Browsing by Author "Dr. MaryAnne Drake, Committee Chair"

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Comparison of Composition, Sensory Properties and Volatile Components of Whey Protein and Serum Protein Concentrates
(2009-03-11) Evans, Joshua Peter; Dr. MaryAnne Drake, Committee Chair; Dr. Lynn Turner, Committee Member; Dr. E. Allen Foegeding, Committee Member
EVANS, JOSHUA PETER. Comparison of Composition, Sensory and Volatile Components of Whey Protein and Serum Protein Concentrates. (Under the direction of Dr. MaryAnne Drake.) Whey proteins are highly functional and nutritious proteins used in a variety of products. Whey protein concentrate (WPC) is one of the most commonly used value-added forms of whey protein. Whey proteins should ideally have a bland flavor to facilitate application in foods, but flavor of these products is highly variable due to the original whey source, processing, and storage. Recent research has highlighted removal of whey proteins from skim milk prior to cheese making. These proteins removed from milk before the cheese making process are referred to as serum or â€œnativeâ€ whey proteins and serum protein concentrate (SPC) when further processed to 34-89% protein. Since SPC are not exposed to the cheese make-process, enzymatic and/or chemical reactions that can lead to off-flavors are reduced. The objectives of this research were to characterize and compare the composition, sensory properties, and flavor chemistry of both whey protein concentrate and serum protein concentrate at protein concentrations of 34 and 80% (SPC34, WPC34, SPC80, WPC80). A second objective was to compare the composition, sensory properties and flavor chemistry of the serum protein and whey protein concentrates made in our study with those of commercial WPC34 and WPC80. SPC and WPC were manufactured in triplicate with each pair of serum and traditional whey protein manufactured from the same lot of milk. At each replication, spray-dried (SD) product from each protein source was collected. Commercial WPC34 and WPC80 were also collected for sensory and volatile analyses. A trained sensory panel documented the sensory profiles of the rehydrated powders. Volatile components were extracted by solid phase micro-extraction (SPME) and solvent extraction followed by solvent assisted flavor evaporation (SAFE) with gas chromatography-mass spectrometry and gas chromatography-olfactometry. Consumer acceptance testing with 6 % protein beverages was conducted with SPC80 and WPC80, as well as commercial WPC80. Fat content of SPC34 and SPC80 was lower and pH was higher than WPC34 and WPC80 (p<0.05). Few sensory differences were documented between the rehydrated SPC and WPC at both protein levels manufactured in this study, but their flavor profiles were distinct from flavor profiles of rehydrated commercial WPC (p<0.05). WPC34 and WPC80 generally had higher concentrations of lipid oxidation products than SPC34 and SPC80 (p<0.05). Lipid oxidation product concentrations were also higher in commercial products compared to pilot plant products (p<0.05). Fifty-six aroma active compounds were identified in the four products manufactured in this study (WPC34, SPC34, WPC80, SPC80), eighteen of these compounds were found in all four products. Overall, aroma active compounds were primarily lipid oxidation products, followed by fermentation, Strecker degradation, Maillard browning, and caramelization products. More aroma-active compounds were identified in the 80% protein samples (46) than in the 34% protein samples (29). Free fatty acid and soapy flavors and bitter taste were identified in beverages made with SPC80, and soapy flavor and bitter taste were documented in beverages made with WPC80 manufactured in this study; these flavors were not present in beverages made with commercial WSPC80. Overall consumer acceptance scores were highest for beverages made with one commercial WPC80 followed by beverages made with the WPC80 manufactured in this study. Differences between products manufactured in this study and commercial samples, as well as variability among commercial samples alone, suggests that additional processing parameters contribute to flavor and flavor variability in WPC. Composition, physical properties and volatile compound composition of SPC are distinct from WPC, and these differences may contribute to flavor differences in ingredient applications.
