Determination of Caffeine Content and Antioxidant Activity of Coffee

Abstract

Attempt has been made to look into caffeine contents and antioxidant activity of coffee grown at Wembera, Goncha, Zegie, and Burie localities of North-West Ethiopia. The caffeine content of the extracts in % w/w has been found to be 1.53 ± 0.003 for Wembera coffee, 1.41 ± 0.040 for Goncha coffee, 1.29 ± 0.033 for Zegie coffee and 0.97 ± 0.049 for Burie coffee. The antioxidant activities of the coffee extracts were measured by using ferric reducing power assay and Rancimat assay. Ferric reducing power assay was used to measure the total antioxidant power of water soluble components of coffee and is expressed as ascorbic acid equivalent antioxidant capacity in milligram per gram of the dried coffee samples. The ferric reducing power values of the extracts were 9.532 ± 0.201, 9.159 ± 0.441, 8.955 ± 0.180, 6.751 ± 0.284 for Wembera, Burie, Goncha and Zegie coffees, respectively. The Rancimat assay was also used to measure antioxidant activity of lipid soluble portions of coffee extracts using sunflower oil as the oxidizable substrate. It was found that all the coffee extracts improved the oxidative stability of sunflower oil. The protection factors were 1.36 ± 0.027, 1.31 ± 0.027, 1.26 ± 0.069 and 1.17 ± 0.015 for Wembera, Burie, Goncha and Zegie coffees respectively. Based on these results, it is suggested that Wembera coffee has the higher caffeine content and antioxidant activities than Burie, Goncha and Zegie coffee varieties.

Development of new analytical methods for the determination of caffeine content in aqueous solution of green coffee beans

“…The results obtained using the three newly developed methods are comparable with the results obtained using UV/Vis spectrophotometry [1] and HPLC [9, 10] from literature (Table 3). This was further confirmed by applying t test to compare the means of the three newly developed methods with the mean of caffeine obtained by using UV/Vis spectrophotometry for the same coffee sample.…”

“…arabica coffee samples as reported by [1] for different Ethiopian C . arabica coffee samples grown in Wembera, Goncha, Zegie and Burie determined by UV–Vis spectrophotometry using dichloromethane for extraction to be 1.53 ± 0.003, 1.41 ± 0.04, 1.29 ± 0.033 and 0.97 ± 0.049 (% w/w), respectively.…”

“…Studies have indicated that the chemical composition of green coffee beans mainly depends on the variety of the coffee, although slight variations are possible due to agro-climatic conditions, agricultural practices (processing and storage), its species, origin and weather of the plantation [1, 10, 31]. Hence the variation of caffeine content of coffee samples may be due to the difference come from geographical origins.…”

“…Since then coffee has become one of the most widely consumed beverages throughout the world due to its pleasant taste, aroma, stimulant effect and health benefits [1]. Coffee comprises more than 90 different numbers of species.…”

“…Many analytical methods have been developed for the determination of caffeine in coffee beans and products containing caffeine including electroanalytical [7, 8]; chromatographic [4, 9, 10] techniques including gas chromatography [11–13], high performance liquid chromatography (HPLC) [4, 10, 14, 15], liquid chromatography-particle beam/electron ionization mass spectrophotometry [16], liquid chromatography-tandem mass spectrometry [17], and spectroscopic techniques [1, 4, 18–22] including nuclear magnetic resonance spectroscopy [23], near infrared spectroscopy [24, 25], near infra-red reflectance spectroscopy [26], and UV–Vis spectroscopy [1, 20, 27, 28], and fluorescence polarization immunoassays [29]. HPLC is the method of choice by many researchers in determining the caffeine contents of beverages, tea leaves and coffee beans.…”