Isolation of Caffeine From Tea Waste Using Subcritical Water Extraction

Abstract

The aim of this study was to investigate the isolation of caffeine from tea waste using subcritical water extraction (SCWE) method. The effect of various operating conditions such as water temperature (100,125,150, 175 and 200C), water flow rate (1, 2 and 4 g/min), mean particle size (0.25, 0.5, 1 and 2 mm) and pressure (20, 30 and 40 bar) on extraction yield and rate were determined. SCWE at 175C, water flow rate of 4 g/min and mean particle size of 0.5 mm was found to be able to recover 0.77% (w/w) of caffeine present in the tea waste within 1.5 h of extraction. In comparison with the SCWE, conventional hot water extraction showed 0.46% (w/w) extraction yield. It was found also that pressure had no effect on extraction yield and rate. A sustainable and environmentally friendly procedure has been used for the Fourier transform infrared determination of caffeine in tea waste extracted samples. PRACTICAL APPLICATIONS Subcritical water extraction (SCWE), as a green solvent, can be used in many different fields of applications. It can be used to extract antioxidant compounds from rosemary plants as well as to extract whitening agents and azo dyes in samples. Additionally, soil can be remediated through SCWE of dioxins. Recently, subcritical water has become of great interest as an alternative solvent for extraction of natural active compounds. In recent years, extraction of flavors, fragrances and antioxidant components from plant materials, and hydrolysis of carbohydrates, vegetable oils and fatty acids have been widely investigated by many researchers. Using subcritical water as a reaction media are some other interesting fields for practical applications.

Extraction of phenolic compounds from Siah‐Sardasht grape skin using subcritical water and ultrasound pretreatment

“…The high coefficient of temperature indicates that the temperature has the greatest effect on the extraction of total polyphenol. The same results were found by Shalmashi, Abedi, Golmohammad, and Eikani () from green tea waste. The probable reason for the significant increase of the TP amount at 150°C was the reduction in the dielectric coefficient of water at high temperatures and better phenolic extraction (Cheigh, Yoo, Ko, Chang, & Chung, ).…”

“…Hence, temperature was the main factor in the SWE of the phenolic compounds. Same results were obtained by Zhang et al (), Singh and Saldana (), and Shalmashi et al (). According to other investigations, this happened because of the diminution of the water dielectric constant due to the high temperature close to the dielectric constant of ethanol or methanol, leading to the inducement of the polyphenol's solubility (Rodriguez‐Meizoso et al, ).…”

High antioxidant activity of coffee silverskin extracts obtained by the treatment of coffee silverskin with subcritical water

“…It was reported that the percentage yield of caffeine extracted by subcritical water extraction from tea waste increased depending on the increase in the extraction temperature from 100 to 175°C. The highest value was obtained at 175°C was 0.77% (w/w) (Shalmashi, Abedi, Golmohammad, & Eikani, 2010). This difference might be due to the fact that most of the caffeine is contained in CS could be extracted even at 25°C, although caffeine in tea waste is located in an area where it can be extracted due to the degradation of cell walls and other cell components (Table 2).…”

Extraction and isolation of catechins from tea

“…For example, SWE has been employed to extract caffeine from tea or tea waste [72,73]. The SWE technique uses hot water at temperatures ranging from 100 to 3741C under high pressures from 10 to 60 bar [71].…”