title: Image analysis and green tea color change kinetics during thin-layer drying.
abstract: This study was conducted to investigate the effect of air temperature and air flow velocity on kinetics of color parameter changes during hot-air drying of green tea, to obtain the best model for hot-air drying of green tea, to apply a computer vision system and to study the color changes during drying. In the proposed computer vision system system, at first RGB values of the images were converted into XYZ values and then to Commission International d'Eclairage L*a*b* color coordinates. The obtained color parameters of L*, a* and b* were calibrated with Hunter-Lab colorimeter. These values were also used for calculation of the color difference, chroma, hue angle and browning index. The values of L* and b* decreased, while the values of a* and color difference (ΔE*ab ) increased during hot-air drying. Drying data were ﬁtted to three kinetic models. Zero, ﬁrst-order and fractional conversion models were utilized to describe the color changes of green tea. The suitability of fitness was determined using the coefficient of determination (R (2)) and root-mean-square error. Results showed that the fraction conversion model had more acceptable fitness than the other two models in most of color parameters.
authors.affiliation: Islamic Republic of Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shahabi
authors.affiliation: Department of Mechanical Engineering of Agricultural Machinery, Faculty of Agricultural Engineering and Technology, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran shahinrafiee@ut.ac.ir.
authors.forename: Shahin
authors.initials: S
authors.lastname: Rafiee
authors.affiliation: Department of Mechanical Engineering of Agricultural Machinery, Faculty of Agricultural Engineering and Technology, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
authors.forename: Seyed Saeid
authors.initials: SS
authors.lastname: Mohtasebi
authors.affiliation: Department of Mechanical Engineering of Agricultural Machinery, Faculty of Agricultural Engineering and Technology, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
authors.forename: Soleiman
authors.initials: S
authors.lastname: Hosseinpour
mesh_terms: D000388:Air; D028241:Camellia sinensis; D003116:Color; D003124:Colorimetry; D003890:Desiccation / Q000379:methods*; D006358:Hot Temperature; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007700:Kinetics; D018515:Plant Leaves; D013662:Tea
chemical_list: D013662:Tea
keywords: Green tea; color changes; hot-air drying; kinetic models