (50.6%) and by the 2,4,6-trinitrobenzenesulphonic acid (23.5%) methods. These results suggest a deleterious effect of the processing of ‘doce de leite’ on the nutritive value of the milk.