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The rhomboidal mixing section is becoming very popular among processors to provide distributive mixing. Currently, several different designs are used but the details of the flow behavior and mixing efficiency is not well understood. This information is needed to be able to design and find the most efficient rhomboid geometry. In this investigation nine different geometries with various pitches (helix of rhomboids) were analyzed using a 3-dimensional boundary element method (BEM). The geometries were compared according to mixing efficiency, pressure and energy consumption. The results were compared to experiments performed with a conventional single screw extruder that was fitted with three different rhomboidal mixing sections. The investigation led to the conclusion that the most effective distributive mixing sections were those with neutral rhomboids (pineapple mixer). However, the neutral rhomboidal mixing section consumes the most pressure in the extruder. It was also concluded that rhomboidal mixing sections deform the material by shear, making them poor dispersive mixing sections.

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A computational model to design plastic food packaging is proposed. The model minimizes the cost of the multi-layer structure satisfying the specific product requirements, using a heuristic optimization algorithm. The product requirements are defined by the expected shelf life, the storage conditions, the water sorption isotherms of foods and the maximum allowable gain or loss of gases (O 2 , CO 2 , N 2 , etc.) and moisture for the packaged food. In order to assure the food shelf life, these product requirements should be fulfilled to estimate the maximum permeance values of the plastic package. The computational algorithm automatically generates different multi-layer film structures that satisfy the product requirements. This algorithm combines different polymeric materials taking into account the barrier properties and cost of each layer, the compatibility between layers, the maximum number of layers and the minimum and maximum film thickness for each layer. Temperature and relative humidity corrections for the permeance calculations are considered. Permeance calculations of several barrier films are compared with oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) measurements. The optimization model algorithm is evaluated by means of standard numerical routines and numerical benchmarking.

Abstract Besides its poor dissolution in polymers, the stability, and bitterness of (-)-epicatechin present challenges for additional developments. Polymer formulations rich in flavonoids or other antioxidants can be developed by hot melt extrusion (HME) for enhancement of stability, release, and taste masking. The formulations are extruded at a temperature substantially below the melting point of (-)-epicatechin to avoid its degradation. The corresponding compound consists of about 50% wt. of an active nutraceutical ingredient, in this case (-)-epicatechin, and food grade polymers (GRAS: generally recognized as safe). In order to identify possible chemical or physical changes in the formulations, they were characterized using various techniques, such as differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, in vitro release profile, sensory analysis, high-performance liquid chromatography, and Fourier transform infrared spectroscopy. The crystallinity of (-)-epicatechin was reduced after melt extrusion, but its chemical structure remained unchanged. The main contribution of this research is to shed light on the preparation of polymeric formulations based on (-)-epicatechin using HME as an encapsulation technique to improve stability, release, and taste masking, which may be scaled up and commercially launched as nutraceutical products.