Viscosimetric Molecular Weight Research Articles

Extraction and characterization of arabinoxylans obtained from nixtamalized brewers' spent grains.

The processes to obtain value-added products from brewers' spent grain, a contaminant industrial waste, require alkaline non-ecofriendly pre-treatments. The arabinoxylans from brewers' spent grain were extracted by nixtamalization evaluating the extraction procedure, antioxidant capacity and molecular characteristics. The best arabinoxylans yields were those extracted with CaO at 100 °C and 25 °C (6.43% and 3.37%, respectively). The antioxidant capacity by 2,2-diphenyl-1-picrylhydrazyl assay of the arabinoxylans after thermal treatment and additional arabinoxylans after thermal treatment proteolysis were 434 and 118 mg TE/g, while by 2,20'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt assay the value was similar (380 μmol TE/g). The intrinsic viscosities and viscosimetric molecular weights were 69 mL/g and 13 kDa for arabinoxylans after thermal treatment, and 15 mL/g and 1.6 kDa for arabinoxylans after thermal treatment proteolysis, respectively. The protein and lignin contents were 3.1% and 6.4% for arabinoxylans after thermal treatment and, 0.9% and 4.6% for arabinoxylans after thermal treatment proteolysis, while their arabinose: xylose ratios were 0.39 and 0.36, with ferulic acid contents of 0.63 and 0.14 mg/g, respectively. Both products of arabinoxylans were molecularly identical by Fourier transform infra-red. Although the purity of the extracted arabinoxylans was improved with proteolysis, their intrinsic viscosity and viscosimetric molecular weight were affected. The extraction of arabinoxylans from brewers' spent grain by CaO nixtamalization alone or after additional proteolysis was successful to obtain purity and good antioxidant capacity.

Influence of the process parameters on β-chitin and α-chitin extraction: probing about the grinding and particles size

Abstract Chitin occurs in biomass as two main polymorphs, named as β- and α-chitin, which differ on their arrangements on the solid state. The control of chitin physical-chemistry properties by adjustments in their extraction process is an important key to improve its applications and derivatization reactions. Thus, the influences of the extraction parameters process on the β and α-chitin characteristics were studied. Squid pens (Loligo sp.) and shrimp shells (Macrobrachium r.), were used as raw material for β-chitin and α-chitin extraction, respectively. The obtained chitin, regardless polymorphs, was subjected to grinding in a knives mill, sieved and classified in different fractions according to the particles size. The fractions were characterized according to the degree of N-acetylation (DA), viscosimetric molecular weight (Mv), crystallinity, morphology and thermal stability. According to the scanning electron microscopy β-chitin particles present a fiber-like characteristic while α-chitin exhibit a flake-like shape. The procedure of grinding affected the DA and Mv of α-chitin (63%

Citrus pectin obtained by ultrasound-assisted extraction: Physicochemical, structural, rheological and functional properties

ABSTRACTTangerine (Citrus reticulata. CRP) and grapefruit (Citrus paradisi. CPP) pectins obtained by ultrasound-assisted extraction (UAE) and conventional extraction (CE) using citric acid were characterized to establish their potential uses as an alternative source of commercial pectin. The pectins obtained by UAE and CE presented a pseudoplastic fluid characteristic with shear thinning behavior, a high esterification degree (CRP 82.30–71.81% and CPP 84.25–72.15%) and were of commercial quality based on galacturonic acid content (CRP 76.03% and CPP 76.03–71.01%). CPP presented greater viscosimetric molecular weight than CRP. Meanwhile, CRP presented greater polyphenol and protein content with respect CPP. The functional properties were influenced by citrus source and extraction method. UAE favored greater yields in a shorter time (CPP: 26.05%, 30 min; CRP: 13.46%, 15 min) compared to CE. UAE combined with the use of citric acid offers an effective alternative for obtaining high-quality pectins with lower polluting effluent, time and energy requirements.

