First Principles

Before proceeding to the detailed study of the application of rheology to cheese, it is pertinent to consider a few basic principles. These will appear obvious to the reader educated in a physical science, but may be less obvious to those from other walks of life. One is taught that matter exists in one of three distinct states: gas, liquid, and solid. This context is mainly concerned with only the latter two. Both are characterized by the fact that any sample has a well-defined volume. Solids have a definite shape which can be altered only by the application of an external agency. Liquids, on the other hand, have no characteristic shape: they take up the shape of the vessel containing them.

The property, then, which distinguishes a solid is its rigidity and this term has been formally adopted by physicists as a measure of the effort required to change the sample's shape. The precise definition will be given later. If the material is a true solid, it will follow that this rigidity is invariant for the material. Furthermore, time does not enter into this, so it is understood that the change is instantaneous and once the effort is removed, the sample will recover its original shape spontaneously. This is, in plain language, the physicist's concept of an elastic solid.

In contrast with the solid, the characteristic by which a layman distinguishes a liquid is its fluidity. This, again, has a precise definition, but in practice it is more convenient to use the inverse concept, which is known as the vis-

L. M. Popplewell and J. R. Rosenau, "Incorporation of Milk Proteins Harvested by Direct Acidification Into Process Cheese Products," Journal of Food Process Engineering 11, 203-220 (1989).

M. Preininger and W. Grosch, "Evaluation of Key Odorants of the Neutral Volatiles of Emmentaler Cheese by Calculation of Odour Activity Values," Lebensm.-Wiss. Technol. 27, 237-244 (1994).

S. Rapposch, "Occurrence and Significance of Nonstarter Lactic Acid Bacteria in Cheese," Deutsche Milchwirtschaft 48, 838841 (1997).

M. Rosenberg, M. McCarthy, and R. Kauten, "Evaluation of Eye Formation and Structural Quality of Swiss-Type Cheese by Magnetic Resonance Imaging," Journal of Dairy Science 75, 2083-2091 (1992).

J. E. Schlesser, S. J. Schmidt, andR. Speckman, "Characterization of Chemical and Physical Changes in Camembert Cheese During Ripening," Journal of Dairy Science 75,1753-1760 (1992).

E. K. Shumaker and W. L. Wendorff, "Factors Affecting Pink Discoloration in Annato-Colored Pasteurized Process Cheese," J. Food Sei. 63, 828-831 (1998).

R. Smeets, "Enzyme-Coagulation," Dairy Technology-Paper 5,1418 (1995).

M. J. Sousa and F. X. Malcata, "Comparison of Plant and Animal Rennets in Terms of Microbiological, Chemical, and Proteolysis Characteristics of Ovine Cheese," J. Agric. Food Chem. 45,7481 (1997).

M. Sutheerawattananonda et al., "Fluorescence Image Analysis of Process Cheese Manufactured With Trisodium Citrate and Sodium Chloride," Journal of Dairy Science 80, 620-627 (1997).

F. Vance et al., "Autolysis of Lactobacillus helveticus and Propion-

bacterium freudenreichii in Swiss Cheeses: First Evidence by Using Species-Specific Lysis Markers," Journal of Dairy Research 65, 609-620 (1998).

R. Warme, H. D. Belitz, and W. Grosch, "Evaluation of Taste Compounds of Swiss Cheese (Emmentaler)," Z. Lebensm.-Unters. Forsch. 203, 230-235 (1996).

B. H. Webb, A. H. Johnson, and J. A. Alford, Fundamentals of Dairy Chemistry, 2d ed., AVI Publishing Co., Westport, Conn., 1974.

G. H. Wilster, Practical Cheesemaking, 11th ed., O.S.C. Cooperative Association, Corvalis, Ore., 1959.

P. Zanerl, "Detection of Clostridia Responsible for Cheese Defects in Raw Milk and Cheese," Deutsche Milkchwirtschaft 44, 936, 938, 940 (1993).

K. Rajinder Nuath John T. Hines Ronald D. Harris Kraft, General Foods, Inc. Glenview, Illinois

Sleeping Sanctuary

Sleeping Sanctuary

Salvation For The Sleep Deprived The Ultimate Guide To Sleeping, Napping, Resting And  Restoring Your Energy. Of the many things that we do just instinctively and do not give much  of a thought to, sleep is probably the most prominent one. Most of us sleep only because we have to. We sleep because we cannot stay awake all 24 hours in the day.

Get My Free Ebook

Post a comment