Comprison of Sensory Properties of Whey and Soy Protein Concentrates and Isolates
(2004-09-15) Russell, Tara Alexandra; Dr. MaryAnne Drake, Committee Chair; Dr. L.A. Jaykus, Committee Member; Dr. T.H. Sanders, Committee Member
In previous years, whey was treated as an insignificant by-product of cheese making, used mainly in animal feed or discarded. Whey and whey components, particularly whey proteins, are now viewed as valuable ingredients due to recent discoveries of functional and bioactive roles. Production and application of soy protein has also increased in recent years. Characterization and comparison of the flavor properties of these value-added ingredients is needed to identify specific ingredient applications and marketing strategies. The goal of this study was to develop a sensory lexicon for whey and soy proteins, and to subsequently identify and compare the descriptive sensory properties of whey and soy proteins. Consumer perception of these products was also investigated. Twenty-four descriptive sensory attributes were identified to evaluate appearance, flavor, and texture/mouthfeel. Following development of the lexicon, twenty-two samples (14 whey proteins and 8 soy proteins) were selected for descriptive sensory analysis. Proteins were rehydrated (10 % solids, (w/v)) and evaluated in triplicate by a highly trained sensory panel (n=10) trained to use the developed language. Results were analyzed by univariate and multivariate analysis of variance. Both whey and soy proteins were differentiated using the identified language (p<0.05). Different sensory attributes distinguished whey proteins from soy proteins. Consumers were knowledgeable of distinct health benefits of dairy and soy products. These results will enhance ongoing research and product development with these nutritional and functional ingredients.
Evaluation of chemical properties and consumer perception of fluid milk from conventional and pasture-based production systems
(2007-10-10) Croissant, Adam Edward; Dr. David Henard, Committee Member; Dr. TimSanders, Committee Member; Dr. Steve Washburn, Committee Member; Dr. MaryAnne Drake, Committee Chair
Flavor and Flavor Chemistry of Liquid Mozzarella and Cheddar Cheese Whey
(2009-09-08) Liaw, Iris; Dr. MaryAnne Drake, Committee Chair; Dr. E. Allen Foegeding, Committee Member; Dr. Lisa Dean, Committee Member; Dr. Timothy Sanders, Committee Member
Whey protein is widely used in numerous ingredient applications. Cheddar and Mozzarella cheeses are the primary sources for dried whey protein production. Differences in the flavor of fresh whey may influence the final whey protein flavor. Whey protein flavor is highly variable and off-flavors in dried whey products can carry through into ingredient applications and negatively affect consumer acceptance. The first objective of this study was to evaluate the impact of antioxidant addition in prevention of flavor deterioration of fluid whey and flavor of whey protein. The second objective of this study was to compare the flavor and flavor stability of fresh and stored liquid Cheddar and Mozzarella whey. For the first objective, Cheddar or Mozzarella liquid whey were manufactured using standard cheese make-procedures. The wheys were then pasteurized and subjected to fat separation. Ascorbic acid, whey protein hydrolysate (WPH), or nitrogen flushing were then administered. Wheys with no antioxidant addition and without fat separation were included as controls. Wheys were stored at 3oC and evaluated by sensory and instrumental analyses after 0, 2, 4, 6, and 8 days. In a subsequent experiment, selected treatments were incorporated into liquid Cheddar whey and processed into whey protein concentrate (WPC). Whey and WPC flavors were documented by descriptive sensory analysis, and volatile components were evaluated by solid phase micro-extraction with gas chromatography mass spectrometry (SPME-GC-MS). Cardboard flavors increased in fluid wheys with storage. Liquid wheys with ascorbic acid, WPH or nitrogen flushing had lower cardboard flavor across storage compared to control whey. Lipid oxidation products, hexanal, heptanal, octanal and nonanal increased in liquid whey during storage, but liquid whey with added ascorbic acid, WPH or nitrogen flushing had lower concentrations of these products compared to untreated controls. Mozzarella liquid whey had lower flavor intensities than Cheddar whey initially and after refrigerated storage. WPC with added ascorbic acid or WPH had lower cardboard flavor and lower concentrations of pentanal, heptanal, and nonanal compared to control WPC. WPC and liquid whey with added WPH, however, had a distinct potato flavor by sensory analysis which was absent in control products or products with added ascorbic acid. In the second study, pasteurized, fat-separated Cheddar and Mozzarella wheys were manufactured in duplicate and evaluated immediately or stored for 3 days at 3oC. Sensory properties were documented by descriptive sensory analysis and volatile components were extracted and characterized by solid phase microextraction with