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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Flavor characterization of selected acidulants in model and food systems

Hartwig, Pam A. 02 September 1994 (has links)
Acidulants can contribute considerably to the flavor of food. However, limited research on differences in acid flavor exists. While numerous researchers have studied acids, most have focused on sourness exclusively. Acids have been shown previously to differ in non-sour components, such as bitterness and astringency. A series of experiments were conducted to determine flavor characteristics of selected acids in different systems. First, selected acids (lactic, malic, citric, acetic) and 2 acid blends (lactic/acetic 1:1 and 2:1) in a model (water) system were evaluated on an equivalent weight (0.2% w/v) and on an equivalent pH basis. Three pH levels were explored: 3.5, 4.5 and 6.5. The technique of free-choice profiling was applied to characterize the flavor profile. Results analyzed by generalized procrustes analysis showed two significant findings: (1) acids differ in sensory character, and (2) the flavor of an acid changes with pH. Second, selected acids (lactic, malic, citric, tartaric) were evaluated in sweetened, flavored drinks on an equivalent weight basis at two concentrations (0.4 and 0.6% w/v). Four flavors were evaluated: orange, cherry, cola and strawberry. Descriptive analysis was used, and the data was analyzed by principal component analysis. Significant differences were found on among acids and concentrations. For the orange flavor system, citric acid enhanced the orange flavor of the drink. Third, selected acids (lactic, citric, acetic) and 2 acid blends (acetic/lactic 1:1 and 2:1) were evaluated in emulsions on an equivalent pH basis. Three pH levels were explored: 3.5, 4.5 and 5.5. These findings support the first study as differences were found among acids, and flavor changes existed when pH changed. / Graduation date: 1995
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152

Sensory and chemical analysis of 1997 Oregon Pinot noir enzyme treated wines

Goldberg, Naomi 04 December 1998 (has links)
Pinot noir has a reputation for lower color stability than other red wine varieties. Because it has relatively low anthocyanin and phenolic content and lacks acylated anthocyanin pigments compared to other red vinifera varieties, color extraction and stability are particularly important. Varying the processing during fermentation of red wine can produce high quality wines. Pectolytic enzymes are used in wine processing for many purposes from increasing juice yield and filtering rates to improving color and phenolic extraction. Macerating enzymes used in this study, Scottzyme Color Pro (Scott Laboratories), Scottzyme Color X (Scott Laboratories), Lallzyme EX (Lallemand), GB Rapidase EX Color (Gist Brocades), and Vinozyme G (Cellulo) were added to 1997 Oregon Pinot noir must prior to fermentation to observe color, aroma and flavor changes. These commercial enzymes have been reported to increase color and improve aroma and flavor of red wines. The effect of these enzymes had not previously been investigated on Oregon Pinot noir but the manufacturers reported increased polymeric phenols, polymeric anthocyanins, tannins, color stability, red hue and saturation of red wine varieties. These enzymes have varying manufacturer recommended usage levels and it is not known how the dosage levels and the enzymes themselves affect Oregon Pinot noir. Sensory evaluations of these wines, at a high and low dosage level, were conducted through free-choice profiling by winemakers and descriptive analysis from a trained panel. In addition, chemical analyses were performed and related to sensory panel results. Overall the addition of these enzymes to Oregon Pinot noir produced wines with greater purple, red descriptors and higher color intensity than the control wine from trained descriptive panel and winemaker panel results. In aroma, the enzyme treated wines were higher in vegetative and earthy descriptors compared to the control. GB Rapidase EX Color (Gist Brocades) was higher in bitterness flavor compared with other samples. Low enzyme wine treatments separated wine samples more from the control then high enzyme wine treatments. The color and appearance, aroma and flavor axes of the profile maps were not significant in the high enzyme treated wines as determined from the winemaker panel. Furthermore, the winemaker panel found acidity the only aroma or flavor descriptor significant in the high dosage ANOVA results. Whereas six descriptors in the low enzyme ANOVA results were significant in separating aroma and flavor samples. Except for Lallzyme EX (Lallemand) treated wine, the hunter colorimeter results showed all low enzyme treated wines were significantly (p<0.05) more red-purple (lower hues) than the high enzyme treated wines. / Graduation date: 1999
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153

