Browsing by Author "Dr. Christopher R. Daubert, Committee Member"

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    An Alternative Frying Process for Wheat and Gluten-Free Donuts
    (2009-04-07) Melito, Helen Shirley; Dr. Jonathan C. Allen, Committee Member; Dr. Christopher R. Daubert, Committee Member; Dr. Brian E. Farkas, Committee Chair; Dr. MaryAnne Drake, Committee Member
    Fried foods are enjoyed worldwide as snacks or part of a meal. However, because these foods are deep-fried in oil, they tend to have a high fat content. Previous study on a partial- (par-) frying, infrared- (IR-) finishing process showed that French fries cooked by this process had significantly lower fat content than fully-fried French fries (13% vs. 19%, respectively, α=0.05). It was hypothesized that this par-frying, IR-finishing process would be able to produce donuts with a lower fat content but instrumentally and sensorially comparable to fully-fried donuts. Experiments were separated into three groups: wheat par-fried, IR-finished donuts, GF fully-fried donuts, and GF par-fried, IR-finished donuts. Four different formulations of GF donuts were tested, each formulation using a different combination of GF flours (commercial GF flour and rice flour) and hydrocolloids (pregelatinized rice flour and xanthan gum). Donuts were fried with and without a methylcellulose coating (0.5 g methylcellulose in 50 g water), which was brushed on before proofing. All of the par-fried, IR-finished donuts were par-fried for 64 s and finished in an IR oven. Two different IR cooking times (45 s or 53 s for wheat donuts, 39 s or 45 s for GF donuts) and four different distance combinations from the IR emitters to the food were tested. Mass, volume, and density changes, percent moisture and fat, crust color, and crust and crumb rheological properties of all donuts were compared to those of fully-fried wheat donuts. Sensory testing was also performed on selected donuts using a 9-point hedonic scale (1: dislike extremely, 9: like extremely) to measure overall acceptance, aroma, taste, and texture/mouthfeel. Statistical analysis (α=0.05) showed that all of the wheat par-fried, IR-finished donuts (25.6%-30.6%), most of the GF fully-fried donuts (26.3%-32.2%), and all of the GF par-fried, IR-finished donuts (23.7%-28.2%) had a significantly lower fat content than the wheat control (33.7%). Setting the emitters in either a height gradient from 45 mm to 25 mm or at a height of 35 mm above the top of the donut and using either IR time produced wheat par-fried, IR-finished donuts that were most instrumentally similar to the control, while using the same emitter settings and an IR-finishing time of 39 s produced GF par-fried, IR-finished donuts that were the most instrumentally similar to the control. Gluten-free fully-fried donuts made with a higher ratio of commercial GF flour to rice flour were more instrumentally similar to the control than donuts made with an equal ratio of commercial GF flour to rice flour, regardless of hydrocolloid used. Sensory scores of the wheat par-fried, IR-finished donuts (overall acceptance of 5.28-5.85) showed no significant differences from the control (5.83) with the exception of one slightly lower appearance score (5.69 for the par-fried, IR-finished donut versus 6.57 for the control). All GF fully-fried donuts (overall acceptance of 4.33-4.68) and all GF par-fried, IR-finished donuts (overall acceptance of 3.81-4.44) received significantly lower sensory scores than the wheat control (6.37 and 6.94, respectively). These results indicated that the GF donuts were not as well liked as the control, possibly due to their dryness. Overall, the par-frying, IR-finishing process was shown to significantly lower the fat content of both wheat and GF donuts while producing donuts instrumentally and sensorially comparable to fully-fried donuts made with the same formulation. This process may be used instead of a full-frying process to produce donuts instrumentally and sensorially similar to fully-fried donuts, but with a significantly lower fat content.
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    Cheese Texture
    (2002-06-17) Brown, Jennifer Amber; Dr. Marcia Gumpertz, Committee Member; Dr. Mary Anne Drake, Committee Member; Dr. E. Allen Foegeding, Committee Chair; Dr. Christopher R. Daubert, Committee Member
    Cheese is a popular food due to its diversity in application, nutritional value, convenience, and good taste. Producing high quality cheeses that meet consumer expectations is crucial in order for cheese makers to remain competitive. These expectations include proper end-use functionality (shred, melt, stretch, etc.) and appropriate texture. Currently, there is not a complete understanding of what characteristics govern these aspects. This study seeks to determine what transitions occur during the early stages of maturation of certain cheeses, specifically, how the changes in physicochemical properties in young cheeses affect textural changes perceived when consumed. Mozzarella and Pizza cheeses were tested at 4, 10, 17, and 38 d of age; Process cheese was tested at 4 d of age. Rheological methods were employed to determine the linear, non-linear, and fracture properties of the cheeses. A trained sensory panel developed appropriate descriptive language and product-specific reference scales to evaluate cheese texture. Both sensorial and rheological methods differentiated the cheese varieties, and patterns were observed as the cheese aged. Rheological analysis showed the cheeses were viscoelastic gels with greater storage (G´, elastic) than loss (G'', viscous) moduli. The overall magnitude of G´ decreased as the cheeses aged; creep recovery analysis confirmed the loss of overall firmness with time. Five sensory terms differentiated the ages of the cheeses within varieties. Correlations between the sensory and rheological methods were observed. Principal component analysis revealed that combinations of both sensory and rheological parameters could distinguish the cheeses based upon variety and age. Comparison of certain large strain rheological methods was also done. Fracture stresses and fracture strains (or apparent strain) at three different strain rates (0.0047, 0.047, and 0.47 -1) were determined using both torsion and vane methods to see how the large strain properties compared in these cheeses. Overall, vane fracture stresses were lower than torsion fracture stresses. As the strain rate increased, the fracture stresses increased. Simple linear regression of the torsion and vane fracture stresses revealed that the torsion fracture stresses were 2.0 times higher than the vane fracture stresses (R²=0.66). Mozzarella is an anisotropic material since the body of this cheese has fibers that are oriented in a specific way. Methodology to appropriately evaluate the sensory perception of such materials was explored. No differences in any of the sensory terms were found between samples tested having the fibers oriented parallel to the force applied and samples tested having fibers perpendicular to the force applied. Finally, the thermal behavior of these cheeses was considered through use of differential scanning calorimetry. Two different heating schemes were used to determine if glass transitions occur in these cheeses and to characterize melting behavior. Glass transition temperatures were determined in the Process cheese. The heating profiles at elevated temperatures (i.e. during melting) were similar in all cheeses at all ages. It is likely that the transitions observed during melting are due to phase changes in certain lipids within the cheese. These results have significant implications in the cheese industry. An understanding of the transitions in both physical and chemical properties in young cheeses can help to explain what causes change in the perceptual texture, which may help in producing customized cheeses. Future testing should focus on how such parameters affect end-use functionality in order develop similar models which will help cheese makers to meet consumer demands.