Sweet whey powder is mainly used as an ingredient in foods and has a potential for increased use with the development of new foods. In view of the many whey powder producers, there is need to establish the quality of the whey powders currently on the market in terms of conformance to specifications, consistency over different seasons, and keeping quality. Selected sweet whey powder from different processors was analysed for microbiological, physicochemical and sensory quality. The whey powder was in most the cases within specifications. There was suggestive evidence of seasonal variability in the cooked flavor and sweet taste. In regard to storage, there was no significant difference in the flavor and aroma of the whey powder with storage except for the oxidized flavor which was marginally significantly different in at least one product. Most of the variation was in the microbiological and physicochemical properties. Of three products considered, rate of deterioration by the Maillard reaction, one was significantly different from the other two, having lower activation energy. Accelerated shelf-life testing deterioration rates compared well with those at ambient conditions for two products, implying that ASLT can be used for shelf-life determinations only if Maillard reaction inhibitors are absent. The flavor and aroma of sweet Cheddar cheese whey powder from one processor over 12 months, was consistent. However, the physicochemical, and microbiological properties were variable mainly between the fall and summer production with the fall production being higher in L* (lightness) and pH, but low in solubility index, and conversely, the summer production being high in solubility index and titratable acidity but low in L*. / Graduation date: 2005

The overall purpose of this study was to develop sensory evaluation methodology whereby wine quality can be predicted from juice quality. Descriptive analysis was used by a trained panel to describe Pinot noir juice and wine from three sources. From each source, one wine and four juice samples (a control and three treatments) were prepared. The following three treatments were applied to the crushed grapes prior to pressing the juice: freezing and thawing; skin contact with 250 ppm Pectinol VR (a pectinase); and skin contact with 250 ppm Rohapect D5L (another pectinase). The trained panel developed descriptive terminology which differed between Pinot noir juice and Pinot noir wine. The juice treatments created subtle, if any, aroma differences. Treatment differences were evident in color, as measured by human perception and by instrumental measurement. Few characteristics of wine aroma and/or color correlated with juice aroma and/or color. Perceived color correlated well with Somer's color density measurement (the sum of the corrected absorbances at 420 and 520 nm.). Some of the same samples were evaluated by a wine industry panel. They appeared to disagree regarding the definition of varietal character. Further research utilizing grapes from many sources is necessary to determine whether Pinot noir wine quality can be predicted from Pinot noir juice quality. / Graduation date: 1987

A lexicon describing the sensory perception of carbonated water was developed. Temporal aspects and differing ingestion conditions were investigated for Bite and Burn sensation using time-intensity (T-I). Four CO₂ levels (0, 1.7, 2.8, and 4.6 volumes) at 3°C and 10°C were tested. Trained panelists used a 16-pt category scale for evaluation in the first study. One swallow (15 ml) and four continuous swallows were evaluated by trained subjects using T-I in the subsequent studies. Lexicon included: salty, sour, bitter, cooling, astringency, bubbly, bubble size, bubble sound, gas expansion feeling, bite, burn, and numbing. Descriptor ratings, except cooling, increased as CO₂ level increased. Bubble size and bubble sound were rated higher for 10°C. Cooling, bite, burn, and numbing were rated higher for 3°C . Descriptors were divided into cooling, taste (salty, sour, bitter, astringency), trigeminal (bite, burn, and numbing), and mechanoreception descriptors (bubbly, bubble size, bubble sound, gas expansion feeling) based on PCA. Average temporal curves for Bite and Burn demonstrated that Burn sensation (steep linear rise and long-lived exponential decay slope) was similar to previously investigated irritants while Bite (steep linear rise and decay slopes, and relatively short duration) was unlike other irritants. Sensations were qualitatively and quantitatively different. Intensity and duration of Bite and Burn were concentration dependent. Cold temperature enhanced perception. Possible psychological habituation or desensitization was observed. Most T-I parameters were correlated for both Bite and Burn. These included CO₂ level dependent and CO₂ level independent parameters. Considerable subject variability was found. Increased exposure to CO₂ solution and increased cooling with ingestion of four continuous swallows was compared to one swallow. T-I curves for Bite (four swallows) were of higher intensity, longer duration, and developed maximum intensity plateaus. Those for Burn exhibited higher maximum intensities. At four swallows, T-I parameter correlations were strengthened, subject variability reduced and replication reproducibility improved by ease of rating afforded subjects by higher intensity sensations. Increased oral CO₂ perception with higher CO₂ levels and enhancement by cold temperature was reconfirmed. Beginnings of maximum intensity, Duration, and reaction time perceptual terminal thresholds were seen for the highest 3°C, CO₂ level. High CO₂ concentration, cold temperature, and exposure time induced these effects. / Graduation date: 1993

