Phase change materials for life science applications

Phase change materials (PCMs) are a class of thermo-responsive materials that can be utilized to trigger a phase transition which gives them thermal energy storage capacity. Any material with a high heat of fusion is referred to as a PCM that is able to provide cutting-edge thermal storage. PCMs are commercially used in many applications like textile industry, coating, and cold storage typically for heat control. These intriguing substances have recently been rediscovered and employed in a broad range of life science applications, including biological, human body, biomedical, pharmaceutical, food, and agricultural applications. Benefiting from the changes in physicochemical properties during the phase transition makes PCMs also functional for barcoding, detection, and storage. Paraffin wax and polyethylene glycol are the most commonly studied PCMs due to their low toxicity, biocompatibility, high thermal stability, high latent enthalpy, relatively wide transition temperature range, and ease of chemical modification. Current challenges in employing PCMs for life science applications include biosafety and/or engineering difficulties. The focus of this review article is on the life science applications, evaluation, and safety aspects of PCMs. Herein, the advances and the potential of employing PCMs as a versatile platform for various types of life science applications are highlighted.Peer reviewe

Mannans as film formers and emulsion stabilizers

Mannans are abundant plant polysaccharides found in the endosperm of certain leguminous seeds (guar gum galactomannan, GG; locust bean gum galactomannan, LBG), in the tuber of the konjac plant (konjac glucomannan, KGM), and in softwoods (galactoglucomannan, GGM). This study focused on the effects of the chemical structure of mannans on their film-forming and emulsion-stabilizing properties. Special focus was on spruce GGM, which is an interesting new product from forest biorefineries. A plasticizer was needed for the formation of films from mannans other than KGM and the optimal proportion was 40% (w/w of polymers) glycerol or sorbitol. Galactomannans with lower galactose content (LBG, modified GG) produced films with higher elongation at break and tensile strength. The mechanical properties of GG-based films were improved by decreasing the degree of polymerization of the polysaccharide with moderate mannanase treatments. The improvement of mechanical properties of GGM-based films was sought by blending GGM with each of poly(vinyl alcohol) (PVOH), corn arabinoxylan (cAX), and KGM. Adding other polymers increased the elongation at break of GGM blend films. The tensile strength of films increased with increasing amounts of PVOH and KGM, but the effect of cAX was the opposite. Dynamic mechanical analysis showed two separate loss modulus peaks for blends of GGM and PVOH, but a single peak for all other films. Optical and scanning electron microscopy confirmed good miscibility of GGM with cAX and KGM. In contrast, films blended from GGM and PVOH showed phase separation. GGM and KGM were mixed with cellulose nanowhiskers (CNW) to form composite films. Addition of CNW to KGM-based films induced the formation of fiberlike structures with lengths of several millimeters. In GGM-based films, rodlike structures with lengths of tens of micrometers were formed. Interestingly, the notable differences in the film structure did not appear to be related to the mechanical and thermal properties of the films. Permeability properties of GGM-based films were compared to those of films from commercial mannans KGM, GG, and LBG. GGM-based films had the lowest water vapor permeability when compared to films from other mannans. The oxygen permeability of GGM films was of the same magnitude as that of commercial polyethylene / ethylene vinyl alcohol / polyethylene laminate film. The aroma permeability of GGM films was low. All films were transparent in the visible region, but GGM films blocked the light transmission in the ultraviolet region of the spectra. The stabilizing effect of GGM on a model beverage emulsion system was studied