High Methoxy Pectin Research Articles

Mouthfeel and flavour of fermented whey with added hydrocolloids

High-methoxy pectin (HMP), propylene glycol alginate (PGA), carboxymethyl cellulose (CMC) and xanthan gum (XG) were added separately to whey fermented by a yoghurt starter culture at concentrations that yielded a viscosity similar to that of commercial fermented milk beverages. Mouthfeel and flavour of the samples were assessed by a highly trained panel, and volatile analysis was performed by proton-transfer reaction mass spectrometry to determine the effect of hydrocolloids on the partition of flavour compounds in the headspace. CMC and HMP produced significantly higher thickness than PGA and XG; PGA caused a ‘gritty’ mouthfeel. The yoghurt aroma of the samples containing CMC and PGA was perceived as less intense compared with the control, consistent with a reduced concentration of key volatile compounds in the headspace of these samples.

Zeta potential of pectin-stabilised casein aggregates in acidified milk drinks

High-methoxy (HM) pectin is commonly used to improve the stability of acidified milk drinks (AMDs) and zeta potential measurements can aid in elucidating the mechanisms responsible for the improved stability. Pectin was added to an AMD model system in concentrations of 0.0%, 0.1%, 0.3% or 0.5% and the samples were subjected to heat treatment at 75 °C for 20 min; control samples were not heated. A change in zeta potential from positive to negative values with addition of pectin was observed. Increasing the pectin concentration resulted in a more negative zeta potential. Heat treatment caused a decrease in the numeric value of the zeta potential, which indicates a partial desorption of pectin from the protein aggregates.

In vitro evaluation and modification of pectinate gel beads containing trimethyl chitosan, as a multi-particulate system for delivery of water-soluble macromolecules to colon

Pectinate beads containing trimethyl chitosan chloride (TMC) as an absorption enhancer were prepared using Coomassie Brilliant Blue G 250 (CB) as a relatively high molecular weight water-soluble model drug. Effects of different formulation variables, such as cross-linker type, cross-linking time, cross-linker concentration, TMC: pectin ratio, pectin concentration and voltage of the bead generator, were assessed on in vitro bead characteristics by release and swelling–erosion studies. The bead formulation was optimized by factorial design. Some measures were taken to improve the bead characteristics and prolong their integrity during the gastrointestinal transit, such as biomineralization of the beads or coating them with high-methoxy pectin (PHM) or Eudragit L30-D 55 (EU). Possible CB-TMC complexation was investigated by Job's Plot method. The suitable system was obtained by coating the optimized core formulation with PHM or EU. TMC was found to form a complex with CB as a model anionic drug. Therefore, TMC-drug interactions can be used to modify the release characteristics of dosage forms.

Role of cosolutes in gelation of high-methoxy pectin. Part 2. Anomalous behaviour of fructose: calorimetric evidence of site-binding

Gels of high-methoxy pectin (DE 70; 1.0 wt%; pH 3.0) in the presence of fructose at concentrations of 50, 55, 60 and 65 wt% showed an intense endotherm followed immediately by an intense exotherm on heating. These transitions occurred over approximately the same temperature-range as initial gelation on cooling (characterised by low-amplitude oscillatory measurements of G′ and G″) and increased in magnitude with increasing concentration of fructose. The displacement of both transitions, and particularly the exotherm, to progressively higher temperature as the rate of heating was increased was much greater than anticipated from simple thermal lag, indicating that the underlying structural changes are slow. The proposed interpretation is that fructose is capable of site-binding to pectin in both the ordered (threefold helix) and disordered state; the endotherm is attributed to helix melting and displacement of fructose; the subsequent exotherm is attributed to re-attachment of fructose to disordered chains, and the slow kinetics of this process to the conformational mobility of disordered pectin. On cooling over the same temperature range, a single exotherm was observed; the absence of detectable splitting is attributed to rapid re-attachment of fructose to conformationally-rigid helices. The magnitude of this endotherm (Δ H≈20 J/g) is close to the value found for cosolutes that show no evidence of site-binding, and to the net change in enthalpy for the endothermic and exothermic processes observed on heating, suggesting that the values of Δ H for displacement and re-attachment of fructose are essentially equal and opposite, with the net change coming from formation or melting of threefold helices. A smaller thermal process at higher temperature (endothermic on heating and exothermic on cooling) is attributed to hydrophobic association, which was also seen as an increase in G′ and G″ on heating in two consecutive cycles of temperature change.

