Oxidized Potato Starch Research Articles

Properties of Oxidized Potato Starch–Potassium Alum Mixtures, and Their Application in Starch Noodles

AbstractThis study explores the effects of potassium alum (PA) on oxidized potato starch (OS) with a carboxyl content of 0.0186%, in terms of their pasting and rheological properties. Furthermore, the application of oxidized starch in the manufacturing of starch noodles is investigated. The results indicate a positive correlation between pasting temperature and PA content (65.6–67.7 °C), while showing a negative correlation with peak viscosity (409–236 BU). The addition of PA leads to reduced dynamic moduli (G′' and G″), consistency coefficient (K), and hysteresis area, accompanied by an elevated fluid behavior index (n). Shear recovery assays demonstrate a positive correlation between PA content and shear resistance, with recovery rates escalating from 76% to 84%. The mouthfeel of starch noodles produced using oxidized starch exhibit comparable to commercial counterparts (PA content 0.35%), but with lower PA levels (at 0.2%). Additionally, these starch noodles have a higher whiteness compared to starch noodles made with potato starch.

THE EFFECT OF POLYDEXTROSE ON RHEOLOGICAL CHARACTERISTICS AND SENSORY PROPERTIES OF REDUCED SUCROSE STARCH-MILK DESSERTS

Introduction. The aim of the study was to assess the impact of replacing sucrose with polydextrose (E 1200) on the rheological characteristics and sensory properties of starch-milk desserts sweetened with steviol glycosides (E 960). The study materials were desserts made of oxidized potato starch (E 1404), skimmed milk powder, curcumin, vanilla flavorsucrose and/or a mixture of polydextrose (E 1200) and steviol glycosides (E 960). As part of the rheological analyses, the pasting characteristics, viscosity curves and mechanical spectra of the desserts were determined. As part of the sensory analysis, palatability and texture were assessed using a quantitative descriptive analysis. The acceptability of the desserts was also assessed. Results and discussion. Based on the results, it was found that the partial or complete elimination of sucrose from the composition of desserts and replacing it with a mixture of polydextrose and steviol glycosides led to a reduction in their maximum viscosity determined at the heating stage in the pasting test, but did not change the starch pasting temperature. The desserts showed shear-thinning non-Newtonian fluid properties, and the modification of the recipe resulted in a reduction of the consistency coefficient and a reduction in the share of elastic properties without a significant impact on the viscous properties of the system. The desserts in which sucrose was completely, or in a greater degree, replaced with polydextrose and steviol glycosides had a cooling effect and had a licorice aftertaste in the sensory assessment, while retaining sweetness similar to the sweetness of the dessert sweetened with sucrose only. The modification of the dessert recipe did not affect the adhesiveness and mouth melting of the finished products, but contributed to a reduction in their viscosity and malleability assessed by the sensory analysis. Both the texture and palatability of the desserts prepared to the recipe, in which two-third of the amount of sucrose or its total amount was replaced with polydextrose and steviol glycosides, turned out to be less sensorily acceptable than the dessert which did not contain polydextrose.

Inherently acidic films based on chitosan lactate-doped starches and pullulan as carries of nisin: A comparative study of controlled-release and antimicrobial properties

Nisin (NIS) Z was incorporated (0.05 %, 0.1 %, 0.2 %) into edible films based on chitosan lactate (CHL) and 75/25 blends of polysaccharides (corn starch (CS), wheat starch (WS), oxidized potato starch (OPS), pullulan (PUL)) with CHL. The increase in the NIS/polymer ratio promoted the diffusion-driven release. Compared with the fully dissolvable CHL and PUL/CHL carriers, the starch/CHL films had limited solubility (≈27–37 %) and, consequently, ensured slower/incomplete release of NIS. The assayable NIS half-release times, determined in water, ranged from <1 min to ∼13 h. Probably due to the similar pH (≈4.5), there were generally no large differences between the antibacterial activities of the formulations. The NIS-supplemented systems limited the growth of some pathogens (B. cereus, L. monocytogenes, S. aureus), phytopathogens (P. carotovorum), and bacterial starter cultures. The NIS improved the UV-blocking ability of the films, but the 0.2 % NIS addition weakened (by ≈17-32 %) the tensile strength of most of the films.

