Caffeine

Zubair, Mohammad; Hassan, M. M. A.; Al-Meshal, I. A.

doi:10.1016/s0099-5428(08)60413-x

Cited by 17 publications

(6 citation statements)

References 78 publications

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“…It is important to note that caffeine does not form a solvate with ethanol (Figure S1); however, the a w values tended to slightly increase from the initial a w when β‐caffeine was stable (e.g., starting a w values 0.65 to 0.80 in Table 2). This is speculated to be from caffeine interacting with ethanol since caffeine is soluble in ethanol (13.3 g/L of ethanol, Zubair, Hassan, & Al‐Meshal, 1986), and the caffeine affects the ethanol–water interactions, thereby increasing the a w . However, when caffeine hydrate formed, the a w decreased because the water was being internalized into the hydrate structure (e.g., the initial 0.85 a w sample in Table 2).…”

Section: Resultsmentioning

confidence: 99%

“…Thus, at these temperatures, caffeine hydrate would not be considered to be a deliquescent crystal. However, the solubility of caffeine in water increases to approximately 166.6 g/L at 80 °C (Zubair et al., 1986) because β‐caffeine is the stable form in a saturated solution above 51 °C (Bothe & Cammenga, 1980) and anhydrates are more soluble than the hydrates (Khankari & Grant, 1995). In addition, increasing the temperature of solutes with a positive heat of solution (β‐caffeine heat of solution is 15.70 ± 0.09 kJ/mol at 298 K (Bothe & Cammenga, 1980)) will increase the solubility and decrease the deliquescence RH with temperature (Lipasek, Li, Schmidt, Taylor, & Mauer, 2013).…”

Section: Resultsmentioning

confidence: 99%

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Relative humidity–temperature transition boundaries for anhydrous β‐caffeine and caffeine hydrate crystalline forms

Allan

Owens

Mauer

2020

Journal of Food Science

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Caffeine is a hydrate‐forming polymorphic crystalline compound that can exist in α, β, and hydrate forms. Phase transitions between hydrate and anhydrous forms of a crystalline ingredient, and related water migration, can create product quality challenges. The objective of this study was to determine the relative humidity (RH)–temperature phase boundary between anhydrous β‐caffeine and caffeine hydrate. The β‐caffeine→caffeine hydrate and caffeine hydrate→β‐caffeine RH–temperature transition boundaries were determined from 20 to 45 °C using a combination of water activity (aw) controlled solution and vapor‐mediated equilibration, moisture sorption, powder X‐ray diffraction, and Fourier‐transform infrared spectroscopy techniques. Two transition boundaries were measured: the β‐caffeine→caffeine hydrate transition boundary (0.835 ± 0.027 aw at 25 °C) was higher than the caffeine hydrate→β‐caffeine transition boundary (0.625 ± 0.003 aw at 25 °C). Moisture sorption rates for β‐caffeine, even at high RHs (>84% RH), were slow. However, caffeine hydrate rapidly dehydrated at low RHs (<30% RH) into a metastable transitional anhydrous state with a similar X‐ray diffraction pattern to metastable α‐caffeine. Exposing this dehydrated hydrate to higher RHs (>65% RH) at lower temperatures (20 to 30 °C) resulted in full restoration to a 4/5 caffeine hydrate. This transitional anhydrous state was unstable and converted to a less hygroscopic state after annealing at 50 °C and 0% RH for 1 day. It was postulated that the caffeine hydrate→β‐caffeine was the true β‐caffeine↔caffeine hydrate phase boundary and that β‐caffeine could be metastable above the caffeine hydrate→β‐caffeine transition boundary. These caffeine RH–temperature transition boundaries could be used for selecting formulation and storage conditions to maintain the desired caffeine crystalline form. Practical Application Caffeine can exist as either an anhydrous (without water) or hydrate (internalized water) crystalline state. The stability of each caffeine crystalline form is dictated by humidity (or water activity) and temperature, and these environmental stability boundaries for the caffeine crystalline forms are reported in this manuscript. Conversions between the two crystalline states can lead to deleterious effects; for example, the presence of caffeine hydrate crystals in a low water activity food (e.g., powder) could lead to the relocation of the water in caffeine to other ingredients in the food system, leading to unwanted water–solid interactions that could cause clumping and/or degradation.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Relative humidity–temperature transition boundaries for anhydrous β‐caffeine and caffeine hydrate crystalline forms

Allan

Owens

Mauer

2020

Journal of Food Science

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“…Caffeine is commonly obtained by two means: extracting from tea or coffee ( , ) and synthesizing from urea or uric acid in several steps ( , ). The cost of caffeine obtained by extraction from tea or coffee is much higher than that obtained by chemical synthesis, largely due to the low caffeine content in tea or coffee.…”