Role of cosolutes in gelation of high-methoxy pectin. Part 1. Comparison of sugars and polyols

Mixtures of high-methoxy pectin (DE 70; 1.0 wt%; pH 3.0) with ethan-1,2-diol, glycerol, xylitol, sorbitol, glucose, fructose or sucrose at concentrations of 50, 55, 60 and 65 wt% were prepared at 95 °C and changes in storage modulus ( G′) and loss modulus ( G″) during cooling to 5 °C, heating to 90 °C and re-cooling to 5 °C (at 1 °C/min) were measured at 1 rad s −1 and 0.5% strain. In all cases, the onset temperature for gelation during cooling and the moduli recorded at 5 °C increased with increasing concentration of cosolute. Both values, however, were substantially lower for the liquid cosolutes (ethan-1,2-diol and glycerol) than for mixtures incorporating the same concentrations of the solid cosolutes. The difference is attributed to inhibition of pectin–pectin interactions by pectin–cosolute interactions, which in turn are inhibited by cosolute–cosolute interactions, these being weaker for the liquid cosolutes than for the solids (as indicated by lower melting points). On heating, there was an initial reduction in modulus, with the same temperature-course as the increase on cooling; for the solid cosolutes, this was followed by an increase attributable to hydrophobic association of methyl ester substituents. No such increase was seen with the liquid cosolutes, but differential scanning calorimetry studies showed two (reversible) thermal transitions in all cases, one over the temperature-range of the initial gelation process on cooling and the other coincident with the increase in modulus on heating in the presence of the solid cosolutes. The absence of any detectable increase in modulus on heating with the liquid cosolutes is attributed to accumulation of cosolute around the polymer chains (i.e. pectin–cosolute interactions) promoting hydrophobic association between methyl ester groups on the same chain, or within small clusters of chains, with, therefore, no contribution to network structure. At high concentrations of the solid cosolutes, the increase in modulus on heating was followed by a decrease at higher temperature; this is attributed to excessive aggregation, and was reflected in lower moduli on subsequent re-cooling to 5 °C, in contrast to the enhancement in gel strength after heating and cooling that was observed at lower concentrations of the same cosolutes.

On the mechanism of stabilisation of acidified milk drinks by pectin

Acidified milk drinks (AMDs) need a stabiliser, e.g. a high methoxy pectin if whey formation is to be avoided. In this work the pectin added to AMDs in order to stabilise them was investigated in terms of effective and non-effective fractions, corresponding to a fraction adsorbed onto casein micelles and a fraction of pectin dissolved in the serum. It turns out that in acidified milk systems of practical concentration less than 20% of the pectin added is directly interacting with casein micelles. The remaining 80% is involved in a network with casein/pectin complexes but plays no role in stabilising the final product. This excess fraction is, however, crucial in effecting sufficient pectin adsorption during the mixing process of yoghurt and pectin solution. Stability in AMDs of practical milk concentrations is concluded to be at least partially associated with the existence of a network of pectin-coated casein micelles. Adsorbed pectin is found to be adsorbed irreversibly. Non-adsorbed pectin is immobilised in a weak network consisting of pectin-coated casein micelles and non-adsorbed pectin.

Monovalent salt-induced gelation of enzymatically deesterified pectin.

Pectin gels were induced by monovalent salts (0.2 M) concurrently with deesterification of high methoxy pectin using a salt-independent orange pectin methylesterase (PME). Constant pH was maintained during deesterification and gelation. If salt or PME was absent, the pectin did not form a gel. The gel strength was influenced by both pH and species of monovalent cation. At pH 5.0, the pectin gel induced by KCl was significantly stronger than the NaCl-induced gel. In contrast, a much stronger gel was produced in the presence of NaCl as compared to KCl at pH 7.0. LiCl did not induce pectin gelation at either pH. Molecular weights of pectins increased from 1.38 x 10(5) to 2.26 x 10(5) during NaCl-induced gelation at pH 7. One proposal to explain these pectin molecular weight changes is a hypothetical PME transacylation mechanism. However, these pectin molecular weight changes can also be explained by metastable aggregation of the enzymatically deesterified low methoxy pectin. We postulate that gelation was induced by a slow deesterification of pectin under conditions that would normally salt out (precipitate) low methoxy pectin in the absence of PME.