Native and Oxidized Starch for Adsorption of Nickel, Iron, and Manganese Ions from Water

The adsorption of heavy metal ions from surface water with ecologically safe and biodegradable biopolymers is increasingly becoming an appealing research challenge. Starch as a biopolymer is exceptionally attractive to solve this problem for its low cost and abundant availability in nature. To expel Ni2+, Fe2+/3+, and Mn2+ from water, we analyzed two native and two oxidized starches, namely potato and corn starch, as bio-adsorbers. The morphology and the surface property of the different starches were studied using SEM. To assess the effectiveness of adsorption onto the starches, we tested three realistic concentrations based on German drinking water ordinance values that were 10-fold, 100-fold, and 1000-fold the limits for Mn2+, Fe2+, and Ni2+, respectively. The concentration of the different ions was measured using the ICP-OES. Furthermore, from subsequent investigations of the adsorption isotherms, we evaluated the adsorption capacities and mechanisms. The adsorption isotherms were fitted using the Langmuir, Sips, and Dubinin–Radushkevich models, whereby Sips showed the highest correlation. Oxidized potato starch achieved viable adsorption capacities of 77 µmol Fe2+/g, 84 µmol Mn2+/g, and 118 µmol Ni2+/g. Investigating the influence of initial swelling in water on the adsorption performance, we found that especially the percentage removal with oxidized starches decreased significantly due to the formation of hydrogen bonds with water molecules at their binding sites with prior swelling.

Physicochemical properties of potato starches oxidised by different concentrations of sodium hypochlorite, and their application in yogurt

Potato starch was modified by oxidation with different concentrations of active chlorine (0.5, 1.0, 2.0, 3.0, and 4.0%); and the physicochemical properties of the oxidised potato starch samples and the use of these starches in set yogurt were investigated as a function of their degree of oxidation. The carboxyl content, carbonyl content, and solubility of the oxidised starches increased with increasing sodium hypochlorite concentrations, while the swelling power decreased. Scanning electron microscopy showed that oxidation caused cracks or pores on the surfaces of the starch granules, and these morphological changes were enhanced by increased oxidant concentrations. Analysis with a Rapid Visco Analyser showed that high degrees of oxidation could improve the starch thermodynamic stability and resistance to retrogradation. Set yogurts made with oxidised potato starches had higher water-holding capacities, higher apparent viscosities, and better sensory qualities than those prepared with native starch.

Photochemical Reactions in Dialdehyde Starch.

In this study potato and corn starch were subjected to oxidation, using sodium periodate, to obtain dialdehyde starch (DAS) containing different amount of aldehyde groups. The obtained modified starch samples have been characterized with chemical analysis, scanning electron microscopy (SEM) and ATR-FTIR spectroscopy. Then, the samples were exposed to polychromatic UV radiation and the course of photochemical reaction has been monitored with ATR-FTIR spectroscopy. The surface properties of the native and dialdehyde starch before and after UV-irradiation have been determined by contact angle measurements and calculation of surface free energy. The crystallinity of the samples has been estimated with X-ray diffraction (XRD). It has been proved that the dialdehyded corn starch contained a higher amount of functional groups was more photostable than the oxidized potato starch. Sodium iodide(V), firmly bound to DAS macromolecules, has been found to have a significant effect on the photooxidative degradation of the tested systems. In addition, the mechanism of photoinduced reactions in the dialdehyde starch has been proposed.

