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Edible polymers such as polysaccharides, proteins, and lipids are biodegradable and biocompatible materials applied as a thin layer to the surface of food or inside the package. They enhance food quality by prolonging its shelf-life and avoiding the deterioration phenomena caused by oxidation, humidity, and microbial activity. In order to improve the biopolymer performance, antimicrobial agents and plasticizers are also included in the formulation of the main compounds utilized for edible coating packages. Secondary natural compounds (SC) are molecules not essential for growth produced by some plants, fungi, and microorganisms. SC derived from plants and fungi have attracted much attention in the food packaging industry because of their natural antimicrobial and antioxidant activities and their effect on the biofilm’s mechanical properties. The antimicrobial and antioxidant activities inhibit pathogenic microorganism growth and protect food from oxidation. Furthermore, based on the biopolymer and SC used in the formulation, their specific mass ratio, the peculiar physical interaction occurring between their functional groups, and the experimental procedure adopted for edible coating preparation, the final properties as mechanical resistance and gas barrier properties can be opportunely modulated. This review summarizes the investigations on the antimicrobial, mechanical, and barrier properties of the secondary natural compounds employed in edible biopolymer-based systems used for food packaging materials.

In this study, two-dimensional unsteady laminar flow over a semi-circular cylinder (SCC) near a splitter plate was investigated numerically. Adding a splitter plate along the wake centreline downstream of the bluff bodies is an efficient passive means of controlling fully developed vortex shedding. Numerical simulations were done for different Reynolds numbers ranging from 100 to 500 in three different gaps ( g: g = 0.0 D to 4.5 D) and two different splitter lengths ( LSP = 1 and 2 D). Results indicate that by increasing the gap ratio, vortex shedding formed in the wake is suppressed and the oscillating amplitude of the lift coefficient decreases. On the other hand, drag, lift, and pressure coefficients representing the flow characteristics also vary as a function of the gap ratio at different Reynolds numbers. Extensive results on streamline patterns, wake characteristics (recirculation length), drag, lift, and pressure coefficients are presented to elucidate the interplay between the gap ratio and the Reynolds number and their influence on drag. Using the splitter plate at the downstream of the SCC causes the stretching of the vortex core and moves the centre of the vortex cores towards the leading edge of the plate. This phenomenon is caused by the reduction of the lift and drag coefficients.

In the current study, droplets dynamics under an asymmetric electric field in a T-junction are numerically studied using COMSOL Multi-physics software. The effect of different factors such as dimensionless length of mother droplet (L*), Capillary number (Ca), and electric capillary number (Cae) are investigated on the breakup process in symmetric T-junctions. Two novel patterns of droplets, namely, hybrid asymmetric splitting mode and sorting patterns, have been observed by imposing an electric field in one branch of the microchannel. It is also concluded that using an electric field is a promising strategy to reach droplets with arbitrary sizes and control over the splitting ratio of daughter droplets precisely in a T- junction by adjusting the electric field strength. After a certain electric capillary number ($$\left. {Ca_{e} } \right|_{Sorting}$$ C a e Sorting ), the mother droplet does not breakup and is sorted on the side of the branch that the electric field imposes. Furthermore, $$\left. {Ca_{e} } \right|_{Sorting}$$ C a e Sorting increases with the increment of L* and Ca.