Viscoelasticity of oxidized starch/low methoxy pectin mixtures in the presence of glucose syrup

The structural properties of mixtures of pectin, oxidized starch and glucose syrup were investigated using small deformation dynamic oscillation. In the absence of added calcium, preparations of low methoxy pectin with glucose syrup formed viscous solutions, which remained crystal‐free at subzero temperatures. Samples of oxidized starch and glucose syrup, on the other hand, exhibited solid‐like behaviour because of the crystalline nature of the amylose‐like helices. Mixtures of the two polysaccharides with the co‐solute clearly showed phase inversion from liquid to solid‐like behaviour with increasing amounts of starch in the formulation. The transformation was reflected in the textural properties of samples, which varied from thick solutions to firm gels. The viscoelasticity of the system was modified further by the introduction of high methoxy pectin. Preparations of high methoxy pectin and glucose syrup formed rubbery gels whose amorphous nature underwent a glass transition during cooling.

A hydrodynamic study of the depolymerisation of a high methoxy pectin at elevated temperatures

The hydrodynamic properties (intrinsic viscosity, [ η]; infinite dilution sedimentation coefficient, s 20, w 0; weight average molecular weight, M w and translational frictional ratio, f/f 0) of a high methoxy pectin have been evaluated at various temperatures (20–60°C). A reduction in the value of all four hydrodynamic parameters is indicative of depolymerisation and is in agreement with an earlier study using viscometry [ Axelos, M.A.V., & Branger, M., (1993). Food Hydrocolloids, 7, 91–102]. The apparent linearity of the Mark – Houwink plot of log[ η] vs log M w suggests that the conformation of the pectin molecule does not change significantly over the temperature range studied. The evaluation of the Mark–Houwink viscosity exponent ( a=0.84) indicates a moderately extended structure. This then allows the calculation of the number of Kuhn statistical lengths per chain from the adapted ‘blob’ theory of Dondos [ Dondos A. (2001). Polymer, 42, 897–901]. The weight average number of Kuhn statistical lengths per chain is reduced from (170±10) to (125±10) when the temperature is increased from 20–60°C. This may be of significance as many high methoxy pectins are exposed to high temperatures during processing in both the food and pharmaceutical industries.

Pressure Effects on Whey Protein–Pectin Mixtures

A food material science approach using microscopy, rheology and denaturation assessment of proteins was applied to describe the behaviour of mixtures of a whey protein isolate (WPI) and a high methoxy pectin (HM-pectin) upon high-pressure treatment (200 to 800 MPa at 25 or 40 °C and holding time of 10 min). The results of high-pressure treatment were compared to a pure heat treatment at 75 °C (5–20 min) and 85 °C (10 min). Similar textures could be obtained after high-pressure treatment of the mix at ambient temperature at all pressure levels tested (200–800 MPa) and after temperature treatments at 75 °C up to 10 min. Significant changes were only obtained in phase separating WPI/HM-pectin mixtures if treated at 40 °C and pressures>400 MPa and after heat-treatment at 85 °C for 10 min, where total WPI denaturation was above 60%. Under such conditions the protein-enriched phase gelled and significantly changed the overall texture as measured by rheology. In the presence of pectin, protein denaturation was decreased in both pressure and temperature treated samples. Microscopic analysis showed that structure formation depends on the processing history. Compared to a pure heat treatment, pressure offers a greater flexibility for fine-tuning the protein denaturation due to an increased freedom in processing parameters (pressure, holding time and temperature).

First- and second-approximation calculations in the relaxation function of high-sugar/polysaccharide systems

The distribution function of Maxwellian relaxation times ( Φ) was derived from the small- deformation dynamic properties of high-sugar/agarose, /deacylated gellan and /high-methoxy pectin mixtures. First-approximation calculations of Φ employed the time derivative of the experimentally measured storage and viscous moduli, with the two traces converging at the theoretically predicted slope of −0.5. Second-approximation calculations were based on Φ, as derived by the first approximation, being a simple power function of relaxation times ( τ − m ). The slope m was measured at various points and used to derive correction factors for shifting the relaxation function to the second approximation. Thus, values of Φ calculated from G′ and G″ were brought into satisfactory agreement, particularly in the recorded portion of the glass transition region. Once the function Φ is accurately determined, it can be readily used for calculations of other viscoelastic properties.

