Introduction of biological and active Modified Atmosphere Packaging through microorganisms

Modified Atmosphere Packaging (MAP) is a technique for modifying internal gas atmosphere of the food package to slow deteriorative reactions inside the package and prolong shelf life of the product. However, due to current limitations of this passive technology, there might be some opportunities for introduction of active MAP through microorganisms. Therefore, the study is conducted on investigation of different types of packaging structures, microorganisms and packaging processes to find the optimum combination of these three factors for creating an active modified atmosphere inside a package. Among non-pathogenic microorganisms, three different groups, which are able to consume oxygen and produce carbon dioxide, are evaluated. These microorganisms, including 1) microaerophiles, 2) facultative fermentative and 3) probiotics, might be able to create modified atmosphere inside the package. They can be incorporated into the packaging structure, either into a closure or into the packaging layer. Moreover, it is also concluded that the physiological state of the microorganisms, either in the form of vegetative cells or spores, has to be in correlation with the packaging process. During the theoretical evaluation of this project, Saccharomyces boulardii is selected in its vegetative form as the potential microorganism to be incorporated into the closure of an orange juice package. Additionally, in the case of applying microorganisms into the packaging film for the creation of MAP, it is investigated whether Bacillus amyloliquefaciens can be the potential microorganism. However, further investigation through laboratory experiments is needed to be able to determine the best conditions for creating MAP by these microorganisms. Different aspects of introducing this method to the market, including safety regulations, environmental aspects and consumer benefits, are furthermore evaluated

Electric field enhancement with plasmonic colloidal nanoantennas excited by a silicon nitride waveguide

We investigate the feasibility of CMOS-compatible optical structures to develop novel integrated spectroscopy systems. We show that local field enhancement is achievable utilizing dimers of plasmonic nanospheres that can be assembled from colloidal solutions on top of a CMOS-compatible optical waveguide. The resonant dimer nanoantennas are excited by modes guided in the integrated silicon nitride waveguide. Simulations show that 100 fold electric field enhancement builds up in the dimer gap as compared to the waveguide evanescent field amplitude at the same location. We investigate how the field enhancement depends on dimer location, orientation, distance and excited waveguide modes

The critical pressure for microfiltration of oil-in-water emulsions using slotted-pore membranes

The influence of geometrical parameters and fluid properties on the critical pressure of permeation of an oil micro-droplet into a slotted pore is studied numerically by solving the Navier-Stokes equations. We consider a long slotted pore, which is partially blocked by the oil droplet but allows a finite permeate flux. An analytical estimate of the critical permeation pressure is obtained from a force balance model that involves the drag force from the flow around the droplet and surface tension forces as well as the pressure variation inside the pore. It was found that numerical results for the critical pressure as a function of the oil-to-water viscosity ratio, surface tension coefficient, contact angle, and droplet radius agree well with theoretical predictions. Our results show that the critical permeation pressure depends linearly on the surface tension coefficient, while the critical pressure nearly saturates at sufficiently large values of the viscosity ratio or the droplet radius. These findings are important for an optimal design and enhanced performance of microfiltration systems with slotted pores.Comment: 25 pages, 8 figure