The Kinetics and Mechanism of Caffeine Infusion from Coffee: the Temperature Variation of the Hindrance Factor

✍ Scribed by Spiro, Michael; Chong, Yuen Ying

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 191 KB
• Volume: 74
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(199707)74:3<416::aid-jsfa868>3.0.co;2-0

✦ Synopsis

The rates of infusion of ca †eine into water at 25.5¡C were measured for green and medium roast Kenyan arabica co †ees in the particle size range 0.85È 1.00 mm. Each type of co †ee was employed in three forms : dry (as received), water-Ðlled but still containing the original amount of solubles, and water-Ðlled and free of solubles other than ca †eine. Intra-bean di †usion coefficients of caffeine were calculated from the rate constants and compared with the known di †usion coefficients of ca †eine in water to provide hindrance factors. These were much larger than the corresponding hindrance factors obtained at 80¡C (Spiro et al, J Sci Food Agric 46, 349È356 ( 1989)). Examination of these results and of partition constants determined at both temperatures enabled the factors contributing to slow internal di †usion to be separated and identiÐed. Factors which were more pronounced at 25¡C were the Ðnite rate of ca †eine dissolution within the bean, complexation of ca †eine with chlorogenic acid and other co †ee solubles, and the adsorption of ca †eine molecules within the bean matrix.