and compared to that of GG, LBG, KGM, and cAX. In addition, GG was enzymatically modified in order to examine the effect of the degree of polymerization and the degree of substitution of galactomannans on emulsion stability. Use of GGM increased the turbidity of emulsions both immediately after preparation and after storage of up to 14 days at room temperature. GGM emulsions had higher turbidity than the emulsions containing other mannans. Increasing the storage temperature to +45 ºC led to rapid emulsion breakdown, but a decrease in storage temperature increased emulsion stability after 14 days. A low degree of polymerization and a high degree of substitution of the modified galactomannans were associated with a decrease in emulsion turbidity.Mannaanit ovat yleisiä kasvipolysakkarideja, joita esiintyy tiettyjen palkokasvien siemenissä (guarkumi, GG; johanneksenleipäpuujauhe, LBG), konjac-kasvin mukulassa ja havupuissa (galaktoglukomannaani, GGM). Tässä tutkimuksessa tutkittiin mannaanien kemiallisen rakenteen vaikutusta niiden kalvonmuodostukseen ja emulsion stabilointikykyyn. Erityisesti keskityttiin kuusen GGM:iin, joka on kiinnostava puunjalostusteollisuuden sivutuote. Pehmitintä tarvittiin kalvojen muodostamiseksi mannaaneista KGM:a lukuunottamatta. Sopiva määrä oli 40 % (polymeerien painosta) glyserolia tai sorbitolia. Galaktomannaanit, joissa oli vähän galaktoosisivuryhmiä (LBG, muokattu GG), muodostivat kalvoja joilla oli korkea murtovenymä ja vetolujuus. GG-pohjaisten kalvojen mekaaniset ominaisuudet paranivat myös, kun polysakkaridin polymerisaatioastetta laskettiin keskisuurella mannanaasikäsittelyllä. GGM-kalvojen mekaanisia ominaisuuksia pyrittiin parantamaan sekoittamalla GGM:a polyvinyylialkoholin (PVOH), maissin arabinoksylaanin (cAX) ja KGM:n kanssa. Muiden polymeerien lisääminen kasvatti GGM-seoskalvojen murtovenymää. Vetolujuus kasvoi kun PVOH:n ja KGM:n määrää kasvatettiin, mutta cAX:n vaikutus oli päinvastainen. Dynaamis-mekaanisessa analyysissä havaittiin GGM:n ja PVOH:n seoksilla kaksi häviömoduulin huippukohtaa, kun muilla kalvoilla oli vain yksi huippukohta. Valo- ja pyyhkäisyelektronimikroskopia varmistivat GGM:n hyvän sekoittuvuuden cAX:n ja KGM:n kanssa. Sen sijaan GGM:n ja PVOH:n seoksilla havaittiin faasierottumista. GGM:a ja KGM:a sekoitettiin selluloosananokiteiden (CNW) kanssa komposiittikalvojen muodostamiseksi. CNW:n lisääminen KGM-kalvoihin sai aikaan useiden millimetrien pituisten, kuitumaisten rakenteiden muodostumisen. GGM-kalvoissa muodostui kymmenien mikrometrien pituisia sauvamaisia rakenteita. Huomattavat muutokset kalvojen rakenteessa eivät kuitenkaan vaikuttaneet kalvojen mekaaniseen ja termisiin ominaisuuksiin. GGM-kalvojen läpäisevyysominaisuuksia verrattiin kaupallisista mannaaneista, KGM:sta, GG:sta ja LBG:sta valmistettujen kalvojen läpäisevyysominaisuuksiin. GGM-kalvoilla oli muista mannaaneista valmistettuihin kalvoihin verrattuna matalin vesihöyrynläpäisevyys. GGM-kalvojen hapenläpäisevyys oli samaa suuruusluokkaa kuin kaupallisella polyetyleeni / etyleenivinyylialkoholi / polyetyleeni -laminaattikalvolla. GGM-kalvojen arominläpäisevyys oli matala. Kaikki kalvot olivat läpinäkyviä näkyvän valon alueella, mutta GGM-kalvot estivät valonläpäisyä ultravioletin valon alueella. GGM:n stabiloivaa vaikutusta virvoitusjuomaemulsiossa verrattiin GG:n, LBG:n, KGM:n ja cAX:n vaikutukseen. Lisäksi GG:a muokattiin entsymaattisesti galaktomannaanien polymerisaatioasteen ja substituutioasteen vaikutuksen selvittämiseksi emulsion pysyvyyteen. GGM:n käyttö lisäsi emulsioiden sameutta sekä heti valmistuksen jälkeen että 14 vuorokauden säilytyksen ajan huoneenlämmössä. GGM-emulsiot olivat sameampia kuin muista mannaaneista valmistetut emulsiot. Säilytyslämpötilan kasvattaminen +45 ºC:een johti nopeaan emulsion hajoamiseen, mutta säilytyslämpötilan lasku lisäsi emulsioiden pysyvyyttä 14 vuorokauden jälkeen. Muokattujen galaktomannaanien matala polymerisaatioaste ja korkea substituutioaste olivat yhteydessä matalaan emulsion sameuteen

Safety considerations of plant polysaccharides for food use: a case study on phenolic-rich softwood galactoglucomannan extract

