Search Results (358)

The initial carbon-to-nitrogen (C/N) ratio is a fundamental parameter for aerobic composting, with a generally recommended optimal range of 25:1 to 30:1. However, in practical applications, the optimal C/N ratio often deviates from the recommended value. We attribute this discrepancy to the limitations of traditional stoichiometric methods in assessing the bioavailability of carbon and nitrogen sources. This study investigated how carbon bioavailability governs composting efficiency and product quality. Laboratory-scale aerobic composting experiments were conducted using six types of raw crop straws and two physically pretreated straws, representing a biodegradability gradient. Results demonstrated that carbon bioavailability significantly modulated the composting performance. Substrates rich in labile carbon pool (LCP), such as wheat straw and extruded cassava plant residue, demonstrated superior thermogenesis, humification, and seed germination indices compared to those dominated by recalcitrant carbon pool (RCP), such as untreated cassava plant residue. Principal component analysis confirmed a strong positive correlation between LCP content and key quality indicators. Microbiological analysis revealed that carbon source variations shaped bacterial succession: Bacteroidota abundance correlated positively with LCP, driving rapid initial degradation, whereas Pseudomonadota were more abundant in RCP-rich treatments, suggesting a role in complex polymer breakdown. This study confirmed that carbon bioavailability, rather than the bulk C/N ratio alone, is a critical limiting factor. This finding logically extends to the role of nitrogen bioavailability, suggesting that a “biochemical C/N ratio”—accounting for the lability of both carbon and nitrogen—could be a more accurate predictor of aerobic composting performance. Full article

This study assessed the effects of eco-efficient aquafeed formulations on the growth, body composition, nutrient retention, and flesh quality of rainbow trout (Oncorhynchus mykiss). Four extruded diets were tested: a conventional control (Ctrl) and three eco-efficient formulations (No-PAP, PAP, and Mix) combining single-cell ingredients, insect meal, selected plant proteins, and aquaculture by-products, with long-chain omega-3 fatty acids (DHA and EPA) supplied primarily from microalgae. Rather than isolating single-ingredient replacements, the objective was to evaluate the efficacy of complex, industry-feasible formulations designed for practical application. These experimental feeds were administered to 800 trout (initial body weight 63 g), distributed across four replicates per diet. After a 97-day trial, results showed no significant differences in growth performance (final weight, weight gain, and relative growth rate) between diets. Feed conversion ratios (~0.78) were within expected ranges for rainbow trout under these conditions. Fillet texture and composition were similar across all groups; however, trout fed the No-PAP diet developed a significantly more yellow tint in fillet color, likely attributed to xanthophyll pigments from plant- and algae-based ingredients. The environmental impact of the diets was driven by specific ingredient choices, as evidenced by a carbon footprint analysis ranging from 1.39 kg CO₂ eq. (PAP diet) to 2.36 kg CO₂ eq. (Ctrl diet). These findings demonstrate that the three alternative formulations matched the efficacy of conventional feed, offering a sustainable option for trout aquafeed production. Full article

This research compared grain sorghum with wheat as an ingredient in extruded, floating tilapia feed, and also studied the impact of pre-extrusion grinding intensity or hammer mill sieve size on extrusion parameters, final product quality and animal performance. With an increase in grind size of the diets from 0.61 to 1.27 mm, higher specific thermal energy was observed; however, specific mechanical energy decreased, leading to lower expansion (pooled bulk density of 405.6 g/L versus 441.5 g/L). Grain source also impacted pellet expansion and quality, with sorghum-based aquatic feed pellets having higher piece density than wheat-based pellets (pooled average of 0.52 g/cm³ versus 0.48 g/cm³) and lower water absorption (pooled average of 255.7% versus 334.4%). Digestibility trends with respect to grain and grind size were not consistent for Nile tilapia fed different extruded diets, but results from a 12-week growth trial showed that tilapia fed the sorghum-based diet had a higher weight gain as compared to wheat-based diets (86.0% versus 81.8%). Grind size or grain did not have a statistically significant impact on feed conversion ratio (FCR), but the sorghum-based feed from medium grind had the lowest FCR of 1.03, while the FCR of other treatments ranged from 1.09 to 1.13. These results indicate that grain sorghum can successfully be incorporated into Nile tilapia diets with positive effects on both physical feed quality as well as the growth of the fish. Full article

