Browsing by Subject "Storage"

Now showing 1 - 3 of 3
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    Editorial: Flavor chemistry of food: Mechanism, interaction, new advances
    (2023) Huang, Mingquan; Fan, Gang; Zhang, Yanyan
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    Der Einfluss von Ölgehalt und Fettsäuremuster auf die Lagerfähigkeit von Saatgut
    (2007) Ghiasvand Ghiasi, Kambiz; Kruse, Michael
    Seed storage with the objective of maintaining the quality for the later sowing is a constant challenge, not only in gene banks but also in agriculture, forestry and horticulture. In 1980 ELLIS and ROBERTS established ?The improved seed viability equation? for the prediction of the storability of seeds. With this equation the loss-of-germination-curve can be computed as a function of the initial seed germination, the storage temperature and the seed moisture content for each species. However, with oil-rich seeds the equation very often misses its aim. With this seeds, the variety and lot specific oil content considerably determines water activity and aging rate. Therefore the objective of the present work was to describe the influence of oil content on the aging behavior of seeds of the oil crops during storage quantitatively, to integrate this influence in the most reasonable way into the viability equation and to improve accuracy of its prediction. The investigation was carried out with storage experiments under controlled conditions in the laboratory at higher temperatures and running times between a few days and six months. First it was examined, whether the usually determined oil content of the entire seed is an informative parameter for water activity in the embryo axis. Experiments with sunflowers with an oil content between 28 and 48 % showed that oil-rich seeds need an about 1 % higher seed moisture content than seeds with lower oil content to have the same water activity in the embryonic axis. The storage of these seeds as well as the seeds of rape with oil contents between 39 and 50 % and flax with oil contents between 36 and 43 % showed that the loss of germination is more consistent with uniform water activity than with uniform seed moisture content. This has not been taken into account in the previous viability equation, so that its prediction contains systematic errors. Therefore extensive storage experiments were carried out with altogether 28 seed lots of rape, sunflower, flax and corn with different moisture contents and a uniform temperature of 45°C. Only for few of the stored lots the prediction of the seed viability equation was found to be correct. To include the oil content into the seed viability equation eight different suggestions were compiled. These were applied in three nonlinear regression models with different restrictions to the results of the storage experiments. The first model permitted the species specific determination of the weighing factors (constants) for the seed viability equation. The second model only allowed to determine the weighing factors for the absolute term and the seed moisture content specifically. Oil content was provided however with a species-nonspecific weighing factor. In the third model all weighing factors were species-nonspecific determined. All eight suggestions achieved better estimations for the aging rate in the species-specific models than the previous viability equation. Where this could be examined statistically, the improvements were significant. The same was found for the models with species-nonspecific weighting factors for the oil content. However, not all suggestions led to a converging result of the regression analysis. All examined species-nonspecific models did not improve the adjustment compared to the previous viability equation. The suggestions were then validated with a new and independent dataset with a storage temperature of seeds of 32°C. It was shown that the change of the temperature reduced the accuracy of the estimations of the nonlinear regression models. The new suggestions nevertheless corresponded better to the observed results than the previous viability equation. Based on these results a suggestion was then selected for the extension of the viability equation by ELLIS and ROBERT, which does not introduce a new weighing factor to the equation as the weighing factor might potentially contribute to a decrease of the precision of a prediction due to its standard error. Finally it was examined whether the fatty acid composition before storage in addition to the oil content affects the aging rate and whether the change of the fatty acid composition is directly connected to the loss of germination during storage. Only with rape, significant relations between the proportion of the fatty acid 14:0, 18:0, 20:0, 22:0 and the aging rate of the seed lots were determined. A uniform change of the fatty acid composition of all examined species could not be observed. Therefore this characteristic could not contribute to the further improvement of the prediction accuracy of the seed viability equation. To summarize, a suggestion to include the oil content into the viability equation was designed that clearly improves the accuracy of the prediction of the viability equation for oil-rich seeds and that contributes to a more appropriate and efficient storage of seeds.
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    Preharvest and postharvest factors affecting the quality profile of onion landraces
    (2021) Romo-Perez, Maria Luisa; Zörb, Christian
    Onion cultivation has been practiced for over 4000 years and does not exist as a wild species. Over time onions have adapted to different climates, creating a wide range of varieties and landraces. Today, in modern agriculture, commercial onion breeders focus almost exclusively on conventional farming which increases the demand for certain well-known varieties and hybrids but lowers the diversity available in the mainstream market. Additionally, a clear need for new varieties of onions is heralded by organic farming systems, where pesticides and chemical fertilizers are banned. A way to preserve biodiversity and enrich the range of varieties available in organic farming systems is to re-evaluate traditional landraces and introduce their benefits to the broader public. Onions are known for their good storability, particular aroma, as well as for their health-promoting benefits due to the rich content of non-structural carbohydrates, flavonoids, and S-containing compounds. However, the quality status and sensorial characteristics of onions can be influenced through preharvest and postharvest factors. Some of those factors are genotype, soil, and storage conditions. Preharvest abiotic factors such as soil salinity can lead to several reduction of yield and quality aspects. Much like many other vegetable species, onions have always been classified as salt-sensitive crop. However, to date, there was very little evidence to that claim, and information about the impact of salinity on onion quality and physiology is lacking. This thesis aims to characterize onion landraces and compare them using targeted and untargeted metabolomics with commercial cultivars when grown under organic farming conditions. A part of this is evaluating the differences of landrace metabolite profile and the storage impact after five months of cold storage. Furthermore, this thesis discusses the effect of increased soil salinity on the metabolism and physiology of onion plants. In chapter 2, yield and quality aspects of studied onion varieties demonstrated that landraces can achieve similar or even better results than modern varieties Sturon and Red Baron when grown under organic farming conditions of South-West Germany. Furthermore, differences between Sturon and landraces demonstrated that parts of the aromatic and flavor properties found in landraces have been lost in modern genotypes (Chapter 3). These results indicate that the maximum potential of the modern onion varieties has not yet been reached and further optimization of their yield and quality parameter could be attained through future breeding programs that include local landraces. Among the studied landraces, Birnförmige, Stunova, and Rijnsburger 4 are the most interesting and promising candidates. For instance, Birnformige demonstrated not only good storability but also high levels of S-containing compounds and fructans. Stunova presented good yield stability and capacity, while Rijnsburger 4 exhibited the highest levels of amino acids suitable as precursors of aromatic substances as well as good storability. Despite several reports claiming that onions are sensitive to salinity, chapter 4 of this thesis demonstrated there is no reduction in plant growth, quality, or aroma in onion plants after moderate Na+ treatments. Nevertheless, in comparison with the landrace Birnformige, modern variety Sturon showed a slight increase of compatible solutes by Na+ accumulation, demonstrating that the potential of certain varieties for onion production under increased soil salinity is actually much higher than previously assumed.