A growing population and concern over the sufficiency of natural resources for feeding this population has motivated researchers and industries to search for alternative and complementary sources of food ingredients and additives. Numerous plant species and parts of plants are explored as raw materials for food production. An interesting example is wood; to date, few wood-based additives or ingredients are authorized for food use. Wood hemicelluloses, such as softwood galactoglucomannans (GGM), constitute an abundant bioresource that shows a highly potential functionality in edible materials. Spruce GGM—“spruce gum”—acts as a multi-functional emulsion stabilizer, and it could be used in various processed food products, replacing less effective, conventional emulsifiers. Before new materials can be released onto the food market, their safety must be evaluated, according to the Novel Food regulation. This review focuses on the safety aspects that must be considered before polysaccharide- and phenolic-rich plant extracts can be awarded the status of authorized food ingredients. In this review, GGM is presented as a case study and examples are given of plant-based polysaccharides that are already authorized for food purposes. The legislation regarding Novel Food ingredients in Europe is also briefly reviewed.Peer reviewe

An overview of nanoemulsion characterization via atomic force microscopy

Nanoemulsion-based systems are widely applied in food industries for protecting active ingredients against oxidation and degradation and controlling the release rate of active core ingredients under particular conditions. Visualizing the interface morphology and measuring the interfacial interaction forces of nanoemulsion droplets are essential to tailor and design intelligent nanoemulsion-based systems. Atomic force microscopy (AFM) is being established as an important technique for interface characterization, due to its unique advantages over traditional imaging and surface force-determining approaches. However, there is a gap in knowledge about the applicability of AFM in characterizing the droplet interface properties of nanoemulsions. This review aims to describe the fundamentals of the AFM technique and nanoemulsions, mainly focusing on the recent use of AFM to investigate nanoemulsion properties. In addition, by reviewing interfacial studies on emulsions in general, perspectives for the further development of AFM to study nanoemulsions are also discussed.Peer reviewe

Rapid and Direct Preparation of Lignin Nanoparticles from Alkaline Pulping Liquor by Mild Ultrasonication

The production of lignin nanoparticles (LNPs) has opened new routes to the utilization of lignin in advanced applications. The existing challenge, however, is to develop a production method that can easily be adapted on an industrial scale. In this study, we demonstrated a green and rapid method of preparing LNPs directly from a sulfur-free alkaline pulping liquor by combining acid precipitation and ultrasonication. The combined method produced spherical LNPs, with a hierarchical nanostructure and a highly negative surface charge, within only 5 min of sonication. The mild, rapid sonication was achieved by sonicating directly without prior drying of the acid-precipitated and dialyzed lignin. Optimization of the method revealed the potential for minimizing acid consumption, shortening the dialysis time, and processing directly the alkaline liquor with as much as 20 wt % lignin. The isolated LNPs were stable during storage for 180 days, at a pH range of 4–7, and in a dispersing medium below 0.1 M NaCl. The LNPs also displayed excellent emulsifying properties, stabilizing oil-in-water emulsions. Thus, this simple and energy-efficient method opens a sustainable, straightforward, and scalable route to the production of organic solvent-free LNPs, with high potential as interface stabilizers of multiphase systems in the food and medical industries.Peer reviewe

Spruce galactoglucomannan stabilized emulsions enhance bioaccessibility of bioactive compounds

The increasing public awareness of health and sustainability has prompted the development of functional foods rich in health-promoting ingredients. Processing technologies and sustainable multifunctional ingredients are needed for structuring these formulations. Spruce galactoglucomannan (GGM), the main hemicelluloses in softwood cell walls, are an abundantly available, emerging sustainable food hydrocolloid that have the ability to efficiently emulsify and stabilize oil-in-water emulsions. In this study, we illustrate how this lignocellulosic stabilizer affects the digestion of polyunsaturated fatty acids (PUFAs) in vitro. A 100% decrease in the initial TAG content was observed during the in vitro digestion, suggesting that complete hydrolysis of the TAGs was achieved by the digestive enzymes. Besides, no release of mono-, di-, and oligosaccharides or phenolic compounds from GGM was detected. Our results demonstrate that the GGM-stabilized emulsion could potentially deliver lipophilic bioactive ingredients and enhance their bioaccessibility. In addition, this bio-stabilizer itself would remain stable in the upper gastrointestinal track and serve as a prebiotic for gut microbiota. We anticipate GGM to complement or even replace many of the conventional carriers of bioactive components in future health care products and functional foods.Peer reviewe

Spruce galactoglucomannan stabilized emulsions enhance bioaccessibility of bioactive compounds

