Browsing by Subject "Flavor"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Covalent Reactions Between Flavors and the Model Protein β-Lactoglobulin
    (2020-07) Anantharamkrishnan, Vaidhyanathan
    Demand for high protein plant and dairy-based diets has been increasing but delivering them has become problematic for the food industry. The flavor issues are due to multifaceted interactions that occur between food proteins and flavoring components. Over 40 years of research has been done on studying temporary interactions between flavor and proteins, but very little work has been done on more permanent interactions – covalent bonding. Covalent bonding takes place between the side chains and terminal amino acids of food proteins and reactive aroma compounds that will change the flavor profile of the product in a permanent manner. β- lactoglobulin (BLG) was chosen as a model protein for this study as it is well characterized in both amino acid sequence and structure, its molecular weight is suitable for intact protein mass spectrometry and it is a major protein used in food industry. This thesis study developed a methodology using UPLC-ESI/qTOF-MS for monitoring the nature and extent of the covalent reactions based upon the change in molecular weight (Protein + flavor) that occurs after reaction. The cross linking of protein with flavor compounds was evaluated using gel electrophoresis. A proteomics approach using LC and tandem MS after enzymatic digestion was taken to identify the sites of post-translational modification between the flavor compounds and the BLG protein. The UPLC-ESI/qTOF-MS methodology in tandem with proteomics and gel electrophoresis yield a detailed view of flavor/BLG interactions that offered insights on minimizing these undesirable reactions in the future. A flavoring typically is created from a mixture of volatile chemicals that generally comprise a variety of functional groups. Some of these flavor components when added to a protein matrix form covalent adducts resulting in a change in flavor character or a loss of its potency. The end result of these reactions create an imbalanced flavor, one that is not acceptable to a consumer. This research study analyzed 47 different flavor compounds from 13 different functional groups for their covalent adduct formation with BLG. Aldehydes, sulfur-containing molecules (especially thiols), and functional group-containing furans were found to be the most reactive of the flavor components studied. Thiol-containing compounds reduced disulfide linkages in BLG to result in disulfide interchange and formation of new disulfide linkages with the free cysteine group. Ketones were generally stable, but α-diketones (e.g., diacetyl) were reactive. Some bases (e.g., pyrazines and pyridines) were non-reactive, while the nucleophilic allylamine was reactive. Hydrocarbons, alcohols, acids, esters, lactones, and pyrans did not give observable levels of adduct formation within the time period studied. Due to the varied environmental conditions present in various food systems, the nature and extent of covalent interactions would likely change. This study investigated the influence of pH, temperature and water activity on the covalent adduct formation between BLG and selected flavor molecules. Covalent adduct formation was slower in acidic pHs. The rate and extent of the reaction increased with increasing pH. The rate of formation of adducts increased with temperature. Higher temperatures (45°C) caused the formation of products that were not observed at lower temperatures (4°C and 25°C). An increase in water activity lead to an increase in formation of adducts for allyl isothiocyanate. There were no observable differences for the effect of water activity on the reaction rate for benzaldehyde, citral and dimethyl disulfide. Results will help in understanding the conditions at which flavor compounds will covalently bond with a protein and ways to potentially avoid it. Thereby, helping the food industry to develop flavor protein matrices that have a longer shelf life.
  • Thumbnail Image
    Item
    Effects of Bran Content, Thermal Treatment, and Storage on Flavor Development and Functionality in Intermediate Wheatgrass Flour
    (2020-01) Luu, Misen
    Intermediate wheatgrass (IWG, Thinopyrum intermedium) is a perennial crop that has garnered attention for its environmental and nutritional benefits. Selected as a promising candidate among other perennial crops for food use, IWG has good flavor, breeding potential, and superior environmental benefits due to its extensive root system and long growing season. Understanding the storage stability of IWG will further improve its likelihood of integration into the food market. Grains, including wheat, are typically processed into flour and stored until use. Grains can be stable for up to 8-12 years; however, flour has a significantly lower shelf-life. While the storage stability of IWG groats has been investigated, the storage stability of IWG flour have not yet been addressed. Thermal treatment may be used to increase grain shelf life by inactivating enzymes that are involved in lipid rancidity, which is a major pathway for the formation of odor active volatile odor active compounds (VOAC). On the other hand, thermal treatment may negatively impact functionality over storage. Reducing the bran content may also increase shelf life by reducing fat content; however, it would be at the expense of reducing the dietary fiber content. Understanding the storage stability of IWG and identifying methods to improve its stability will not only enhance commercialization potential, but will also incentivize farmers to plant IWG. The objectives for this research study were to: (1) Evaluate the effects of prior grain storage, bran content, and steam treatment on the development of flavor in IWG flour over storage at 43% relative humidity and (2) Evaluate the effects of prior grain storage, bran content, and steam treatment on the functionality of IWG flour over storage at 43% and 65% relative humidity. Prior to storage, compositional analysis of IWG and hard red wheat (HRW, control), from two growing seasons, were carried out following official AOAC and AACCI methods. IWG groats were subjected to steam treatment