Browsing by Subject "Perennial crop"

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    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.
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    Genetic diversity and population structure of Vaccinium vitis-idaea
    (2018-09) Prochazka, Jolene
    Developing an understanding of the levels of diversity present at stages across the domestication continuum is key to retaining, or eventually introducing, diversity into domesticated plant lineages. There are special challenges associated with achieving this for perennial crops and their wild relatives, which are often clonal. This is because in species capable of asexual reproduction, it is necessary to first differentiate between clonal ramets and unique genets before measuring genetic diversity. We assessed the clonal structure and genetic diversity in wild populations of lingonberry (Vaccinium vitis-idaea). This survey included 195 individual samples across 15 populations, assayed at 18 nuclear microsatellite loci to reveal the sexual and asexual reproductive strategies of this species. Five of the fifteen populations were found to consist of only two clones each, while other populations maintained a higher number of genetically unique individuals. He across all samples was 0.517 while Ho was higher, at 0.567, with a negative, but nonsignificant, value of FIS (– 0.097 ± 0.038, P = 0.276) across populations. Most of the variation was found within individuals (82%), with a moderate amount of variation between populations (17%), consistent with low levels of population structure at this geographical scale. Wild lingonberry populations at the southern edge of their range in Minnesota exist as both large, clonal organisms and also as mixtures of multiple different clones in a single population. Despite the domination of multiple populations by only a few clones, the species as a whole appears much like a sexually-reproducing species at the genetic level. Some populations are very limited in clonal diversity, meaning that they are subject to extirpation if they fail to thrive under future climatic conditions. This investigation was continued by using eight microsatellite loci to employ clonal analysis and assess the genetic diversity and population structure for 269 V. vitis-idaea samples across modern, historical, world-wide wild, and cultivated groupings. This survey of a perennial, clonal plant over a relatively small geographic range across 50 years did not find clones that persisted over space or time. One location was represented by two preserved herbarium samples, and thorough sampling of that same modern site did not reveal the persistence of a clone after 20 years. The only clones identified from herbarium samples were from the same locations at the same point in time. Performing AMOVA over these four groupings, most of the diversity (72%) was still contained within separate individuals, suggesting weak population structure. As we analyzed population structure across modern, historical, wild, and cultivated groupings, the most surprising result was the differentiation of the modern from the historical grouping. This is indicated by a significant population pairwise FST between the modern and historical grouping (FST = 0.199, P < 0.001), demonstrating an impressive change in lingonberry populations in Minnesota over a contemporary timeframe (from the 1950s to today). Overall, the comparison of historical and modern samples shows that these clonal population dynamics may be variable across time, with high turn-over despite their capacity for asexual reproduction.