This paper presents an evaluation of two new approaches to improve the surface quality and the mechanical properties of ceramic parts printed by fused deposition of ceramic (FDC). Dip-coating and aerosol-treatment are performed in order to reduce the staircase effect in the vertical printing direction, which typically represents the weakest orientation in most additive manufacturing processes, particularly in fused filament fabrication (FFF). The post-treatments are applied on two highly filled alumina feedstocks. A commercial aerosol-treatment machine for fused deposition modeling is used with ethanol as solvent. A suspension composition for dip-coating is developed to reduce the surface roughness without compromising the printing resolution. The influence of these post-processing steps on the mechanical properties and surface roughness of the green and sintered parts is investigated using perthometer measurements and four-point bending tests in the vertical build direction on as-processed, aerosol-treated, and dip-coated samples. The mechanical results are compared to extruded strand samples. An improvement in surface quality is achievable by dip-coating despite reduction in the parts strength, with a reduction of 65% of the R_z values in the sintered state compared to untreated samples. Aerosol-treatment neither improves the surface quality nor the mechanical properties of the parts. The feedstock and post-processing steps developed in this research aim at printing dense ceramic parts with high surface quality, serving as a basis for developing ceramic parts with higher strength. This advancement will facilitate the utilization of FDC in structural and aesthetic design applications. Full article

High-moisture extrusion (HME) is critical for plant-based meat analogs with meat-like fibrous structures. To expand HME protein sources, this study explored mung bean protein (MBP) substitution (0–50%, dry basis) effects on structural, textural and functional properties of soy protein concentrate (SPC)–wheat gluten (WG) HME products. At 20% MBP addition, the proteins formed a dense layered fibrous network, and the fibrous degree of the extrudates reached the peak. MBP > 40% disrupted the continuous protein network. The optimal rehydration for 20% MBP dried extrudates was 60 °C for 40 min, preserving fibrous texture. Protein interaction analysis indicated that hydrogen bonds and disulfide bonds played an important role in stabilizing the protein network structure. Overall, MBP can be incorporated into SPC-WG-based HME products to diversify protein sources, providing a feasible strategy for developing high-quality, nutritionally diversified plant-based meats. Full article

Excessive sodium consumption is a global public health problem that demands technological innovations in processed foods. This study aimed to reduce the sodium content in extruded corn snacks while maintaining perceived saltiness by substituting common salt with compound microparticles (70% NaCl, 30% starch). Two drying methods were evaluated: spray drying and conventional oven drying. The snacks were subjected to physicochemical, instrumental (texture and colour), density, porosity, microstructural, and sensory analyses (intensity scale, n = 104). The results demonstrated that the particles obtained by spray drying allowed a 28% reduction in the final sodium content without statistically differing in saltiness perception compared to the control. In contrast, the oven treatment reduced saltiness perception compared to the standard. Images obtained by scanning electron microscopy, along with porosity measurements, demonstrated a significant increase in porosity in the spray-dried sample. This allows rapid dissolution of the salt in the mouth, maintaining a salty taste even with reduced sodium content. It was concluded that the use of salt–starch microparticles via spray drying was a viable strategy for producing snacks with reduced sodium content without compromising sensory quality. Full article