directly above a boiling water bath at 100°C for 2 minutes. After equilibration at room temperature for 24 hours, IWG groats were milled into refined, partially refined (75% bran), and whole flour, while HRW groats were milled into whole and refined flour. Flour samples were stored at ambient temperature at 43% and 65% relative humidity (RH) for up to 9 months of storage. Samples were analyzed periodically for changes in flavor and dough functionality. VOACs were extracted from flour following a dynamic headspace purge and trap protocol and analyzed by gas chromatography-olfactory-mass spectrometry. VOACs were measured at the beginning, middle, and end of storage. A descriptive analysis was used to document the nature and extent of differences in sensory properties and was conducted with eight trained sensory panelists to describe differences in aroma, flavor, taste, and aftertaste in tortillas made from the stored flour. Dough functionality was measured every 3 months of storage. Rheological and mixing properties were measured using a Farinograph® and a texture analyzer equipped with a Kieffer rig. Gluten strength was measured using Brabender® GlutoPeak. Starch pasting profile was analyzed by Micro-Visco-Amylograph®. IWG had significantly higher protein, insoluble fiber, total dietary fiber, and fat content than HRW. The steam treatment employed resulted in a significant decrease in lipase and LOX activity, without significantly reducing antioxidant content. Over storage, identified odor active VOACs included alkyl and enal aldehydes, alcohols, and furans, which are products of lipid oxidation. By the end of storage, whole IWG flour showed significantly greater intensity of nearly all identified VOACs, such as pentanal, hexanal, 1-octen-3-ol, and 2-pentylfuran, in comparison to HRW flour. However, due to IWG’s higher antioxidant content, the induction period of VOACs in IWG was longer than that of HRW, indicating better short term storage stability. IWG was described as grassier and earthier compared to HRW, due to the presence of alkyl aldehydes, 2-pentylfuran, and 1-octen-3-ol. Steaming resulted in significantly lower intensities of VOACs, attributed to a reduction in enzyme activity. Partial refinement also resulted in a significant reduction in the intensity of VOACs. IWG had more earthy, grassy and Play-Doh® aromas, and higher intensities of peanut butter and beany flavor than HRW samples. IWG had greater intensity rating of flavor and the five basic taste (sweet, salty, bitter, sour, and umami) and aftertaste than HRW samples. Samples with lower bran content had lower overall flavor, bitter and salty taste, and overall aftertaste. Steamed IWG samples had lower overall aroma, flavor and aftertaste compared to not-steamed IWG samples. IWG flour had increases in dough development time, stability, resistance to extension, and gluten aggregation over short term storage, indicating an increase in dough strength. IWG also had improvement in starch pasting properties over storage, including peak, hold, and final viscosity. Partial bran refinement resulted in better dough functionality and starch pasting properties due to less interference of the fiber with the formation of the gluten network and a higher starch to non-starch ratio, respectively. Steaming resulted in higher dough development time and resistance to extension but had a slightly negative impact on starch pasting viscosity values. Partial refinement of IWG resulted in lower intensities of off-odor flavor compounds, lower sensory attributes ratings, and improved functionality, while maintaining the nutritional benefits associated with the bran. The interruption of enzymatic activity by steam treatment helped off-set unfavorable flavor development, thus could be used to prolong the shelf-life of IWG flour. Together, these two processing practices make IWG viable for commercial use.
  • Thumbnail Image
    Item
    Influence of Molecular Mobility and Free Volume on the Oxidative Stability of Spray Dried Orange Oil
    (2017-05) Hohman, Abbie
    The objective of this research was to determine whether molecular mobility and/or free volume influences the oxidative stability of spray dried orange oil. Encapsulated orange oil was prepared by spray drying using maltodextrin, gum acacia and HiCAP® 100 as carrier materials. The physical properties of the spray dried orange oil were characterized by: viscosity, particle size, moisture content, volatile retention, and absolute density. The molecular mobility was determined by glass transition, free volume was measured positron annihilation lifetime spectroscopy (PALS) and orange oil oxidation was determined by gas chromatography. The infeed viscosity and resultant particle size of the unloaded powders decreased as the molecular weight of the carrier material decreased. Differences between the viscosity of the unloaded and loaded emulsions was due to the addition of orange oil as it is less viscous than water and does not hydrate carrier materials yet contributes to the total percent spray drier infeed solids. The reconstituted emulsion particle size was much smaller than the infeed emulsion particle size due to the high shear of the atomizer in the spray drier. The moisture content and absolute density were independent of carrier material type. The moisture content increased with increasing water activity however, the absolute density was unaffected by a change in water activity. The volatile retention of the spray dried powders improved greatly upon the addition of emulsifier to the carrier wall material. The size of the molecular voids and orange oil oxidation decreased while molecular mobility increased with decreasing molecular weight of the carrier material. As the relative humidity increased, the average size of the molecular voids and the molecular mobility increased. The effect of water activity on the oxidation of spray dried carrier systems appeared to increase to a certain point and then decrease with increasing water activity. Spray dried carrier systems that were formulated as a blend of carbohydrate and emulsifier provided a balance between molecular mobility and molecular free volume that provided the greatest protection against the oxidation of spray dried orange oil.
