| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Food Science and Technology, University of Georgia, Athens 30602-2106
Confocal scanning laser microscopy was used to observe coagulum formation resulting from milk acidification. Reconstituted nonfat dry milk was steamed for 15 min, inoculated with yogurt culture or mixed with glucono-
-lactone, and incubated at 40°C on a warm microscope stage. The pH was monitored on the slide simultaneously with observation of gel microstructure development. Coagulum formation was observed as a continuous process; gelation of the milk was initiated at pH 5.35, as determined by casein micelle aggregation and the cessation of bacterial cell movement. As the pH continued to drop, nonreflective, casein-free spaces around encapsulated microorganisms increased, which was attributed to contraction of the casein network. Direct-acidified milk at pH 5.0 had a three-dimensional microstructure with more uniform sizes and distribution of nonreflective spaces than did cultured yogurt. At pH 4.4, the structural differences between the various acidified milk gels were less apparent. The pH gradient within the milk gel was observed using a fluorescent molecular probe that was sensitive to pH. Areas of relatively high pH corresponded to the light-reflecting areas of the gel, confirming their identity as casein.
Key Words: yogurt • microstructure • confocal scanning laser microscopy
Submitted on February 2, 1995
Accepted on August 21, 1995
This article has been cited by other articles:
|
|
 |
|
  D. H. Purohit, A. N. Hassan, E. Bhatia, X. Zhang, and C. Dwivedi Rheological, sensorial, and chemopreventive properties of milk fermented with exopolysaccharide-producing lactic cultures J Dairy Sci, March 1, 2009; 92(3): 847 - 856. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. N. Hassan ADSA Foundation Scholar Award: Possibilities and Challenges of Exopolysaccharide-Producing Lactic Cultures in Dairy Foods J Dairy Sci, April 1, 2008; 91(4): 1282 - 1298. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. N. Hassan and S. Awad Application of Exopolysaccharide-Producing Cultures in Reduced-Fat Cheddar Cheese: Cryo-Scanning Electron Microscopy Observations J Dairy Sci, December 1, 2005; 88(12): 4214 - 4220. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. N. Hassan, J. F. Frank, and K. B. Qvist Direct Observation of Bacterial Exopolysaccharides in Dairy Products Using Confocal Scanning Laser Microscopy J Dairy Sci, July 1, 2002; 85(7): 1705 - 1708. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Ferrando and W.E.L. Spiess Review: Confocal scanning laser microscopy. A powerful tool in food science Revision: Microscopia laser confocal de barrido. Una potente herramienta en la ciencia de los alimentos Food Science and Technology International, January 1, 2000; 6(4): 267 - 284. [Abstract] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