Both consumer and descriptive analyses were used to study the shelf-life of packaged, roasted and ground coffee in order to evaluate the utility of using sensory data in a shelf life model, and to examine the ability of consumers to detect a difference between treated and control samples. Two types of coffee, which differed in bean roast, blend and origin, were evaluated and were referred to as moderate roast and high roast. Samples were packaged under <2%, 9%, or 21% oxygen in airtight laminated foil packages. Over the course of 84 days, the samples were stored in 20��C, 30��C, or 40��C conditions and samples for all treatments were removed throughout the storage. The control samples were packaged at <2% oxygen and stored at -35��C for the duration of the study. Descriptive results illustrated a time trend in the moderate roast coffee along Factor 1, characterized by changes in the attributes of paper aroma, paper flavor, paper aftertaste, wood flavor, body, and oily mouthfeel. This trend resulted in significant differences between the control and the 40��C high oxygen 7 day stored samples in paper aroma (p=0.000) and paper flavor (p=0.000), as well as significant differences between the control and the 40��C high oxygen 49 day stored samples in paper aroma (p=0.002), paper flavor (p=0.000), paper aftertaste (p=0.000), body (p=0.000), and wood flavor (p=0.002). Factor I data from the 40��C high oxygen, moderate roast coffee were utilized in an Arrhenius shelf-life model. A second order model was fit to the data, indicating curvature in relationship for the rate of change over temperature for Factor 1 attributes. The model successfully generated a predictive curve for storage at 40��C. Consumers evaluated 30��C stored samples packaged under high oxygen and stored for either 4 or 7 days, and packaged under low oxygen and stored for 42 and 84 days. Consumer results indicated that it was difficult for consumers to detect differences between the moderate roast coffees. Consumers were readily able to tell significant differences between the high roast coffee treatments and the control sample (p<0.05). / Graduation date: 2000

Random fields are frequently used in computational simulations of real-life processes. In particular, in this work they are used in modeling of flow and transport in porous media. Porous media as they arise in geological formations are intrinsically deterministic but there is significant uncertainty involved in determination of their properties such as permeability, porosity and diffusivity. In many situations description of properties of the porous media is aided by a limited number of observations at fixed points. These observations constrain the randomness of the field and lead to conditional simulations. In this work we propose a method of simulating the random fields which respect the observed data. An advantage of our method is that in the case that additional data becomes available it can be easily incorporated into subsequent representations. The proposed method is based on infinite series representations of random fields. We provide truncation error estimates which bound the discrepancy between the truncated series and the random field. We additionally provide the expansions for some processes that have not yet appeared in the literature. There are several approaches to efficient numerical computations for partial differential equations with random parameters. In this work we compare the solutions of flow and transport equations obtained by conditional simulations with Monte Carlo (MC) and stochastic collocation (SC) methods. Due to its simplicity MC method is one of the most popular methods used for the solution of stochastic equations. However, it is computationally expensive. The SC method is functionally similar to the MC method but it provides the faster convergence of the statistical moments of the solutions through the use of the carefully chosen collocation points at which the flow and transport equations are solved. We show that for both methods the conditioning on measurements helps to reduce the uncertainty of the solutions of the flow and transport equations. This especially holds in the neighborhood of the conditioning points. Conditioning reduces the variances of solutions helping to quantify the uncertainty in the output of the flow and transport equations. / Graduation date: 2013