  • Thumbnail Image
    Item
    Storage Stability of Intermediate Wheatgrass (Thinopyrum Intermedium) Flour as Impacted by Agronomic Practices, Breeding, and Commercial Germination and Extrusion Techniques
    (2023-10) Loehr, Leslie
    Intermediate wheatgrass (IWG, Thinopyrum intermedium) is a perennial cereal grain capable of aiding the agricultural community in reducing the global environmental detriments of commercial agricultural practices. Factors such as soil erosion, lack of carbon sequestration, and nitrogen leaching are all current issues that need to be addressed with IWG potentially providing a sustainable solution. In addition to its environmental benefits, IWG provides ample nutritional advantages such as a relatively high protein, dietary fiber, and antioxidant content compared to one of the most ubiquitous cereal grains globally: wheat. However, a lack of understanding regarding on-going breeding program progress coupled with the absence of data on the storage stability post-processing of IWG grains contributes to little incentive for producers, processors, and consumers to focus on switching to this sustainable grain. Therefore, the objectives of this study were to: (1) screen 11 lines of IWG for differences in composition and enzyme activity as affected by breeding and agronomic practices, (2) determine the compounded impact of fat content, enzyme activity, and antioxidant content and activity on the storage stability of novel IWG cultivars and (3) identify the chemical changes induced by extrusion and germination of IWG grains and their impact on the storage stability of whole flours. Prior to treatment and storage, 11 samples of IWG were analyzed for proximate composition, protein profile, starch and total dietary fiber content, antioxidant content and activity, and enzyme activity utilizing AOAC and AACC standard methods. These results, primarily antioxidant content and activity, fat content, and enzyme activity, informed the selection of samples to be subjected to extrusion and germination treatments and subsequent ambient storage. Once selected, these samples underwent commonly used procedures for both extrusion and germination of cereal grains. Post-treatment and milling into whole flour, the samples were subjected to storage and analyzed periodically for carotenoid and hydroxycinnamic acid (HCA) content using high performance liquid chromatography, antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and leucomethylene blue (LMB) assays (all at 0, 1, 3, 6, and 8 months of storage), lipase and lipoxygenase enzyme activity via a copper soap assay and ferrous oxidation-xylenol orange (FOX) assay, respectively (at 0, 3, 6, and 8 months of storage), free fatty acids and peroxide value content via AOAC titration methods (940.28 and 965.33, respectively; both at 0, 1, 3, 6, and 8 months of storage), and volatile odor compounds (VOC) via dynamic purge-and-trap followed by gas chromatography coupled with olfactometry and mass spectrometry analysis (GC-O-MS) at 0, 3, and 8 months of storage). The first commercial cultivar and the new IWG varieties continue to hold a strong nutritional advantage over hard red wheat (HRW), and all samples also contained relatively higher ferulic acid and lutein contents and had high antioxidant activity. Additionally, protein and total dietary fiber content was higher in IWG than in HRW. Variance among the samples was more strongly linked to genetic makeup rather than geographic growing location, confirming promise for individual cultivars to perform similarly regardless of agronomic effects. Based on their fat content, enzyme activity and antioxidant profile, MN1601-SYN2, MN1603-SYN3, and MN-Clearwater varieties were selected for extrusion and germination processing followed by 8 months of ambient storage. Extrusion caused complete inactivation of lipase activity, while germinated samples retained their lipase activity. Lipase activity was determined to be more influential to hydrolytic rancidity than fat content alone, giving an advantage to the extrusion process. The abundantly present antioxidants combated oxidative rancidity, with carotenoids playing a major role, as evidenced by the significant (P < 0.05) loss in lutein and zeaxanthin between 3-6 months of storage. This observed loss occurred at the same time as FFAs, PV, and VOC (primarily hexanal and 2-pentyl-furan) experienced abrupt increases. These findings are quite insightful for future IWG breeding progress. In addition, the work provided a comprehensive understanding of how common post-harvest processing affects the storage stability of IWG flour, an essential information to promote its use as a food ingredient.