Effect of oxidised starch on high methoxy pectin–sucrose gels formed by rapid quenching

The effect of progressive replacement of sucrose by oxidised starch in mixtures with high methoxy pectin (1.0 wt%; degree of esterification 70.3%; pH 3) has been characterised by low amplitude oscillatory measurements (1% strain) of storage modulus ( G′), loss modulus ( G″), loss tangent (tan δ) and complex dynamic viscosity ( η ∗) across the frequency range 0.1–100 rad s −1. Samples were prepared at 90°C, and measured 1 h after rapid quenching to 5°C. In the main series of experiments, the total concentration of cosolute (sucrose plus oxidised starch) was held constant at 65 wt%, and the starch concentration was varied between 0 and 50 wt% (i.e. 65–15 wt% sucrose). The observed moduli showed an initial sharp decrease (particularly evident at low frequency) and subsequent steady increase with increasing concentration of starch. Critical gel spectra were recorded at ∼9 wt% starch (56 wt% sucrose) and ∼41 wt% starch (24 wt% sucrose). The moduli of the mixed systems at low starch concentration, before the loss of gel structure, remained close to those for 1.0 wt% pectin at the same sucrose concentrations but in the absence of starch, and at high starch concentrations became close to those of the starch component in the absence of pectin. In the intermediate region, however, the overall moduli were substantially (up to ∼10×) higher than those of the individual constituents. The origin of this behaviour was explored by quantitative analysis of the results from a subsidiary series of experiments in which the sucrose concentration was held fixed at 50 wt% and the concentration of oxidised starch (in mixtures with 1.0 wt% pectin at pH 3) was varied between 0 and 15 wt%. The observed values of G′ and G″ at 0.1, 1.0, 10 and 100 rad s −1 could be matched, to within experimental error, by values calculated on the basis of excluded volume effects within a monophasic solution, with the volume occupied by 1 g of oxidised starch corresponding to ∼1.8 g of solvent and the volume occupied by 1 g of (partially associated) pectin corresponding to ∼20 g.

Co-gelation of high methoxy pectin with oxidised starch or potato maltodextrin

In a continuation of the work reported in the preceding paper, the effect of oxidised starch on gelation of high methoxy pectin was studied under different experimental conditions. The main changes in procedure were: (i) gelation was induced by slow cooling (1°C min −1) instead of rapid quenching; (ii) the pectin concentration was reduced from 1.0 to 0.5 wt%; and (iii) mixtures were prepared at pH 4 and subsequently acidified to pH 3, rather than being prepared directly at pH 3. The temperature-course of structure formation (increase in G′ and G″) during cooling (from 95 to 5°C), and the final moduli at 5°C, are consistent with the conclusions reached for the mixtures gelled by quenching: (i) the effective concentration of both polymers is raised by mutual exclusion; and (ii) the initial reduction in moduli observed on partial replacement of sucrose by oxidised starch is due to the reduction in sucrose content, rather than to the presence of starch. An analogous series of experiments, under identical conditions, was carried out using potato maltodextrin in place of oxidised starch. In contrast to the pectin–oxidised starch systems, there was no evidence of any significant exclusion effects in the pectin–maltodextrin mixtures, but the changes in moduli observed during cooling indicate that maltodextrin, unlike oxidised starch, is almost as effective as sucrose in promoting self-association of high methoxy pectin at acid pH. These differences in behaviour are attributed to a high population of short, linear chains and oligomeric fragments in maltodextrin, facilitating segmental contacts with pectin, in contrast to the densely branched (partially depolymerised amylopectin) structure of oxidised starch, which will limit segmental contacts, but resist penetration by pectin chains, with consequent increase in effective concentrations of pectin and starch.

