Cocoa (Theobroma cacao L.) hulls: a posible commercial source of pectins

Commercial exploitation of cocoa (Theobroma cacao L.) generates a volume of hulls that could be used in the production of pectins on an industrial scale. Therefore, pectins from cocoa hulls were extracted at different pH and temperature conditions, and their main chemical characteristics were evaluated. EDTA at 0.5% was used for the extraction at pHs 3, 4 and 5 and temperatures of 60, 75 and 90 degrees C, under a 3 2 factorial design. The response variables were yield, content of anhydrous galacturonic acid (AGA), content of metoxil, degree of esterification and equivalent weight of the pectins extracted. The strength of the pectic gel was determined with a TA-XT2 texturometer. Strawberry jam was made with the pectin extracted, and its acceptability was determined using a 7-point hedonic scale. The results obtained were as follows: an extraction yield from 2.64 to 4.69 g/100 g; an AGA content between 49.8 and 64.06 g/100 g; a content of metoxil between 4.72 and 7.18 g/100 g; a degree of esterification between 37.94 and 52.20%; an equivalent weight from 385.47 to 464.61 g/equivalent of H+, and a degree of gelation between 28.64 and 806.03 g force. The pectin extracted at pH 4 and 90 degrees C showed a gelation power of 422.16 g force, purity 62.26 g/100 g of AGA, and a yield of extraction of 3.89 g/100 g and allowed to prepare ajam with an average level of liking of "like moderately". Pectins from cocoa hulls show potential application in the food industry, but it is necessary to optimize the extraction parameters to increase its yield.     

Preparation and functional properties of soy hull pectin

Soy hulls (400 g), a co-product of the soybean processing industry, were used as a source of pectin which was extracted by0.05 N hydrochloric acid and precipitated with alcohol. The effect of various ratios of hull to extraction solvent (1∶10, 1∶15, 1∶20, and 1∶25) on the yield and purity of soy hull pectin was measured. The soy hull pectin extracts contained 63.07 to 68.72% galacturonic acid at various hull/solvent ratios. The pectin yield increased from 7.68 to 13.73% as the hull/solvent ratio increased from 1∶10 to 1∶15. Changes in pectin yield for higher hull/solvent ratio were insignificant (16.31–13.28% for 1∶20–1∶25 ratio, respectively). The hull/extraction solvent ratio did not significantly affect the pectin content and degree of esterification. Diffuse reflectance Fourier transform infrared spectroscopy of soy hull pectin revealed a similar surface structure to commercial-and analytical-grade pectins. The solubility of soy hull pectins was independent of solvent extraction ratios and pH. Rheology studies showed that pectin solution viscosity increased as the ratio of extraction solvent to hull decreased.     

Gelation of pectinic acids in the presence of calcium counterions

Pectins are polysaccharides which are able to gel in the presence of calcium ions if their degree of esterification is lower than 40%. From a purified pectin, a de-esterification was carried out by alkali and by enzymes in order to obtain samples with a different charge density and esterification pattern (random or blockwise distribution of carboxylic acid sites). The pectin-calcium interactions were studied in a dilute solution of calcium pectinates by conductimetry. If the concentration of highly charged polymer is increased, a multichain association can occur: the same process is observed with dilute solutions (c_p≤10-3 eq. 1^?1) but in the presence of an excess of calcium ions. This first step of the gelation was followed by light scattering and by viscometry. The gelling system can be described by a power law including a critical ratio (equivalent concentration of calcium ions/pectin carboxylic sites) and quasi-critical exponents. The values of these critical parameters have been discussed as a function of charge density of the pectins, their esterification pattern, their concentration, and the nature of the divalent counterion.     

