A leitura como um processo cognitivo
Figueiredo, Olívia Maria
1999-01-01
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You search for extraction and 8,991 records were found.
Gomphrena globosa L. is a source of betacyanins, molecules with high colorant power. In order to replace conventional extraction techniques, microwave (MAE) and ultrasound assisted extraction (UAE) processes were optimized by the response surface methodology (RSM) to maximize the recovery of betacyanins from G. globosa. A five-level full factorial design of 24 combinations and 4 replicates was implemented for MAE and UAE. The optimum processing conditions for MAE (t = 8 min; T = 60 °C; Et = 0%; and S/L = 5 g/L) conducted to an extraction yield of 39.6 ± 1.8 mg/g dry weight, while for UAE (t = 22 min; P = 500%; Et = 0%; and S/L = 5 g/L) a value of 46.9 ± 4.8 mg/g was achieved, validating the UAE more suitable to obtain the target compounds. This technique can provide extracts rich in betacyanins and with high potential to be used as nat...
Codfish is worldwide mostly consumed salt-cured due to the highly appreciated sensory characteristics promoted by salt. During the salting process huge amounts of salted wastewater are generated –
approximately 22% w/w of the codfish – carrying ca. 250 g/L of sodium chloride and ca. 10 g/L of organic compounds, namely proteins and free amino acids. In this study, the salt load of wastewater generated during the salting process of codfish (Gadus morhua) was successfully reduced by ethanol extraction. The effects of time, sample:ethanol ratio, pH and temperature on salt extraction by ethanol addition were assessed by a onevariable-at-a-time approach and then by performing a 32 fractional factorial design. The effects of pH were
also assessed in absence of ethanol. The maximum amount of salt precipitated in the wastewater was ca. 33%, a...
The aerial parts of Pterospartum tridentatum, a wild growing species in Portugal used in
traditional medicine and gastronomy, were harvested at different stages (vegetative phase, flowering
phase and beginning of dormancy) in two locations in Portugal (Malcata and Gardunha mountains),
and the respective aqueous extracts have been studied. The influence of the seasonal variation in the
extraction yield, total phenolic content and antioxidant activity was evaluated. The extraction was
carried out in boiling water in consecutive steps. After each step, the aqueous extract was separated
and fresh water was added maintaining the same plant material. The procedure was repeated seven
times, within an overall time period of 180 minutes.
Higher extraction yields were achieved with plant stems collected at the vegetative phases, either f...
Liquid-liquid extraction of platinum(IV) from chloride media was carried out using N,N -
dimethyl-N,N -dicyclohexyltetradecylmalonamide (DMDCHTDMA) in 1,2-dichloroethane.
Platinum can be effectively extracted by DMDCHTDMA without addition of tin(II) chloride,
since extraction percentages (%E) of 88% and 99% have been achieved from 6 M
and 8 M HCl, respectively. Moreover, platinum can be successfully stripped through a simple
contact with a 1 M HCl solution. The effect of some experimental parameters such as
equilibration time, diluent, extractant and HCl concentrations was systematically investigated.
The loading capacity of DMDCHTDMA was also evaluated. Data obtained from
successive extraction-stripping cycles suggest a good stability pattern of DMDCHTDMA.
Preliminary extraction data achieved with single metal ion solutions p...
High hydrostatic pressure (HHP) was applied to the extraction of phenolic compounds from watercress (Nasturtium officinale). The process was optimized by response surface methodology using a five-level central composite design combining the independent variables of processing time (t, 1.5–33.5 min), pressure (P, 0.1–600 MPa) and solvent (S, 0–100% of ethanol, v/v). The individual and grouped phenolic compounds, analyzed by HPLC-DAD-ESI/MS, and the extraction yield were used as response variables. The theoretical models were fitted to the experimental data, statistically validated, and used in the prediction and optimization steps. The optimal HHP conditions for the extraction of phenolic compounds were: t = 3.1 min, P = 600 MPa and S = 100%, and originated 64.68 ± 2.97 mg/g of extract. This study highlighted the HHP as a promising tech...
Liquid-liquid extraction of platinum(IV) from chloride media was carried out using N,N'-dimethyl-N,N'-dicyclohexyltetradecylmalonamide (DMDCHTDMA) in 1,2-dichloroethane. Platinum can be effectively extracted by DMDCHTDMA without addition of tin(II) chloride, since extraction percentages (%E) of 88% and 99% have been achieved from 6 M and 8 M HCl, respectively. Moreover, platinum can be successfully stripped through a simple contact with a 1 M HCl solution. The effect of some experimental parameters such as equilibration time, diluent, extractant and HCl concentrations was systematically investigated. The loading capacity of DMDCHTDMA was also evaluated. Data obtained from successive extraction-stripping cycles suggest a good stability pattern of DMDCHTDMA. Preliminary extraction data achieved with single metal ion solutions pointed out...
Carob kibbles are an important renewable source of valuable compounds, such as fermentable sugars and phenolic compounds. However, the selective recovery of these compounds is not a trivial task. In this work, a strategy was developed to enable the recovery of both classes of compounds by means of awater-based extraction.One-step extraction recovered only approximately 20% of the phenolic compounds, corresponding to an extraction yield of 0.6 g Gallic acid equivalents (GAE)/100 g dry mass of carob kibbles. The obtained extract contained a significant amount of carbohydrates (110 g/L). The alternative two-step extraction developed enabled higher compound selectivity together with an increase in the yield of the phenolic compounds to about 70%, corresponding to 1.9 gGAE/100 g carob dry matter.The two-step extraction was easily scaled-up ...
he well-known correlation between diet and physiology demonstrates the great possibilities of food to maintain or improve our health, increasing the interest in finding new products with positive physiological effects. Nowadays, one of the top research areas in Food Science and Technology is the extraction and characterization of new natural ingredients with biological activity that can be further incorporated into a functional food, contributing to consumer's well-being. Furthermore, there is a high demand for effective encapsulation methodologies to preserve all the characteristics of bioactive compounds until the physiological action site is reached. Scope and approach: In this review, the relevance of developing standard approaches for the extraction of the highly diverse bioactive compounds was described, as it defines the suitabi...
The present paper describes a procedure to isolate volatiles from rock-rose (Cistus ladanifer L.) using simultaneous distillation–extraction (SDE).
High-value volatile compounds (HVVC) were selected and the influence of the extraction conditions investigated. The effect of the solvent nature
and extraction time on SDE efficiency was studied. The best performance was achieved with pentane in 1 h operation. The extraction efficiencies
ranged from 65% to 85% and the repeatability varied between 4% and 6% (as a CV%).
The C. ladanifer SDE extracts were analysed by headspace solid phase microextraction (HS-SPME) followed by gas chromatography with
flame ionization detection (GC-FID). The HS-SPME sampling conditions such as fiber coating, temperature, ionic strength and exposure time were
optimized. The best results were achieved with a...
Benthic microalgae are important primary producers in intertidal shallow systems. Their biomass can be estimated by the assessment of chlorophyll a concentration. A rapid and reliable method of measuring chlorophyll a is by spectrophotometer. There is however, no standard protocol for the analysis of benthic chlorophyll a. Although the most common solvent generally used is 90% acetone, some authors showed better results with methanol and ethanol. Some pre-treatments, such as the addition of fine inert granules or ultrasound bath, have also been suggested as factors that improve the extraction efficiency. Sediment samples were collected from two sites, muddy and sandy, located within Ria Formosa (Portugal). The aim of this work was to test the effectiveness of different pre-treatments in the extraction and to develop an optimal method f...
