Effect of Pre-shearing and Temperature on the Yield Stress of Stirred Yogurt

Won Byong Yoon¹^,^*

¹Department of Food science and Biotechnology, Division of Biotechnology, School of Bioscience & Biotechnology, Kangwon National University

^*Corresponding author: Won-Byong Yoon, Department of Food Science and Biotechnology, Division of Biotechnology, School of Bioscience & Biotechnology, Kangwon National University, Chuncheonsi, Gangwon-do, 200-701, Korea, Tel: +82-33-250-6459; Fax: +82-33-241-0508, E-mail : wbyoon@kangwon.ac.kr

ⓒ Copyright 2009 Korean Society for Food Engineering. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Jan 07, 2009; Revised: Feb 04, 2009; Accepted: Feb 13, 2009

Published Online: Feb 28, 2009

Abatract

The yield stress of stirred yogurt was measured by the vane viscometer at different pre-shearing conditions, such as pre-shear speed, pre-shear time, and wait time, and temperature (12-38°C). The yield stress ranged from ~17.6 to 10 Pa and from 34.2 to 11.9 Pa, depending on the pre-shearing conditions and temperature, respectively. The preshear speed and the wait time significantly affected the yield stress. The temperature dependence of the yield stress was described by the Eyring’s kinetic model. The linear function of the temperature on the yield stress was limited at the 22°C, and at the above 22°C, the yield stress was maintained to be a constant (~12.5 Pa).

Keywords: yogurt; yield stress; vane viscometer; Eyring’s kinetic model