Changes of Quality in Stirred Yogurt during Storage at Various Conditions of Temperature and Shaking

저장온도와 교반조건을 달리한 요구르트의 저장 중 품질변화

  • Lee, H.J. (Institute of Dairy Food Research, Seoul Dairy Co-op.) ;
  • Suh, D.S. (Institute of Dairy Food Research, Seoul Dairy Co-op.) ;
  • Shin, Y.K. (Institute of Dairy Food Research, Seoul Dairy Co-op.) ;
  • Goh, J.S. (Dept. of Dairy Sci., Kangweon National University) ;
  • Kwak, H.S. (Institute of Dairy Food Research, Seoul Dairy Co-op.)
  • 이호진 (서울우유협동조합 기술연구소) ;
  • 서동순 (서울우유협동조합 기술연구소) ;
  • 신용국 (서울우유협동조합 기술연구소) ;
  • 고준수 (강원대학교 낙농학과) ;
  • 곽해수 (서울우유협동조합 기술연구소)
  • Published : 1992.08.01

Abstract

This study was carried out to investigate the changes of quality in yogurt during delivery and storage. To do this, microbiological, physico-chemical and sensory properties in stirred yogurt were studied at different temperatures $(10^{\circ}C$ & $20^{\circ}C)$ and shakings (100 rpm & 200 rpm for 30 min). Titratable acidity and TCA soluble nitrogen in yogurt were increased in accordance with increase of temperature and time, while pH, lactose and lactic acid bacteria tended to be decreased. Interestingly enough, shaking conditions almost did not influence these studies. In sensory evaluation it showed that acidity was strong and sweetness was weak as increasing the storage temperature and time, but there were no significant differences until 10 days at $10^{\circ}C$ and 3 days at $20^{\circ}C$. Off-flavor was developed after 12 days at $10^{\circ}C$ with only 200 rpm shaking and after 6 days at $20^{\circ}C$ in both shaking conditions. These yogurts were not suitable for consumer. Viscosity in the yogurt became high as the temperature and time were increased. Viscosity was lower in yogurt shaked at 200 rpm than in non-shaked yogurt. Finally, this study indicates that temperature and shaking during delivery of yogurt may be critical in keeping quality of yogurt.

Keywords

yogurt;quality;shaking;sensory property