Fabrication and Characterization of Native and Oxidized Potato Starch Biodegradable Films

The need to replace conventional polymers due to environmental pollution caused by them has led to increased production of biodegradable polymers such as starch. Thus, the application possibilities of starch have increased. In this study, we produced and characterized biodegradable films derived from native and oxidized potato starch. The film-forming solution was prepared with different concentrations of extracted starch (native or oxidized) and a plasticizer (glycerol or sorbitol). Then, the mechanical, barrier, morphological, and structural properties of the films were characterized. The moisture content of the films varied from 15.35 ± 1.31 to 21.78 ± 0.49%. The elastic modulus of the films ranged from 219 ± 14.97 to 2299 ± 62.91 MPa. The film of oxidized starch plasticized with sorbitol in the lowest content was the most resistant and flexible; moreover, this film also presented lower water vapor permeability and low solubility in water. Fourier-transform infrared spectroscopic analysis of the biodegradable films indicated the presence of same functional groups as those of starch with bands in the same regions. The film thickness was lower for the films plasticized with glycerol whereas the color variation (ΔΈ) was lower for the ones plasticized with sorbitol. In case of both plasticizers, the increase in their content decreased the ΔΈ value. All the biodegradable films presented stability against water absorption owing to their low solubility in water. Morphological evaluation revealed the presence of partially gelatinized starch granules in the films. The roughness parameter (Rq) of the films varied from 3.39 to 10.9 nm, indicating that their surfaces are smooth. X-ray diffraction studies showed a B-type pattern for the starches, which is representative of tubers. Further, the films present higher relative crystallinity (RC) compared to the starches. The biodegradable starch films are uniform, transparent and with low solubility in water. The oxidation of starch and use of sorbitol as a plasticizer resulted in improved properties of the starch films, which is suitable for application.

Ascorbic acid- and sodium ascorbate-loaded oxidized potato starch films: Comparative evaluation of physicochemical and antioxidant properties

The purpose of this study was to compare the effects of increasing concentrations of ascorbate ions (AIs, 0–100mM) in the form of ascorbic acid (AA) and sodium ascorbate (SA) on the properties of edible oxidized potato starch films. The browning reactions were faster in the SA-added films than in those of AA-added. In, turn, AA recrystallized faster than its sodium salt. The highest concentration of SA increased the water vapor permeability of the films. The mechanical strength and stiffness of the films gradually decreased with the increase of AI content. Fourier-transform infrared spectroscopy spectra suggested that addition of SA provoked a more intensive structural changes in the films than AA. X-ray diffraction showed that 25 and 50mM AI-added films exhibited higher crystanility than the control. The films with AA and SA did not differ in terms of dissolving behavior, ability to release AI, and consequently, antioxidant activity.

Improving the cross‐linking degree of oxidized potato starch via addition of nanocrystalline cellulose

Nanocrystalline cellulose (NCC) has attracted considerable interest in the starch modification field due to its biodegradability, renewability, and high biocompatibility. Here, oxidized potato starch was cross‐linked with sodium hexametaphosphate ((NaPO3)6) at different temperatures, pH values, and (NaPO3)6 and NCC concentrations. The bound phosphorus content and the substitution degree of the oxidized cross‐linked potato starch were measured to analyze the effect of NCC on the cross‐linking reaction. The structure of the oxidized cross‐linked potato starch was further analyzed using Fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results showed that when (NaPO3)6 cross‐linked the starch, the addition of NCC promoted the cross‐linking reaction in the oxidized potato starch. In comparison to the native starch, the thermal stability of the oxidized cross‐linked starch was increased. Additionally, the cross‐linking reaction occurred mainly in the non‐crystalline region of the potato starch and only partly in the crystalline region due to degree of crystallinity decreasing. The optimum conditions for the oxidized potato starch cross‐linking reaction were 1.0 wt.% (NaPO3)6 and 5.0 wt.% NCC at 50°C and a pH of 10.5. Under these conditions, the bound phosphorus content of the potato starch increased by 4.87% compared to the same conditions without NCC addition. In summary, NCC is a good additive to improve the cross‐linking degree of oxidized potato starch.

