The Effect of Fat Content and Aging on the Texture of Cheddar Cheese

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Title: The Effect of Fat Content and Aging on the Texture of Cheddar Cheese
Author: Rogers, Neal Robert
Advisors: Christopher Daubert, Committee Member
Mary Anne Drake, Committee Member
E. Allen Foegeding, Committee Chair
Abstract: Low fat cheese has recently gained popularity for the health conscious consumer, but these cheeses often have undesirable characteristics such as lack of opacity and rubbery textures which contribute to negative consumer perceptions. The overall structural reasons for these differences are not understood. Determining why these textural differences occur, and what role fat plays in this structural change, was the goal of this research. In this study, two sets of cheeses were tested. The first set consisted of five cheeses, two of these cheeses were at normal fat contents for Cheddar cheese (33% fat), two were at “low†fat contents (6% fat), and one cheese at a “reduced†fat content (16% fat), these were tested at 0.5, 3, 6, and 9 months of age. The second set of cheeses consisted of Cheddar cheeses with fat contents of 3%, 8%, 13%, 18%, 23%, 28%, and 33% tested at 2, 4, 8, and 12 weeks of age. Sensory analysis was conducted using an established sensory lexicon broken into sets of terms related to hand, first bite, and chewdown (breakdown of the cheese during chewing) aspects of texture. Structural properties of the first set of cheeses were analyzed using stress sweeps, creep/recovery, torsional fracture with non-linear analysis, and adhesive tack tests. The second set of cheeses, which used a refined set of rheological tests, was tested using stress sweeps, temperature controlled frequency sweeps, torsional fracture, and a twin cycle compression test designed to assess percent recoverable energy. The results can be divided into three distinct regions of material behavior, linear, non-linear, and fracture. These regions represent the stress/strain response from low to high magnitude respectively. These results were then compared to sensory to determine relationships. The first set of cheeses showed strong relationships between sensory terms and the critical stress and strain and the BST model related non-linear curve shape. Some correlation was seen with fracture values, but these were not as high as terms related to the non-linear region of the cheeses. These results showed that the strain weakening behavior of the non-linear region is affected by the fat content, with higher fat cheeses breaking down more as strain increases than lower fat cheeses. Using this information, the second set of cheeses was evaluated with a focus on the non-linear region. Percent recoverable energy, which measures breakdown within the non-linear region, showed strong relationships with all of the sensory terms, with critical point and fracture values showing lower, but still significant correlations. These relationships, coupled with knowledge about oral processing, leads to the conclusion that the non-linear, strain weakening behavior of Cheddar cheese is the key structural region in understanding texture. Determining how fat causes these differences in the non-linear region was another key point of this study. Mechanical spectra, measured across a range of temperatures showed that fat in cheese behaved as an active filler component of the filled gel model. At lower temperatures (10ºC to 15ºC), fat appeared to play the dominant role in the overall structure of the cheese. Once the temperature was increased (>15ºC), the fat became more liquid and the protein network became the dominant component. This information along with fracture and non-linear data painted a picture of fat as the weakening point in the structure, and as fat content increased, the cheeses became weaker and would breakdown more. This suggests that a suitable replacement filler for fat would have to produce similar weakening effects to be able to match full fat texture.
Date: 2009-01-21
Degree: MS
Discipline: Food Science

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