CaCO₃ and NaHCO₃, respectively serving as chemical leavening agents, can promote the expansion of protein or starch extrudates, thereby forming a porous structure. However, the characteristics of this porous structure under the combined regulation of CaCO₃ and NaHCO₃ remained unclear. The results indicated that increasing the proportion of NaHCO₃ promoted the expansion of the extruded protein–starch gel network, with its expansion ratio significantly increasing from 2.29 to 3.17 (p < 0.05). This expansion resulted in larger pores, which corroborated the observed significant increase in water holding capacity (WHC). Conversely, an increase in the proportion of CaCO₃ led to a denser porous structure accompanied by a reduction in WHC. Meanwhile, the extrudate with a CaCO₃/NaHCO₃ ratio of 0:2 exhibited the lowest hardness, measuring 8.87 N. As the proportion of NaHCO₃ increased, the pH shifted toward the alkaline range. This increase in pH enhanced the flexibility of the protein structure, leading to a significant rise in the proportion of disordered structures in the protein secondary structure, such as random coil and β-sheet, which facilitated the formation of an elastic gel network. In conclusion, both CaCO₃ and NaHCO₃ significantly modulated the porous structure of the protein–starch gel network formed during extrusion. This provides a new perspective for investigating the relationship between the protein–starch gel network and the quality characteristics of extruded products. Full article

In this study, thermoplastic polyurethane (TPU) parts were fabricated using fused filament fabrication (FFF) by varying key process parameters, namely extruder temperature (210–230 °C), layer thickness (200–400 µm), and printing speed (30–50 mm/s). A Box–Behnken experimental design was used to systematically evaluate the combined influence of these parameters on surface roughness (R_a), dimensional deviation (DD), and ultimate tensile strength (UTS). After fabrication, all specimens were subjected to a Tetrahydrofuran (THF)-based chemical smoothing process to modify surface characteristics. Surface roughness measurements showed a substantial reduction after chemical smoothing, with values decreasing from an initial range of 13.17 ± 0.21–15.87 ± 0.23 µm to 4.01 ± 0.18–7.35 ± 0.16 µm, corresponding to an average decrease of approximately 50–72%. Dimensional deviation improved moderately, from 260–420 µm in the as-printed condition to 160–310 µm after post-processing, representing a reduction of about 20–38%. Mechanical testing revealed a consistent increase in UTS following chemical smoothing, with values improving from 30.24–40.30 ± 0.52 MPa to 33.97–47.94 ± 0.36 MPa, yielding an average increase of approximately 10–24%. Then, the experimental data were used for multi-objective optimization of the FFF process parameters, using a non-dominated sorting genetic algorithm (NSGA-II) implemented in Python 3.11, to identify best parameter combinations that provide a balanced surface quality, dimensional accuracy, and mechanical performance. Full article

In additive manufacturing technologies, the use of pastes and inks based on materials such as clay to create three-dimensional objects layer by layer has opened new possibilities in fields such as engineering and biomedicine. This review article aims to provide a comprehensive understanding of 3D printing of ceramic pastes through Direct Ink Writing (DIW), also referred to as Robocasting. DIW offers specific advantages for ceramic 3D printing, including the ability to extrude highly loaded pastes with customized rheological properties to accommodate a broad spectrum of ceramic compositions, varying from conventional clays to advanced ceramics. It is characterized by filament deposition control, which facilitates the fabrication of complex, porous, or customized architectures while simultaneously minimizing material waste. Through a bibliometric analysis of the literature published between 2020 and 2024, the most relevant studies regarding printing system architectures, ceramic paste formulations, and adjustment of parameters to obtain high-quality parts were identified. This work presents relevant and accurate explanations of the DIW technology, supporting researchers and industry professionals seeking to initiate or improve ceramic 3D printing processes for a wide range of applications. Full article

