RESUMO
Response surface methodology (RSM) has been used to optimize the extraction conditions of antioxidants with relatively low caffeine content from green tea by using ultrasonic extraction. The predicted optimal conditions for the highest antioxidant activity and minimum caffeine level were found at 19.7% ethanol, 26.4 min extraction time, and 24.0 ° C extraction temperature. In the predicted optimal conditions, the experimental values were very close to the predicted values. Moreover, the ratio of (EGCg + ECg)/EGC was identified a major factor contributing to the antioxidant activity of green tea extracts. In this study, ultrasonic extraction showed that the ethanol concentration and extraction time used for antioxidant extraction could be remarkably reduced without a decrease in antioxidant activity compared to the conventional extraction conditions.
Assuntos
Antioxidantes/química , Fenóis/química , Extratos Vegetais/química , Chá/química , Cafeína/química , Catequina/análogos & derivados , Catequina/química , UltrassomRESUMO
To observe the role of sarcoplasmic protein (SP) on myofibrillar protein (MP) denaturation under a hydrostatic pressure (HP), MP isolated from bovine muscle was treated with 300 MPa by increasing concentrations of SP (0, 0.8, 1.6, and 3.2 mg/ml) from bovine. SDS-PAGE patterns of soluble proteins in 0.1M NaCl (pH 7.4) indicated that a protein (about 100 kDa) from MP decreased with increasing concentrations of SP and that a 97 kDa protein from SP observed with 0.1 MPa was not observed with 300 MPa. SDS-PAGE patterns of soluble proteins in 0.6 M NaCl (pH 7.4) and Ca-ATPase activity showed that the denaturation of myosin heavy chain (MHC) was accelerated with increasing SP concentrations with the 300 MPa treatment. Thus, the addition of SP enhanced HP-induced denaturation of MHC and of a protein from MP of about 100 kDa.
