Stick–slip motion and controlled filling speed by the geometric design of soft micro-channels

HypothesisLiquid can move by capillary action through interconnected porous materials, as in fabric or paper towels. Today mass transport is controlled by chemical modification. It is, however, possible to direct mass transport by geometrical modifications. It is here proposed that it is possible to tailor capillary flow speed in a model system of micro-channels by the angle, size and position of attached side channels.ExperimentsA flexible, rapid, and cost-effective method is used to produce micro-channels in gels. It involves 3D-printed moulds in which gels are cast. Open channels of micrometre size with several side channels on either one or two sides are produced with tilting angles of 10 – 170\ub0. On a horizontal plane the meniscus of water driven by surface tension is tracked in the main channel.FindingsThe presence of side channels on one side slowed down the speed of the meniscus in the main channel least. Channels having side channels on both sides with tilting angles of up to 30\ub0 indicated tremendously slower flow, and the liquid exhibited a stick-slip motion. Broader side channels decreased the speed more than thinner ones, as suggested by the hypothesis. Inertial forces are suggested to be important in branched channel systems studied here

Lingonberry (Vaccinium vitis-idaea) press-cake as a new processing aid during isolation of protein from herring (Clupea harengus) co-products

High acid-consumption and lipid oxidation are challenges when recovering functional proteins from herring co-products via pH-shift-processing. Here, lingonberry press-cake (LP), which is abundant in organic acids and phenolics, was added to alkali-solubilized herring-co-product-proteins (2.5–30 % LP per dry weight) aiming to aid protein precipitation, save hydrochloric acid (HCl) and provide oxidative stability. The results revealed 5–30 % LP addition reduced HCl-consumption by 13–61 % and 19–79 % when precipitating proteins at pH 5.5 and 6.5, respectively. Higher LP% decreased protein content and lightness of protein isolates but raised the lipid content. Precipitation at pH 6.5 used less acid, reduced total protein yield and raised moisture content and darkness of isolates. Contrary to controls, lipid oxidation-derived volatiles did not develop in protein isolates precipitated with 10 % and 30 % LP, neither during the process itself nor during 21 days on ice. Altogether, LP was identified as a promising all-natural processing-aid to use during herring protein isolation

Hydrogels as a water bolus during hyperthermia treatment

The feasibility of using hydrogels as a water bolus during hyperthermia treatment was assessed. Three types of gels, high methoxyl (HM) pectin/alginate, xanthan/locust bean gum (LBG) and xanthan/LBG/agarose were evaluated based on their dielectric, rheological and mechanical properties. The most suitable, xanthan/LBG/agarose gel was further used as a water bolus in a hyperthermia array applicator. The gels composed of polysaccharides carrying low charge displayed dielectric properties close to those of water, while the dielectric properties of HM pectin/alginate gel was deemed unsuitable for the current application. The mechanical examination shows that the xanthan/LBG gel has a non-brittle behaviour at room temperature, in contrast to the agarose gel. The moduli of the xanthan/LBG gel weaken however considerably between the temperature range of 40 \ub0C and 50 \ub0C, reducing its potential to be used as water bolus. The ternary system of xanthan/LBG/agarose had advantageous behaviour as it was dominated by the thermal hysteresis typical of agarose upon temperature increase, but governed by the typical non-brittle behaviour of the xanthan/LBG at low temperatures. The final evaluation within the hyperthermia applicator showed excellent signal transmission from the antennas. The agarose/xanthan/LBG gel reduced the scattering of electromagnetic waves, enabled a tight closure between the body and the antennas, and offered a less bulky solution than the currently used water-filled plastic bags. The results presented here open up a new application area for hydrogels in improving heat delivery during hyperthermia treatment and other near-field microwave applications