A maturity trial study of Pinot noir wines : aroma profile by sniffing gas chromatographic effluent

Miranda-Lopez, Rita 07 December 1990 (has links)
The quality of wine is highly influenced by the weather. Temperature, solar radiation and humidity influence the formation and concentration of aroma-active compounds and aroma-active precursors in the grapes. Pinot noir grapes require a slow ripening, under cool temperatures, in order to achieve their fullest flavor. The main objective of this study was to provide an overall aroma picture that could help, along with the chemical indices, to decide the optimum harvesting time to obtain certain distinctive aroma attributes in the wine. This particular work represents the first stage in a broad plan aimed to understand the dependence of the wine flavor chemistry on the ripening of the grapes. This maturity trial was planned to last several years; it was expected that the outcome and techniques developed in the present study would be essential in delineating the steps to follow. The results of the aroma analyses for the 1987 and 1988 vintages are reported here. In each vintage, Pinot noir grapes were harvested at three different times, covering a range from early to late maturity. A sniffing technique based on gas chromatographic aroma detection by a trained panel was implemented. This technique has proved to be a useful tool to measure qualities and intensities of aromas. The method was effective in detecting many of the aroma-active compounds and in identifying aroma differences between the wines studied. The aroma profiles for the wines were found to be very different from each other within and across vintages. There were only 10 aroma peaks common to all three 1987 wines, 16 aroma peaks common to the 1988 wines, and 4 aroma peaks common to both vintages. Late maturity wines had more aroma-active peaks than the other 2 wines for both vintages. The 1988 wines had a higher number of aroma-active peaks than the 1987 wines. The percentages of aroma-active peaks not detected by the Flame lonization Detector (FID) were 45% in the 1987 wines, and 66% in the 1988 wines. The overall climatic conditions in those years were very different. The 1987 season was characterized as hot and dry, producing an early harvest. The weather in 1988 was more of a typical season for Oregon, producing a normal to late harvest. Further study is needed to fully understand the flavor chemistry occurring during grape ripening. / Graduation date: 1991
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154

Sensory changes in high pressure processed vs. heat processed food systems over time

Rodakowski, Andrea M. 23 February 1999 (has links)
This study was undertaken to determine the sensory differences in high pressure vs. heat processed food systems after storage at ambient and refrigerated temperatures as determined by a trained sensory panel. Spanish rice and spaghetti with meat sauce were prepared and treated with heat and with high pressure processing (HHP). A citrus fruit mix consisting of pieces of orange, grapefruit, and pineapple was processed by mild heat and HHP, and heat alone. One day after processing, treated products were tested along with untreated controls. Products were stored at either 22°C or 3°C, and tested at 10, 30, 60, 90, and 120 days. Sensory testing was done by a panel trained in a QDA-type method, and data was analyzed by univariate and multivariate methods. For spaghetti with meat sauce, significant differences (p>0.05) were found between processing methods stored at the same temperature in appearance and texture attributes, with the high pressure processed samples closer to unstored product than those treated by heat. Differences in treatments first appeared in 'dry appearance' at 10 days, and by 120 days there were differences in 'tomato integrity', 'pasta integrity', 'brightness of color', and 'firmness of pasta' as well. Most of these differences were due to the stickiness caused by the extra amylose leaking out of the heat treated pasta over time. For Spanish rice, there were no statistically significant differences between samples processed by the two methods and stored at the same temperature. The Spanish rice was formulated with parboiled rice, which allows very little amylose leakage, so it did not show amylose-related effects as the spaghetti with meat sauce did. The fruit mix processed with HPP and mild heat had significantly higher ratings in appearance attributes 'brightness of color' and piece integrity', and lower ratings in 'cooked' descriptors than product treated with heat alone stored at the same temperature. / Graduation date: 2000
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155