Modulation of extraction variables of pectin from Manilkarazapota fruit peel,its bio characterization,and comparative study using dynamic light scattering studies

Influence of variables has a great impact upon yield of pectin. The present study was organized to harmonize these variables and examine the extracted pectin. In view of this, bio-characterizion and structure analysis of pectin through FTIR was performed. Additionally, a polydispersity and particle size study was also conducted using dynamic light scattering (DLS) of the Manilkarazapota fruit peel. The best extraction variables according to the response optimization predicted model were noted as pH of 5 at 61.11°C for 90 min of heating time, which lead to a 3.7% yield. Bio-characterization revealed that pectin extracted at pH 5 has characteristics similar to HM pectin influence of methoxyl content, degree of esterification, and Galacturonic acid content at 5.11%, 73. 63%, and 77.7%, respectively. The FTIR spectrum depicted a similar surface structure to food-grade pectin. DLS studies revealed that extracted pectin at pH 5 has a particle size in the range of 390.21–421.17 nm and polydispersity (?) of 28.2%-29.3%. These findings indicate that sapodilla is a potential source of pectin for food and pharmaceutical preparation.     

Sugar-beet pulp pectin gels as biosorbent for heavy metals: Preparation and determination of biosorption and desorption characteristics

The present work reports the feasibility of using sugar-beet pectin gels for the removal of heavy metals from aqueous solutions. Sugar-beet pectin hydro- and xerogels were tested in the batch biosorption and desorption of cadmium, lead and copper. Pectins were successfully extracted and demethylated from the sugar-beet pulp, an agricultural residue, and gelled in the presence of CaCl₂. The stability of the hydro- and xerogel pectin beads made them suitable for biosorption of heavy metals in different conditions. Biosorption data were fitted to the pseudo-second order kinetic model and the Langmuir isotherm model, obtaining the corresponding parameters. Treated and untreated beads were characterized using FTIR and SEM to determine possible binding mechanisms. The main mechanisms involved were ion exchange with calcium of gel structure and chelation or complexation with carboxyl groups. After biosorption, calcium in the gels was substituted by metal cations reorganizing the structure of the gel matrix in a way that was visible using scanning electron microscopy. HNO₃ 0.1 M was the best eluant for the reutilization of the gels and recovered all the adsorbed metal unlike HCl and H₂SO₄. Sugar-beet pectins could be used as an efficient biosorbent for the treatment and recovery of Cu, Pb and Cd from wastewater.     

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.     

Multifunctional hybrid organosilicate materials prepared by the sol-gel method

It has been shown that a comparison of the calculated parameters of solubility δ, activation energies of structure formation ΔG _str, and pH values of combined solutions makes it possible to predict and control the influence of the used chemical reagents on the aggregate stability of the composites and the properties of the synthesized gels. The synthesized gels possess high performance characteristics and can be used as sealing, compacting, and water isolation materials in construction, oil extraction, and other branches of industry.     

Über das verhalten von pektin gegenüber farbadsorbern vom Typ „Wofatit EZ”︁

In percolating aqueous apple pectin solutions on the colour adsorber ?Wofatit EZ”?, especially the fractions with low molecular weight are adsorbed. Contrarily to galacturonic acid as well as to high-molecular pectin these fractions cannot be regained by washing with water. The lower the weight-average molecular weight of the tested pectins, the higher is the adsorption effect. Moreover the percolates show a decreased content in substances reducing 3,5-dinitrosalicylic acid. They contain pectins of a slightly increased degree of esterification. Therefore, preparative separation of degraded fractions from high-molecular pectin preparations by means of highly porous discolouring resins seems to be possible. However, during regeneration of Wofatit EZ by alkali and acid the adsorbed pectin fractions are desorbed to a great extent.     

Protein Subunit Composition Effects on the Thermal Denaturation at Different Stages During the Soy Protein Isolate Processing and Gelation Profiles of Soy Protein Isolates

