Novel microscopy-based approaches to study the film formation mechanism and associated mechanical response in polymer lattices

In this paper, we present the results from novel microscopy-based approaches aimed at providing further insight into the mechanism of film formation and associated mechanical response in polymer lattices. Firstly, a ‘simple’ methodology, combining the use of variable pressure scanning electron microscopy and a recently introduced enhanced coolstage (–50 to +50°C), was successfully developed and not only used to study dynamic processes, e.g. different stages of latex film formation, but also for high-resolution imaging of ‘freeze-dried’ structures. By using the enhanced freeze-drying capability of the system, it was also possible to preserve the structure and features of the studied system with minimum shrinkage and distortion and in the case of polymer lattices at a desired stage of film formation. Moreover, specimens can then be readily imaged, without the need of conductive coatings and at much lower chamber gas pressures, thus minimizing the beam skirting effects and allowing higher resolutions to be achieved. The second and final part of our study consider the mechanical response of the studied latex dried under different conditions, with the particular emphasis on the effects of drying rate [% relative humidity (RH)]. Atomic force microscopy force distance curve measurements revealed that while the %RH did not have an effect on the structures formed, it did have an effect on the adhesive properties of the studied system. It is strongly believed that the methodologies developed and used here can be applied to other material systems, including biologicals and pharmaceuticals.     

THE INFLUENCE OF COOKING METHOD ON THE QUALITY OF PORK PATTIES

Pork patties were subjected to traditional frying, cooking in a microwave oven (microwaves  +  grill), hot air cooking in a cyclojet (Electrim JI-9101 RP, Taiwan) and cooking in a steam-convection (combi) oven (hot air  +  30% steam) (BECK FCV 4 EDS, BECK GmbH, Jagsthausen, Germany). Products cooked in the combi oven (BECK FCV 4 EDS) were characterized by the smallest cooking loss, the highest retention of water and the lowest content of fat compared to other samples. The content of hydroxymethylfurfural in fried and cyclojet-cooked patties was almost twofold higher than in microwave and combi oven-cooked samples. The intensity of lipid oxidation was also higher in fried and cyclojet-cooked meat than in the other two products. The intensity of meat flavor was the strongest in the combi oven-cooked patties. All products were characterized by a low intensity of fatty flavor. The highest scores for overall acceptability were given to the combi oven-cooked patties, whereas the lowest scores were given by the panelists to the microwave-cooked patties.

PRACTICAL APPLICATIONS

Pork patties are an important meat product both in catering production for direct consumption and in convenience food industry when intended for refrigerated or frozen storage. As cooking is a main stage in preparation of patties for consumption, it is essential to use a method of cooking that ensures the high nutritional and sensory quality of products. Most often, pork patties are subjected to deep frying or traditional frying; however, several other cooking methods can be used. The present work shows that the combi oven cooking enables production of patties of desirable nutritional and sensory characteristics and low content of unfavorable compounds.