The increasing public awareness of health and sustainability has prompted the development of functional foods rich in health-promoting ingredients. Processing technologies and sustainable multifunctional ingredients are needed for structuring these formulations. Spruce galactoglucomannan (GGM), the main hemicelluloses in softwood cell walls, are an abundantly available, emerging sustainable food hydrocolloid that have the ability to efficiently emulsify and stabilize oil-in-water emulsions. In this study, we illustrate how this lignocellulosic stabilizer affects the digestion of polyunsaturated fatty acids (PUFAs) in vitro. A 100% decrease in the initial TAG content was observed during the in vitro digestion, suggesting that complete hydrolysis of the TAGs was achieved by the digestive enzymes. Besides, no release of mono-, di-, and oligosaccharides or phenolic compounds from GGM was detected. Our results demonstrate that the GGM-stabilized emulsion could potentially deliver lipophilic bioactive ingredients and enhance their bioaccessibility. In addition, this bio-stabilizer itself would remain stable in the upper gastrointestinal track and serve as a prebiotic for gut microbiota. We anticipate GGM to complement or even replace many of the conventional carriers of bioactive components in future health care products and functional foods.Peer reviewe

Sensory profile of hemicellulose-rich wood extracts in yogurt models

Wood is an abundant and sustainable source of emerging food ingredients, namely hemicelluloses that fulfil a number of requirements for functional hydrocolloids. Hemicelluloses, especially spruce galactoglucomannans (GGM) and birch glucuronoxylans (GX), have potential to be used as stabilizers in various foods such as yogurts, beverages, dressings, and desserts. However, in addition to good technological functionality, safety, and low price, the applicability and market potential of new hydrocolloids is determined by their sensory properties. The present study reports, for the first time, the sensory profile of spruce GGM and birch GX in food. Sensory profiles from generic descriptive analysis of GGM- and GX-rich extracts, processed by spray drying or ethanol precipitation, were compared in three types of model food systems: water solutions, yogurt with solutions, and yogurt with emulsions stabilized by GGM or GX. Gum Arabic was included for comparison with a commercial ingredient known to have a mild flavor. The results showed that GGM and GX have a woody flavor, which can be reduced by ethanol precipitation and, in yogurt, masked by other food ingredients.Peer reviewe

Emulsion characterization via microfluidic devices : A review on interfacial tension and stability to coalescence

Emulsions have gained significant importance in many industries including foods, pharmaceuticals, cosmetics, health care formulations, paintings, polymer blends and oils. During emulsion generation, collisions can occur between newly-generated droplets, which may lead to coalescence between the droplets. The extent of coalescence is driven by properties of dispersed and continuous phases, e.g. density, viscosity, ion strength and pH, and system conditions, e.g. temperature, pressure or any external applied forces. In addition, the diffusion and adsorption behaviors of emulsifiers which govern the dynamic interfacial tension of the forming droplets, the surface potential, and the duration and frequency of the droplet collisions, contribute to the overall rate of coalescence. An understanding of these complex behaviors, particularly those of interfacial tension and droplet coalescence during emulsion generation, is critical for the design of an emulsion with desirable properties and the optimization of the processing conditions. However, in many cases, the time scales over which these phenomena occur are extremely short, typically a fraction of a second, which makes their accurate determination by conventional analytical methods extremely challenging. In the past few years, with advances in microfluidic technology, many attempts have demonstrated that microfluidic systems, characterized by micrometer-size channels, can be successfully employed to precisely characterize these properties of emulsions. In this review, current applications of microfluidic devices to determine the equilibrium and dynamic interfacial tension during the droplet formation, and to investigate the coalescence stability of dispersed droplets applicable to the processing and storage of emulsions, are discussed.Peer reviewe

Novel nanobiocomposite hydrogels based on sage seed gum-Laponite: Physico-chemical and rheological characterization

In this study, the physico-chemical and rheo-mechanical properties of sage seed gum hydrogel, reinforced by various ratios (0-25 wt.%) of Laponite, were investigated. Particles size measurements indicated the formation of large SSG-Laponite microstructures upon nanoparticle adding, due to the interactions generated between the anionic SSG and the charged surfaces of clay platelets. Laponite affected the surface tension and density of the SSG-based systems significantly, but only influenced the-potential above 20 wt.%. The dynamic rheological behavior of SSG-based nanocomposites reflected the reinforcing effect of secondary structures and percolated three-dimensional network, suggested a structural modification of the hydrogels with the Laponite loading. An improvement in texture profile analysis parameters was observed in Laponite content 5 wt.%, whereas for nanoparticles > 5 wt.%, a significant decrease was obtained. In conclusion, Laponite improved the rheological and physico-chemical properties of SSG-based hydrogel and extended its potential as promising future bio-products for industrial applications.Peer reviewe