Interrelationships among changes in flavor and aroma, and composition of stored strawberry juice concentrate

Lundahl, David S. 27 January 1989 (has links)
Sensory evaluation and instrumental methods were applied to the evaluation of strawberry juice concentrate (68°Brix) stored at 20°C which had been produced both commercially (C-SJC) and in a pilot plant (SJC). Sensory evaluation included taste and aroma ratings by intensity scaling and time-intensity of taste, and visual colorimetry by matching Munsell color chips. Instrumental analyses included tristimulus colorimetry (i.e. Hunter colorimeter), spectrophotometric colorimetry for pigment analyses, titrametric analyses for acidity (pH and titratable acidity) and free α-amino acids (formol number), and headspace gas analyses for CO₂ and O₂. During six days storage of C-SJC, a decrease in concentration of anthocyanins and increase in polyphenolics (tannin) was associated with an increase in astringency. Free α-amino acids were observed to decrease, while CO₂ was released. These changes were associated with an increase in musty/moldy and pungent aromas. Free sugars and titratable acidity did not change. The pilot plant SJC was processed from blanched and unblanched fruit to evaluate the relative importance of oxidase activity (i.e. polyphenoloxidase) prior to pasteurization. The blanching treatment increased the astringency and sourness in unstored SJC. These affects were associated with an increase in concentration of polyphenolics (tannin). During storage, the blanch treatment decreased the rate of anthocyanin loss and decreased the release rate of CO₂, yet degradation rates were still high. The 0₂ concentration in headspace did not change significantly during storage indicating that polyphenoloxidase (PPO) activity during storage was low. The musty/moldy and pungent aromas increased similarly to C-SJC. A chemical mechanism accounting for these changes is proposed where products from the oxidative degradation of ascorbic acid contribute directly or indirectly to the degradation of anthocyanins to yield browning. Further, high initial concentrations and subsequent decreases during C-SJC storage of free α-amino acids indicate that Strecker degradation is a participating mechanism. Associations of browning with the development of off-flavors suggest this chemical mechanism forms odor-active volatile compounds. / Graduation date: 1989
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156

Sub-threshold effects on the perceived intensity of recognizable odorants : the roles of functional groups and carbon chain lengths

Lopetcharat, Kannapon 06 September 2002 (has links)
Sub-threshold effects were studied in binary and tertiary mixtures comprising a panel-recognition-concentration odorant and sub-threshold odorant(s). Sub-threshold condition was maintained by controlling the sub-threshold concentration as percentages of subjects' individual detection threshold. The perceived intensities (overall intensity and several descriptors) of recognizable odorants were rated using magnitude estimation. Sub-threshold suppression was common and concentration independent in mixtures comprising odorants with different functional groups. Suppression was observed at the lowest sub-threshold concentration tested (30% level). At sub-threshold concentrations, acetic acid suppressed the perceived intensity of acetaldehyde and ethanol but not vice versa. Acetaldehyde and ethanol, however, suppressed each other when one was at sub-threshold concentrations in binary mixtures. Enhancement was observed in tertiary mixtures containing acetaldehyde at panel recognition concentration and was dependent on sub-threshold concentrations of acetic acid and ethanol. In mixtures that contained aliphatic acids with different carbon chain lengths (acetic acid, propanoic acid and n-butanoic acid), sub-threshold enhancement and suppression depended on concentrations and molecular similarity of mixture components. Sub-threshold effects were not observed when the acids were two carbon-atoms different. 50% and 70% sub-threshold levels caused sub-threshold enhancement; however, higher concentrations caused decrease in intensity. Sub-threshold suppression was observed in mixtures containing n-butanoic acid as a recognizable odorants with propanoic acid at a 10% level in a binary mixture and acetic acid and propanoic acid in a 30%-30% combination in the tertiary mixture. / Graduation date: 2003
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157

Development of methods for analysis and sensory threshold determination of malt derived flavor components in beer

