Rheological and high gelling properties of mango (Mangifera indica) and ambarella (Spondias cytherea) peel pectins

Ambarella and mango peels are good sources of pectins (15–20%), with high degree of methylation (60–78%) and high molar masses. Ambarella and mango ( Améliorée and Mango varieties) peel pectins were extracted using HCl or oxalic acid/ammonium oxalate (OAAO). Purified pectins were analysed for their flow behaviour and phase diagrams were established at pH 3 as sucrose vs. pectin concentration. The gelation kinetics and mechanical spectra of these pectin gels were studied and compared to those of commercial citrus (lime) pectins. At a concentration of 1% (w/v), all pectic solutions had a shear thinning behaviour but at 0.6% (w/v), only OAAO-extracted pectins exhibited such behaviour. Phase diagrams showed that at pH 3, gelation of OAAO mango extracted pectins was possible at low polymer concentration (0.2%; w/w) for a sucrose concentration of 60% (w/w). OAAO-extracted pectins exhibited a higher gelling ability than HCl-extracted ones. Sucrose (45–50%) and pectin (0.2–0.6%) concentration had a deep impact on the gel strength. Our results enable to conclude that the OAAO extraction from mango and ambarella peels allowed the recovery of pectins that exhibit high gelling properties.     

Pectin Extraction from Lemon By-Product with Acidified Date Juice: Effect of Extraction Conditions on Chemical Composition of Pectins

Mixtures of date and lemon pectins were extracted from lemon by-product with acidified date juice under different conditions of temperature, pH and time. Individual pectins from date and lemon, respectively, were also extracted using the same experimental conditions, then analysed and compared to pectin mixtures. It was found that the use of extreme conditions resulted in higher galacturonic acid content, lower degree of methylation, lower neutral sugar content, lower molecular weight and darker colour pectins. Examination of the individual neutral sugars showed that the main ones were galactose (1.6–5.4%), arabinose (1.6–4.2%) and rhamnose (0.5–0.8%). The Gal A/Rha molar ratios varied from ∼53 to ∼149. Moreover, mixture of pectin extracted at the optimal extraction conditions (84.34 °C, pH 2.8 during 3 h 34 min) had interesting properties, with a high galacturonic acid content (63.4%), low degree of methylation (∼35%) and a mass molecular weight of about 243 kg/mol.     

High‐temperature conditioning induces chilling tolerance in mandarin fruit: a cell wall approach

BACKGROUND: High‐temperature conditioning (3 days at 37 °C and 95% relative humidity), which protects ‘Fortune’ mandarins from chilling injury (CI), manifested as pitting in the outer part of the peel (flavedo), was applied prior to cold storage (2 °C) in order to investigate the involvement of cell wall composition in the chilling tolerance of mandarins. RESULTS: Both low‐temperature storage and high‐temperature conditioning barely modified the alcohol‐insoluble substance (AIS) content or the degree of pectin esterification in the flavedo. Water‐soluble pectins (WSP) were higher in heat‐conditioned than in non‐conditioned fruits at the onset of CI. In addition, the heat‐conditioning treatment was able to increase chelator‐soluble pectins (CSP) after short cold storage periods. Covalently bound polyuronides in alkali‐soluble pectins (ASP) increased only in fruits with high incidence of CI. Cellulose and hemicellulose increased at 2 °C in both conditioned and non‐conditioned fruits, indicating that these polysaccharides may be altered by low temperature but are not related to chilling‐induced damage. CONCLUSION: High‐temperature conditioning may reduce chilling‐induced flavedo pitting in ‘Fortune’ mandarin fruit by maintaining normal levels of WSP and increasing putative sites for calcium bridge formation within the cell wall, but not by inducing changes in other matrix cell wall components. Copyright © 2012 Society of Chemical Industry     

A light scattering study on the effects of pH on pectin aggregation in aqueous solution

Light-scattering measurements were carried out on pectins in aqueous solutions of pH ranging from about 4 to 2. The following pectin samples were used: three low methoxyl pectins which were demethylated by ammonia, acid and enzyme (all with a nearly similar methoxyl content from 6.1 to 6.2%), and pectin-NF with 12.04% methoxyl groups and sodium poly-galacturonic acid. When the pH of a 0.05% pectin solution containing 0.1 M NaCl was brought to pH 2 by adding HCl, the mol. wt and radius of gyration increased markedly, thus indicating that pectin molecules aggregate when the pH is lowered.     

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.     

