Freeze-drying is an important processing unit operation in food powder production. It offers dehydrated products with extended shelf life and high quality. Unfortunately, food quality attributes and grinding characteristics are affected significantly during the drying process due to the glass transition temperature (during drying operation) and stress generated (during grinding operation) in the food structure. However, it has been successfully applied to several biological materials ranging from animal products to plants products owning to its specific advantages. Recently, the market demands for freeze-dried and ground food products such as spices, vegetables, and fruits are on the increase. In this study, the effect of the freeze-drying process on quality attributes, such as structural changes, the influence of glass transition during grinding, together with the effect on grinding efficiency in terms of energy requirement, grinding yield, and morphological changes in the powder as a result of temperature, drying time were discussed. An overview of models for drying kinetics for freeze-dried food sample, and grinding characteristics developed to optimize the drying processes, and a prediction of the grinding characteristics are also provided. Some limitations of the drying process during grinding are also discussed together with innovative methods to improve the drying and grinding processes.

The progress of food 3D printing (3DP) applications demands a full understanding of the printing behavior of food materials. Computational fluid dynamics (CFD) simulation can help determine the optimum processing conditions for food 3DP such as layer height, deposit thickness, volume flow rate, and nozzle shape and diameter under varied material properties. This paper mainly discusses the application of CFD simulation for three core processes associated with 3DP: (1) flow fields in the nozzle during the extrusion process; (2) die swelling of materials at the die (the exit part of the nozzle); and (3) the residual stress of printed products. The major achievements of CFD simulation in food 3DP with varied food materials are discussed in detail. In addition, the problems and potential solutions that modelers encountered when utilizing CFD in food 3DP were explored.

Verbascum sinaiticum (Qetetina or yeahya Joro) is a medicinal plant with secondary metabolites such as phenolics, flavonoids, glycosides, saponins, and alkaloids. This study was designed to optimize the ultrasonic-assisted extraction (UAE) parameters to enhance the phenolic content and characterize the phenolic compounds using ultra-high-performance liquid chromatography, coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC-ESI-QTOF-MS/MS), and antioxidant activities in Verbascum sinaiticum extract. Extraction time, sample-to-solvent ratio, and extraction temperature were considered for UAE optimization. It was found that UAE generated the highest extraction yield (21.6%), total phenolic content (179.8 GAE mg/g), total flavonoid content (64.49 CE mg/g), DPPH (61.85 µg/mL), and ABTS (38.89 µg/mL) when compared to maceration extraction. Metabolite analysis in this study showed the detection of 17 phenolic compounds, confirming antioxidant capacities. The optimization parameters have significant effects on phenolic compounds. Scanning electron microscopy showed the presence of structural changes when UAE was used over the maceration method. The optimized UAE parameters for extraction temperature (41.43 °C), sample-to-solvent ratio (36.32 g/mL), and extraction time (33.22 min) for TPC were obtained. This study shows the potential application for UAE of Verbascum sinaiticum leaves in the development of pharmaceutical and nutraceutical products.

The rheological characteristics of pea protein (PP100%) and alginate (AG100%) as pure and mixed gels with different levels of pea protein (AP90:10, AP80:20, and AP70:30) were investigated via large-amplitude oscillatory shear (LAOS) and Fourier transform infrared (FTIR). Small-angle oscillatory shear (SAOS) was carried out for the samples, and a slight frequency dependence of the storage modulus (G′) and the loss modulus (G″) was observed for the pastes and gels, indicating the formation of a weak network, which is crucial for understanding the gel’s mechanical stability under small levels of deformation. Elastic and viscous Lissajous curves from the LAOS measurement at different levels of strain (1 to 1000%) elucidated that the mixed gels formed a strong network, which showed breakdown at high deformation (>100% strain). The synergistic strengthening of the network of the mixture was noticeable in the Fourier transform and Chevyshev harmonic analyses. This analysis indicated that the nonlinearity of e₃/e₁ and v₃/v₁ started at higher levels of strain for the mixed gels. The FTIR spectra revealed that there was no strong interconnection by crosslinking between pea protein and sodium alginate, indicating that the synergistic effect mainly came from electrostatic interactions. These findings suggest that combining alginate with pea protein can enhance the mechanical properties of gels, making them suitable for various food applications.

Computational fluid dynamics (CFD) was utilized to investigate the deposition process and printability of rice paste. The rheological and preliminary printing studies showed that paste formed from rice to water ratio (100:80) is suitable for 3D printing (3DP). Controlling the ambient temperature at $47\pm 5$ °C also contributed to improving the printed sample’s structural stability. The viscoelastic simulation indicated that the nozzle diameter influenced the flow properties of the printed material. As the nozzle diameter decreased (1.2 mm to 0.8 mm), the die swell ratio increased (13.7 to 15.15%). The rise in the swell ratio was a result of the increasing pressure gradient at the nozzle exit ($5.48\times {10}^6\mathrm{Pa}\mathrm{to}1.53\times {10}^7\mathrm{Pa}$). The additive simulation showed that the nozzle diameter affected both the residual stress and overall deformation of the sample. CFD analysis, therefore, demonstrates a significant advantage in optimizing the operating conditions for printing rice paste.

Verbascum sinaiticum (V. sinaiticum), locally known as “Qetetina” in Ethiopia, is a rich source of phenolic compounds, but its stability and sensory limitations restrict its application. This study evaluated the physicochemical, functional, morphological, structural, storage stability, and in vitro digestibility characteristics of V. sinaiticum extract encapsulated with 100% Gum Arabic (GA), 100% maltodextrin (MD), and a mixed coating material (MD:GA = 8:2 ratio) using freeze-drying. MD-based microcapsules demonstrated superior functional properties, including high water solubility (98.48%), low moisture content (1.36%), low hygroscopicity (14.61%), and high encapsulation efficiency (81.31%). During 32 days of storage, MD microcapsules retained 71.84% of total phenolic content and showed minimal release under gastric and thermal conditions, while GA encapsulates were less stable. Structural analysis using XRD, FTIR, and SEM confirmed successful encapsulation, with compact morphology, consistent phenolic preservation, and structural integrity. Furthermore, encapsulation masked the undesirable sensory attributes of the extract, enhancing its potential use in nutraceuticals. Overall, freeze-drying with MD provided the most effective encapsulation system, significantly improving the stability and storage potential of V. sinaiticum extract.