Oxidized xylan additive for nanocellulose films – A swelling modifier

Polymeric wood hemicelluloses are depicted to join cellulose, starch and chitosan as key polysaccharides for sustainable materials engineering. However, the approaches to incorporate hemicelluloses in emerging bio-based products are challenged by lack of specific benefit, other than the biomass-origin, although their utilization would contribute to sustainable material use since they currently are a side stream that is not valorized. Here we demonstrate wood-xylans as swelling modifiers for neutral and charged nanocellulose films that have already entered the sustainable packaging applications, however, suffer from humidity sensitivity. The oxidative modification is used to modulate the water-solubility of xylan and hence enable adsorption in an aqueous environment. A high molecular weight grade, hence less water-soluble, adsorbed preferentially on the neutral surface while the adsorbed amount on a negatively charged surface was independent of the molecular weight, and hence, solubility. The adsorption of the oxidized xylans on a neutral cellulose surface resulted in an increase in the amount of water in the film while on the negatively charged cellulose the total amount of water decreased. The finding of synergy of two hygroscopic materials to decrease swelling in hydrophilic bio-polymer films demonstrates the oxidized macromolecule xylan as structurally functional component in emerging cellulose products

Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene

Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP-TMP-AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP

Effect of physicochemical properties, pre-processing, and extraction on the functionality of wheat bran arabinoxylans in breadmaking – A review

Arabinoxylan (AX) is an abundant hemicellulose in wheat bran and an important functional component in bakery products. This review compares preprocessing and extraction methods, and evaluates their effect on AX properties and functionality as a bread ingredient. The extraction process results in AX isolates or concentrates with varying molecular characteristics, indicating that the process can be adjusted to produce AX with targeted functionality. AX functionality in bread seems to depend on AX properties but also on AX addition level and interactions with other components. This review suggests that the use of AX with tailored properties together with properly optimized baking process could help increasing the amount of added fiber in bread while maintaining or even improving bread quality

The effect of sulfate half-ester groups on cellulose nanocrystal periodate oxidation

Periodate oxidation introduces aldehyde functionality to cellulose. The use of dialdehyde cellulose has been demonstrated for crosslinking and as a chemical intermediate towards functionalized cellulose. Commercially available cellulose nanocrystals (CNCs) typically carry a surface sulfate half-ester functionality, which results from their manufacture via sulfuric acid hydrolysis and subsequent esterification. The sulfate half-ester group is a bulky group carrying a net negative charge above pH 2 that modifies the colloidal and electro-chemical properties of the CNCs. Periodate oxidation is regioselective to the bond between carbons in positions 2 and 3 in the anhydroglucose unit while the sulfate half-ester groups are mostly considered to be located in carbon in position 6. This regioselectivity could be the reason why the role played by the sulfate half-ester group on modification by periodate oxidation has not previously been elucidated. Here, the influence of the sulfate half-ester on the oxidation of CNCs, which is shown to steer the oxidation kinetics and the properties of the resulting materials, is studied. Conventional physicochemical analysis of the oxidant consumption is accompanied by elemental analysis, Fourier-transform infrared, X-ray photoelectron and solid-state nuclear magnetic resonance spectroscopy, and wide-angle x-ray scattering analyses; the zeta potential is used to characterize the colloidal properties of the suspensions and atomic force microscopy for determining particle dimensions. The presence of the sulfate half-ester group decreases the rate of oxidation. However, the content of the sulfate half-ester groups decreases when degree of oxidation reaches approx. 50%. We demonstrate that the CNC surfaces are affected by the oxidation beyond the C2–C3 bond cleavage: insight into the kinetics of the oxidation process is a prerequisite for optimizing CNC oxidation

Radial discharge high shear homogenization and ultrasonication assisted pH-shift processing of herring co-products with antioxidant-rich materials for maximum protein yield and functionality