gas chromatrography-mass spectrometry (SPME-GC-MS), direct solvent extract (DSE) with solvent assisted flavor evaporation (SAFE) with GC-MS and gas chromatography-olfactometry (GC-O) with aroma extract dilution analysis (AEDA). Cheddar and Mozzarella wheys were distinct by sensory and volatile analyses (p<0.05). Fresh Cheddar whey had higher intensities of buttery and sweet aromatic flavors and higher cardboard flavor intensities following storage compared to Mozzarella whey. Fifty aroma-active compounds were identified by GC-O. High aroma impact compounds (FDlog3 > 8) in fresh Cheddar whey included diacetyl, 1-octen-3-one, 2-phenethanol, butyric acid, and (E)-2-nonenal, while those in Mozzarella whey included diacetyl, octanal, (E)-2-nonenal, and 2-phenethanol. Concurrently, fresh Cheddar whey had increased concentrations of diacetyl, 2/3-methyl butanal, (E)-2-nonenal, 2-phenethanol, and 1-octen-3-one compared to fresh Mozzarella whey. Lipid oxidation products increased in both whey types during storage but increases were more pronounced in Cheddar whey than Mozzarella whey. Collectively, these studies suggest that lipid oxidation is a primary source of flavor and flavor degradation in fluid whey. Similar aroma-active compounds at different concentrations comprise the flavor of Cheddar and Mozzarella whey and these influence observed differences in lipid oxidation and flavor during subsequent storage. Addition of an antioxidant to liquid whey prior to further processing may be beneficial to flavor of spray dried whey protein.
Flavor Formation in Skim Milk Powder and Flavor Carry-Through into Ingredient Applications
(2005-11-23) Caudle, Alissa Dawn; Dr. MaryAnne Drake, Committee Chair; Dr. Timothy Sanders, Committee Member; Dr. Lee-Ann Jaykus, Committee Member
Skim milk powder (SMP) is commonly used as a food ingredient. Both processing procedures and storage conditions have been noted as important contributors to SMP flavor. Research has not addressed how or if SMP flavor variability impacts consumer acceptance of ingredient applications. Further, many studies have addressed the importance and impact of SMP storage on flavor variability, but the impact of SMP processing on flavor formation has not been extensively researched. In this study, we examined both the impact of SMP flavor variability on consumer acceptability in SMP ingredient applications as well as the flavor formation of SMP throughout production, with emphasis on steps where heat was applied.
The Impact of Agglomeration on Flavor and Flavor Stability of Whey Proteins
(2007-10-25) Zevchak, Sarah Elizabeth; Dr. E. Allen Foegeding, Committee Member; Dr. Lynn Turner, Committee Member; Dr. MaryAnne Drake, Committee Chair
Descriptive sensory analysis of freshly produced WPC80 and WPI has documented a variety of flavors in these products including sweet aromatic, cardboard/wet paper, pasta water, brothy, cucumber, and soapy flavors, astringent mouthfeel and bitter taste. Concurrent volatile analysis has revealed an array of heat-induced and lipid and protein oxidation compounds. The purported shelf life of WPC80 and WPI varies from 12 to 18 months depending on the supplier. However, to our knowledge, no studies have addressed stability of WPC80 or WPI or the impact of agglomeration on the flavor and flavor stability of WPC80 and WPI. In this study, agglomerated (re-wet and single pass) and non-agglomerated samples of WPC80 and WPI from different facilities were analyzed for flavor and selected physical properties over the course of fifteen months. Descriptive sensory analysis and volatile analysis were conducted every 2 months. Samples were tested every six months for solubility, bulk volume, dispersibility, moisture, and color (L,a,b). Proximate analysis was conducted at time zero. Consumer acceptance tests were conducted on representative samples after 0, 6, 9, 12 and 15 months storage using vanilla protein shakes and peach flavored beverages with WPC80 and fruit flavored clear acidified beverages with WPI. Agglomerated powders displayed higher bulk volume and dispersibility than their non-agglomerated counterparts. Solubility, bulk volume, dispersibility, moisture and color did not significantly change with storage time. Higher intensities of lipid oxidation flavors (cardboard, raisin/brothy, cucumber, and fatty) were noted in agglomerated powders compared to control powders (p<0.05). Sensory results were confirmed by volatile analysis results which showed increased formation of aldehydes and ketones in agglomerated products compared to control powders (p<0.05). Acceptance tests with protein beverages revealed few differences in consumer acceptance between agglomerated and non-agglomerated whey proteins or between fresh versus stored whey proteins although trained panelists documented consistent differences. Agglomeration or agglomeration with lecithin decreased the storage stability of whey proteins. These results indicate that the optimum shelf life at 21C for non-agglomerated powders is between 12-15 months and 8-10 months for agglomerated powders.
