Degree Of Acetylation Research Articles

Bioinspired pH-sensitive riboflavin controlled-release alkaline hydrogels based on blue crab chitosan: Study of the effect of polymer characteristics

Recently, the application of natural biocompatible polymeric hydrogels for the conception of drug delivery matrices has attracted widespread interest. Thus, in the present study, riboflavin pH-sensitive drug delivery hydrogels were developed based on blue crab chitosan (Cs), via direct dissolution in alkali/urea aqueous solution at low temperatures. First, the effect of Cs characteristics in terms of acetylation degree (AD) and molecular weight (Mw) on the structural, mechanical, thermal, swelling and in vitro biodegradation of Cs-based hydrogels were studied. Data from overall analysis revealed that Cs with low AD and high Mw exhibited improved mechanical properties, as evidenced by the compressive and rheological behaviors tests, thermal resistance, swelling behavior and in vitro degradation kinetics. However, hydrogels pore sizes were reduced with the AD decrease and Mw increase. Additionally, hydrogels in PBS (pH 5.5) underwent quicker degradation, compared to those immersed in PBS (pH 7.4). In the drug delivery model, the kinetics of Riboflavin release, through the Cs-based hydrogels were monitored. The Riboflavin release exhibited typical deliverance patterns, with significantly higher released amounts in more acidic systems. Therefore, drug encapsulation within the conceived pH-sensitive Cs-based hydrogels could provide suitable and promoting microenvironment for drugs delivery.

Controlling Barrier and Mechanical Properties of Cellulose Nanocrystals by Blending with Chitin Nanofibers.

Chitin nanofibers (ChNFs) and cellulose nanocrystals (CNCs) have been proposed as materials for renewable packaging with low O2 transmission that protect food, medicine, and electronics. A challenge in biomass-derived functional materials is tuning both barrier and mechanical properties, while minimizing process steps. A concept that merits additional study in this field is tuning of the barrier and mechanical properties by use of oppositely charged biomass-derived fibers, through interactions that support dense film formation. We report free-standing films formed by solution casting of blends of aqueous suspensions of CNCs and ChNFs with either low degree of acetylation (LChNFs, higher charge) or high degree of acetylation (HChNFs, lower charge). While neat CNC films had the highest O2 permeability (OP), the OP was lowered by 91% by addition of at least 25 wt % LChNFs to CNCs to an OP value near 1.7 cm3 μm/m2/d/kPa. Interestingly, blends of CNCs with less highly charged, larger HChNFs had equivalently lower OP as with LChNFs. The tensile strength and strain at break of blended ChNF/CNC films was optimal compared to neat cellulose or chitin when at least 50 wt % LChNFs or HChNFs were blended with CNCs. We show that the ability to tune properties of ChNF/CNC blends was coincident with the formation of aggregates of chitin and cellulose nanomaterials, which appear to support formation of dense layers of tortuous fiber networks.

High-Strength Nanostructured Films Based on Well-Preserved α-Chitin Nanofibrils Disintegrated from Insect Cuticles.

The α-chitin nanofibril is an alternative to nanocellulose as a building-block for strong films and other nanomaterials. The hypothesis of high film strength for films based on mildly treated insect cuticles was tested. Fibrils from the cuticle of Ruspolia differens (a long-horned bush cricket grasshopper locally known as senene) are disintegrated by a mild process, subsequently characterized by transmission electron microscopy, NMR, Fourier transform infrared spectroscopy, and XRD, and used to prepare strong and transparent films. A mild process (with 20% NaOH treatment for 2 weeks and at room temperature) was used to largely remove the strongly bound protein associated with chitin. The purpose was to reduce chitin degradation. The native structure of chitin was indeed well preserved and close to the native state, as is supported by data for degree of acetylation, molar mass, crystallinity, and crystallite dimensions. The diameter of the smallest chitin fibrils was as small as 3-7 nm (average 6 nm) with lengths larger than or around 1 μm. A stable and well-dispersed colloidal chitin fibril suspension in water was achieved. A nanostructured chitin film prepared by filtration showed high optical transmittance (∼90%) and very high tensile strength (220 MPa). The high tensile strength was attributed to the well-preserved chitin structure, high intrinsic fibril strength, and high colloidal stability of the fibril suspension. Strong, transparent insect chitin films offer interesting alternatives to nanocellulose films because of different resource origins, surface chemistries, and potential antimicrobial properties.