Production and characterization of films based on blends of chitosan from blue crab (Callinectes sapidus) waste and pectin from Orange (Citrus sinensis Osbeck) peel

The objective of this study was to develop and characterize films based on blends of chitosan and pectin, produced in laboratory scale, from industrial wastes. The chitosan was obtained by termoalcaline deacetylation of chitin, extracted from blue crab (Callinectes sapidus) waste and characterized according to degree of deacetylation (DD) and viscosimetric molecular weight (Mw); and pectin was extracted by conventional heating, from orange (Citrus sinensis Osbeck) peel and characterized according to degree of esterification (DE) and molecular weight (Mw). The Ch:P based films were prepared by the casting method in different Ch:P ratios [0: 100, 25:75, 50:50, 75:25 and 100:0], and compared to two controls [0:100 and 100:0], of commercial pectin and chitosan. Glycerol was used as a plasticizer at concentrations of 0.2g/g macromolecules. The addition of high concentrations of pectin in the formulations resulted in films with high solubility and an increase in moisture. No significant difference (P>0.05) in the degree of swelling (DS) and water vapor permeability (WVP) of the films was observed. Ch:P blend films were less stiff and therefore more elastic and flexible than films based on only one biopolymer. The control films presented better results in terms of color, being brighter and less opaque than other film formulations. These data suggest that chitosan or pectin obtained from agro-industrial waste is a potential matrix to produce biodegradable films for future food applications.

Covalently Cross-Linked Arabinoxylans Films for Debaryomyces hansenii Entrapment.

In the present study, wheat water extractable arabinoxylans (WEAX) were isolated and characterized, and their capability to form covalently cross-linked films in presence of Debaryomyces hansenii was evaluated. WEAX presented an arabinose to xylose ratio of 0.60, a ferulic acid and diferulic acid content of 2.1 and 0.04 µg∙mg−1 WEAX, respectively and a Fourier Transform Infra-Red (FT-IR) spectrum typical of WEAX. The intrinsic viscosity and viscosimetric molecular weight values for WEAX were 3.6 dL∙g−1 and 440 kDa, respectively. The gelation of WEAX (1% w/v) with and without D. hansenii (1 × 107 CFU∙cm−2) was rheologically investigated by small amplitude oscillatory shear. The entrapment of D. hansenii decreased gel elasticity from 1.4 to 0.3 Pa, probably by affecting the physical interactions between WEAX chains. Covalently cross-linked WEAX films containing D. hansenii were prepared by casting. Scanning electron microscopy images show that WEAX films containing D. hansenii were porous and consisted of granular-like and fibre microstructures. Average tensile strength, elongation at break and Young’s modulus values dropped when D. hansenii was present in the film. Covalently cross-lined WEAX containing D. hansenii could be a suitable as a functional entrapping film.

Eucalyptus pulp as an adsorbent for biodiesel purification

This work proposes the use of eucalyptus pulp as an adsorbent for biodiesel purification. Methyl sunflower biodiesel was produced by alkaline transesterification and passed through a column containing the adsorbent. The evaluated impurities were free glycerol, methanol, water content and alkali metals (Na+, K+, Ca2+ and Mg2+). The cellulose fibers were fractionated by sieving in three fractions (sieve pore sizes of 500, 600 and 1,180 μm). The pulp was characterized by infrared, x-ray diffraction, viscosimetric molecular weight, water content, morphological analysis and fiber content of α-cellulose and hemicelluloses. The size of fibers, mass of adsorbent (0.2 and 1.0 g), column diameter (1.0 and 1.3 cm) and the aid of pressure for filtration (atmospheric or 18 psi) on the impurities removal were also evaluated. The physicochemical characterization of biodiesel was performed following tests in accordance with the limits set by the European Standard for oxidative stability at 110 °C, density at 20 °C, water content, acid value, free glycerol, kinematic viscosity at 40 °C, and residual methanol. The optimal condition was observed using 1.0 g of cellulose in a column of 1.3 cm in diameter under pressure of 18 psi was applied. In this condition the free glycerol, methanol and water content in the permeate presented values of 0.0081 ± 0.0001, 0.268 ± 0.009 % w/w and 636 mg kg−1, respectively. The results indicate that this cellulosic adsorbent is a promising material for biodiesel purification instead of using water washing, avoiding the generation of high wastewater volumes.