During the extrusion of novel nickel-based powder superalloy bars, the die is subjected to elevated temperatures, high pressures, and severe friction, which readily lead to abrasive wear and thermal-fatigue damage. These failures deteriorate the quality of the extruded products and significantly shorten the service life of the die. Frequent repair and replacement of the tooling ultimately increase the overall manufacturing cost. This study investigates the friction and wear behavior of H13 and 5CrNiMo hot-work tool steels under extreme transient high-temperature conditions by combining finite element simulation with tribological testing. The temperature and stress distributions of the billet and key tooling components during extrusion were analyzed using DEFORM-3D. In addition, pin-on-disk friction and wear tests were conducted at 1000 °C to examine the friction coefficient, wear morphology, and subsurface grain structural evolution under various loading conditions. The results show that the extrusion die and die holder experience the highest loads and most severe wear during the extrusion process. For 5CrNiMo tool steel, the wear mechanism under low loads is dominated by mild abrasive wear and oxidative wear, whereas increasing the load causes a transition toward adhesive wear and severe oxidative wear. In contrast, H13 tool steel exhibits a transition from abrasive wear to severe oxidative wear. In 5CrNiMo steel, friction-induced recrystallization, grain refinement, and softening lead to the formation of a mechanically mixed layer, which, together with a stable third-body layer, markedly reduces and stabilizes the friction coefficient. H13 steel, however, undergoes surface strain localization and spalling, resulting in persistent fluctuations in the friction coefficient. The toughness and adhesion of the oxide film govern the differences in wear mechanisms between the two steels. Owing to its higher Cr, V, and Mo contents, H13 forms a dense but highly brittle oxide scale dominated by Cr and Fe oxides at 1000 °C. This oxide layer readily cracks and delaminates under frictional shear and thermal cycling. The repeated spalling exposes the fresh surface to further oxidation, accompanied by recurrent adhesion–delamination cycles. Consequently, the subsurface undergoes alternating intense shear and transient load variations, leading to localized dislocation accumulation and cracking, which suppresses the progression of continuous recrystallization. Full article

Starches play a crucial role in determining the expansion, texture, and structural development of extruded meat analogs through their gelatinization behavior and interactions with proteins. In this study, corn, pea, tapioca, sweet potato, and potato starches were incorporated into soy protein-based formulations and processed under low-moisture and high-moisture extrusion conditions to investigate starch-dependent physicochemical properties. Amylose/amylopectin composition and starch pasting properties were evaluated, and the resulting extrudates were characterized in terms of expansion behavior, water-related properties, textural attributes, and internal structure. Distinct differences in pasting behavior were observed among starches, with potato starch exhibiting high peak viscosity and pea starch showing strong viscosity development during cooling. These differences were closely associated with extrusion outcomes, influencing expansion ratio and texture formation. In low-moisture extrusion, starches susceptible to thermal and shear degradation showed increased solubilization, whereas in high-moisture extrusion, enhanced starch gelatinization promoted starch–protein interactions and contributed to improved textural integrity and structural alignment. Overall, the results demonstrate that starch type is a key determinant of expansion behavior, texture, and structural organization in extruded meat analogs, highlighting the importance of starch selection and processing conditions for tailoring product quality. Full article

In aquaculture, feed production influences nutrition, performance, water quality, and overall profitability. This study evaluated the effects of three levels of internal fat (IF), resulting from the inclusion of 0%, 2%, or 4% fat in the preconditioner during extrusion, and their interaction with two extruder screw configurations: medium-shear (MS) and high-shear (HS), on kibble physical quality and extrusion parameters. Increasing IF resulted in a quadratic increase in amylose–lipid complexation under the HS configuration (p = 0.030; r2 = 0.9) and a linear reduction (p < 0.001) in specific mechanical energy (SME) with a strong negative Pearson correlation (r −0.9; p = 0.009) in both configurations. Fat inclusion also reduced mass temperature and die pressure (p < 0.05), leading to lower starch gelatinization degree (p < 0.05) from 87.9 ± 0.6% to 83.4 ± 0.3% in MS configuration and 95.6 ± 0.7 to 86.3 ± 0.8% in HS configuration, increased bulk and piece density (p < 0.001), and reduced radial expansion (p < 0.001). These changes decreased floatability (p < 0.05) and water stability, increasing mushiness (p < 0.01). Increased shear partially improved SME transfer, starch cooking, expansion, floatability, and mushiness; however, the negative effects of 4% IF could not be fully mitigated. Overall, higher IF compromised kibble structure, starch gelatinization, and floatability, while screw configuration resulted in only a limited compensatory effect. Full article