Overexpression of ThSAP30BP from Tamarix hispida improves salt tolerance

Histone deacetylases (HDACs) play an important regulatory role in plant response to biotic and abiotic stresses. They improve plant stress resistance by increasing the degree of histone acetylation associated with stress-responsive genes. SAP30BP, a human transcriptional regulatory protein, can increase histone deacetylase activity by regulating the deacetylation levels of lysines 9 and 14 in histone H3. In this study, a ThSAP30BP gene was cloned and characterized from Tamarix hispida (a kind of woody halophyte). The expression patterns of ThSAP30BP under different abiotic stresses and hormone treatments were detected by qRT-PCR. The results showed that ThSAP30BP was significantly upregulated at most time points under various stress treatments, suggesting that ThSAP30BP may be related to the abiotic stress response of T. hispida. To further analyze the salt stress resistance function of the ThSAP30BP gene, the plant overexpression vector pROKII-ThSAP30BP was instantaneously constructed and transformed into T. hispida. Meanwhile, the empty vector pROKII was also transformed as a control. The activities of SOD and POD, the contents of H2O2 and MDA, the relative conductance and the staining of NBT, DAB and Evans blue were analyzed and compared under salt stress. The results showed that the overexpression of ThSAP30BP in T. hispida reduced the accumulation of ROS in plants and the cell death rate under salt stress. These results suggested that ThSAP30BP may play an important physiological role in salt tolerance of T. hispida.

Cellulose triacetate from different sources: modification assessment through thermal and chemical characterization

Abstract Modification techniques have been widely employed to improve cellulose properties, thus increasing the diversity of industrial applications. While wood pulp cellulose is the most common source for industrial production, little has been studied about the effects of the cellulose source and its purity on modification. Therefore, this article investigates the influence of cellulose source (e.g. wood or cotton) on its modification (acetylation), by estimating the obtained degree of substitution (DS) through Fourier-transform infrared (FT-IR), proton nuclear magnetic resonance (1H NMR) and back titration. The intense reduction in samples’ crystallinity after acetylation was a result of breakage of inter- and intra-molecular hydrogen bonds, thus confirming acetylation. Although Avicel showed the highest cellulose content and was virtually free of hemicellulose and lignin, this did not affect the acetylation degree, as all samples were successfully triacetylated. The techniques used in this study were ideal for detecting acetylation and estimating the DS, which makes them good tools for modification studies of cellulose derivatives.

Optimising wheat straw alkali-organosolv pre-treatment to enhance hemicellulose modification and compatibility with reinforcing fillers

Hemicellulose acetylation, filler compatibility and film hydrophobicity were enhanced by optimising alkali-catalysed organosolv treatment conditions for wheat straw before hemicellulose extraction. Two optimum (OPT) conditions were established by varying organosolv components’ concentrations [ethanol (EC) (50–80%) and NaOH (1–13%)], and time (2–6 h), in a Box-Behnken experimental design. The OPT1 (1% NaOH/50% EC/6h) that enhanced acetylation and filler compatibility, and OPT2 (13% NaOH/80% EC/5h) that enhanced hydrophobicity by minimising degree of acetylation (DS), uronic acid content and arabinose/xylose ratio. The films made from OPT2 hemicellulose had higher water contact angle (68.1°) than OPT1 hemicellulose (39.90°). However, OPT1 hemicellulose had a higher DS (1.7 vs 0.4), and their acetylated nanocellulose reinforced films had higher tensile strength (10.59 vs 4.87 MPa) and Young modulus (590.15 vs 323.64 MPa) than OPT2 hemicellulose. Therefore, hemicellulose acetylation, hydrophobicity and filler interaction can be engineered by manipulating the organosolv treatment conditions.

Anti-Oxidant and Anti-Diabetes Potential of Water-Soluble Chitosan-Glucose Derivatives Produced by Maillard Reaction.

