Rapeseed (Brassica napus L.) is the most abundant oilseed crop in the European Union, but it is not utilized to its full potential. Its oil is widely used in the food industry. However, the protein-rich residual seed components after the oil extraction are mostly used for animal feed. These components have come into focus as a promising plant protein source, due to the everincreasing demand for protein for human consumption. Yet, the utilization as a food ingredient has been limited hitherto, because of the presence of various antinutritional compounds (ANC) such as glucosinolates and proteinase inhibitors (PI). These compounds are associated to numerous issues related to health and taste and therefore require special attention when developing food ingredients. This thesis focuses on increasing the applicability of plant proteins isolated from rapeseed pressed cake as a food ingredient. Novel rapeseed protein products that were produced by an aqueous processing method (WO/2012/149941) were investigated. This processing method allowed the selective isolation of various products, omitting the unwanted ANC. By using rapeseed protein products that also contain other compounds such as fiber and lipids, a new appealing approach is offered that may become of high interest to the food industry, as elaborated purification procedures to obtain very pure compounds become obsolete. Consequently, extensive processing costs, the use of much resources and the production of various side streams are reduced, making the process more sustainable. To increase the applicability of the rapeseed protein the effect of salt on the solubility of a water-insoluble globulin protein product was analyzed, focusing on evaluating physico-chemical parameters in the presence of other compounds, such as lipids and fibers. Thereby a holistic approach was applied in order to assess the potential of rapeseed protein as a food ingredient in contrast to previous studies that focused on investigating pure protein products. Additionally, assessing physicochemical parameters provides valuable insights that can be used when designing a process to isolate proteins. Different food applications incorporating the novel rapeseed protein products were tested, revealing the high potential of the produced products in a wide application range as thickener, stabilizer and/or foaming agent. Furthermore, the reduction of glucosinolates and PI were considered to be key targets to increase the applicability of the protein products. Intact glucosinolates can be removed by processing, but if they are exposed to the enzyme myrosinase, which is present in all plants containing glucosinolates, numerous products are formed that are harder to remove and are associated with potential health risks. PI diminish the nutritional value of rapeseed proteins, as they affect their digestibility due to limitations in amino acid utilization. So far, a harsh heat treatment is applied in the food industry to inactivate myrosinase and PI, which also affects other proteins and compounds of rapeseed, decreasing its applicability. Thus, more targeted methods to control myrosinase and PI are in demand. In order to elucidate factors affecting the activity of myrosinase and the stability of PI with the aim of allowing a targeted, selective inactivation method, different model systems were consequently explored in this work in order to establish a set of reliable analysis methods. These can be transferred to other, more complex, structurally related systems. The activity of myrosinase isolated from white mustard (Sinapis alba L.) influenced by different factors such as temperature and ascorbic acid was investigated, utilizing hitherto not applied scattering techniques, as for example small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS), to evaluate the structure of the enzyme and correlate the findings to the activity of the enzyme. PI were analyzed using two well-studied PI isolated from soybean (Glycine max L. Merr), the Kunitz trypsin inhibitor (KTI) and the Bowman-Birk chymotrypsin/trypsin inhibitor (BBI). Disulfide bonds, which contribute significantly to the stability of the PI, were reduced by reducing agents, in particular zinc, which has previously not been used for this purpose in food products, considerably lowering the trypsin inhibitor activity. This novel approach enables a more targeted inactivation of PI, than the hitherto used thermal treatment, as it directly targets the PI. Additionally, it may lead to an increased nutritional value of the food product, as the sulfur-rich PI can be maintained in the product. To monitor the reduction of disulfide bond, a novel method was developed using micellar electrokinetic capillary chromatography and the glutathione redox reaction, which can be linked to the measured activity of the trypsin inhibitors. Rapeseed protein is an ongoing, complex research field, which constantly grows due to the development of different processes for their isolation, which has a profound impact on the protein. This thesis highlights the potential of protein isolated from rapeseed pressed cake as a food ingredient, offering various approaches to reduce the interference of ANC, as shown using different model systems, and sets of measurements to study these. This is the first work evaluating protein products isolated from rapeseed pressed cake with residual lipid content, as opposed to rapeseed meal, which is produced by extracting the oil using organic solvents and contains no lipids. Further research along with the investigations undertaken in this study will support the full utilization of rapeseed.