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Effect of water temperature and time on caffeine extraction from coffee



The stimulating effect of coffee is mainly depended on caffeine availability in products. Caffeine levels in grains of two coffee species, Coffea arabica and Coffea robusta, have been quantified via the maximal absorbance of standard caffeine at 288 nm. Three popular coffee brands in Vietnam were selected for quality assessment based on the qualitative information printed on their labels. Caffeine level in C. robusta is always higher than that of C. arabica at any time durations and temperatures of extraction. Best combination between time and temperature for caffeine extraction is 15 min and 90°C or 100°C. About 90% of caffeine has been removed from coffee powder by routine percolated. The extracted caffeine is tightly correlated with extracting sequence by the equation of y = 1.7647x with R = 0.9963. The chosen coffee -1.5023 2 products have higher caffeine contents, at least 2.5 times than those appeared on their labels.
λmax = 288 nm
Absorbance intensity
Wavelength (nm)
... Sample preparation for HPLC. Extraction of caffeine from tea samples was done with hot water as solvent according to the method of Nhan and Phu [16]. Two (2) grams of each sample was weighed and transferred into a beaker. ...
Tea is commonly consumed in Nigeria. Caffeine, a major constituent in tea, has some beneficial pharmacological properties, but can negatively affect human health if consumed excessively. The objective of the study was to evaluate some physicochemical properties and caffeine content of teas marketed in FCT, Abuja, Nigeria. Ten commercial brands of teas (8 black teas and 2 green teas) were assessed for weight variation, moisture content and pH tests using standard methods. Extraction of caffeine was carried out and the identity determined by thin layer chromatography and melting points, respectively. High performance liquid chromatography (HPLC) method for analysis of caffeine was developed, validated, and applied to determine caffeine content in the tea brands. Results of the weight, moisture content and pH tests of the samples ranged from 2.07–2.33 g, 5.65–11.0 % and 4.9–5.5, respectively. Caffeine was isolated from all the samples and showed same Rf value (0.46) with that of the reference standard. Melting points ranged from 236.0–238.5 °C. Caffeine content ranged from 12.25–21.76 mg/g for black teas and 13.35–15.05 mg/g for green teas. The study provides information on the stability, acidity and caffeine content in some commercially available tea brands.
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Bancha is a popular type of green tea in Japan, rich in tea polyphenols (TPs) and has a more astringent aroma with a less aromatic and strong character that complements functional foods. The blanching process is used to extract TPs and remove unwanted microorganisms, as well as inhibit phenolic oxidation. This study proposed a green tea blanching process followed by spray drying the extracts with maltodextrin. Furthermore, it is focused on maximizing the major chemical components of green tea (i.e., catechins, caffeine, and phenolic contents) based on powder particle size obtained through Multiple Response Surface Methodology optimizations. The results show that the proposed model accurately predicts leached-spray dried green tea’s total catechin and caffeine content, with a coefficient of 0.9475 and 0.8692, respectively. This process yielded composite desirability of 0.9751, while individual desirability yielded excellent results of 1.0000, 0.9188, 1.0000, and 0.9839 for catechin, caffeine, phenol content, and powder. The settings appear to yield functional results for entire responses. Due to the concerns in tropical skin nutrition applications, smaller particle size green tea can promote better adsorption than larger sizes.
The study presented a facile and efficient extraction method of main indole alkaloids from the fresh leaves of Mitragyna speciosa. A water extract containing three main indole alkaloids, namely mitragynine (MG), paynantheine (PT), and speciogynine (SG), was obtained by boiling the fresh leaves in water followed by partitioning with dichloromethane. The extraction yield of 1.0 % (w/w) was obtained under the optimized conditions. The contents of MG, PT, and SG obtained from water extraction were determined by high‐performance liquid chromatography analysis and were found to be comparable to those obtained from methanol extraction. However, because the extraction yield obtained from using methanol was tenfold higher than that from using hot water, this indicated the presence of some undesirable materials in the methanol but not in water extract. This method provided an alkaloid‐rich extract of M. speciosa. The procedure was easy to perform, inexpensive, environmentally benign, and could be easily scaled up from laboratory to industrial scale. The present study demonstrated a facile and efficient extraction method of main indole alkaloids from the fresh leaves of Mitragyna speciosa. An alkaloid‐rich extract containing mitragynine and analogs was obtained by boiling the fresh leaves in water followed by partitioning with dichloromethane. The obtained extract was chlorophyll‐free, which would be either beneficial for further usage without purification or following easy purification. The method was facile as well as inexpensive and could be easily scaled up to industrial scale.
Of the known biochemical actions of caffeine, only inhibition of adenosine receptors occurs at concentrations achieved during normal human consumption of the drug. Under normal physiological conditions, adenosine is present in sufficient concentrations to activate A1 and A2a receptors. Via actions on A, receptors, adenosine decreases neuronal firing and the release of neurotransmitters. The exact mechanisms are not known, but several possibilities are discussed. Via actions on A2a receptors, adenosine - and hence caffeine - can influence dopaminergic neurotransmission. Caffeine can induce rapid changes in gene expression and, somewhat later, marked adaptive changes. These include antiepileptic and neuroprotective changes. Thus, caffeine has a number of central effects directly or indirectly related to adenosine receptors. Some of these are potentially useful, and drug development based on the actions of caffeine should be interesting.
Simple sugars, oligosaccharides, polysaccharides, and their derivatives, including the methyl ethers with free or potentially free reducing groups, give an orange-yellow color when treated with phenol and concentrated sulfuric acid. The reaction is sensitive and the color is stable. By use of this phenol-sulfuric acid reaction, a method has been developed to determine submicro amounts of sugars and related substances. In conjunction with paper partition chromatography the method is useful for the determination of the composition of polysaccharides and their methyl derivatives.