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Citations
... The slow drying observed for the shade drying is attributable to the low temperatures and high relative humidifies of the air observed during the drying progressions. This is in agreement with studies conducted by Fudholi et al. [21] as they realized that at low air temperatures, the relative humidity is higher, slowing down the drying process and as a result increases the drying time [22,23]. ...
Purpose
Coffee leaves, generally considered as an agri-waste are traditionally consumed as coffee leaf tea and are known to have medicinal properties. Leaves were valorized by exploring effects of different drying and steeping methods on its phytochemicals and formulation of a functional beverage.
Methods
The efficiency of drying systems such as sun, shade, and cross-flow (45 ± 1 °C), on drying kinetics, phytochemicals, volatiles and antioxidant potentials from coffee leaves were analysed. Subsequently, effect of steeping processes like hot infusions, cold infusions and cold brew on the physiochemical properties, phytochemical profile and sensory attributes of the functional beverage from coffee leaves were studied.
Results
Cross-flow drying was significant based on kinetics, rapid drying rate, moisture ratio, modelled successfully by Page equation (R² = 0.998). Chlorogenic acid (32–33 mg/g) was one of the major phytochemicals followed by quercetin (2–4 mg/g), caffeine (2–5 mg/g) and trigonelline (3–8 mg/g) contributing to significant antioxidant activities. Methyl salicylate is key volatile imparting warm-spicy aroma. Hot infusions (HI) asserted significant yield (47.7%), pH (6.54), Brix (1.3), phenolics (89.9 mg/g) and other phytochemicals ensued by cold infusions and cold brew with an appealing hue. The principal component analysis renders HI as superior steeping process with enhanced sensory profile.
Conclusion
Thus, the study provides insights on valorising coffee leaves in designing a functional beverage that finds new avenues in the coffee industry.
Graphical Abstract
... The slow drying process observed for the shade drying is attributable to the low temperatures and high relative humidities of the air observed during the drying processes. This is in agreement with studies conducted by Ahmad et al. (2016) as they realized that at low air temperatures, the relative humidity is higher, slowing down the drying process and as a result increases the drying time. Drying was unexpectedly faster under ambient conditions (about 30°C) compared to oven drying at 50°C. ...
Decoctions of ambang (Xymalos monospora) leaves are claimed to have therapeutic potentials but they are seasonal and highly perishable because of its high moisture content. To improve on the use of this plant, drying studies were carried out on its leaves in an effort to produce a green tea. Green tea was produced under 3 different drying conditions including shade, sun and electric drying. The effects of drying method and temperature (50, 60 and 70 °C) on the kinetics, proximate composition and total phenolic content of the teas were analyzed. Drying method had a significant effect on the drying kinetics and quality of the green tea produced. Drying occurred entirely in the falling rate period suggesting that the principal mechanism of drying was by diffusion. Kinetics of the drying processed were modeled successfully by the Page and Modified Page equations. Activation energy for the drying process as determined using K-values from the modified page equation was 27.89 kJ/mol. Significant differences were observed in the quality parameters of teas produced. Protein, carbohydrate and total phenolic content were also dependent on the type of solvent used for extraction. The green tea produced at 60 °C had most of its properties comparable to the commercial green tea used as a reference in the study. It is recommended that to produce good quality tea from ambang leaves, drying should be done at 60 °C for 6 h to obtain a tea with the following composition; moisture content (6.56 ± 0.01), total polyphenols (8.29 ± 0.08), Proteins (2.99 ± 0.13), ash (8.40 ± 0.15) and fiber content (20.43 ± 2.60).