Influence of the drying route on the depolymerization and properties of chitosan

In this work, a chitosan sample with a high degree of deacetylation (DD >95%) obtained from freshwater shrimp shells was subjected to drying processes in an electric oven and by supercritical CO2. The results indicated that drying chitosan particles with supercritical CO2 resulted in a very significant increase in specific surface area and pore volume, and also increased the material's crystallinity index. This drying route led to a more than 10-fold reduction in viscosimetric molecular weight (from 35.3 to 3.0 kDa), indicating that the physical drying process caused the chitosan to depolymerize, which usually occurs by enzymatic and chemical methods, according to the literature. Low molecular weight chitosan is essential for some applications in the field of biomedicine (drug delivery for example); hence, drying via the CO2 route can be considered a promising technique for the production of high value-added materials with applications in this area. POLYM. ENG. SCI., 55:1969–1976, 2015. © 2014 Society of Plastics Engineers

Rheological and antioxidant power studies of enzymatically grafted chitosan with a hydrophobic alkyl side chain

The enzyme-mediated grafting of hydrophobic alkyl side chains onto Chitosan (Ch) has been successfully achieved using octyl gallate and horseradish peroxidase. The properties of the resulting materials have been studied by rheology and electron paramagnetic resonance (EPR) spectroscopy in order to envisage its potential applications as bioactive food additive. The chemical structures of the octyl gallate-grafted Ch were corroborated by ATR-FTIR, 1HRMN, viscosimetric molecular weight and ζ potential. The antioxidant capacity of materials determined by EPR show that functionalized Ch radical scavenging increases with grafting, which was related to the aromatic ring in the octyl gallate. The Ch with the highest grafting exhibited an antioxidant capacity of 81%. Solutions of the materials in acetic acid and lactic acid exhibited a shear-thinning flow behavior which also increased with the grafting. The viscoelastic properties of solutions were characterized by oscillatory shear measurement and the result showed fluid-like viscoelastic behavior. The elasticity of the solutions decreased with the plasticizer addition.

Characterization of water extractable arabinoxylans from a spring wheat flour: rheological properties and microstructure.

In the present study water extractable arabinoxylans (WEAX) from a Mexican spring wheat flour (cv. Tacupeto F2001) were isolated, characterized and gelled and the gel rheological properties and microstructure were investigated. These WEAX presented an arabinose to xylose ratio of 0.66, a ferulic acid and diferulic acid content of 0.526 and 0.036 µg/mg WEAX, respectively and a Fourier Transform Infra-Red (FT-IR) spectrum typical of arabinoxylans. The intrinsic viscosity and viscosimetric molecular weight values for WEAX were 3.5 dL/g and 504 kDa, respectively. WEAX solution at 2% (w/v) formed gels induced by a laccase as cross-linking agent. Cured WEAX gels registered storage (G’) and loss (G’’) modulus values of 31 and 5 Pa, respectively and a diferulic acid content of 0.12 µg/mg WEAX, only traces of triferulic acid were detected. Scanning electron microscopy analysis of the lyophilized WEAX gels showed that this material resembles that of an imperfect honeycomb.