Effect of pH, sugar type and thermal annealing on high-methoxy pectin gels

The effect of cosolutes on the formation and properties of high-methoxy pectin gels (pectin concentration 0.5 wt%; DE 70.3) has been investigated by small-deformation oscillatory measurements of storage and loss moduli ( G′ and G″) and by compression testing at 5°C. Solutions were prepared at ∼95°C and pH was varied by addition of citric acid. With 65 wt% sucrose as cosolute, a critically crosslinked network was formed on cooling to 5°C at pH 4.7. The changes in moduli observed for this composition during cooling were fully reversible on heating, with no thermal hysteresis. Progressive reduction in pH to below the p K a of the galacturonic acid residues caused a sharp, sigmoidal increase in moduli at 5°C, attributed to association of pectin chains into a pectinic acid network. On heating to ∼15°C, the gel moduli decreased, following the same temperature-course as the changes observed on cooling, but further increase in temperature caused large increases in moduli, consistent with hydrophobic association of methyl ester substituents. These increases became more pronounced as the strength of the gel structure at low temperature was decreased by reduction in sucrose concentration or increase in pH. Heating to 95°C and re-cooling caused a substantial increase in gel strength ( G′ from small-deformation measurements and breaking stress under compression), which is attributed to segregation of chain sequences of high and low ester content during thermal cycling, with the less highly esterified sequences giving stronger pectinic acid junctions at 5°C. Replacement of sucrose by glucose or fructose caused large changes in gelation temperature, in the order: fructose<sucrose<glucose. The departure from the normal order of effectiveness (fructose<glucose<sucrose) anticipated from compatibility with water structure and observed experimentally for the same sugars in combination with other biopolymers is attributed to inhibition of intermolecular association by strong hydrogen-bonding of primary alcohol groups on the sugars (2 per residue in fructofuranose, 1.5 per residue in sucrose, and 1 per residue in glucopyranose) to the carboxylic acid and methyl ester groups of pectin.

Pressure- and heat-induced gelation of mixed β-lactoglobulin/polysaccharide solutions: scanning electron microscopy of gels

This study concerns the microstructure of pressure-induced gels (P-gels, 450 MPa, 25°C, 30 min) of mixed β-lactoglobulin/anionic polysaccharide solutions (12% w/w protein, pH 7.0, plus 0.1–1% w/w sodium alginate, low methoxy pectin or high methoxy pectin). Mixed biopolymer solutions were compatible at ambient temperature and atmospheric pressure in the concentration range studied. Scanning electron microscopy of mixed P-gels from 12% protein-0.1% polysaccharide (PS) solutions revealed microalveoles with a honeycomb structure, suggesting that pressure promoted the formation of water in water emulsion with two distinct phases of different protein and PS concentrations. Increasing PS concentration from 0.1 to 1% (w/w) progressively converted the micro-alveolated structure of P-gels into a coarser porous structure with large pores and “pillars”, and protein microparticles located in the pores. The trend to phase separation and protein microparticulation increased with PS concentration and varied in the following decreasing order: ALG≫LMP≫HMP. Phase separation phenomena and the resulting P-gel microstructure probably depend on the net negative charges carried by the PS and on the imparted solution viscosity. Heating the mixed protein–polysaccharide solutions at 87°C for 40 min also induced phase separation, porous structures and protein microparticulation. The results suggest that phase separation in the presence of an anionic polysaccharide is triggered by β-lactoglobulin unfolding and/or aggregation.

Viscoelasticity of Oxidised Starch and Low Methoxy Pectin in the Presence of Glucose Syrup

The structural properties of mixtures with pectin, oxidised starch and glucose syrup were investigated using small deformation dynamic oscillation. The composition of the mixture, pH and temperature course of analysis were designed to imitate the development of confectionery products. In the absence of added calcium, preparations of low methoxy pectin with glucose syrup form viscous solutions, which remain crystal-free at subzero temperatures. Samples of oxidised starch and glucose syrup. on the other hand, exhibit solid-like behavior due to the crystalline nature of the amylose-like helices. Mixtures of the two polyssacharides with the co-solute show clearly the phase inversion from liquid to solid-like behavior with increasing amounts of starch in the formulation. The transformation is reflected in the textural properties of samples which vary from thick solutions to firm gels. The viscoelasticity of the system can be modified further by the introduction of high methoxy pectin. 1hus preparations of high methoxy pectin and glucose syrup form rubbery gels whose amorphous nature undergoes a glass transition during cooling. The energetic requirement for the formation of the biological rubber was in good agreement with corresponding data in the literature.