This study focussed on the evaluation of thermal denaturation at three different stages during soy protein isolation and the effect of subunit composition on the formation of heat-induced soy protein gels. Soy protein isolates (SPI) were prepared from 12 high protein lines, Harovinton variety and 11 derived null-lines which lacked specific glycinin (11S) and β-conglycinin (7S) protein subunits. Protein denaturation during SPI processing was monitored by differential scanning calorimetry (DSC). The results showed that hexane extraction of oil from soybean flours at 23 °C or 105 °C did cause changes in protein conformation. Rheological measurements showed that lines with different subunit compositions and 11S:7S ratio had distinctive gelation temperatures and resulted in gels with different network structures. All lines formed particulate gels at 11% protein. The 11S:7S ratio was not correlated to final stiffness, measured as the storage modulus G′, of SPI gels. Lower gelation temperatures were usually observed for 7S-rich lines. The absence of A3 and the combination of A1, A2 and A4 subunits of 11S fraction may suggest the formation of stiffer gels. A more detailed study of the frequency dependence of G′ for the various networks formed also indicated that differences in subunit composition influenced the network structures.     

Preparation and optimization of calcium pectate beads for cell encapsulation

A variety of natural polymers are considered suitable for cell entrapment. Pectin, a natural polysaccharide found in the cell walls of all higher terrestrial plants, presents great potential for cell encapsulation because of its ability to form gels. In this study, we investigated the influences of intrinsic and extrinsic factors on the formation and properties of calcium pectate (CP). Beads of CP prepared with 30–35% methyl esterification presented improved gel properties. The molecular weight (M_w), calcium content, and gel time did not significantly affect the gel properties. The gelling properties, sphericity factor (SF), and swelling ratio were significantly influenced by the degree of methyl esterification (DE) and pectin concentration. The DE (<40%), M_w, and calcium concentration had negative effects on the SFs of CP beads. Moreover, increases in the DE (<40%) and pectin concentration increased the swelling ratio. The C3A cells encapsulated in optimized CP beads maintained good viability and proliferation for up to 2 weeks. In conclusion, CP beads are a potential encapsulation material for cell immobilization and application in related fields. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45685.     

Stability of Lactobacillus bulgaricus immobilized in K-carrageenan gels

The future application of immobilized microorganism techniques will depend on the development of systems which are technologically applicable on an industrial scale. These techniques must permit high microbial concentrations and must allow mass transfer to take place with low diffusional limitations. In addition, the mechanical separation of the immobilized microorganisms must be achieved economically, K-carrageenan was used as an ionotropic gel carrier for the immobilization of Lactobacillus bulgaricus (ATCC 11842), and the effects of gel stability on productivity and the rate of product formation were investigated. K-carrageenan gels had higher mechanical and chemical stability than alginate gels. The storage stability of microorganisms immobilized in K-carrageenan was good enough to retain biocatalytic activity during prolonged storage at 4°C.     

Study on strength and gelation time of polyacrylamide/polyethyleneimine composite gels reinforced with coal fly ash for water shut‐off treatment

This study investigates the influence of coal fly ash (CFA) as a reinforcing material on the strength and the gelation of polyacrylamide (PAM)/polyethyleneimine (PEI) composite gels. Pure PAM/PEI gel and PAM/PEI gels containing CFA up to 2 wt % were synthesized via the cross‐linking reaction between PAM and PEI solutions at room temperature (25°C) in distilled water dispersed with CFA. The strength of each composite gel was measured at temperature of 80°C, while the gelation was determined from 80°C to 95°C. Rheological measurements indicated that the strength of PAM/PEI composite gels filled with CFA contents was significantly rigid and stronger than that of pure PAM/PEI gel as a result of the enhanced interfacial interaction of well‐dispersed CFA contents in PAM/PEI gel matrix. The gelation times of PAM/PEI gels containing CFA up to 2 wt % deviated from the gelation time of pure PAM/PEI gel. It was further observed that an increase in temperature resulted in a decrease in gelation time of PAM/PEI gel containing 2 wt % CFA. The scanning electron microscopy revealed the surface micrographs of PAM/PEI gels filled with CFA to be very dense without any noticeable micropores. The micropores were absent as scanning was performed on the dried composite gels. It also establishes the strong interaction between CFA and PAM/PEI gel matrix. Experimental findings showed that PAM/PEI composite gels reinforced with CFA are potential candidates for total water shut‐off treatment in oilfields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41392.     