The Impact of Organic Acids and pH on the Virulence Factor Expression of E. coli O157:H7.
(2005-04-11) Adhikari, Sahana Das; Dr. MaryAnne Drake, Committee Chair; Dr. LeeAnn Jaykus, Committee Member; Dr. Donn Ward, Committee Member
Acidification is used as a hurdle in many minimally processed foods. Decreased pH (pH 5.5) may enhance survival and virulence factor expression of E. coli O157:H7 (EC). The objective of this research was to determine the effect of different organic acids and pH on the expression of three virulence factor genes (stx2, hlyA, eaeA) in EC. Gene fusions containing the lacZ gene inserted into the stx2, eaeA or hlyA genes were created in E. coli O157:H7 with and without a functional rpoS gene. Overnight cultures were inoculated into tryptic soy broth acidified with citric, malic, lactic, or hydrochloric acid at pH 6.0, 5.5, 5.0, or 4.5 or apple juice (pH 3.5). Cell growth characteristics were characterized, and β-galactosidase activity of stressed or control cells (neutral pH, no acid) was subsequently determined to follow virulence factor production. Production of all three virulence factors was increased at pH 5.5 or 5.0 compared to production at neutral pH (p<0.05). Acid type impacted production of EaeA and StxII, but had no effect on HlyA. Production of StxII and HlyA was not detected in apple juice. At pH 5.5, cell growth was slowest in lactic acid, followed by malic and citric acids then HCl. At pH 5.0, the slowest growth was observed in citric acid, followed by malic acid, lactic acid and HCl. At pH 4.5, no growth occurred in citric, malic and lactic acids, and cell numbers decreased over a period of 5 days. In HCl at pH 4.5, cells grew slowly and increased by 2 logs over a 5-day period. Sublethal acid stress impacts virulence factor expression of E. coli O157:H7 and these effects are impacted by pH and acid type.
The Roles of Fat and pH on the Detection Thresholds and Partition Coefficients of Three Compounds: Diacetyl, Delta-Decalactone, and Furaneol in Water, Oil, and Emulsions.