Studies on Pectins as Potential Hydrogel Matrices for Controlled-Release Drug Delivery

Polymeric hydrogels are widely used as controlled-release matrix tablets. In the present study, we investigated high-methoxy pectins for their potential value in controlled-release matrix formulations. The effects of compression force, ratio of drug to pectin, and type of pectin on drug release from matrix tablets were also investigated. The results of the in vitro release studies show that the drug release from compressed matrix tablets prepared from pectin can be modified by changing the amount and the type of pectin in the matrix tablets. However, compression force did not significantly affect the drug release. The mechanisms controlling release rate were discussed with respect to drug diffusion through the polymer matrices, but may be more complex.

Separation of Egg White Lysozyme by Anionic Polysaccharides

ABSTRACTAnionic polysaccharides (Na‐alginate, Na‐carboxyl‐methyl‐cellulose, high methoxy pectin and κ‐carrageenan) were evaluated for their suitability towards simple and more efficient separation of lysozyme from salted or fresh duck eggs and hen egg whites for use in foods. Only κ‐carrageenan interacted and formed precipitates with lysozyme. Recovery of lysozyme from fivefold diluted salted duck egg whites was 60–65% and 78–81% from fresh duck and hen egg whites using 0.7%κ‐carrageenan. The recovered lysozyme from the salted duck egg whites was stable during storage at 4°C for 35 days.

Effect of high-methoxy pectin on properties of casein-stabilized emulsions

We report on the effect of high-methoxy pectin on the stability and rheological properties of fine sunflower oil-in-water emulsions prepared with αs1-casein, β-casein or sodium caseinate. The aqueous phase was buffered at pH 7.0 or 5.5 and the ionic strength was adjusted with sodium chloride in the range 0.01–0.2 M. Average emulsion droplet sizes were found to be slightly larger at the lower pH and/or with pectin present during emulsification. Analysis of the serum phase after centrifugation indicated that some pectin becomes incorporated into the interfacial layer at pH 5.5 but not at pH 7.0. This was also supported by electrophoretic mobility measurements on protein-coated emulsion droplets and surface shear viscometry of adsorbed layers at the planar oil–water interface. A low pectin concentration (∼0.1wt%) was found to give rapid serum separation of moderately dilute emulsions (11vol% oil, 0.6wt% protein) and highly pseudoplastic rheological behaviour of concentrated emulsions (40vol% oil, 2 wt% protein). We attribute this to reversible depletion flocculation of protein-coated droplets by non-adsorbed pectin. At ionic strength below 0.1 M, the initial average droplet sizes, the creaming behaviour, and the rheology were found to be similar for emulsions made with either of the individual caseins (αs1 and β) or with sodium caseinate. At higher ionic strength, however, whereas emulsions containing β-casein or sodium caseinate were stable, the corresponding αs1-casein emulsions exhibited irreversible salt-induced flocculation which was not inhibited by the presence of the pectin.

Extraction and Physico-Chemical Characterization of Pectins from Sugar Beet Pulp

Sugar beet pulb (SBP) pectins were isolated from the proteolysis hydrolysates or extracted by HCl (pH 1.5, 85°C for 1–6 h and pH 1.5, 4 h at 40–90°C), ethylenediamine tetraacetate (EDTA, 0.2%, pH 3.3, 85°C, 1, 4 h), ammonium oxalate (AO, 0.2%, pH 3.3, 4 h), and sodium hexametaphosphate (SHP, 0.2%, pH 3.3, 4 h). An optimal HCl extraction (pH 1.5, 85°C, 4 h) yielded 16.94% pectin from the dewaxed and protein-free SBP. The HCl extracted pectin contained 84.61% galacturonic acid and low ash, 2.69%. The degree of methylation was over 60% in all the pectin samples, indicating that the sugar beet pectin is a high methoxy pectin. The degree of acetylation ranged between 10.80% and 14.78%, resulting in poor gelling capacity of the pectins. The pectins also contained 7.21% to 10.73% neutral sugars, which were mainly arabinose and galactose. The molecular-average weights ranged between around 60000 and 90000 Da. It was found that lignin in SBP cell walls is tightly associated with pectin. Besides the esterified ferulic acid, seven other phenolic monomers, principally vanillin and p-hydroxybenzoic acid, were initially identified in the alkaline nitrobenzene oxidation of bound lignin in the isolated pectin samples.