Date of Award:

5-2003

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Science

Committee Chair(s)

Donald J. McMahon

Committee

Donald J. McMahon

Committee

Darren Cornforth

Committee

Craig Oberg

Abstract

A correlation between the USU stretch test and the pizza fork test would allow the stretch properties of Mozzarella cheese to be measured objectively. The Utah State University (USU) Stretch Test uses a modified texture-profile analyzer to pull strands of cheese from a melted reservoir, measuring the load exerted on the probe during stretching. Parameters measured by the USU stretch test include Melt Strength (FM), which is the maximum load exerted on the probe, Stretch Load (SL), which is the load exerted on the probe at any specified point following FM, and Stretch Extension (SE), which was defined as the extension of the probe at a selected load. To begin with, it was determined that the greatest repeatability and cheese performance was obtained by tempering 50 g of shredded cheese for 45 min at 65°C and using a three-pronged hook with a diameter of 25 mm as the probe. These conditions were then applied in a correlation study in which a low correlation was seen between the USU stretch test and the pizza fork test, with the greatest correlation being seen with FM (R2 = 0.22). A more extensive look at the effect of the tempering temperature used in the USU stretch test on the degree of correlation between the two tests was conducted by tempering cheeses at 65, 70, 75, 80, and 85°C. In this experiment, the highest correlation between the two tests was seen at both 80 and 85°C. Values of R2 at 80°C for SL10-15 and SEF (Stretch Extension at FM) were 0.75 and 0.70, respectively. At 85°C, the highest degree of correlation was seen at SL10-15 (R2 = 0.72) and SE0.1 (R2 = 0.69). A multiple linear correlation study was also conducted. A high degree of correlation between the USU stretch test and the pizza fork test was seen at 80°C when two parameters were used (SEF and SL22, R2 = 0.85, Adj. R2 = 0.80) and when four parameters were used (FM, slope from 10 to 20 cm, SE0.1, and SL22, R2 = 0.97, Adj. R2 = 0.93). A set of cheese was then analyzed by the USU stretch test and the pizza fork test at three different intervals of aging (21, 40, and 60 days after manufacture). This data was combined with previously collected data to show that the USU stretch test can be used to characterize the functional properties of a cheese using the parameters of FM, SEF, as well as SE0.1.

It was concluded that the USU stretch test can provide a better characterization of a pizza cheese than can the pizza fork test. Whereas the pizza fork test is only able to record the distance that the cheese can stretch, the USU stretch test is capable of measuring a variety of parameters, which provides not only an indication of how far the cheese will stretch, but also other important functional properties related to the cheese, such as viscosity, elasticity, and the thickness of the strands being stretched.

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