The Effect of Rotational Speed and Applied Pressure During the Rubbing Process on Some Physical Properties of Black Tea

Mahdavi, Mostafa; Azadbakht, Mohsen; Abbaszadeh Mayvan, Ahmad

doi:10.22104/ift.2025.7867.2237

The Effect of Rotational Speed and Applied Pressure During the Rubbing Process on Some Physical Properties of Black Tea

Document Type : Research Article

Authors

¹ Department of Biosystem Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

² Department of Bio-System Mechanical Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.

³ Department of Biosystems Engineering, Faculty of Water and Soil Engineering, Gorgan University of Agricultural Sciences and Natural Resources

10.22104/ift.2025.7867.2237

Abstract

In this research, an attempt was made to design and evaluate a semi-industrial tea rolling machine. The study investigated the effect of roller rotational speed and the pressure applied to the green tea leaves on the quality of the rolled tea. First, prepared and weighed tea samples were rolled using the semi-industrial rolling machine with a capacity of 10 kg. The independent parameters were chosen at three pressure levels: 170, 340, and 680 kg/m², and three rotational speeds: 20, 30, and 40 RPM. Finally, the percentage of breakage, rolling time, and sensory quality were measured. The analysis of the percentage of breakage in samples due to the roller speed and pressure showed that as both speed and pressure increased, the percentage of breakage also increased. For the rolling time, it was concluded that only the independent factor of pressure had a significant effect on the required rolling time. By increasing the pressure of the roller, the time needed for the samples to roll decreased significantly. Ultimately, it was concluded that the best levels for the effective independent factors on the percentage of breakage were a pressure factor of 170 N and a rotational speed of 20 RPM. In the sensory test, the best aroma and flavor were related to the samples under a pressure of 340 N and a rotational speed of 30 RPM.

Graphical Abstract

Highlights

With the increase in speed and pressure, the percentage of breakage has also increased.
Increasing the pressure of the friction cylinder, the time required for the samples to dry has decreased significantly.
Samples under the conditions of 30 rpm and 340 N had the best quality in terms of flavor and aroma evaluation.

Keywords

Main Subjects

Food engineering

References

[1] Nair, K. P. (2020). Tea (Camellia sinensis L.). In tree crops: harvesting cash from the world's important cash crops. Cham: Springer International Publishing, 333-362. https://doi.org/10.1007/978-3-030-62140-7-9.

[2] Safarinejad, M. R. (2007). Adult urolithiasis in a population-based study in Iran: prevalence, incidence, and associated risk factors. Urol. Res., 35(2), 73-82. https://doi.org/10.1007/s00240-007-0084-6.

[3] Abdolmohammadi, P., & Cama, G. (2020). The main institutional and social players in iran. in contemporary domestic and foreign policies of Iran. Cham: Springer International Publishing, 89-127. https://doi.org/10.1007/978-3-030-45336-7-4.

[4] Noorzai, M. T., & Kutlar, A. (2025). Afghanistan's agricultural export advantage: a comparative study (2011-2019) with focus on key trading partners (Iran, Pakistan, Tajikistan, India, and Turkey). Sakarya Üniversitesi İktisat Dergisi, 14(1), 1-28. https://doi.org/10.37460/sid.1536433.

[5] Turkiewicz, I. P., Wojdyło, A., Tkacz, K., & Nowicka, P. (2020). Carotenoids, chlorophylls, vitamin E and amino acid profile in fruits of nineteen Chaenomeles cultivars. J. Food Compos. Anal., 93, 103608. https://doi.org/10.1016/j.jfca.2020.103608.

[6] Pou, K. J., Paul, S. K., & Malakar, S. (2019). Industrial processing of CTC black tea. In caffeinated and cocoa based beverages. Woodhead Publishing, 8, 131-162. https://doi.org/10.1016/B978-0-12-815864-7.00004-0.

[7] Abhiram, G. (2024). The evolution of tea harvesting: a comprehensive review of machinery and technological advancements. J. Biosyst. Eng., 49(4), 346-367. https://doi.org/10.1007/s42853-024-00238-9.

[8] Tang, M. G., Zhang, S., Xiong, L. G., Zhou, J. H., Huang, J. A., Zhao, A. Q., ... & Liu, A. L. (2023). A comprehensive review of polyphenol oxidase in tea (Camellia sinensis): Physiological characteristics, oxidation manufacturing, and biosynthesis of functional constituents. Compr. Rev. Food Sci. Food Saf., 22(3), 2267-2291. https://doi.org/10.1111/1541-4337.13146.

[9] Pou, K. J., Paul, S. K., & Malakar, S. (2019). Industrial processing of CTC black tea. In Caffeinated and cocoa based beverages. Woodhead Publishing, 131-162. https://doi.org/10.1016/B978-0-12-815864-7.00004-0.

[10] Zhang, S., Wu, S., Yu, Q., Shan, X., Chen, L., Deng, Y., ... & Li, J. (2023). The influence of rolling pressure on the changes in non-volatile compounds and sensory quality of congou black tea: The combination of metabolomics, E-tongue, and chromatic differences analyses. Food Chem.: X, 20, 100989. https://doi.org/10.1016/j.fochx.2023.100989

[11] Hossain, M. A., Ahmed, T., Hossain, M. S., Dey, P., Ahmed, S., & Hossain, M. M. (2022). Optimization of the factors affecting BT-2 black tea fermentation by observing their combined effects on the quality parameters of made tea using Response Surface Methodology (RSM). Heliyon, 8(2). https://doi.org/10.1016/j.heliyon.2022.e08948

[12] Azadbakht, M., Torshizi, M. V., Ziaratban, A., & Ghajarjazi, E. (2016). Application of Artificial Neural Network (ANN) in predicting mechanical properties of canola stem under shear loading. Agric. Eng. Int. CIGR J., 18(2), 413-425.

[13] Marsilio, V., Lanza, B., Campestre, C., & De Angelis, M. (2000). Oven‐dried table olives: textural properties as related to pectic composition. J. Sci. Food Agric., 80(8), 1271-1276.

https://doi.org/10.1002/1097-0010(200006)80.

[14] Hao, Z., Wang, J., Zhuang, J., Feng, X., Lv, H., Feng, J., ... & Chu, Q. (2025). Another inner truth of shaking: Water migration and transformation-advanced physicochemical alterations in tea leaves. Food Chem., 467, 142338. https://doi.org/10.1016/j.foodchem.2024.142338