Effect of extraction conditions on yield and degree of esterification of durian rind pectin: An experimental design

The effect of time (1 and 4 h), pH (2.0 and 2.5) and temperature (80 and 90 °C) on yield and degree of esterification (DE) of durian rind pectin was investigated. The yield and DE of the extracted pectin ranged from 2.1 to 10.3% (w/w, based on dry weight of durian rind) and 45.6–64.8% respectively. Yield was significantly affected by time, temperature and pH, and interactions between temperature and pH, and heating time and pH. DE was significantly affected by heating time and pH, and interactive effects of temperature and pH, and heating time and pH. The extraction yield was not related to DE. By considering pectin yield and DE, the acid extraction of durian rind pectin at 80 °C, for 4 h and at pH 2.5 could be suitable.     

Electrochemically prepared acrylamide/N,N′-methylene bisacrylamide gels

Acrylamide/N,N-methylene bisacrylamide gels were synthesized electrochemically at room temperature in the presence of an initiator only, without using chemical activator. Various electrode systems were examined and silver was chosen as a working electrode material. Working conditions were determined and the effect of bisacrylamide concentration and electrode voltage on gelation times was examined.     

Study of cryostructuration of polymer systems. XIV. Poly(vinyl alcohol) cryogels: Apparent yield of the freeze–thaw‐induced gelation of concentrated aqueous solutions of the polymer

Poly(vinyl alcohol) (PVA) cryogels, which are formed as a result of freeze–thaw treatment of concentrated solutions of the polymer, were studied in respect to the amount of gel and sol fractions in these heterogeneous macroporous gel materials depending on the conditions of the thawing step of similar cryotropic gelation. It was shown that the yield of gel fraction (the efficiency of the gelation process) was not quantitative; this was controlled by the initial PVA concentration in the solution to be frozen, and to a higher extent, by the thawing rate, when the yield increased with slowing of the defrostation process. The sol fraction could be extracted from the PVA cryogels by their rinsing with water at room temperature; the extraction of the sol was accompanied with the variations of the swelling parameters of the gels (initial slight upswelling and subsequent gradual deswelling), as well as with analogous, in their character, variations of the gel strength. It was also demonstrated that at the evaluation of the fusion enthalpies of PVA cryogels with the aid of the Eldridge–Ferry equation a consideration of the values of gel‐fraction yield gave rise to the significantly higher ΔH values than in traditional cases commonly used for the thermoreversible gels, where such an yield was not taken into account. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1822–1831, 2000     

Investigation of gelation behavior of polyvinyl alcohol-glutaraldehyde system

The polyvinyl alcohol-glutaraldehyde gel system was investigated in this work. The gelation kinetics under oil field environments and effects on the structures and properties of the gels formed were discussed. The basic characteristics of this gel system were determined. The fundamental data during gelation were obtained and application of the gel system for the tertiary oil recovery was evaluated. Under the experimental condition, among the gelation time t, initial pH of the system, and glutaraldehyde concentration x, there exists the relation ln t(pH, x) = 2.35pH - 0.85 ln x - 10.91 It is conspicuous that the gelation of this gel system is less sensitive to hardness and salt contents; the gels formed under the relevant condition were quite stable. Thus, the application of this gel system for tertiary oil recovery under hostile environments is very promising. © 1997 John Wiley & Sons, Inc.     

Thermoreversible gelation of a polystyrene–poly(ethylene/butylene)–polystyrene triblock copolymer in n‐octane/4‐methyl‐2‐pentanone solutions

The thermoreversible gelation of a triblock copolymer polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene in n‐octane and two solvent mixtures of n‐octane and 4‐methyl‐2‐pentanone with a high n‐octane content has been studied. n‐Octane and 4‐methyl‐2‐pentanone are selective solvents for the middle poly(ethylene/butylene) block and the end polystyrene blocks, respectively. The influence of the solvent composition on the sol–gel transition and the mechanical properties of the gels was studied. The gel formation temperature increased with the copolymer concentration and the n‐octane content in the solvent system. The mechanical properties of the different gels were studied through oscillatory shear measurements. The concentration dependence of the elastic storage modulus showed an exponent close to that expected for gels in good solvents (2.25) that possess a structure similar to those of chemical networks. © 2002 Society of Chemical Industry     

