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Açaí has a high content of anthocyanins and unsaturated fatty acids, and drying parameters can affect the stability of these compounds. This study used a conductive thin-film dryer at a laboratory scale to mimic the (vacuum) drum drying of açaí pulp. The effect of drying chamber pressure on the drying kinetics and powdered product characteristics was investigated. Hot air drying and freeze-drying experiments were performed as references. A pilot-scale conductive dryer, namely a vacuum drum dryer, was used as well to dry açaí pulp. Conductive drying at low pressures led to lower boiling temperatures and shorter drying times but also more vigorous bubble formation. The anthocyanin content and antioxidant activity of contact-dried samples at low pressures were comparable to those of freeze-dried and significantly higher than those of hot air-dried. However, conductive drying caused greater lipid oxidation compared to freeze-drying and hot air drying. Oil loss was observed during vacuum drum drying except for the lowest pressure and the shortest drying time. Therefore, the results suggest that chamber pressure during conductive thin film drying should be carefully selected to obtain high-quality açaí powder.

Thermoreversible food materials are suitable for hot-extrusion 3D food printing (HE-3DFP) to customize food designs and enable on-demand food production. A challenge of HE-3DFP is to control the material phase transition such that it melts to allow flow and extrusion and rapidly solidifies afterwards to obtain stable printed structures. We here report on the use of thermal imaging to simultaneously monitor material cooling and deformation of common thermoreversible food materials during HE-3DFP. Thermographic and rheological measurements show that the structural deformation is driven by slow material cooling and prolonged printing time. The surface temperature of printed objects is a good indicator for structural stability. Solidification mechanisms such as cross-linking or strong particle jamming are required to prevent deformation in time (i.e. creep) during printing. Thus we recommend to set the printing temperature just above material's gelation temperature to ensure proper extrudability and structural stability of the printed foods.

3D food printing is considered a promising method to prepare personalized foods having unique macroscopic design and composition. It is still challenging to create 3D printed foods with tailored microstructure, e.g. fibrous microstructures, to print meat-like foods. In this study we investigated the preparation of 3D printed model food gels that have macro- and microscale aligned fibrous structures using sodium caseinate - sodium alginate (SC/SA) blends with extrusion-based printing. A bath containing an agar fluid gel was used to allow precise deposition and solidification of the SC/SA blend after the printing process. Besides, the influences of nozzle type and printing speeds on texture were assessed. We succesfully created aligned micron-size fibrous structures and macroscale aligned filament bundles. Filaments extruded using tapered nozzles had finer fibrous structures compared to those extruded using straight nozzles. Both printing speed and nozzle type significantly influenced Young's moduli of 3D printed model food gels. A higher printing speed resulted in smaller Young's moduli of individual printed filaments. This study shows that anisotropic structures can be created by extrusion-based 3D printing of phase-separated sodium caseinate - sodium alginate blends. The results of this study might become relevant when striving for meat analogues made by 3D-printing.

The enzymatic conversion of cellulosic-rich waste streams of white asparagus into cellobiose and cello-oligosaccharides (COS) is proposed for producing a natural carrier agent. The enzyme cocktail ‘Celluclast’ was used to steer towards maximum conversion and minimum formation of monosaccharides to obtain an enzymatic hydrolysate with a high glass transition temperature (Tg). Different enzyme loadings and hydrolysis times were tested in combination with a sodium hydroxide pre-treatment of the asparagus fibre. A loading of 700 nkat/g substrate and 7 h of hydrolysis time resulted in the best yield/purity combination, namely a conversion of 36 g/100 g cellulose with 81% celllobiose/COS. The same hydrolysis conditions were tested in a larger bench-scale experiment (conversion of 45 g/100 g cellulose) and the soluble hydrolysates were concentrated and spray-dried. The high Tg (108 °C) of the spray-dried hydrolysates of asparagus fibre proves its potential usage as a carrier agent for spray drying.