Chitosan-sugar derivatives demonstrate some useful biology activities (for example anti-oxidant and anti-microbial activities). In this study, water-soluble chitosan–glucose derivatives (WSCGDs) were produced from a water-soluble chitosan hydrochloride (WSC) with 12.5 kDa of molecular weight and 24.05% of degree of acetylation (DA) via Maillard reaction with the heating temperatures of 100 °C and 121 °C. The Maillard reaction between WSC and glucose was investigated by measuring the absorbances at 420 nm and 294 nm, indicating that the reaction took place more effectively at 121 °C. All WSCGDs exhibited higher anti-oxidant activity than WSC, in which WSCGDs obtained at the treatment 121 °C for 2 h, 3 h, and 4 h expressed the highest ability (IC50 range from 1.90–1.05 mg/mL). Increased anti-α-amylase and anti-α-glucosidase activities were also observed in WSCGDs from the treatment at 121 °C. In detail, the highest IC50 values of anti-α-amylase activity were 18.02 mg/mL (121 °C, 3 h) and 18.37 mg/mL (121 °C, 4 h), whereas the highest IC50 values of anti-α-glucosidase activity were in range of 7.09–5.72 mg/mL (121 °C, for 1–4 h). According to the results, WSCGD obtained from 121 °C for 3 h was selected for further characterizing by high performance liquid chromatography size exclusion chromatography (HPLC SEC), colloid titration, FTIR, as well as 1H-NMR, indicating that the derivative of WSC and glucose was successfully synthesized with a molecular weight of 15.1 kDa and degree of substitution (DS) of 34.62 ± 2.78%. By expressing the excellent anti-oxidant and anti-diabetes activities, WSCGDs may have potential use in health food or medicine applications.

Trimethylchitosan hydrochloride obtained from lobster carapace chitin on a bench scale

Starting from the chitin obtained from the lobster carapace, chitosan was obtained. This polymer, due to its high biodegradability, biocompatibility and mucoadhesivity, has a wide use in the pharmaceutical and food industry. Currently, it has great importance in the development of biomaterials for the regeneration of bone and cartilaginous tissues. However, its applications are limited by the insolubility at pH greater than 6. To increase its solubility, different methodologies have been reported. The intensive methylation of the chitosan has been one of the methodologies that have been studied in the last years, generating the N,N,N-trimethylchitosan. This molecule has the characteristic of having permanent positive charges in the chain as a consequence of the quaternization of the amino groups present in the structure of chitosan. Previous studies showed the influence of the agitation rate and the reaction time on the methylation process of the chitosan, using as an alkylating agent the dimethyl sulfate. This allowed to establish a technological process to transform the chitosan. The aim of this work was to obtain N,N,N-trimethylchitosan chloride from chitosan obtained chitin from lobster carapace bench scale. Infrared spectroscopy, Energy dispersive X-ray spectrometry, Nuclear Magnetic Resonance and Intrinsic viscosity were used to characterize the product obtained. The results of the analysis by Infrared spectroscopy, Energy dispersive X-ray spectrometry and Nuclear Magnetic Resonance showed that the methylation process of the chitosan proposed in this work was effective to obtain the desired product. The degree of quaternization, degree of dimethylation and degree of acetylation were 49.2%, 57.5% and 13.3%, respectively. While the value of the intrinsic viscosity [ɳ] of the sample was 78.5 cm3/g. The results corroborate the possibility of modifying chitosan by applying the methodology proposed in this work.

Chitosan–Azide Nanoparticle Coating as a Degradation Barrier in Multilayered Polyelectrolyte Drug Delivery Systems

Therapeutics, proteins or drugs, can be encapsulated into multilayer systems prepared from chitosan (CS)/tripolyphosphat (TPP) nanogels and polyanions. Such multilayers can be built-up by Layer-by-Layer (LbL) deposition. For use as drug-releasing implant coating, these multilayers must meet high requirements in terms of stability. Therefore, photochemically crosslinkable chitosan arylazide (CS–Az) was synthesized and nanoparticles were generated by ionotropic gelation with TPP. The particles were characterized with regard to particle size and stability and were used to form the top-layer in multilayer films consisting of CS–TPP and three different polysaccharides as polyanions, namely alginate, chondroitin sulfate or hyaluronic acid, respectively. Subsequently, photo-crosslinking was performed by irradiation with UV light. The stability of these films was investigated under physiological conditions and the influence of the blocking layer on layer thickness was investigated by ellipsometry. Furthermore, the polyanion and the degree of acetylation (DA) of chitosan were identified as additional parameters that influence the film structure and stability. Multilayer systems blocked with the photo-crosslinked chitosan arylazide showed enhanced stability against degradation.