Preparation and characterization of oxidized starch/poly(N,N-dimethylaminoethyl methacrylate) semi-IPN cryogels and in vitro controlled release evaluation of indomethacin

Fabrication of novel semi-interpenetrating polymer network (semi-IPN) cryogels by cross-linking polymerization of N,N-dimethylaminoethyl methacrylate (DMAEM) in the presence of either oxidized potato starch (OPS) or oxidized wheat starch (OWS) and their characterization are presented in the paper. The influence of the nature of entrapped polymer on the properties of the composite cryogels was evaluated by the swelling kinetics, FT-IR spectroscopy, scanning electron microscopy, and response at external stimuli such as temperature, pH, and ionic strength. Indomethacin (IDM), taken as a model anti-inflammatory drug, was easily loaded into the composite cryogels by the solvent sorption-evaporation strategy. The in vitro release of IDM from the semi-IPN cryogels was low in simulated gastric fluid at pH 1.3, irrespective of the nature of the entrapped oxidized starch, and consistent in simulated intestinal fluid (SIF) at pH 7.4, the influence of the entrapped polysaccharide being evident. The release mechanism of IDM from the composite cryogels was discussed based on two kinetic models, finding that the drug release at 37°C was pseudo-Fickian diffusion, regardless the cryogel composition.

Physicochemical and antioxidant properties of biopolymer/candelilla wax emulsion films containing hop extract – A comparative study

Emulsion films based on different biopolymers: carboxymethyl cellulose (CMC), oxidized potato starch (OPS), soy protein isolate (SPI), gelatin (GEL) and containing different concentrations of ethanolic hop extract (EHE: 0, 0.1, 0.25, 0.50%) were obtained and evaluated in terms of microstructure, water affinity, optical, mechanical, and antioxidant properties. SEM analysis showed that EHE improved homogeneity of wax in the protein films. In contrast, EHE induced the increase in wax particle size in CMC films. With the exception of CMC films, the presence of EHE reduced the solubility of films (p < 0.05). Incorporation of EHE significantly increased the water vapor permeability (WVP) of the polysaccharide-based films while had no effect on the WVP of protein-based films. The increase in EHE addition level resulted in films with enhanced barrier properties against UV light. SPI films were characterized by the best UV-blocking properties. EHE decreased visible light transmission of the polysaccharide films, while an opposite trend was observed for SPI films. The derivatives of structural polymers (GEL and CMC) produced films with higher mechanical strength and stiffness compared with the plant storage polymers. EHE caused a significant reduction in toughness of GEL and CMC films but did not affect the mechanical strength of OPS and SPI films. As the content of EHE increased, the films showed an increase in ferric reducing antioxidant power, metal chelating power and antiradical activity. The films susceptible to solubilization (CMC and SPI) had higher release of EHE and, consequently, better antioxidant activity compared to water-swollen films (OPS and GEL).

Oxidized potato starch based thermoplastic films: Effect of combination of hydrophilic and amphiphilic plasticizers

Different combinations of hydrophilic (glycerol and water) and amphiphilic (isoleucine) plasticizers were studied in the production of thermoplastic starch (TPS) powders and films from oxidized potato starch. All powder samples had an irregular and shrivelled morphology. In all mixtures containing isoleucine, this additive exuded from the starch matrix and re‐crystallized during spray drying, resulting in hollow particles. The crystallinity and moisture sensitivity of freshly prepared films depended on the isoleucine content in the plasticizer formulation. Increasing the content led to a decrease in moisture absorption. Isoleucine formulated films showed the best tensile strength, whereas glycerol‐rich ones showed better strain at break values. All glycerol plasticized formulations and the spray dried non‐modified starch were amorphous. Glycerol reduced the glass transition temperature to 128°C and glycerol formulated films showed the highest moisture uptake due to its hydrophilic nature. At a relative humidity (RH) of 50%, the rate of retrogradation was low, but at RH 100% all TPS films showed a high rate of retrogradation.

