DETERMINATION OF OPTIMUM CONDITIONS FOR THIN-LAYER DRYING OF LEMON BALM LEAVES (MELISSA OFFICINALIS L.)

Amer, Baher M. A.

doi:10.21608/mjae.2012.102611

DETERMINATION OF OPTIMUM CONDITIONS FOR THIN-LAYER DRYING OF LEMON BALM LEAVES (MELISSA OFFICINALIS L.)

Document Type : Original Article

Author

Baher M. A. Amer

Lec., Agric. Eng.; Fac. of Agric.; Cairo University-Egypt.

10.21608/mjae.2012.102611

Abstract

Drying kinetics of Melissa officinalis were investigated in a laboratory scale hot air dryer at an air velocity of 0.5, 0.75 and 1.00 m/s and temperature range of 30, 40 and 50°C to find out the optimum drying conditions in terms of drying rate.
Drying rate increased significantly with the increase in air temperature. Drying rate increased with the increase of air velocity up to 1.0 m/s. Above this air velocity, drying rate became independent of air velocity. The optimum drying air conditions was the temperature of 50°C and air velocity of 1.0 m/s, when drying time was considered. The experimental data were fitted to determine the drying constant “k” for drying lemon balm in thin layer. Hence, optimum lemon balm in color may be dried at an air temperature of 40°C and air velocity of from 0.75 to 1.0 m/s and this is the maximum air temperature may be recommended to describe the thin layer drying of lemon balm. The effective moisture diffusivity was determined of lemon balm during drying. The effective moisture diffusivity of Melisa increased linearly from 9.2×10^-10 to 2.16 ×10^-9 m²/s as drying air temperature increased from 30 to 50°C. The activated energy of Melissa officinalis was calculated and found to be 24.62 kJ/mol.

Main Subjects

Processing Engineering of Agricultural Products

References

Abdel Ghaffar, E. A., Shokr, A. Z., Rashwan, M. A. and Shaaban, S. S. (2011). Effect of natural and solar energy drying systems on drying characteristics of Marigold medical plants. Misr J. of Ag. Eng., 28 (3): 719-733.

Akpinar, E. K. (2006). Mathematical modelling of thin layer drying process under open sun of some aromatic plants. Journal of Food Engineering, 77, 864–870.

Alibas, I. (2007). Energy consumption and color characteristics of nettle leaves during microwave, vacuum and convective drying. Biosystems Engineering,96(4): 495-502.

Arafa, G. K. (2007). Optimum drying conditions for thin-layer drying of sweet basil. Misr J. of Ag. Eng., 24 (3): 540-556.

Argyropoulos, D., Kudadam, J., and Müller, J. (2009). Color Degradation of Lemon Balm (Melissa officinalis L.) as Affected by the Drying Process. 5^th CIGR Section VI International Symposium on Food Processing, Monitoring Technology in Bioprocesses and Food Quality Management. Potsdam, Germany.

Buser, M. D., Stone, G. H., Bruswitz, Moness, N. O. and Whitelock, D. P. (1999). Thin-layer drying of marigold flowers and flower components for petals removal. Transactions of the ASAE. 42(5): 1367-1373.

Crank, J. (1975). The Mathematics of Diffusion; Oxford University Press: Oxford.

Halsey, G. (1985). Physical adsorption on uniform surface. Chemical Physics. 16 (10): 931-936.

Lee, G., and Hsieh, F. (2008). Thin‐layer drying kinetics of strawberry fruit leather. Transactions of the ASABE, 51(5): 1699-1705

Matouk, A. M.; Abedel-Latif. S. M.; El-Hadidi, Y. M. and Tharwat, A. (2002). Drying of ear corn. Part II: Thin layer drying equations. The 10^th Conf. Misr J. of Ag. Eng., 19 (4): 139-154.

Mosallam, M. A., Zaalouk, A. k. and Werby, R. A. (2011). Thin layer drying of watermelon seeds (Colocynthis Citullus). Misr J. of Ag. Eng., 28 (2): 440-450.

Rizvi, S. S. H. (1986). Thermodynamic properties of foods in dehydration. In: Rao, M. A. and S. S. H. Rizvi (Ed.), Engineering properties of foods (pp. 190-193). Marcel Dekker Inc., New York.

Shokr, A. Z., Abdel Ghaffar, E. A., Rashwan, M. A. and Shaaban, S. S. (2011). Development of the drying characteristic coefficients of dried Marigold plants by using of an electrical laboratory drying system. Misr J. of Ag. Eng., 28 (1): 181-200.

Soysal, Y. (2004). Microwave drying characteristics of parsley. Biosystems Engineering, 89, 167–173.

Zogzas, N. P., Maroulis, Z. B., and Marinos-Kouris, D. (1996). Moisture Diffusivity Data Compilation in Foodstuffs. Drying Technology, 14: (10), 2225 - 2253.