Spectroscopic Interrogation of the Acetylation Selectivity of Hardwood Biopolymers

AbstractAcetylation of wood is an age‐old chemical platform known to improve its chemical and physical properties in direct correlation with the degree of acetylation. However, as of yet, no systematic study has been undertaken to probe the selectivity of acetylation of wood. A fundamental understanding of the molecular basis for acetylation of the constituent biopolymers, viz., holocellulose, and lignin for tropical hardwood, an emerging building material, is therefore undertaken. Wood samples are treated with acetic anhydride at 120 °C over a wide range of time periods. The degrees of acetylation and acetyl content of the tropical hardwood are measured to reveal that the acetyl content in which the hydroxyl groups of wood correspond to an increment in weight percent gain as confirmed by FT‐IR for individual wood biopolymers and whole wood. However, surprisingly,31P‐NMR establishes the order of reactivity for the hydroxyl groups as lignin > hemicelluloses > whole wood in direct opposition to their proportions in wood, but in correlation to their direct accessibilities and reactivities.

Facile design of pressure-sensing color films of liquid crystalline cellulosic/synthetic polymer composites that function at desired temperatures

We have developed a facile method for material design of pressure-sensing films for various operating temperatures using cholesteric liquid crystalline (ChLC) cellulose derivatives. A series of acetylated hydroxypropyl celluloses (AHPCs) with different degrees of acetylation (DSAc) was prepared and their concentrated solutions in monomeric solvents showed coloration based on the selective reflection of ChLC. The critical coloration concentration of the AHPC/monomer solutions decreased with increasing DSAc because the twist angle of the cholesteric helix increased by introducing acetyl groups. The ChLC solutions were subsequently subjected to in situ polymerization to immobilize the ChLC structure in the produced composites. The ChLC structure was well immobilized in the composites with moderate compatibility between the component polymers. The obtained AHPC/polymer ChLC composites exhibited compression-induced mechanochromism, and consistent pressure sensitivity was achieved at various temperatures by selection of the counter polymer species. This approach is applicable for designing pressure-sensing films tailored to the operating temperature.

Straightforward extraction and selective bioconversion of high purity chitin from Bombyx eri larva: Toward an integrated insect biorefinery

Chitins of different purity grades (45%, 89.7% and 93.3%) were efficiently extracted from Bombyx eri larva and fully physico-chemically characterized. Compared to commercially available and extracted α-chitin from shrimp shell, the collected data showed that insect chitins had similar characteristics in terms of crystallographic structures (α-chitin), thermal stability and degree of acetylation (>87%). The major differences lay in the crystallinity indexes (66% vs 75% for shrimp chitin) and in the morphological structures. Furthermore, low ash contents were determined for the insect chitins (1.90% vs 21.73% for shrimp chitin), making this chitin extraction and purification easier, which is highly valuable for an industrial application. Indeed, after only one step (deproteinization), the obtained chitin from Bombyx eri showed higher purity grade than the one extracted from shrimp shells under the same conditions. Insect chitins were then subjected to room temperature ionic liquid (RTIL) pretreatment prior to enzymatic degradation and presented a higher enzymatic digestibility compared to commercial one whatever their purity grade and would be thus a more relevant source for the selective production of N-acetyl-D-glucosamine (899.2 mg/g of chitin-2 stepsvs 760 mg/g of chitin com). Moreover, for the first time, the fermentescibility of chitin hydrolysates was demonstrated with Scheffersomyces stipitis used as ethanologenic microorganism.

