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Title: Activation energy measurements in rheological analysis of cheese

item Tunick, Michael

Submitted to: International Dairy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2010
Publication Date: 10/1/2010
Citation: Tunick, M.H. 2010. Activation energy measurements in rheological analysis of cheese. International Dairy Journal. 20:680:685.

Interpretive Summary: The properties of cheese may be analyzed by slightly deforming a sample and measuring how it responds. If the sample is heated during this procedure, information is obtained on the way the protein and fat behave as the structure breaks down. The activation energy, which is the energy required for heated cheese to flow, can also be calculated, although it has rarely been applied to cheese. Several cheese varieties with widely varying compositions and characteristics were analyzed in this manner, and their activation energies provided information on how quickly the structure collapsed and the cheese flowed. Calculation of activation energy will allow scientists to gain a better understanding of the melting properties of cheese, and cheese manufacturers will be able to more accurately predict the behavior of their products.

Technical Abstract: Activation energy of flow (Ea) was calculated from temperature sweeps of cheeses with contrasting characteristics to determine its usefulness in predicting rheological behavior upon heating. Cheddar, Colby, whole milk Mozzarella, low moisture part skim Mozzarella, Parmesan, soft goat, and Queso Fresco cheeses were heated from 22 to 70 deg C, and Ea was calculated from the resulting Arrhenius plots. Protein content and moisture in nonfat substance were highly correlated with Ea. The Ea values for goat cheese and Queso Fresco, which did not flow when heated, were < 60 kJ/mol. Cheddar, Colby, and the Mozzarellas did flow upon heating, and their Ea values were between 100 and 150 kJ/mol. Parmesan, the hardest cheese, flowed rapidly with heat and had an Ea of 240 kJ/mol. Ea provides a means of quantitating the flow of cheese, and together with elastic modulus and viscous modulus provides a picture of the behavior of cheese as it is heated.