Biopolymer/candelilla wax emulsion films as carriers of ascorbic acid – A comparative study

The comparative studies were performed in order to assess the most suitable matrix polymer for ascorbic acid (AA). The antioxidant (0.5, 1.0, 2.0% w/w) was included into sorbitol-plasticized emulsion films based on different biopolymers: carboxymethyl cellulose (CMC), oxidized potato starch (OPS), soy protein isolate (SPI), and gelatin (GEL). AA reduced the mechanical strength of the films in a concentration dependent manner. GEL and CMC produced films with higher mechanical strength and stiffness compared to the plant storage polymers. The moisturizing action of AA inhibited plasticizer recrystallization in the protein-based films. It was found, that non-enzymatic browning of the films prepared at lower pH values (OPS and GEL) was slower than those of casted at higher pH (CMC and SPI). SPI films displayed the most intensive browning development. The highest AA retention was achieved in OPS films, while the lowest in GEL films. The AA stability increased with increasing AA concentration. A significant correlation existed between the antioxidant activity of films and the concentration of AA released into aqueous food simulant. CMC films, due to rapid dissolution, tended to have the highest ferric reducing antioxidant power (FRAP) and antiradical activity. In turn, water-swollen GEL films had the lowest antioxidant activity. Prolonged testing in an emulsified linoleic acid model system revealed that at higher AA incorporation levels the films did not differ in their anti-lipid peroxidation capacity.

Characterization of films based on chitosan lactate and its blends with oxidized starch and gelatin

Minimal inhibitory concentration (MIC) of chitosan lactate (CHL) was tested against bacteria and phytopathogenic fungi. Then, the structural, physicochemical and antimicrobial properties of films based on CHL, oxidized potato starch (OPS), and gelatin (GEL) were investigated. With the exception of Rhizopus nigricans, CHL was effective against the target organisms. Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) were more sensitive to CHL than Gram-negative bacteria (Pectobacterium carotovorum and Escherichia coli). Cryo-SEM images showed total miscibility between the polymers in the blends and the ATR-FTIR spectra revealed that there was an interaction among the polymeric components. Pure CHL films displayed the highest moisture content (25.51%), water vapor permeability (48.78gmmm−2d−1kPa−1), and the lowest tensile and puncture strength (2.00 and 1.45MPa, respectively) among the studied films. CHL50/GEL50 films had lower permeability, higher mechanical strength, and lower elongation compared to CHL50/OPS50 films. Films obtained from CHL and CHL50/GEL50 were completely water-soluble and did not show sorbitol recrystallization. The incorporation of CHL into OPS and GEL films did not affect their transparency and improved UV-blocking capacity. CHL films were the only ones that exhibited antibacterial efficiency. Antifungal activities against Alternaria alternata and Monilinia fructigena were detected for CHL and CHL50/GEL50 films.

Absorption of whey protein isolated (WPI)-stabilized β-Carotene emulsions by oppositely charged oxidized starch microgels