Influences of combined enzyme-ultrasonic extraction on the physicochemical characteristics and properties of okra polysaccharides

This study obtained two novel polysaccharides from okra by enzyme-assisted and combined enzyme-ultrasonic methods while comparing with previously established hot-water, ultrasonic methods, for their food application potentials. Structural characteristics and physicochemical properties were evaluated and their relationships with functional properties and biological activities including viscosity, emulsifying abilities, antioxidant and antimicrobial activities were observed. All okra polysaccharides (OKPs) showed similar structural features as revealed by 1H NMR, in accordance with FT-IR spectroscopy. The result of monosaccharide composition confirmed isolated OKPs as acidic heteropolysaccharides consisting of galactose, glucose, rhamnose, arabinose, galacturonic and glucuronic acid, in the varying molar percentages of 33.8–38.6%, 12.4–17.9%, 13.7–17.5%, 3.0–9.9%, 19.0–21.2%, and 6.7–8.3%, respectively. All OKPs were broadly polydispersed with molecular weights (Mw) ranging between 129 and 193 × 103 g mol−1, polysaccharide content ranging from 43.95 to 70.75%, a high degree of acetylation (20.81–37.88%) and low methyl-esterification (26.9–38.95%). Combined enzyme-ultrasonic extracted polysaccharide (CEUP) exhibited superior properties such as solubility, emulsifying capacity, high antioxidant activity and showed more potency in Escherichia coli and Listeria monocytogenes inhibition, extending its versatility in food applications. Principal component analysis (PCA) revealed CEUP to possess unique characteristics different from other samples, substantiating the significance of combined extraction technology over single techniques. Overall, the present study suggests OKP extracted by enzyme-ultrasonic technology as a potential new source of food hydrocolloid with novel functional and biological properties adoptable in the food industry as coating material and food ingredients.

Cytosolic Acetyl-CoA Generated by ATP-Citrate Lyase Is Essential for Acetylation of Cell Wall Polysaccharides.

Plant cell wall polysaccharides, including xylan, glucomannan, xyloglucan and pectin, are often acetylated. Although a number of acetyltransferases responsible for the acetylation of some of these polysaccharides have been biochemically characterized, little is known about the source of acetyl donors and how acetyl donors are translocated into the Golgi, where these polysaccharides are synthesized. In this report, we investigated roles of ATP-citrate lyase (ACL) that generates cytosolic acetyl-CoA in cell wall polysaccharide acetylation and effects of simultaneous mutations of four Reduced Wall Acetylation (RWA) genes on acetyl-CoA transport into the Golgi in Arabidopsis thaliana. Expression analyses of genes involved in the generation of acetyl-CoA in different subcellular compartments showed that the expression of several ACL genes responsible for cytosolic acetyl-CoA synthesis was elevated in interfascicular fiber cells and induced by secondary wall-associated transcriptional activators. Simultaneous downregulation of the expression of ACL genes was demonstrated to result in a substantial decrease in the degree of xylan acetylation and a severe alteration in secondary wall structure in xylem vessels. In addition, the degree of acetylation of other cell wall polysaccharides, including glucomannan, xyloglucan and pectin, was also reduced. Moreover, Golgi-enriched membrane vesicles isolated from the rwa1/2/3/4 quadruple mutant were found to exhibit a drastic reduction in acetyl-CoA transport activity compared with the wild type. These findings indicate that cytosolic acetyl-CoA generated by ACL is essential for cell wall polysaccharide acetylation and RWAs are required for its transport from the cytosol into the Golgi.

Comparison of citrus pectin and apple pectin in conjugation with soy protein isolate (SPI) under controlled dry-heating conditions

In this study, we selected two most commonly-available commercial pectin, i.e. citrus pectin and apple pectin as the grafting polysaccharides to prepare soy protein isolate-pectin conjugates. Despite the similar degrees of methoxylation and acetylation for two pectin samples, apple pectin showed much more complex structures compared to citrus pectin, with a 2.20-fold higher molecular weight and large numbers of side chains. The conjugates were prepared under controlled dry-heating conditions and achieved the degree of graft of 25.00% and 21.85% for citrus and apple pectin, respectively. Formation of the conjugates was further confirmed by SDS-PAGE gel electrophoresis and IR spectra. Attributed to the strong steric-hindrance effect of pectin, the fluorescence intensity and surface hydrophobicity of the soy protein isolate were significantly decreased after Maillard reaction. However, both solubility and emulsifying properties of the conjugates were significantly improved. Results indicated that both pectin samples played favorable roles in protein modification.

