Easy, Effective Cheese Softening Point Determination

Softening point, or SP, is the temperature at which a substance softens and stretches under a defined weight and flows vertically down a defined distance (the flow distance). A ball is normally used as a weight to promote the flow of the substance; using this technique, both thermal values and rheological properties such as meltability, flow propensity and stretchiness (summarized in Table 1) can be studied [1].

Cheese is an increasingly common ingredient in prepared foods. As it becomes elastic at elevated temperatures, SP measurement is an effective means of characterizing its behavior, and food scientists increasingly employ SP to ensure flavorful results.

Table 1: Textural properties of melted cheese.

Procedure

Here, we investigated three melted cheeses using METTLER TOLEDO's Excellence Dropping Point System. Cheddar, emmentaler and mozzarella were subjected to simultaneous duplicate experiments, with each sample measured three times (n=6). The Excellence instrument permits video observation during and after the measurement, as shown in Figure 1.

During the course of an SP experiment, the flow distance is monitored constantly. SP temperature can be determined at the moment when the sample has flowed a distance of 19 mm; an example of a distance diagram is sketched in Figure 2.

Because factors such as motion affect the flow of the sample from the cup, the overall force experienced by the flowing sample can be mathematically formulated as follows:

d = c₀ + c₁*T + c₂*[exp(c₃*T+ c₄)]
(eq. 1)

where:
d is the vertical flow distance
T is the temperature
c₀ and c₁ are linear terms
c₂, c₃ and c₄ are parameters of the exponential term

The most important parameter is c₃, because it indicates how rapidly the exponential function decays – or in experimental terms, how quickly the cheese softens.

In the conventional signal processing field, c₃ is known as the time constant (τ) and can be expressed as a reciprocal. Since we are considering temperature and not time dependence, we call this term the temperature constant τ_T. τ_T can be obtained after curve fitting and can be used to distinguish between SP samples.

Results

Table 2 summarizes the results of the three melted cheeses. They indicate that, for both SP and τ_T, there is a progression of results with increasing temperature, and τ_T from cheddar to emmentaler to mozzarella.

Mozzarella exhibits the highest SP of 72.5 °C – a full 10 °C higher than the other two. The SPs of cheddar and emmentaler are close: 60.1 °C and 62.7 °C, respectively. Should two different cheeses share a similar SP, τ_T values assist in distinguishing between them.

Table 2: Softening point and temperature constant (τ_T) results. Uncertainties express standard deviations (n=6). SP results in °C.

Conclusions

Heating modifies the original microstructure of a cheese, and with it, its texture. SP data indicates the temperature at which this thermal change takes place, while τ_T indicates how quickly it occurs. Measuring the SP sheds light on the interplay among parameters such as meltability, viscosity and stretchiness in a phenomenological way, providing insight into a cheese's suitability for specific recipes.

[1] R.Kapoor, L.E. Metzger, CRFSFS (7), 2008:194-214.