Detalhes bibliográficos
| Ano de defesa: |
2016 |
| Autor(a) principal: |
Andolfatto, Suelen
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| Orientador(a): |
Felsner, Maria Lurdes
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| Banca de defesa: |
Não Informado pela instituição |
| Tipo de documento: |
Dissertação
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| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Estadual do Centro-Oeste
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| Programa de Pós-Graduação: |
Programa de Pós-Graduação em Química (Mestrado)
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| Departamento: |
Unicentro::Departamento de Química
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| País: |
Brasil
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| Palavras-chave em Português: |
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| Palavras-chave em Inglês: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://tede.unicentro.br:8080/jspui/handle/jspui/742
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Resumo: |
Syrups and cane molasses are products derived from sugarcane. Both have been receiving good acceptance in the domestic and international markets due to its sugars, minerals and vitamins contents and they are considered highly nutritious and versatile food. However, there are few studies on quantification of metals in these products. Thus, the purpose of this study was to develop and validate an analytical method for direct determination of Mn, Zn, Fe and Mg in syrups and cane molasses samples by Atomic Absorption Spectrometry in Flame (FAAS). Univariate tests in order to optimize the sample preparation conditions for the quantification of metals in cane syrup and cane molasses using direct analysis by suspension sampling were performed. After choosing the best sample preparation procedure, aqueous suspensions from syrups and cane molasses were prepared, which were analyzed directly by FAAS. The solutions were prepared by weighing 3.0 g of sample and swelled to 25.0 mL, except for Mg, where the mass / volume ratio was of 0.1 g in 100.0 mL, in order to avoid successive dilutions. To confirm the reliability of the developed method a validation study was performed and parameters such as linearity, limits of detection (LD) and quantitation (LQ), precision and accuracy were evaluated applying different statistical tests. Subsequently, the samples used in the study were assessed for its nutritional quality and through a chemometric tool, Principal Components Analysis, PCA, it which was applied to verify the similarities and differences between samples. Analytical curves obtained with external standard were employed for all elements analyzed, where they showed good linearity in the investigated concentration range, with values of Fregression >> Fcritical and no lack of fit of linear model was observed. The limits of quantification (LQ) obtained were low, with values of 0.07; 0.03; 0.12 and 0.02 mg g-1 for Mn, Zn, Fe and Mg, respectively. The precision of the method was verified by the relative standard deviations (RSD (%)) and by comparison weighted variances between two analytical methods for sample preparation (direct analysis and wet digestion), applying an F-test. The RSD (%) values proved to be suitable since they were lower than recommended by AOAC (RSD (%) <5.3 for Fe and Mg and RSD (%) <7.3 for Mn and Zn). Regarding the comparison of the developed method with the reference method, the Fcalculated values for all metals were lower than Fcritical with p > 0.05, proving that there are not significant differences in precision between the compared methods. The accuracy was evaluated by comparison with a reference method (wet digestion), applying a paired t-test and a linear regression analysis for samples of syrups and cane molasses, and by recovery tests. The results obtained from paired t-test revealed no significant differences between the compared methods since the values found for tobserved were lower than the tcritical with p > 0.05. Moreover, the high Fregression values obtained in the linear regression test confirmed that linear models for Mn, Zn, Fe and Mg are suitable and that the contents of these metals exhibit a linear relation between the sample preparation methods evaluated. The recoveries were adequate and vary between 91% and 109% for the four evaluated elements. These results indicate that the direct analysis presents adequate accuracy. Thus, it is suggested that this methodology can be applied in the quality control syrups and cane molasses with advantages over traditional methods of sample preparation as speed, low cost and reduction of toxic waste. From a nutritional point of view, only the cane syrups samples M05 e M06 were considered Mn sources. For Zn, Fe e Mg none of the sample of cane syrups reached the limit of 15% of the recommended daily intake of 100 g of solid food. Now, in relation to cane molasses samples, most were characterized by high concentrations of Mn, Fe and Mg, and they could be regarded as sources of these elements. Through the Principal Component Analysis (PCA) it was possible to verify the differences and similarities between the samples used in the study. In the arrangement of data in PCA, it was observed that the sugar cane molasses samples have higher levels of Mn, Fe and Mg when compared with cane syrups samples. It is suggested that this behavior may be related to the industrial process applied for each product. The fact that cane molasses is a byproduct of the production of granulated sugar, causes the mineral profile of cane molasses samples to differentiate of the profile of the cane syrups samples , once the sugar cane juice used in the production passes through various stages of concentration to get the final product, there may be a higher concentration of metal present when compared to the cane syrups production process. |
