O uso da ressonância magnética nuclear na análise do perfil químico de sucos de uva do tipo integral e néctar
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2017-12-14
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Universidade Federal de Goiás
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The present study aims to trace the chemical profile and to quantify carbohydrates glucose, fructose and sucrose in both integral and nectar grape juices through 1H NMR experiments using two quantification methods – external and electronic (ERETIC) reference. Both methods were efficient and in one single experiment were able to quantify simultaneously the three carbohydrates, to characterize the main constituents, as well as allowed us to know the level of fruit maturity and ethanol content in the juices. We have also observed a high content of fructose in the integral grape juice, which can mean a healthy risk since at elevated concentrations this monosaccharide could lead to insulin resistance syndrome and hyperuricemia. Furthermore, an alarming fact is that among the 24 brands of nectar grape juices analyzed, only four brands fulfilled the established limits of sucrose content and two of them were present with a sucrose content higher than 10 times that allowed by current legislation, being such nonconformity undetectable by methods actually used. The statistical analyzes demonstrate the influence of relaxation time on the trend of grouping the data, associating the same sample in completely different groups when not observed the time of five times the relaxation time (T1). Other observation was also allowed us to observe the distinct grouping between the nectar samples, which were qualified as sweetened with apple juice, and this information was not included on the label at the time of analysis, even though it was established by legislation.
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SANTANA, M. J. O uso da ressonância magnética nuclear na análise do perfil químico de sucos de uva do tipo integral e néctar. 2017. 150 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2017.