Lukes, Bryce K. 17 May 1988 (has links)
Malt, wort and beer samples representing a single pilot brew were extracted from Celite columns with Freon 114. Total extracts were analyzed by gas chromatography/mass spectrometry. Compounds were identified that were unique or common to beer, wort or malt and quantities present were determined for those common to the three sample types. Concentrated extracts were separated by liquid chromatography on partially deactivated silica gel packed in Teflon tubes, using Freon 11 as the solvent. Fractions from liquid chromatography were analyzed by descriptive sensory evaluation. Those fractions selected as bearing cereal-like, grassy, nutty or malty aroma characteristics were analyzed by gas chromatography. Freon extracts and fractions were found suitable for descriptive sensory evaluation and this was used to advantage in locating fractions with the desired aroma characteristics. Cereal-like, grassy, nutty or malty aroma characters were associated with liquid chromatographic fractions containing primarily alcohols, aldehydes and ketones. The Ascending Method of Limits for determination of the threshold of added substances in beer was critically reviewed and a new threshold test was developed. The new test design reduces the sample requirement from eighteen to twelve for each session. In contrast to the Ascending Method of Limits, the new test design was amenable to statistical evaluation and statement of a level of confidence for the threshold intervals determined. Both a nine-point intensity scale of difference from the labeled reference and a category scale were applied to the new test design. Intensity scale data were normalized and subjected to analysis of variance and a series of one-sided t-tests to determine individual and combined panel threshold intervals. Category scale data were analyzed by a rank sums test to determine individual thresholds and the R-index values thus obtained were subjected to analysis of variance and orthogonal contrasts of means to establish the combined panel threshold. The intensity scale method applied to the new test design provided the lowest and narrowest estimates of the threshold interval in comparative testing with the category scale method and the Ascending Method of Limits and, in addition, required fewer replications than the category scale method to establish the threshold interval. / Graduation date: 1989
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158

Influence of sugar and acid on sensory qualities and desirability of blackberry juice drink using response surface methodology

Perng, Chiou-mey 08 July 1988 (has links)
Response Surface Methodology (RSM) was used to study the effect of two variables, sugar level (12-16 °Brix) and acid level (0.3-0.7 % T.A.) on sensory qualities and desirability of blackberry juice drinks. Three blackberry juice levels (10%, 15%, and 20%) were used to study the influence of juice flavor on sensory qualities and desirability of the juice drinks. A trained panel evaluated three attributes, blackberry flavor, sweetness, and sourness intensities, of the juice drinks. The consumer panel gave desirability and three attributes just-right ratings. A Balanced Complete Block Design was used. Blackberry flavor intensity was enhanced by sugar level. Blackberry flavor intensity was enhanced by acid level to a point about 0.5% T.A., and then decreased. Blackberry flavor intensity was not related to °Brix:acid ratio and was only related to the sweetness:sourness ratio at the 20% juice level. Sweetness and sourness intensities increased with increasing sugar and acid levels. There was a suppression effect of sugar and acid on each other in the juice drink. The relationships of sweetness, sourness, and sweetness:sourness ratios to °Brix:acid ratios were all linear. Desirability rating was related to °Brix:acid and sweetness:sourness ratios for the 10% and 20% juice levels, for 15% juice level no association was found. The formula which received the closest to "just right" ratings and highest overall desirability rating had in a °Brix of 15.4 and a % titratable acidity of 0.64, resulting in a °Brix:acid ratio of 24 and a corresponding sweetness:sourness ratio of slightly less than 1.0. In general, the 15% juice level was the best because of its sugar and acid tolerance and high desirability. / Graduation date: 1989
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159

Quality assessment of Asian noodles made from U.S. wheat flours using sensory descriptive analysis