Biopolymeric Films of Amphiphilic Derivatives of Chitosan: A Physicochemical Characterization and Antifungal Study

The chemical modification of chitosan has been an active subject of research in order to improve the physicochemical and antifungal properties of chitosan-based films. The aim of this study was to evaluate the physiochemical and antifungal properties of films prepared with chitosan and its derivatives containing diethylaminoethyl (DEAE) and dodecyl groups (Dod). Chitosans and selected derivatives were synthesized and characterized, and their films blended with glycerol and sorbitol (5%, 10%, and 20%). They were studied by means of the evaluation of their mechanical, thermal, barrier, and antifungal properties. The collected data showed that molecular weight (Mw), degree of acetylation, and grafting with DEAE and Dod groups greatly affected the mechanical, thickness, color, and barrier properties, all of which could be tailored by the plasticizer percentage. The antifungal study against Aspergillus flavus, Alternaria alternata, Alternaria solani, and Penicillium expansum showed that the films containing DEAE and Dod groups exhibited higher antifungal activity than the non-modified chitosans. The mechanical properties of highly soluble films were improved by the plasticizers at percentages of 5% and 10%, indicating these derivatives as potential candidates for the coating of seeds, nuts and fruits of various crops.

QSAR analysis of coumarin-based benzamides as histone deacetylase inhibitors using CoMFA, CoMSIA and HQSAR methods

Histone deacetylases (HDACs) as the promising therapeutic targets for the treatment of cancer and other diseases, modify chromatin structure and contribute to aberrant gene expression in cancer. Inhibition of HDACs is emerging as an important strategy in human cancer therapy and HDAC inhibitors (HDACIs) enable histone to maintain a high degree of acetylation. In this work, molecular modeling studies, including CoMFA, CoMFA-RF, CoMSIA and HQSAR and molecular docking were performed on a series of coumarin-based benzamides as HDAC inhibitors. The statistical qualities of generated models were justified by internal and external validation, i.e., cross-validated correlation coefficient (q2), non-cross-validated correlation coefficient (rncv2) and predicted correlation coefficient (rpred2), respectively. The CoMFA (q2, 0.728; rncv2, 0.982; rpred2, 0.685), CoMFA-RF (q2, 0.764; rncv2, 0.960; rpred2, 0.552), CoMSIA (q2, 0.671; rncv2, 0.977; rpred2, 0.721) and HQSAR models (q2, 0.811; rncv2, 0.986; rpred2, 0.613) for training and test set of HDAC inhibition of HCT116 cell line yielded significant statistical results. Therefore, these QSAR models were excellent, robust and had better predictive capability. Contour maps of the QSAR models were generated and validated by molecular docking study. The final QSAR models could be useful for the design and development of novel potent HDAC inhibitors in cancer treatment. The amido and amine groups of benzamide part as scaffold and the bulk groups as a hydrophobic part were key factors to improve inhibitory activity of HDACIs.

Iron-rich chitosan-pectin colloidal microparticles laden with ora-pro-nobis (Pereskia aculeata Miller) extract

