Using tea stalk lignocellulose as an adsorbent for separating decaffeinated tea catechins

Decaffeination of tea extracts by using poly(acrylamide-co-ethylene glycol dimethylacrylate) as adsorbent

“…The DG°values for catechins were much smaller than those for caffeine, suggesting that the adsorption of catechins were more spontaneous and favorable. This result was consistent with the previous study about using tea stalk lignocellulose as an adsorbent for separating decaffeinated tea catechins (Ye et al, 2009). The decrease in DG°values for caffeine and catechins with increasing temperature reflected an increase in spontaneity and feasibility of adsorption at higher temperatures.…”

“…After adsorption and elution almost all caffeine (99%) was removed while 63.6-71.4% epigallocatechin gallate were remained. Ye et al (2009) also confirmed that tea stalk lignocellulose is an alternative low-cost adsorbent for preparing decaffeinated tea catechins. Scientists are continuously trying to find novel selective adsorbents that can be utilized for decaffeination in factory scale.…”

“…However, equilibrium adsorption amount decreased with increasing temperature, it was suggested that an increase in desorption rate with temperature was faster than adsorption rate. The free energy change is related to the adsorption properties, i.e., from À20 kJ mol À1 to 0 kJ mol À1 for physisorption and from À80 kJ mol À1 to À400 kJ mol À1 for chemisorption (Ye et al, 2009). From this view, adsorption of caffeine might belong to physisorption process, while adsorption of catechins was not a pure physisorption process.…”

“…However, withdrawal effects of excessive caffeine exposure have also been reported extensively in animal and human studies, such as sleep deprivation (Hindmarch et al, 2000), reducing fertility rates and increasing miscarriages (Bech et al, 2005), increasing the seizures frequency and aggravating seizures (Luszczki et al, 2006). Therefore, avoidance of excessive caffeine ingestion was recommended (Nawrot et al, 2003), and alternatives for effective decaffeination of food materials have been actively considered (Park et al, 2007;Beltrán et al, 2006;Sakanaka, 2003;Liang et al, 2007;Ye et al, 2007;Ye et al, 2009).…”

Structural and thermodynamic factors on adsorptive interaction of certain flavonoids onto polymeric resins and activated carbon

“…The absolute free energy values of adsorption on XAD-7 are higher than that XAD-4 for all the FVs considered herein. The Gibbs free energy is related to physisorption when ranged from −20 kJ mol −1 to 0 kJ mol −1 , and to chemisorption when ranged from −400 kJ mol −1 to −80 kJ mol −1 [42]. As shown in Table 7, the absolute G values of all FVs are smaller than 20 kJ mol −1 indicating that the adsorption of these eight FVs on macroporous resins is a physical adsorption enhanced by electrostatic effect.…”