Química Nova
URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/13323
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Item Saponificação assistida por micro-ondas na extração de diterpenos em café arábica torrado(Sociedade Brasileira de Química, 2017) Bianchin, Mirelli; Yamashita, Fabio; Benassi, Marta de ToledoThe extraction of kahweol and cafestol involves saponification reaction. This step is important for the efficiency of the extraction as the diterpenes are susceptible to structural changes during hydrolysis. The microwave-assisted saponification has been successfully used in different matrices, but there is no previous report of the use of this technique in the saponification of diterpenes. Therefore, the effect of microwave-assisted saponification on the extraction of kahweol and cafestol in roasted coffee was evaluated. A 32 factorial experimental design was used in order to evaluate the effect of temperature (70, 80, and 90 ºC) and reaction time (4, 8, and 12 min). The quantification of diterpenes was performed by high-performance liquid chromatography and the results were compared to with those obtained by a method, which uses thermostatic bath for saponification. Temperature and time had a significant effect (p < 0.05) on diterpenes levels. For simultaneous saponification of kahweol and cafestol, the optimal reaction conditions were 80 ºC / 12 min. The use of microwave-assisted procedure lead to lower yields of kahweol (24%) and cafestol (35%) compared to reference method. However a significant reduction of reaction time (80%) was achieved, and the procedure also has the advantage of controlled process conditions and the possibility of extended scale.Item Metodologia para análise simultânea de ácido nicotínico, trigonelina, ácido clorogênico e cafeína em café torrado por cromatografia líquida de alta eficiência(Sociedade Brasileira de Química, 2006) Alves, Sandriel Trindade; Dias, Rafael Carlos Eloy; Benassi, Marta de Toledo; Scholz, Maria Brígida dos SantosA reverse phase liquid chromatography method was developed for simultaneous determination of trigonelline, caffeine, nicotinic and chlorogenic (5-CQA) acids in roasted coffee. A gradient of acetic acid/acetonitrile was used as mobile phase and detection was carried out in the UV. The samples were extracted with acetonitrile/water (5:95 v/v) at 80 ºC/10 min. Good recovery (89 to 104%), repeatability and linearity were obtained. Detection limits of 0.01, 0.15, 0.04 and 0.04 mg mL-1 were observed for nicotinic acid, trigonelline, 5-CQA and caffeine. The method, applied to arabica and robusta coffees with different degrees of roasting, was efficient and fast (~35 min) and also allowed identification of cinnamic acids.