Addition of acids to foods allows for enhanced food safety. Acids are the primary form of defense against microbial contamination in refrigerated foods, while use of acids in conjunction with heat or high hydrostatic pressure processing lowers energy usage resulting in cost reduction. However, addition of acids to food or beverage formulations often reduces palatability due to higher sourness and this has limited the food industry's ability to better utilize them as preservatives. This study was aimed at gaining a better understanding of sourness suppression and its underlying mechanisms so that such limitations might be ultimately overcome. This work was divided into three parts dealing with the suppression of the sourness of citric, lactic and malic acids, as perceived by a trained sensory panel in a) binary mixtures with sugars, b) binary mixtures with salts and c) tertiary mixtures. The results of the first part showed that suppression was not mediated by sugar molarity or weight, but was significantly influenced by its perceived sweetness intensity in most cases. Sucrose and fructose were more effective than glucose in suppressing acid sourness and the data supported a separate receptor site/mechanism for glucose. Suppression was thought to have both central and peripheral components. In binary acid-salt mixtures sodium acetate (NaAc) affected the most sourness reduction, along with the largest concurrent pH increase (above 4.4). Sodium chloride (NaCl) mixtures showed significant suppression without a pH increase. Sodium gluconate (NaGluc) mixtures showed moderate suppression with citric and malic acids with pH increases remaining below 4.4, but showed little effect on lactic acid sourness. Saltiness appeared to drive suppression only in the case of NaCl, while pH change was responsible for reduction of sourness with NaAc and NaGluc. The tertiary trials indicated that a two-component multiple masker was more effective when its components stimulated different (as opposed to similar) receptors/receptor mechanisms in the taste system, irrespective of taste quality. Furthermore, a two-component masker was more effective than each component alone, and both components of a two-component masker did not have to be effective individually for them to function together as an effective multiple masker. / Graduation date: 2002

The effect of HTST pressure blanching processing parameters, as compared to conventional steam blanching, on enzyme activity, moisture, drip loss, shear force, sensory attributes and consumer acceptability of frozen sweet corn were determined. Complete inactivation of catalase and peroxidase required HTST treatments of 60 psi and 75 psi, respectively. No lipoxygenase activity was detected in the blanched corn. Moisture content increased slightly and maximum shear force decreased in the HTST blanched corn as compared to the steam blanched samples. No differences were observed in total work of compression and shear or drip losses in frozen corn prepared by the two blanching processes. Blanch pressures of 60 psi and 75 psi resulted in corn equivalent in sensory qualities to the control steam blanched product as judged by a trained panel. The 30 psi blanch treatment was rated higher in stale/oxidized, fishy, bitter, and other undesirable descriptors. Stale/oxidized and sweet/caramel character increased with storage time. Consumer tests resulted in no significant differences in acceptability across blanch treatments or storage time. / Graduation date: 1988

The processing parameters of and processing procedures for sweetened blueberry flavored carbonated milk beverages were developed in this study. Foam formation of the milk after carbonation was controlled by a precharging of the vessel headspace. A combination of heat treatment (85°C, 30 minutes) and CMC addition was conducted to minimize the acid coagulation of casein with added fruit concentrate. Both carbonated and noncarbonated, sweetened blueberry flavored milk were evaluated by a trained panel. The effect of carbonation and sweetener source on taste properties in a blueberry flavored milk beverage system were discussed. Carbonation enhanced the sensory rating of overall intensity, sweetness and blueberry flavor. There was no significant carbonation effect on perceived viscosity. The sweetener source (sucrose, HFCS, pear concentrate and aspartame) caused a significant effect on the sensory rating of viscosity, but a nonsignificant effect on that of overall intensity, sweetness and blueberry flavor. Two consumer panels evaluated the carbonated, sweetened blueberry flavored milk beverages. The percentage of panelists who liked the products was approximately 50%. The results from the distributions of responses on a "just right" scale indicated that the carbonation and sweetness level probably were optimum formulations, and the level of blueberry flavor was too low. The results also implied that sucrose and HFCS were more appropriate sweeteners in flavored carbonated milk beverages than aspartame and pear concentrate. Two obstacles for consumer potential were the rapid separation phenomenon and the unattractive color of the products. / Graduation date: 1988