This study investigated the fabrication and characterization of polylactic acid (PLA)-based ceramic composite filaments for fused deposition modeling (FDM) 3D printing. Boron carbide (B₄C) and silicon carbide (SiC) were incorporated into PLA at various weight fractions (1–40 wt. % for B₄C and 1–20 wt. % for SiC) to produce composite filaments using a commercial extruder. The rheological properties, thermal stability, and printability of the filaments were evaluated. Filaments with low ceramic content exhibited satisfactory quality, whereas those with higher loadings required reprocessing to improve their dimensional stability and surface morphology. Successful printing was achieved with SiC contents of up to 8 wt. % using single-extruded filaments and up to 20 wt. % using double-extruded filaments. Rheological tests revealed that filaments with low ceramic content exhibited shear-thinning behavior, whereas those with higher loadings displayed nearly Newtonian-like behavior. Thermal analysis using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) determined the optimal processing temperature range for the composite filaments to be between 200 °C and 270 °C. High-temperature microscopy was used to study the temperature behavior of the B₄C-containing filaments and set the optimum printing temperature. The results demonstrate the feasibility of producing PLA-based ceramic composite filaments for FDM 3D printing with the potential to tailor the thermal and functional properties of the printed parts for specific applications. Full article

The present study aimed to model and optimize the fortification of corn-based extruded flips with quinoa flour to improve their nutritional, functional, and sensory quality while maintaining desirable technological properties. Corn flour was partially replaced with quinoa flour at levels of 0, 10, 20, and 30%, and the mixtures were processed using a twin-screw extruder at three screw speeds (350, 500, and 650 rpm). The influence of formulation and mechanical energy input on product quality was evaluated through comprehensive characterization, including bulk density, expansion index, texture, color, chemical composition, mineral profile, amino acid and fatty acid composition, and descriptive sensory attributes. Response surface methodology (RSM) was applied to model the effects of quinoa addition and screw speed on 56 quality responses. The Z-score approach was employed to identify optimal processing conditions. The results showed that from a technological and nutritional perspective, formulations containing 20–30% quinoa processed at medium to high screw speeds (500–650 rpm) provided the most balanced products. Z-score optimization identified that the sample with 20% quinoa extruded at 650 rpm showed a balanced combination of enhanced nutritional characteristics and preserved physical and sensory quality. Full article

Quality regulation of extruded expanded foods represents a critical technological challenge in this field. Current research has predominantly focused on the impact of extrusion processing parameters, largely overlooking the regulatory role of die structure. This study presents an integrated “CFD + Extrusion Process” methodology to systematically explore the effects of die design and process conditions on expanded product quality. Computational fluid dynamics (CFD) simulations evaluated the influence of nozzle number (12–15) and L/D ratio (1.25–2.5) on flow uniformity, the CFD results identified an optimal die configuration of 14 nozzles with L/D = 1.25, which minimized flow variance (velocity variance: 1.09 × 10⁻⁵ (m/s)²; viscosity variance: 2.777 (Pa·s)²) and established a stable flow foundation. Building on this, the RSM-based experiments revealed how process parameters specifically fine-tune quality attributes: screw speed and moisture content significantly (p < 0.05) affected Water Absorption Index (WAI) and Water Solubility Index (WSI), whereas moisture and temperature were the dominant factors (p < 0.05) governing bulk density and starch gelatinization. The findings of this study can provide a theoretical reference for the precise control of the quality of expanded food products. Full article