(2009-01-08) Leksrisompong, Pattarin; Dr. Tim Sanders, Committee Member; Dr. MaryAnne Drake, Committee Chair; Dr. Allen Foegeding, Committee Member
The effect of fat and pH on the best estimate threshold (BET) of 3 prominent dairy product flavor compounds with varying physicochemical properties: diacetyl, delta-decalactone, and furaneol, in water, oil and oil-in-water model emulsions (at 10 and 20 % fat at neutral and acidified pH 5.5) were investigated. The headspace-matrix partition coefficients (KHS/matrix) of each compound in the different matrixes were established. The rheology and particle size of the emulsions used in this study were also investigated. The particle size and the viscosity of the emulsions did not affect the BET or the partition coefficients. Reducing fat from 20 to 0 % did not affect the BET value or partition coefficient of diacetyl (P>0.05). Increasing fat content increased the BET value and decreased the partition coefficient (P<0.05) of the most lipophilic compound in the study, delta-decalactone. Fat did not affect the BET of furaneol (P>0.05) but did have an effect on the partition coefficient (P<0.05). At pH 7, addition of fat decreased the partition coefficient of furaneol whereas at pH 5.5, addition of fat increased the partition coefficient of furaneol. Adjustment of pH from 7.0 to 5.5 did not impact the BET values of delta-decalactone, but did affect the partition coefficients of furaneol at all fat levels and impacted diacetyl at 0 % fat. The partition coefficient results generally agreed with the BET values on the effect of fat and pH, although, the partition coefficient test was more sensitive to the differences in the matrix composition than a threshold test.
Sample processing strategies for optimal PCR detection of pathogens in foods
(2006-03-09) Isonhood, James Harold Jr.; Dr. Donn R. Ward, Committee Member; Dr. Lee-Ann Jaykus, Committee Co-Chair; Dr. MaryAnne Drake, Committee Chair; Dr. Craig Altier, Committee Member
The research in this manuscript highlights new and improved methods to concentrate pathogens from a complex food matrix and detect them via PCR. These contributions to the science of rapid pathogen detection are unique in that they are designed to measure the efficacy of the concentration or capture technique without using a pre-enrichment step. To address the potential of pathogen concentration to facilitate PCR detection, the following objectives were performed: (i) evaluating the performance of differential centrifugation as a means to concentrate and clarify the food sample for rapid PCR detection of Listeria monocytogenes, without pre-enrichment and (ii) investigating the efficacy of a novel immuno-capture device to capture E. coli O157:H7 and Salmonella typhimurium from foods. For the first objective, we investigated filtration followed by a two-step, differential centrifugation as a means to concentrate bacteria and remove a large portion of the food sample prior to DNA extraction, PCR amplification, and Southern hybridization of L. monocytogenes targeting a unique region of 16S rDNA. Simple high speed centrifugation (11,950 x g) was also investigated to test the efficacy of our two-step method. Our method incorporated use of a 11g sample of ready-to-eat deli salad diluted 1:10 with 99ml 0.9% sterile normal saline. The two-step method was able to reduce the sample volume by approximately 10-fold rather than only 5-fold for simple high speed centrifugation. The two-step method was 1,000 fold (10⁶ to 10³ CFU/g) more sensitive than when using high speed centrifugation alone, and bacterial recoveries indicated that both methods produced similar recoveries. Following DNA extraction, PCR amplification, and Southern hybridization, detection was achieved at input levels of 10⁵ CFU/g for chicken salad, 10⁴ CFU/g for macaroni salad, and 10³ CFU/g for potato and seafood salads, with no pre-enrichment. In our second objective, we evaluated the efficacy of a novel immuno-capture system (Pathatrix™) to capture S. typhimurium in buffered peptone water (BPW), ground turkey and nonfat dry milk and E. coli O157:H7 from BPW, ground beef and romaine lettuce. The Pathatrix system is unique in that it is designed to sample an entire 25g sample by circulating the homogenized 250ml volume across a surface of immunomagnetic beads. The samples were seeded with bacteria at levels ranging from 10⁶ to 10⁰ CFU/25g. The E. coli O157 format was able to capture 100 % of input E. coli O157:H7 and PCR amplification was able to detect the pathogen at 10⁰ CFU/25g. The Salmonella format was not as robust, only capturing approximately < 1 % of cell input, but was able to produce a significant PCR detection limit of 10² CFU/25g when Pathatrix was preceded with the two-step centrifugation method. The two-step centrifugation further clarified the sample and improved detection by 1000-fold (10⁵ to 10² CFU/25g). This research provides further clues to expedite sample processing throughput prior to employing rapid methods for detection of pathogens in foods. It is our hope that knowledge of these techniques can help reduce or eliminate the need for preenrichment when screening food systems via PCR and other rapid methods.