Cross-processing herring co-products with antioxidant-rich helpers including lingonberry-press-cake, shrimp-shells and seaweed was reported to mitigate lipid oxidation but reduce protein yield. Here, four strategies were used to counteract such yield-reduction; optimizing solubilization/precipitation pH, increasing raw-material-to-water-ratio, replacing single-stage-toothed- by radial-discharge- high-shear-mechanical-homogenization (RD-HSMH) and ultrasonication (US). The effects of RD-HSMH and US on lipid oxidation, protein structural and functional properties were studied. Combining four strategies improved total protein yield by 5–12 %, depending on helper type. More than the confirmed antioxidant effects, cross-processing also improved protein water solubility and emulsification activity but reduced gelation properties. RD-HSMH generally improved protein emulsifying and gelation properties but reduced protein water solubility. US reduced protein water solubility and gelation properties. Altogether, it was recommended for all helpers to increase solubilization pH to 12 and raw-material-to-water-ratio to 1:6 followed by RD-HSMH at 8000 rpm for 90 s, aiming for maximum protein yield and emulsifying and gelation properties

Impact of Glucose on the Nanostructure and Mechanical Properties of Calcium-Alginate Hydrogels

Alginate is a polysaccharide obtained from brown seaweed that is widely used in food, pharmaceutical, and biotechnological applications due to its versatility as a viscosifier and gelling agent. Here, we investigated the influence of the addition of glucose on the structure and mechanical properties of alginate solutions and calcium-alginate hydrogels produced by internal gelation through crosslinking with Ca2+ . Using1H low-field nuclear magnetic resonance (NMR) and small angle neutron scattering (SANS), we showed that alginate solutions at 1 wt % present structural hetero-geneities at local scale whose size increases with glucose concentration (15–45 wt %). Remarkably, the molecular conformation of alginate in the gels obtained from internal gelation by Ca2+ crosslinking is similar to that found in solution. The mechanical properties of the gels evidence an increase in gel strength and elasticity upon the addition of glucose. The fitting of mechanical properties to a poroelastic model shows that structural changes within solutions prior to gelation and the increase in solvent viscosity contribute to the gel strength. The nanostructure of the gels (at local scale, i.e., up to few hundreds of \uc5) remains unaltered by the presence of glucose up to 30 wt %. At 45 wt %, the permeability obtained by the poroelastic model decreases, and the Young’s modulus increases. We suggest that macro (rather than micro) structural changes lead to this behavior due to the creation of a network of denser zones of chains at 45 wt % glucose. Our study paves the way for the design of calcium-alginate hydrogels with controlled structure for food and pharmaceutical applications in which interactions with glucose are of relevance

Side chains affect the melt processing and stretchability of arabinoxylan biomass-based thermoplastic films

Hydrophobization of hemicellulose causes melt processing and makes them stretchable thermoplastics. Understanding how native and/or appended side chains in various hemicelluloses after chemical modification affect melt processing and material properties can help in the development of products for film packaging and substrates for stretchable electronics applications. Herein, we describe a one-step and two-step strategy for the fabrication of flexible and stretchable thermoplastics prepared by compression molding of two structurally different arabinoxylans (AX). For one-step synthesis, the n-butyl glycidyl ether epoxide ring was opened to the hydroxyl group, resulting in the introduction of alkoxide side chains. The first step in the two-step synthesis was periodate oxidation. Because the melt processability for AXs having low arabinose to xylose ratio (araf/xylp<0.5) have been limited, two structurally distinct AXs extracted from wheat bran (AXWB, araf/xylp = 3/4) and barley husk (AXBH, araf/xylp = 1/4) were used to investigate the effect of araf/xylp and hydrophobization on the melt processability and properties of the final material. Melt compression processability was achieved in AXBH derived samples. DSC and DMA confirmed that the thermoplastics derived from AXWB and AXBH had dual and single glass transition (Tg) characteristics, respectively, but the thermoplastics derived from AXBH had lower stretchability (maximum 160%) compared to the AXWB samples (maximum 300%). Higher araf/xylp values, and thus longer alkoxide side chains in AXWB-derived thermoplastics, explain the stretchability differences