Lactic Acid Extraction and Enzymatic Esterification for the Ethyl Lactate Production from Rice

Polylactic acid has received much attention because of its biodegradable characteristics. However, to produce the polylactic acid, enormous energy is required at the current purification processes developed up to now. In this work, in order to reduce energy consumption, we proposed a novel purification method which combines lactic acid extraction and enzyme esterification instead of the dehydration and the chemical esterification which are conventionally used. As a result, the new purification method is found to be excellent as the solvents used in this work. It revealed that some solvents (diethyl ether, tert-butyl methyl ether, and methy isobuthyl ketone) have excellent abilities for both lactic acid extraction and enzymatic esterification.     

Effect of drug loading on the properties of temperature‐responsive polyester–poly(ethylene glycol)–polyester hydrogels

Hydrogels that can undergo gelation upon injection in vivo are promising systems for the site‐specific delivery of drugs. In particular, some thermo‐responsive gels require no chemical additives but simply gel in response to a change from a lower temperature to physiological temperature (37 °C). The gelation mechanism does not involve covalent bonds, and it is possible that incorporation of drugs into the hydrogel could disrupt gelation. We investigated the incorporation of drugs into thermo‐responsive hydrogels based on poly(?‐caprolactone‐co‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(?‐caprolactone‐co‐lactide) (PCLA–PEG–PCLA). Significant differences in properties and in the response to incorporation of the anti‐inflammatory drug celecoxib (CXB) were observed as the PEG block length was varied from 1500 to 3000 g mol^?1. Linear viscoelastic moduli of a PCLA–PEG–PCLA hydrogel containing a 2000 g mol^?1 PEG block were least affected by the incorporation of CXB and this gel also exhibited the slowest release of CXB, so the incorporation of phenylbutazone, methotrexate, ibuprofen, diclofenac and etodolac was also investigated for this hydrogel. Different drugs resulted in varying degrees of syneresis of the hydrogels, suggesting that they interact with the polymer networks in different ways. In addition, the drugs had varying effects on the viscoelastic and compressive moduli of the gels. The results showed that the effects of drug loading on the properties of thermo‐responsive hydrogels can be substantial and depend on the drug. For applications such as intra‐articular drug delivery, in which the mechanical properties of the hydrogel are important, these effects should thus be studied on a case‐by‐case basis. © 2019 Society of Chemical Industry     

Gelation of soybean oil with polybutadiene

In this study self‐supporting, resilient, load bearing polybutadiene ‐ soybean oil gels were obtained. The gels were made by dissolving polybutadiene (PBD) in soybean oil (SO) and selectively crosslinking PBD with a free radical source. PBD concentration, free radical source concentration, and the temperature and time of the crosslinking reaction were varied, and the effects of these changes on the mechanical properties of the gels were examined. Our experiments show that successful gelation is possible within PBD concentration limits of 7.5 to 12%, peroxide concentration between 25 to 100% (based on PBD), temperature between 110°C and 130°C and reaction times of 3 hours with tert.butyl‐peroxybenzoate as the free radical source. The crosslinking reaction was followed by IR and H‐NMR spectra, and the crosslinking density was followed by compression testing and swelling behavior. Higher radical source concentration and higher PBD concentration gave gels with better mechanical properties. The spectra and the viscosity increase of SO extracted from the gels indicate that there is dimer and trimer formation of SO during the reaction. The spectra of the PBD extracted from gels indicate that SO was added to PBD in a small but measurable amount. Integration of peak intensities in the NMR spectrum of methylene groups of PBD and methylene groups of triglyceride indicated one triglyceride molecule for approximately 45 repeating units in PBD. The modulus of the best gel sample (PBD 10%. peroxide 50%) was 1.96 × 10^?2 MPa. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2240–2246, 2005