Research and application of new enviromental-frendly technology without using chemicals for extraction of chitin from shrim shells

Vietnam has a huge amount of rich-protein shrimp shells, containing chitin, a biological polymer that has many potential applications in different areas of life. However, this shrimp by-products are processed mainly by alkali-acid method, causing environmental pollution and can not recovery the protein in the starting material. For the first time in Vietnam, we have carried out research and successfully applied electrochemical technology to extract and purify the chitin from shrimp shells. This is a new technology for chitin extraction, that do not use alkali and acid as in the other chemical methods, so it is very friendly to the environment. The electrolysis is performed on the model device of size of 6 ´ 10 ´ 16.7 cm (with a capacity of 1 liter) at different NaCl concentrations in 90 minutes. After electrolytic extraction of chitin on the device the highest pH value of catolite solution is 12.43 at a concentration of 4% NaCl, and the lowest pH of anolite is 1.95 at NaCl concentrations of 1%. From the results of measuring the pH value of the electrode solutions and determination of protein extracted in the electrode cells were determined the optimal electrolyte concentration (that is 1% of NaCl) and minimal time (that is 1.0 - 1.5 hours) in DC current of 400 A/m2. Chitin preparations obtained by electrochemical technology have high purity, white or yellowish-white colour, no foreign odors, virtually no protein, with low mineral residues (< 0.4%) and average viscosimetric molecular weight from 240 to 1000 kDa.

Enzymatic Cross-Linking of Alkali Extracted Arabinoxylans: Gel Rheological and Structural Characteristics

Ferulated arabinoxylans were alkali-extracted from wheat bran at different incubation times (0.0, 0.5, 1.0, 1.5 and 2.0 h). Wheat bran ferulated arabinoxylans (WBAX) arabinose-to-xylose ratio, ferulic acid content, intrinsic viscosity and viscosimetric molecular weight values decreased as the incubation time of extraction increased. WBAX enzymatic cross-linking capability was affected by incubation time while an increase in WBAX concentration from 5 to 6% (w/v) favored gelation. The WBAX gels formed presented a macroporous structure with mesh size ranging from 40 to 119 nm and hardness values varying from 1.7 to 5 N.

A Novel Pectin Material: Extraction, Characterization and Gelling Properties

A novel pectin was acid extracted from chickpea husk (CHP). CHP presented a 67% (w/w) of galacturonic acid, an intrinsic viscosity of 374 mL/g and a viscosimetric molecular weight of 110 kDa. Fourier transform infrared spectroscopy spectrum of CHP indicated a degree of esterification of about 10%. The CHP-calcium system formed ionic gels with a storage (G′) modulus of 40 Pa and gel set time (G′ > G″) of 3 min at 1% (w/v), and a G′ of 131 Pa and gel set time of 1 min at 2% (w/v). The G′ of CHP gels was not greatly affected by temperature. The results attained suggest that chickpea husk can be a potential source of a gelling pectin material.

Preparation and Property of Poly(N-isopropylacrylamide) (PNIPAAm)/Clay/Linear Polyacrylamide (PAAm) Nanocomposite Hydrogels

In this study, a linear polyacrylamide (PAAm) with an average viscosimetric molecular weight 3.97 × 103 kg mol−1 was added to the prereaction solution for the preparation of poly(N-isopropylacrylamide) (PNIPAAm)/clay nanocomposite hydrogels. The effects of the linear PAAm on the optical transparency and tensile property of the resulting PNIPAAm/clay/linear PAAm hydrogels were systematically investigated. The results revealed that the optical transparency and mechanical tensile properties of the resultant hydrogels strongly depended on the linear PAAm content. In particular, 5 wt% loading of linear PAAm led to almost fivefold decreases of transmittance at 25°C and a onefold increase of the tensile elongation at break. These characteristic changes were explained by a typical interpenetrating microstructure, which was formed by PNIPAAm due to the incorporation of linear PAAm in the PNIPAAm/clay network. The dynamic rheological test and infrared spectroscopy analysis on the mixed solutions consisting of linear PAAm and clay platelets further confirmed the interaction.

