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The purpose of this paper is to investigate the effect of residence time distribution in extruders along with the incorporation of nutraceuticals on the final quality of the products with respect to several pivotal responses.

Corn–rice flour blend fortified with isolated nutraceutical concentrates at two (low and high) levels was extruded at barrel temperature (110°C), screw speed (260 rpm) and feed moisture (17 percent). Extrudates were collected at an interval of 24 s followed by analysis for radial expansion (RE), bulk density (BD), water absorption index (WAI), sensory score (SS), textural hardness, colorimetric values (L*, a* and b*) and color difference (E).

The entire data were fitted to zero- and first-order kinetic models. There was a gradual decrease in RE, SS and L* value, whereas an increase in BD, textural hardness and a* value of extrudates fortified with the three nutraceutical concentrates was observed with the successive time interval of 24 s along with a more pronounced effect on color difference (E) observed during the last stages of extrusion time. The zero-order kinetic model was well fitted for BD and a* value, whereas the first-order kinetic model showed better results for RE, WAI, SS, textural hardness, L* value, a* value and b* value of fortified extrudates.

Nutraceuticals like β-glucans, lignans and γ oryzanol exhibit numerous health-beneficial effects. This study analyzes the kinetics of changes in various responses of extrudates fortified with these nutraceutical concentrates during extrusion.

Lactobacillus rhamnosus GG, a probiotic of human origin, known to have health beneficial effects can be exposed to osmotic stress when applied in food production as important quantities of sugars are added to the food product. The aim of this study is to assess the mode of action of non‐electrolytes stress on its viability.

Investigations were carried out on stationary phase cells treated with 0‐1.5M sugars, by means of flow cytometric method (FCM) and plate enumeration method. Osmotically induced changes of microbial carboxyfluorescein (cF)‐accumulation capacity and propidium iodide‐exclusion were monitored. The ability of the cells to extrude intracellularly accumulated cF upon glucose energization was ascertained as an additional vitality marker, in which the kinetics of dye extrusion were taken into consideration as well. Sugar analysis by HPLC was also carried out.

The results of FCM analysis revealed that with sucrose, only cells treated at 1.5M experienced membrane perturbation but there was a preservation of membrane integrity and enzymatic activity. There was no loss of viability as shown by plate counts. In contrast, the majority of trehalose‐treated cells had low extent of cF‐accumulation. For these samples a slight loss of viability was recorded on plating (logN/N_o ∼ −0.45). At 0.6M, cells had similar extrusion ability as the control cells upon glucose energization. However, 20 per cent of sucrose‐treated cells and 80 per cent of trehalose‐treated cells extruded the dye in the first 10min.

This finding pointed out the importance of trehalose to enhance the dye extrusion activity, which is regarded as an analogue of the capability of cells to extrude toxic compounds. Sugars exert different effects on the physiological and metabolic status of LGG but none caused a significant viability loss. LGG can be a choice probiotic bacterium in sugar‐rich food production e.g. candies, marmalade etc., in which exposure to high osmotic pressure is be expected.

This paper aims to describe the physiological analysis of L. rhamnosus VTT E‐97800 and its adaptive response to osmotic stress induced by trehalose.

Cells of L. rhamnosus E800 in the stationary phase of growth were subjected to osmotic stress induced by trehalose treatments. The effects of osmotic stress on the viability of the study strain were determined by conducting flow cytometric analysis with carboxyfluorescein diacetate (cFDA) and propidium iodide (PI) and by observing the corresponding cells growth on MRS agar plates. Osmotic‐induced changes of esterase activity and membrane integrity were monitored. Ability to extrude intracellular accumulated cF (additional vitality marker) was taken into consideration.

The fluorescence‐based approach gave additional insights on osmotic induced changes of cellular events, which could not be explicitly assessed by culture techniques. Trehalose treatments caused a transient membrane permeabilization as revealed by a gradual decrease in esterase activity (a measure of enzyme activity and thus of viability) with increase in trehalose molarity. However, culturability on MRS agar was not significantly affected. Membrane integrity was maintained and there was an improvement in the ability of cells to extrude intracellular accumulated cF.

The paper provides a comparative study of the conventional culture techniques and the flow cytometric viability assessment which showed that esterase activity cannot be relied on to ascertain the culturability and viability status of an organism.

This paper aims to present a survey concerning the accuracy of thermoplastic polymeric parts fabricated by additive manufacturing (AM). Based on the scientific literature, the aim is to provide an updated map of trends and gaps in this relevant research field. Several technologies and investigation methods are examined, thus giving an overview and analysis of the growing body of research.