Iron deficiency represents a global nutrition gap that calls for innovative strategies including food fortification, while overcoming the drawbacks of taste and reactivity of iron. The aim of this work was to develop iron-rich colloidal microparticles laden with a Brazilian plant food extract from ora-pro-nobis (OPN, Pereskia aculeata Miller). We formulated electrostatic self-assembled complexes of oppositely charged chitosans and pectin laden with aqueous OPN extract. After characterisation of the physical properties, selected formulations were examined in their colloidal stability (50 mM NaCl, Dulbecco's modified eagle medium (DMEM), simulated gastric fluid (SGF) and simulated intestinal fluid (SIF)), production yield, iron association efficiency, transmission electron microscopy (TEM), cellular cytotoxicity and iron uptake using Caco-2 cells. The ζ-potential varied from ~ −25 mV to ~ +23 mV regardless of the degree of acetylation (DA) of chitosan. The production yield ranged between 20 and 26%. The particles were stable at DMEM, SGF and SIF during 3 h. Iron association efficiency was ~60% for systems charge ratio (n+/n–) = 5.00. TEM analyses revealed invariably spherical morphology. OPN-laden microparticles did not present cytotoxicity against Caco-2 cells. Higher cellular ferritin levels were determined for the particles comprising OPN extract and n+/n– = 5.00. We obtained in vitro proof of concept of the efficiency of chitosan/pectin particles to delivering iron from a Brazilian edible plant extract. The industrial potential of this approach as a viable alternative for iron fortification or supplementation by the food industry is yet to be realised.

Short communication: Stabilization of milk proteins at pH 5.5 using pectic polysaccharides derived from potato tubers

Potato pectin has unique molecular characteristics that differentiate it from commercially available pectins sourced from citrus peels or apple pomace, including a higher degree of branching and a higher acetyl content. The objective of this study was to evaluate the ability of potato pectin to stabilize milk proteins at an acidic pH above their isoelectric point, pH 5.5, at which no citrus- or apple-derived pectins are functional. Potato pectin was extracted from raw potato tubers by heating at pH 4.5 and 120°C for 30 min after removing starch solubilized using a dilute HCl solution adjusted to pH 2. The potato pectin was found to have a galacturonic acid content of 17.31 ± 3.29% (wt/wt) and a degree of acetylation of 20.20 ± 0.12%. A portion of the potato pectin was deacetylated by heating it in an alkaline condition. The deacetylation resulted in a galacturonic acid content of 19.12 ± 4.64% (wt/wt) and a degree of acetylation of 3.03 ± 0.03%. Particle size distributions in acidified milk drink (AMD) samples adjusted to pH 5.5 demonstrated that the acetylated and deacetylated potato pectins were capable of inhibiting the aggregation of milk proteins to the largest degree at a pectin concentration of 1.0 and 0.25% (wt/wt), respectively. Pectin molecules that were not bound to milk proteins in these AMD samples were quantified after centrifugally separating milk proteins and pectin bound to them from the serum. We found that, for the acetylated and deacetylated potato pectins, all or approximately half of the pectin molecules were bound to milk proteins at a pectin concentration of 0.25 or 1.0% (wt/wt), respectively. These results suggest that the presence of acetyl groups is a critical factor that determines how potato pectin molecules bind electrostatically to milk protein surfaces, form 3-dimensional structures there, and function as a stabilizer. The present results demonstrate that potato pectin can stabilize milk proteins at pH 5.5 and potentially enable the development of novel AMD products with improved functionality for casein-containing products with moderately acidic pH profiles.

Rapid and efficient extraction of chitin and chitosan for scale-up production: Effect of process parameters on deacetylation degree and molecular weight

Chitin and chitosan have been successfully produced, from Moroccan shrimp shells, using the microwave technology. This efficient extraction method of chitin and chitosan was evaluated and demineralization, deproteinization and deacetylation steps were investigated. The effect of the reaction time, the HCl and the NaOH concentration, at different powers (90 W, 160 W, 350 W, 500 W and 650 W) was studied. The results shown that a chitosan with low degree of acetylation has been extracted using 50% of NaOH solution, at power range 500–650 W, and the deacetylation reaction was more than 80% completed after 10 min. Microwave assisted extraction allowed to produce chitosan with medium and high molecular weight (300–360 kDa).Chitin deacetylation by microwave heating was more efficient than the conventional heating, and high desacetylation degree was obtained using microwave heating in just a few minutes. This technology can save huge amount of energy when implemented on industrial scale, it's a highly economical extraction method. By this technology, we have successfully produced the chitosan CTS with low NaOH concentration (30%), which allows to avoid manipulating an extremely high concentration of a corrosive substance, especially at industrial scale. Chitosan CTS has a degree of acetylation of 23.4% and a molecular weight of 165 kDa.