Potential of chitosan from Mucor rouxxi UCP064 as alternative natural compound to inhibit Listeria monocytogenes

Listeria monocytogenes is widely distributed in nature and the infection listeriosis is recognized as a potential threat for human health because of its mortality rate. The objective of this study was to evaluate the growth profile and chitosan production by Mucor rouxxi UCP 064 grown in yam bean (Pachyrhizus erosus L. Urban) medium. It was also to assess the anti-L. monocytogenes efficacy of the obtained chitosan. Higher values of biomass of M. rouxxi (16.9 g.L(-1)) and best yield of chitosan (62 mg.g(-1)) were found after 48 h of cultivation. Residual glucose and nitrogen in the growth media were 4.1 and 0.02 g.L(-1) after 96 h, respectively. Obtained chitosan presented 85 % of degree of deacetylation and 2.60 x 10(4) g.mol(-1) of viscosimetric molecular weight. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of chitosan against L. monocytogenes ATCC 7644 were, respectively, 2.5 and 5.0 mg.mL(-1). At 2.5 and 5.0 mg.mL(-1) chitosan caused cidal effect in a maximum time of 4 h. Bacterial count below 2 log cfu.mL(-1) were found from 2 h onwards and no recovery in bacterial growth was noted in the remainder period. These results show the biotechnological potential of yam bean medium for chitosan production by Mucor rouxxi and support the possible rational use of chitosan from fungi as natural antimicrobial to control L. monocytogenes.

Potential of chitosan from Mucor rouxxi UCP064 as alternative natural compound to inhibit Listeria monocytogenes

Listeria monocytogenes is widely distributed in nature and the infection listeriosis is recognized as a potential threat for human health because of its mortality rate. The objective of this study was to evaluate the growth profile and chitosan production by Mucor rouxxi UCP 064 grown in yam bean (Pachyrhizus erosus L. Urban) medium. It was also to assess the anti-L. monocytogenes efficacy of the obtained chitosan. Higher values of biomass of M. rouxxi (16.9 g.L-1) and best yield of chitosan (62 mg.g-1) were found after 48 h of cultivation. Residual glucose and nitrogen in the growth media were 4.1 and 0.02 g.L-1 after 96 h, respectively. Obtained chitosan presented 85 % of degree of deacetylation and 2.60 x 104 g.mol-1 of viscosimetric molecular weight. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of chitosan against L. monocytogenes ATCC 7644 were, respectively, 2.5 and 5.0 mg.mL-1. At 2.5 and 5.0 mg.mL-1 chitosan caused cidal effect in a maximum time of 4 h. Bacterial count below 2 log cfu.mL-1 were found from 2 h onwards and no recovery in bacterial growth was noted in the remainder period. These results show the biotechnological potential of yam bean medium for chitosan production by Mucor rouxxi and support the possible rational use of chitosan from fungi as natural antimicrobial to control L. monocytogenes.

Growth of Cunninghamella elegans UCP 542 and production of chitin and chitosan using yam bean medium

Microbiological processes were used for chitin and chitosan productions by Cunninghamella elegans (UCP 542) grown in a new economic culture medium. The assay was carried out to evaluate the growth of C. elegans using yam bean ( Pachyrhizus erosus L. Urban) medium, in different times of growth (24, 48, 72 and 96 hrs), incubated at 28oC in an orbital shaker at 150 rpm. The lyophilized biomass was determined by gravimetry. The polysaccharides were extracted by alkali-acid treatment, and characterized by infrared spectroscopy, titration and viscosity. C. elegans grown in the yam bean medium and produced higher yields of biomass (24.3 g/ mL) in 96 hrs. The high level was chitosan (66 mg/g), and chitin (440 mg/g) were produced at 48 and 72 hrs of growth, respectively. The polysaccharides showed degree of deacetilation and viscosimetric molecular weight as: 6.2% and 3.25 x10 4 g/mol for chitin, and 85% and 2.72 x 10 4 g/mol for chitosan, respectively. The results obtained suggest high biotechnological potential of yam bean as an economic source to produce chitin and chitosan by C. elegans . In addition, the new medium using yam bean for production of the chitin and chitosan may be used for many purposes to reduce the cost price of fermentation processes.