The effect of sweeteners on fruit flavor perception was studied through the use of fruitiness power functions for unsweetened and sweetened model systems. In the first part of the study, two isosweet concentrations of aspartame and sucrose were determined and combined with five concentrations of orange and strawberry flavorants. Fruitiness power functions were developed and compared to determine the effect of each sweetener on the fruit flavor. For the second part of the study in the first experiment, one isosweet concentration of sucrose, aspartame, acesulfame-K and 1:1 blended APM/Ace-K was combined with five concentrations of each of three orange flavorants. Fruitiness power functions were developed and compared to determine how each sweetener effected the fruit flavor of each flavorant. The second experiment addressed the question of whether or not subjects associated sweet taste with fruitiness or if there was an actual change in the volatile composition of the aroma between the unsweetened reference and the sweetened solutions. Fruit aroma of the middle concentration of each flavorant sweetened with the four sweeteners was compared to the corresponding unsweetened reference. Enhancement of fruitiness was observed in the aspartame sweetened systems at low flavor levels. The power function slopes of both flavorants were lowered by the addition of aspartame which resulted in a slower rate of growth in fruitiness perception with the addition of flavorant to the system. In both the orange and strawberry flavored systems the aspartame sweetened solutions were rated higher in fruitiness than the sucrose sweetened solutions. The enhancement was more pronounced in the orange flavored system, suggesting a flavorant effect. The sweeteners affected the fruitiness perception of the three orange flavorants in different magnitudes but the patterns were similar. The three fruitiness slopes were all lowered by the addition of each sweetener. Flavor enhancement was greatest in flavor 1 sweetened with aspartame or aspartame/acesulfame-K. The higher relative placement and low slope of the fruitiness power functions in aspartame sweetened systems caused the enhancement effect to be greatest over the lower concentrations of each flavorant. In the second experiment, the fruit aroma of aspartame sweetened solutions in flavor 1 was significantly higher than the other sweetened solutions. The fruit aroma of the second and third flavorants was not significantly changed by the sweeteners. / Graduation date: 1992

The taste qualities of acidulants have not been studied in detail despite the fact that they are widely used by the food industry. Studies on characterizing the sensory properties of organic and inorganic acids are very limited. Reported studies are commonly on threshold, equi-sour and the time intensity values of sourness. A series of experiments were conducted to determine the sensory properties of selected acidulants by different sensory and multivariate methods. First, the technique of Free-Choice Profiling was applied in order to characterize the sensory profile of some selected acids (adipic, citric, fumaric, glucono-delta-lactone, hydrochloric, lactic, malic, phosphoric, quinic, succinic, tartaric, citric:fumaric, citric:malic and fumaric:malic) on a weight (0.08% w/v or v/v) basis. Results analyzed through Generalized Procrustes Analysis indicate that on a weight basis (w/v or v/v), acids differed in their flavor and taste dynamics. Likewise, acids were described differently by individual panelists. Second, the sourness power functions of the selected acidulants were generated from five molar concentrations by magnitude estimation involving 16 trained panelists. Equi-sour concentrations were determined by regressing the log of the rescaled response (sensory) on the log of the stimuli (physical). The calculated equi-sour levels ranged from 0.48 ml/L for HCl to 2.34 g/L for glucono-delta-lactone when citric add was set at 1.0 g/L. These theoretical equi-sourness were then tested by using an alternative sensory method, the directional difference from control test. Third, the sensory profile of the acidulants at their equi-sour levels was characterized using two sensory methods, free-choice profiling and the conventional descriptive analysis. The former was analyzed by Generalized Procrustes Analysis while the latter was analyzed by Principal Component Analysis. The two sensory methods gave similar patterns of information regarding the add samples. The similarities of several organic acids and their mixtures were very evident. Hydrochloric and phosphoric acids were astringent while succinic add was bitter and had a monosodium glutamate taste. It was concluded that adds had other sensory properties aside from sourness that must be considered in a given food application. / Graduation date: 1993