Section: Introductionmentioning

confidence: 99%

Effect of Microbial Fermentation on Caffeine Content of Tea Leaves

Xiao-gang

Wan

et al. 2005

J. Agric. Food Chem.

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Caffeine is widely used in the food and pharmaceutical industries. For safety concerns, natural caffeine is preferred over synthetic products despite of its high cost. To explore more economical methods of acquiring natural caffeine, we adopted a microbial fermentation technique to increase the caffeine content of tea leaves. Our studies showed that the caffeine content in tea leaves increased reasonably after treating leaves with microorganisms for a period of time (i.e. orthodox pile-fermentation), and the amount of caffeine content increase varied significantly between black and green teas (27.57% and 86.41%). These results suggested that the change of caffeine content in tea leaves during the pile-fermentation depended not only on the growth and reproduction of microorganisms, but also on the tea composition.

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“…Caffeine is a water-soluble substance. Its solubility in water is 1 g per 50 ml (Zubair, Hassan, and Al-Meshal, 1986). The octanol/water partition coefficient (log P) of caffeine is -0.091 to -0.07 (Leo, Hansch, and Elkins, 1971;Sigma-Aldrich, 2014).…”

Section: List Of Figuresmentioning

confidence: 99%

“…It is a substance commonly used as a mild stimulant and is found in various dietary sources such as coffee, tea, and cocoa. Since caffeine is a water-soluble substance (1 g per 50 ml) (Zubair et al, 1986), it is often used as a hydrophilic model molecule in research papers (Boucaud et al, 2001;Dreher et al, 2002;Garland et al, 2012;Schlupp et al, 2014;Abd, Roberts, and Grice, 2016). Caffeine is used in the treatment of cellulite with a variety of mechanisms such as to prevent lipid accumulation and to stimulate lipid breakdown in adipocytes (Herman and Herman, 2013).…”

Section: Chapter II Literature Review Caffeinementioning

confidence: 99%

Development of elastic liposomes of caffeine for the treatment of cellulite

Kao-ian

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In this study, caffeine elastic liposomes were developed for cellulite treatment by using the combination of surfactant and ethanol. The elastic liposomes studied consisted of phosphatidylcholine as the structural lipid, Span® 80 or Tween® 80 of the same molar ratio (5-10% w/w and 15-25% w/w of total lipid, respectively) as the edge activator and various concentrations of ethanol (5-25% v/v). The effects of type and amount of surfactants and concentration of ethanol on physical properties i.e., vesicle formation, size and size distribution and elasticity of blank liposomes were investigated. The blank liposome formulations with highest elasticity of each surfactant were selected to prepare the caffeine-containing elastic liposomes. These elastic liposomes were characterized for physical properties including entrapment efficiency and physical stability. The skin delivery of caffeine from the chosen elastic liposome formulations were carried out in vitro with modified Franz diffusion cells under the non-occlusive condition using newborn pig skin as the model membrane. The results showed that the complete vesicle formation was observed at low ethanol concentrations (5-15% v/v). The vesicle size of liposomes composed of Span® 80 and Tween® 80 was in the range of 5.84-8.08 µm and 3.73-5.27 µm, respectively. The combination of surfactant and ethanol showed significant effects on physical properties of elastic liposomes. The elasticity of liposomes containing Span® 80 and Tween® 80 was in the range of 27.07-79.86% and 8.44-15.74%, respectively. The formulations with highest elasticity, S7.5_5 with Span® 80 7.5% w/w and ethanol 5% v/v and T20_5 with Tween® 80 20% w/w and ethanol 5% v/v, were chosen to load caffeine. In general, physical properties of caffeine elastic liposomes were similar to the corresponding blank liposomes. However, caffeine loading decreased the elasticity of caffeine-entrapped elastic liposome formulations by approximately 20-30% compared to that of the blank elastic liposomes. The elasticity values of the caffeine-loaded elastic liposome formulations S7.5_5 and T20_5 were 53.46±8.63% and 11.93±0.46%, respectively. The entrapment efficiency values of S7.5_5 was lower than that of T20_5 (35.05±0.60 and 41.31±3.32% w/w, respectively). Skin permeation from S7.5_5 and T20_5 were significantly higher than that from the hydro-alcoholic solution used as the aqueous phase of these elastic liposomes. However, despite the profound difference in elasticity between the 2 formulations, no significantly differences were seen in most permeation parameters studied. The only significant difference detected was the enhancement factor of caffeine amount in the skin, the mean of which was almost doubled for the S7.5_5 formulation when compared to the T20_5 formulation.

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Caffeine

Cited by 17 publications

References 78 publications

Relative humidity–temperature transition boundaries for anhydrous β‐caffeine and caffeine hydrate crystalline forms

Relative humidity–temperature transition boundaries for anhydrous β‐caffeine and caffeine hydrate crystalline forms

Effect of Microbial Fermentation on Caffeine Content of Tea Leaves

Development of elastic liposomes of caffeine for the treatment of cellulite

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