β-Carotene is a natural antioxidant that is beneficial for human health. β-Carotene is well known for its aqueous insolubility and its sensitivity to environmental stimuli. To achieve the targeted delivery of β-Carotene to human intestine, a microgel system was developed. The microgel is made of oxidized potato starch polymers, which are obtained by chemical cross-link process by sodium trimetaphosphate (STMP). At pH<pI (WPI: pH5), as in the acidic condition in stomach, the positively charged WPI emulsified β-Carotene nanoemulsion droplets were absorbed by the negatively charged starch microgel particles, which prevented the early release of β-Carotene in stomach. At pH>pI, as in the intestinal condition, WPI–β-Carotene nanoemulsion droplets and microgel particles both carry negative charges. Under this condition, β-Carotene will be released from microgel. In this study, we investigated the absorption capacity of β-Carotene nanoemulsion droplets by oxidized starch microgel particles of various degrees of oxidation (DO) and the cross-link density (Rcross-linker/polymer(w/w)) is investigated as a function of pH and salt concentrations. We found that DO30% with Rcross-linker/polymer(w/w)=0.1 was the optimal gel type for nanoemulsion droplets absorption, and pH3 and ionic strength of 0.06M were the optimal conditions for nanoemulsion droplets absorption. The swelling capacity of the microgel particles rather than its ζ-potential was dominant in governing the absorption capacity. The in vitro release experiment under stimulated gastrointestinal fluids suggested that β-Carotene emulsions droplets remained stable at the gastric condition and were majorly released under the intestinal condition. The results suggested that the oxidized starch microgel could be used to prevent the early release of β-Carotene in the stomach and target delivery of them to the intestine.

Physicochemical and Antimicrobial Properties of Biopolymer-Candelilla Wax Emulsion Films Containing Potassium Sorbate – A Comparative Study

Thecomparativestudieswereperformedinorderto assess the most suitable matrix polymer for potassium sorbate (KS). Thepreservative(1.0, 2.0,3.0,4.0 %w/w) was included into edible films made from different biopolymers: carboxymethyl cellulose (CMC), oxidized potato starch (OPS), soy protein isolate (SPI), gelatin (GEL), sorbitol, candelilla wax, and emulsifier. The incorporation of KS dra- matically reduced the toughness of all tested films. The plas- ticizing action of KS was the weakest in CMC-based films, which exhibited the highest initial stiffness and the lowest stretchability. With the exception of GEL films, KS addition caused an increase in water vapor permeability of the films. Moreover, except for CMC films, increased KS content in the films led to increase in the stickiness, moisture content, and solubility. CMC-based films, regardless of the concentration of KS, had unchanged hygroscopicity and were completely water-soluble.In mostcases, KS reduced transmissionof light through the films. OPS, SPI, and GEL films, in contrast to CMC-based ones, exhibited sorbitol crystallization; however, the addition of KS successfully overcame this disadvantage. The antimicrobial effectivenessofall testedfilmsincreased by increasing the KS concentration. The kind of carrier used affected antimicrobial effectiveness of KS, and SPI films tended to have the weakest antibacterial and antifungal activity, especially at low KS content. The data given here may provide a useful guide in establishing the best compro- mise between conflicting film property demands. Taken to- gether, our findings suggest that the CMC films could be the best carrier for KS.

Effect of candelilla wax on functional properties of biopolymer emulsion films – A comparative study

The overall research objective was to compare the effects of increasing concentrations of candelilla wax (CnW) on the physicochemical and morphological properties of edible films based on different biopolymers: carboxymethyl cellulose (CMC), oxidized potato starch (OPS), soy protein isolate (SPI), and gelatin (GEL). The findings are discussed in terms of the stability of emulsion formulations. CnW was incorporated into film-forming solutions at 0, 0.5, 1.0, 1.5, and 2.0%; sorbitol and Tween 40 were used as the plasticizer and surfactant, respectively. It was found that, with the exception of GEL films, wax incorporation significantly decreased the WVP of the films (from 11.1 to 41.7% compared to the controls). Regardless of the wax concentration used, OPS films had the lowest WVP compared to other films. GEL-based films, in turn, were characterized by the highest mechanical resistance and elongation. The incorporation of CnW decreased both all the analyzed tensile parameters and the puncture strength of the films. Generally, as CnW concentration increased, the transparency and redness of the films decreased, while UV blocking ability and yellowness increased. The 0.5% CnW addition was the most effective in improving water barrier properties, and simultaneously had the lowest impact on the other physical properties of films. For OPS, SPI, and GEL films, sorbitol recrystallization was observed over time. Wax accelerated the sorbitol crystal growth process. CMC films, in contrast to those obtained using other polymers, were completely water soluble and did not exhibit sorbitol crystallization. The emulsion films differed from the wax-free in their surface characteristics.

