Cold atmospheric pressure plasma treatment of food matrices

Abstract

The application of cold atmospheric pressure plasma (CAPP) was suggested as an innovative nonthermal technology for inactivating undesirable microorganisms on the surface of heat-sensitive food products. Moreover, CAPP may offer a promising approach for the tailored modification of product properties along value-added chains of plant and animal related products. Therefore, this thesis puts emphasis on providing evidence for the possible utilization of plasma-induced surface and ingredient interactions as a tool for the selective modification of secondary metabolite profiles in plants and techno-functionality of flours and proteins from peas. Further, the knowledge gained on plasma assisted modification of plant-based materials was transferred to animal-based materials from edible insects taking additionally into account microbial decontamination as another key issue in insect processing. The thesis imparts the detailed characterization of selected raw materials, the identification of proper CAPP setups and corresponding product-specific process parameters by performing process accompanying monitoring of plasma characteristics required to achieve desired modifications. Detailed investigations of the plasma-induced effects were conducted following a top-down approach by using suitable analytical methods providing insights into possible underlying mechanisms from macroscopic to molecular level. The macroscopic level of analysis included quality (color/texture), compositional (protein/fat/dry matter contents) and microbial (surface/overall total viable counts) methods, followed by determining techno-functional (water/fat binding/emulsification) and protein (solubility/water/fat binding/emulsification) properties, as well as protein structure (surface hydrophobicity/fluorescence properties/CD spectroscopy) on the microscopic and structural level, down to analysis of the protein composition (SDS-PAGE/tryptophan content/amino acid composition) on the molecular level. The results provide a scientific basis regarding the targeted use of the CAPP technology for functionalization and modification of high-protein food components and could therefore contribute to the bio-economic and resource efficient production of dry high-value protein products, as protein functionality plays a key role in improving existing products, developing new products, and utilizing alternative protein sources as new ingredients. Consequently, feedback on the applicability of CAPP for tested raw materials was derived by evaluating the effectiveness of the treatment regarding the desired process goal, and by identifying product-specific characteristics allowing transferability of the CAPP process with the long-term goal of combining plasma treatments with existing unit operations in established product-specific process lines. Initial approaches regarding the CAPP treatment of complex food matrices by using a plasma device, which is promising for the application in industrial scale, aimed at the development of innovative process combinations with focus on “plasma-drying” as a prospective future unit operation, which may contribute to reducing the expected costs of CAPP treatments. The potential of CAPP processing to become a routine tool for the food industry in the coming years is also reflected throughout all parts of this work, and thus, it provides a substantial contribution to promoting the successful admission of the CAPP technology in the food sector.