Janto, Mimi 11 December 1997 (has links)
As a major wheat exporter to countries all over the world, the United States has to produce wheat that satisfy different quality requirements requested by their customers. Over the past decade the United States has encountered a major problem, that of losing market share in Asia to Canada and Australia. The major reason was that the United States was unable to supply Asian countries with quality wheat suitable for noodle production. To overcome the problem, the U.S. wheat industry needs to understand the specific quality requirements required for Asian noodles. Research on understanding sensory characteristics of Asian noodles was proposed to bridge the communication barrier regarding Asian noodle quality. Descriptive analysis was utilized for this study to provide sensory characteristics of noodles from different Asian countries. In the first study, four classes of U.S. wheat flour samples were evaluated for their ability to make high quality Taiwanese noodles. Taiwanese noodle industry representatives came to the United States and made 4 major types of their noodles using U.S. wheat flours; they evaluated them by employing both the Taiwanese industries' scoring system and modified descriptive analysis. The results of this study indicated that hard white wheat was suitable for making two types of Taiwanese noodles (dry and yee noodles), a blend of hard red winter and hard red spring wheat was suitable for wet noodles, and a blend of hard red winter and white wheat was suitable for fresh noodles. The second study was undertaken to better understand the texture profile of noodles from various Asian countries. Sensory texture characteristics of fresh noodles from Taiwan, Thailand, and Malaysia were identified. A total of 16 patent flour samples for Taiwan, and 18 straight grade flour samples each for Thailand and Malaysia, were milled from hard white wheat varieties and made into each Asian country's noodles. A texture profile of each country's noodles was developed by an Oregon State University descriptive panel while quality evaluation was performed by each countries' noodle experts. The results characterized the Taiwanese noodles as the smoothest, springiest, and highest in integrity of noodles; the Thai noodles were the hardest, most dense, cohesive noodles and also higher in starch between teeth and toothpull; and the Malaysian noodles were the softest, least dense, cohesive, and sticky noodles. The optimum protein to achieve specific texture quality for each country was identified. / Graduation date: 1998
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160

Instrumental and sensory texture profile analysis of Asian wheat noodles

Pipatsattayanuwong, Siriporn 06 May 1998 (has links)
Texture, a critical property of Asian wheat noodles, is normally assessed by sensory evaluation. However, sensory evaluation may be impractical for wheat breeders and noodle researchers who need to evaluate a large number of samples and have limited sample. Instrumental Texture Profile Analysis (TPA) has been widely employed to evaluate Asian wheat noodle texture. Nevertheless, a standardized method for performing TPA on these products has not been established. A series of studies were conducted to develop a testing method to best relate TPA results to sensory texture characteristics of Asian wheat noodles. First, the optimum TPA testing conditions (crosshead speed and degree of deformation) were determined for each noodle category (alkaline, instant fried, salted flat, and salted round), and were defined as the conditions which best related their results to the sensory data. Partial Least Squares (PLS2) was used to examine relationships between sensory first-chew characteristics (hardness, cohesiveness, springiness, denseness, starch between teeth, and toothpull) and TPA output (peak areas and heights). Response Surface Methodology determined the optimum TPA conditions (crosshead speed and % deformation) as follow: 1 mm/s and 85 % for alkaline, 1 mm/s and 70% for instant fried and salted round, and 5 mm/s and 65 % for salted flat noodles. Second, the effects of two sample cooking factors: noodle weights (20, 50, 100 g) and noodle to water ratios (1:10, 1:20) and three holding factors: media (with, without water), temperatures (25, 55 °C), and times (2, 15, 30 min), on the TPA results were investigated. Cooking factors did not significantly affect the TPA results but higher holding temperatures, the use of water as a holding media, and longer holding time significantly decreased most TPA parameters' values. Third, relationships between TPA and sensory first-chew parameters were examined for each noodle category. Predictive models of each sensory first-chew attribute were developed using linear and nonlinear (Fechner and Stevens) models, with single and multiple parameters. Hardness could be satisfactorily predicted by a single TPA parameter (area 1 or area 2), but other attributes required multiple parameters in the models to be satisfactorily predicted. Different model types were selected for each sensory attribute and noodle category. TPA peak area 1 and 2 were the best predictors for first-chew characteristics of cooked Asian wheat noodles. / Graduation date: 1998
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