Permutations of keywords, which concern materials, technologies and the accuracy of thermoplastic polymeric parts fabricated by AM, are used for a systematic search in peer-review databases. The selected articles are screened and ranked to identify those that are more relevant. A bibliometric analysis is performed based on investigated materials and applied technologies of published papers. Finally, each paper is categorised and discussed by considering the implemented research methods.

The interest in the accuracy of additively manufactured thermoplastics is increasing. The principal sources of inaccuracies are those shrinkages occurring during part solidification. The analysis of the research methods shows a predominance of empirical approaches. Due to the experimental context, those achievements have consequently limited applicability. Analytical and numerical models, which generally require huge computational costs when applied to complex products, are also numerous and are investigated in detail. Several articles deal with artificial intelligence tools and are gaining more and more attention.

The cross-technology survey on the accuracy issue highlights the common critical aspects of thermoplastics transformed by AM. An updated map of the recent research literature is achieved. The analysis shows the advantages and limitations of different research methods in this field, providing an overview of research trends and gaps.

The purpose of this study is to understand how printing parameters and subsequent annealing impacts porosity and crystallinity of 3D printed polylactic acid (PLA) and how these structural characteristics impact the printed material’s tensile strength in various build directions.

Two experimental studies were used, and samples with a flat vs upright print orientation were compared. The first experiment investigates a scan of printing parameters and annealing times and temperatures above the cold crystallization temperature (T_cc) for PLA. The second experiment investigates annealing above and below T_cc at multiple points over 12 h.

Annealing above T_cc does not significantly impact the porosity but it does increase crystallinity. The increase in crystallinity does not contribute to an increase in strength, suggesting that co-crystallization across the weld does not occur. Atomic force microscopy (AFM) images show that weld interfaces between printed fibers are still visible after annealing above T_cc, confirming the lack of co-crystallization. Annealing below T_cc does not significantly impact porosity or crystallinity. However, there is an increase in tensile strength. AFM images show that annealing below T_cc reduces thermal stresses that form at the interfaces during printing and slightly “heals” the as-printed interface resulting in an increase in tensile strength.

While annealing has been explored in the literature, it is unclear how it affects porosity, crystallinity and thermal stresses in fused filament fabrication PLA and how those factors contribute to mechanical properties. This study explains how co-crystallization across weld interfaces is necessary for crystallinity to increase strength and uses AFM as a technique to observe morphology at the weld.

The purpose of this study was to evaluate the effects of the addition of flaxseed and amaranth at different proportions on the hydration kinetics, colour and sensory qualities of instant-extruded cereals, important aspects related to the functionality and acceptability of food products.

Instant-extruded cereals were made with different proportions of flaxseed (6.6–9.3%), amaranth (18.7–33.1%), and maize grits (63.8–67.3%); and characteristics such as hydration kinetics, colour parameters and sensory properties were evaluated.

The kinetics of milk absorption showed that the extruded cereals maintained their texture and crispness for a sufficiently long time (≤20 min). The L*, a* and chroma* values of the extruded cereals were significantly affected (p < 0.05) by the flaxseed content. Sensory evaluation showed that all the extrudates had good acceptance in terms of flavour, texture, and colour attributes in relation to high-fibre commercial cereals; according to the preference test, they were as acceptable as commercial extruded cereals when consumed with milk. The addition of high-fibre and protein-containing grains such as flaxseed (8.6–9.3%) and amaranth (18.7–22.9%) in instant-extruded cereals allowed the production of products with acceptable physical and sensory characteristics.

In this study a novel instant-extruded cereal with flaxseed and amaranth was developed. The evaluation of the physical and sensory characteristics of instant-extruded cereals is essential to guarantee consumer acceptability, especially if functional ingredients with a high content of dietary fibre and protein are added.

Material extrusion additive manufacturing processes inevitably produce bead-shaped surface patterns on the walls of parts, which create stress concentrations under load. This study aims to investigate the influence of such stress concentrations on the strength along the build direction (“Z-strength”).

This work consists of two main parts – an experimental demonstration to show the significance of stress concentrations on the Z-strength, followed by numerical modeling to evaluate the theoretical stress concentration factors (k_t) for such shapes. Meso-scale finite element analysis (FEA) was performed to evaluate k_t at the roots of the intersecting bead shapes. The critical bead shape parameters influencing k_t were identified, and parametric FEA studies were performed on different bead shapes by varying the normalized parameters.

The experimental results showed that up to a 40% reduction in the effective Z-strength could be attributed only to the presence of surface bead shapes. Bead overhang and root radius were identified as critical shape parameters influencing k_t. The results of the parametric FEA studies were used to generate a single empirical equation to determine k_t for any bead shape.

