Document Type : Research Paper

Abstract

As a native fermented dairy drink, doogh is an important industrial product in Iran. However, its characteristics have not been completely evaluated. This study evaluated the flow behavior, particle size distribution and stability of non-fat doogh as affected by the row material employed (fresh skim milk or skim milk powder) and the total solids (TS) content of the final drink. The viscosity of samples produced using fresh skim milk was 1.73 ± 0.24cPs. Those produced using skim milk powder exhibited higher viscosity resulting from bigger particle size. Increasing the TS content caused the viscosity of the doogh to increase, but the volume of the separated serum was reduced. Flow behavior became non-Newtonian at higher TS contents. Evaluations indicated that the colloidal particles existing in doogh were distributed among a wide range of sizes. Different particle shapes with complex structures were observed.

Keywords

Afonso, I. M., and Joao, M. M. 1999. Rheological monitoring of structure evolution and development in stirred yoghurt. J. Food Eng. 42, 183–190.
Akin, N., and Rice, P. 1994. Main yoghurt and related products in Turkey. Cultured Dairy Products J. 29(3): 23.
Anon. 1991. Doogh: Characteristics and examination. ISIRI. Standard Number 2453. (in Farsi)
Farhoodi, F. 1998. Milk Technology. Research and Education Jahad of Tehran Corporation Press. (in Farsi)
Foroughinia, S., Abbasi, S., Himidi Esfahani, Z. 2007. Effect of Individual and Combined Addition of Salep, Tragacantin and Guar Gums on the Stabilization of  Iranian Doogh. Iranian J. Nutrition Sci. Food Technol. 2, 15-25. (in Farsi)
Fox, P. F. 2003. The major constituents of milk. Chapter 1 in Smit, G. (Ed.), Dairy Processing: Improving Quality.
Keogh, M. K. and O’Kennedy, B. T. 1998. Rheology of stirred yogurt as affected by added milk fat, protein and hydrocolloids. J. Food Sci. 63(1): 108-112
Kiani, H., Mousavi, S. M. and Emam-Djomeh, Z. 2008. Rheological properties of Iranian yoghurt drink, Doogh. Inter. J. Dairy Sci. 3(2):71-78.
Koksoy, A. and Kilic, M. 2003. Effects of water and salt level on rheological properties of Ayran, a Turkish yoghurt drink. Inter. Dairy J. 13, 835-839.
Koksoy, A., Kilic, M. 2004. Use of hydrocolloids in textural stabilization of a yoghurt drink, Ayran. Food Hydrocol. 18, 593-600.
Laurent, M. A. and Boulenguer, P. 2003. Stabilization mechanism of acid dairy drinks (ADD) induced by pectin. Food Hydrocol. 17, 445-454.
McClements, D. J. 1999. Food Emulsions: Principles, Practice and Techniques. CRC Press LLC.
Sedlmeyer, F., Brack, M., Rademacher, B. and Kulozik, U. 2004. Effect of protein composition and homogenisation on the stability of acidified milk drinks. Inter. Dairy J. 14, 331–336.
Smit, G. 2003. Dairy Processing: Improving Quality. CRC Press LLC.
Tamime, A. Y. and Robinson, R. K. 1999. Yoghurt Science and Technology. Woodhead Publishing Ltd.
van Hooydonk, A. C. M., Boerrigter, I. J. and Hagedoorn, H. G. 1986. pH-induced physico-chemical changes of casein micelles in milk and their effect on renneting: 2. Effect of pH on renneting of milk. Netherlands Milk and Dairy J. 40, 297-313.
Vasbinder, J., Peter, J., van Mil, J. M., Bot, A. and de Kruif, K. G. 2001. Acid-induced gelation of heat-treated milk studied by diffusing wave spectroscopy. Colloids and Surfaces B: Biointerfaces. 21, 245-250.
Walstra, P. and Jenness, R. 1984. Dairy Chemistry and Physics. New York: Wiley.