Synthesis, characterization, and application of the sodium poly(styrenesulfonate) produced from waste polystyrene cups as an admixture in concrete

AbstractWasted polystyrene (PS) plastic cups were used in the synthesis of sodium poly(styrenesulfonate) (NaPSS). The produced polyelectrolyte was water‐soluble. The viscosimetric molecular weight was 126,146 g mol−1. The sulfonation of the polymer was estimated through FTIR spectroscopy and chemical analysis of the number of sulfonic groups. The presence of bands at 1326 and 1188 cm−1 in the infrared spectra was characteristic for sulfonic groups. The polymer was obtained with 60.3% of sulfonation. An aqueous solution of NaPSS was used as an admixture in concrete of portland cement. The results showed that the slump increasing of the concrete was up to 300% with 0.3% content of NaPSS per weight of cement. It was possible to reduce the water content of the concrete in 13.2% using NaPSS solution as an admixture. The compressive strength gain was 23.9% after 28 days of curing. The results indicated that NaPSS, produced from waste PS cups, can be satisfactorily used either as a plasticizer or as an admixture for water reduction in concrete. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1534–1538, 2005

Caracterização de quitosanas comerciais de diferentes origens

A quitosana é um polissacarídeo linear obtido da desacetilação da quitina. As propriedades físico-químicas da quitosana são função do grau médio de acetilacão <img border=0 id="_x0000_i1026" src="../../../../img/revistas/po/v13n4/19880x1.gif" align=absmiddle>e da massa molar média (<img border=0 id="_x0000_i1027" src="../../../../img/revistas/po/v13n4/19880x2.gif" align=absmiddle>). Várias aplicações da quitosana foram propostas na literatura, principalmente no tratamento de águas, produção de cosméticos, drogas e medicamentos, aditivos alimentícios, membranas semipermeáveis e no desenvolvimento de biomateriais. Neste trabalho, três diferentes tipos de quitosanas comerciais foram caracterizados por ressonância magnética nuclear de hidrogênio (RMN ¹H), espectroscopia de absorção na região do infravermelho (IV), titulação condutimétrica e análise térmica (TG e DSC) com o objetivo de comparar as características de quitosanas provenientes de diferentes fornecedores. A massa molar média das amostras foi determinada a partir de medidas de viscosidade intrínseca. Os resultados obtidos por estas técnicas mostraram diferenças quanto ao grau médio de acetilação (ou desacetilação), em função da procedência do material. Os resultados obtidos da análise térmica permitiram acompanhar os processos de desidratação, decomposição e a temperatura de transição vítrea (Tg).

Synthesis and characterization of new arylamine chitosan derivatives

AbstractThe synthesis of new chitosan derivatives and their complete characterization by elemental analysis, Fourier transform infrared, thermogravimetric analysis, and cross‐polarity/magic‐angle‐spinning 13C NMR is described. A chitosan that was 96.5% deacetylated and had a viscosimetric molecular weight of 131,000 g/mol was prepared. N‐(3,5‐Diethylaminobenzoyl) chitosan with a degree of substitution of 29% and N‐(4‐ethylaminobenzoyl) chitosan with a degree of substitution of 60% were obtained. Such derivatives could be used as metal‐chelating polymers, as flocculants, and in biomedical applications because of the aryl amine moieties in their structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 807–812, 2004

Synthesis and characterisation of fluorescent polyacrylonitrile copolymers with 1,8-naphthalimide side chains

Radical polymerisation of acrylonitrile in the presence of five polymerisable fluorescent 4-allylamino-1,8-naphthalimide dyes, has been investigated. It was found that the monomeric dyes took part in the polymerisation and were covalently bound in the polymer chain obtaining fluorescent side-group polyacrylonitrile. It was established that 0.70–0.88 wt.% of the dyes are chemically bound to the polymer chain. Their effect on the polymerisation rate was established and the average viscosimetric molecular weight, of the obtained coloured copolymers estimated. The absorption and some basic photophysical characteristics of low and high molecular weight fluorescent dyes in dimethylformamide are reported. The influence of the studied monomeric 1,8-naphthalimide dyes on the photostability of the coloured polyacrylonitrile, was established.