Predictive models for Z-strength often focus on crystallization kinetics and polymer chain interdiffusion to predict interlayer adhesion strength. The authors propose that the results of such studies must be combined with surface bead-shape induced stress concentration factors to obtain the combined, “effective” Z-strength.

This study aims to investigate the impact of layer thickness, extrusion temperature, extrusion speed and build plate temperature on the tensile strength, crystallinity achieved during fabrication (herein, in-process crystallinity) and mesostructure of Poly(lactic acid) specimens. Both tensile strength and in-process crystallinity were optimized and verified as the function of processing parameters, and their relationship was thoroughly examined.

The four key technological parameters were systematically varied as factors on three levels, using the statistically designed experiment. Surface response methodology was used to optimize tensile strength and crystallinity for the given ranges of input factors. Optimized factor settings were used in a set of confirmation runs, where the result of optimization was experimentally confirmed. Material characterization was performed using differential scanning calorimetry and X-ray diffraction analysis, while the effect of processing parameters on mesostructure was examined by scanning electron microscopy.

Layer thickness and its quadratic effect are dominant contributors to tensile strength. Significant interaction between layer thickness and extrusion speed implies that these parameters should always be varied simultaneously within designed experiment to obtain adequate process model. As regards, the in-process crystallinity, extrusion speed is part of two significant interactions with plate temperature and layer thickness, respectively. Quality of mesostructure is vital contributor to tensile strength during FDM process, while the in-process crystallinity exhibited no impact, remaining below the 20 per cent margin regardless of process parameter settings.

According to available literature, there have been no previously published investigations which studied the effect of process parameters on tensile strength, mesostructure and in-process crystallinity through systematic variation of four critical processing parameters.

The purpose of the present paper is to quantify and analyze the strain-rate dependence of the yield stress for both unfilled acrylonitrile-butadiene-styrene (ABS) and short carbon fiber-reinforced ABS (CF-ABS) materials, fabricated via material extrusion additive manufacturing (ME-AM). Two distinct and opposite infill orientation angles were used to attain anisotropy effects.

Tensile test samples were printed with two different infill orientation angles. Uniaxial tensile tests were performed at five different constant linear strain rates. Apparent densities were measured to compensate for the voided structure. Scanning electron microscope fractography images were analyzed. An Eyring-type flow rule was evaluated for predicting the strain-rate-dependent yield stress.

Anisotropy was detected not only for the yield stresses but also for its strain-rate dependence. The short carbon fiber-filled material exhibited higher anisotropy than neat ABS material using the same ME-AM processing parameters. It seems that fiber and molecular orientation influence the strain-rate dependence. The Eyring-type flow rule can adequately describe the yield kinetics of ME-AM components, showing thermorheologically simple behavior.

A polymer’s viscoelastic behavior is paramount to be able to predict a component’s ultimate failure behavior. The results in this manuscript are important initial findings that can help to further develop predictive numerical tools for ME-AM technology. This is especially relevant because of the inherent anisotropy that ME-AM polymer components show. Furthermore, short carbon fiber-filled ABS enhanced anisotropy effects during ME-AM, which have not been measured previously.

Additive manufacturing (AM), also known as three-dimensional (3D) printing technology, has been used in the health-care industry for over two decades. It is in high demand in the health-care industry due to its strength to manufacture custom-designed and personalized 3D constructs. Recently, AM technologies are being explored to develop personalized drug delivery systems, such as personalized oral dosages, implants and others due to their potential to design and develop systems with complex geometry and programmed controlled release profile. Furthermore, in 2015, the US Food and Drug Administration approved the first AM medication, Spritam® (Apprecia Pharmaceuticals) which has led to tremendous interest in exploring this technology as a bespoke solution for patient-specific drug delivery systems. The purpose of this study is to provide a comprehensive overview of AM technologies applied to the development of personalized drug delivery systems, including an analysis of the commercial status of AM based drugs and delivery devices.

This review paper provides a detailed understanding of how AM technologies are used to develop personalized drug delivery systems. Different AM technologies and how these technologies can be chosen for a specific drug delivery system are discussed. Different types of materials used to manufacture personalized drug delivery systems are also discussed here. Furthermore, recent preclinical and clinical trials are discussed. The challenges and future perceptions of personalized medicine and the clinical use of these systems are also discussed.

Substantial works are ongoing to develop personalized medicine using AM technologies. Understanding the regulatory requirements is needed to establish this area as a point-of-care solution for patients. Furthermore, scientists, engineers and regulatory agencies need to work closely to successfully translate the research efforts to clinics.

This review paper highlights the recent efforts of AM-based technologies in the field of personalized drug delivery systems with an insight into the possible future direction.