A Study of Controlled Uptake and Release of Anthocyanins by Oxidized Starch Microgels

Anthocyanins are well-known antioxidants, but they are sensitive to environmental conditions. Herein we used oxidized starch microgel to prevent their early degradation and deliver them to the target place. The aim of this study was to investigate the uptake and the release ability of anthocyanins by the oxidized starch microgels and measure their in vitro gastrointestinal release. The gels were made of oxidized potato starch polymers, which were chemically cross-linked by sodium trimetaphosphate (STMP). In this study, the uptake and release behaviors of anthocyanins by starch microgel were investigated under various pH and salt concentrations. The microgel of high degree of oxidation and high cross-link density had a high uptake capacity for anthocyanins at low pH and salt concentration; 62 mg anthocyanins had been absorbed per gram of dry DO100% (degree of oxidation 100%) microgel at pH 3 with ionic strength 0.05M. The in vitro study of the release was investigated under stimulated gastrointestinal fluid. The anthocyanins were identified and quantified by UV/vis detection. The results indicated that the oxidized starch microgels had a potential for being a carrier system for protecting anthocyanins from degradation in the upper gastric tract and for delivering them to the intestine. This paper provides a good reference for an intestinal-targeted delivery system of vulnerable functional ingredients by oxidized starch microgel.

Understanding the role of plasticisers in spray-dried starch

Amorphous thermoplastic starch (TPS) films were produced by compression moulding of solution spray-dried TPS powder and by direct solution casting. Oxidised potato starch was used as a feedstock for production of plasticised formulations containing glycerol or urea, or their combinations with maltodextrin (DE=19.1) as processing aid.The crystallinity index of freshly moulded films made from solution spray-dried powder was significantly lower than that for casted films. FTIR analysis showed that starch interacted in hydrogen bond formation with glycerol and urea plasticisers, reducing the glass transition temperature to 136°C and 106°C, respectively. Formulations containing maltodextrin did not show a Tg. Glycerol-plasticised and co-plasticised films immediately started to retrogradate in the presence of moisture, while urea based systems only showed slow recrystallization at the highest moisture exposure. In line with retrogradation behaviour, urea plasticised and co-plasticised films exhibited a more ductile behaviour, whereas glycerol based ones showed more brittle behaviour.

Antimicrobial lysozyme-containing starch microgel to target and inhibit amylase-producing microorganisms

The aim of this study is to determine the release of lysozyme from oxidized starch microgels and subsequently test its antimicrobial activity. The gels are made of oxidized potato starch polymers, which are chemically cross-linked by sodium trimetaphosphate (STMP). The microgel is negatively charged and interacts with positively charged lysozyme by electrostatic attraction. Application of the lysozyme-containing starch particles to environments contaminated with microbes, may lead to hydrolysis of the starch by microbial enzymes. As a result, lysozyme is released in the environment where it inhibits microbial growth. In this study, first bacteria were screened for amylase production and lysozyme sensitivity. Then, the bacteria were mixed with empty gel particles (i.e., without lysozyme) in a Nutrient Broth liquid medium to test whether the bacteria that can produce amylase are also able to degrade oxidized starch gel. Subsequently the amylase-producing lysozyme sensitive bacteria, Bacillus licheniformis 7558 and Bacillus subtilis 168, were selected for further quantification of the antimicrobial activity of the gel-lysozyme particles after incubation with these bacteria in Nutrient Broth liquid suspensions. The results prove that the starch microgel has a potential as antimicrobial carrier targeting amylase-producing and lysozyme-sensitive bacteria. The controlled antimicrobial delivery for inactivating undesired microorganisms may find applications in food related systems, where amylase-producing bacteria may be abundantly present.