Characterization of Pectins and Some Secondary Compounds from Theobroma cacao Hulls

ABSTRACT This paper describes the chemical characterization of cocoa hulls, a potential source of high-methoxyl pectins (HMP). The content of some antinutritive compounds and potentially toxic compounds is also reported. Use of 2-propanol is proposed for the preliminary clean-up of the hulls and for the washing of the gel. Antinutritive and potentially toxic compounds seem not to limit the use of cocoa hulls. Lindane and ochratoxin A were easily removed together with fat using 2-propanol during preliminary clean up. The pectins (partially purified, yield: 1.29 ± 0.08%) showed a high methoxylation degree (%DE) of 60.53 ± 6.09%, and a viscosity of 16,200 cPs (5 rpm 20 °C). Washing procedures permit the decrease of the gel acidity from pH 1.97 to pH 3.76.     

Effect of extraction conditions on the yield and purity of apple pomace pectin precipitated but not washed by alcohol

ABSTRACT:  A study of the influence of extraction conditions (pH: 1.5 to 2; temperature: 80 to 90 °C; extraction time: 1 to 3 h), on the yield and purity of apple pomace pectin without elimination of impurities by alcohol washing was carried out. The alcohol precipitate yields varied from 2.9% to 8.9% depending on the pH. At pH 1.5, these yields were higher than those obtained at pH 2 contrary to the galacturonic acid purity (%w/w). Compounds other than pectins were solubilized from the cell walls of apple pomace at pH 1.5, and they were precipitated with alcohol. The apple pectins obtained from the different extraction procedures were highly methylated (54.5% to 79.5%), especially when the conditions (temperature, pH) were drastic. Similar conclusions can be drawn for the neutral sugar content that decreased at pH 1.5 (arabinose, xylose, and galactose) or at the highest temperatures and extraction times (arabinose and galactose). The phenomenon of demethylation and pectin degradation of neutral sugars chains can be observed at acid pH, and for long extraction times. The presence of high quantities of mannose or fructose, glucose, and xylose in the alcohol precipitate showed that pectin precipitation with ethanol was not specific.     

柠檬皮高酯果胶的分步提取及表征

本研究采用草酸对柠檬皮进行分步提取,得到两种不同性能的高酯果胶(HMP-1、HMP-2),系统地探究了提取条件HMP-1和HMP-2得率和黏度的影响,对HMP-1、HMP-2进行物化性质表征,并通过原子力显微镜(AFM)进行微观结构观察。实验结果表明,在料液比1:20,pH 1.7,70℃1.5 h的反应条件下,HMP-1得率为19.22%,1%溶液的黏度为104.55 mPa·s,分子量为550.4 ku,酯化度为75.22%,胶凝度为218.24°SAG,在酪蛋白等电点附近具有较高的电位绝对值;在料液比1:10,pH 1.7,80℃1.5 h的反应条件下,HMP-2的得率为9.74%,1%溶液的黏度为49.23 mPa·s,分子量为424.7 ku,酯化度为64.34%,胶凝度为171.12°SAG。AFM结果表明,HMP-1呈现较长的线性形态,HMP-2则呈现较为分散、细碎的状态。本研究实现了柠檬皮果胶的分步提取,得到不同类型的果胶,有助于果胶的多元化发展及精准应用。     

De‐esterification pattern of Valencia orange pectinmethylesterases and characterization of modified pectins

BACKGROUND: Pectinmethylesterase (PME, E.C. 1.1.11) isozymes from Valencia orange preparations with different specific activities were used to de‐esterify citrus and sugar beet pectins. Enzymatic modification offers the opportunity to create pectins of tailored functionality and gelling ability. RESULTS: Based on nuclear magnetic resonance spectra, catalysis by all PME extracts produced block‐wise de‐esterification patterns in both citrus and sugar beet pectins. PME activity resulted in increased numbers of contiguous de‐esterified groups and decreased numbers of contiguous esterified groups. De‐esterification by PMEs increased the elastic property (G′) of citrus and sugar beet pectins in the presence of calcium from 10 to 571 and from 0.05 to 201 Pa, respectively. CONCLUSIONS: The results demonstrate the predilection of citrus PMEs toward block wise de‐esterification of pectins and the relationship between calcium binding ability and de‐esterification degree and patterning. Within a narrow range of de‐esterification (37–48%) and with a narrow distribution of contiguous groups, PME modification did not markedly change gelling ability. At lower or higher de‐esterification values, a 2‐fold increase or 50‐fold decrease, respectively in G′ values was observed. Copyright © 2008 Society of Chemical Industry     

De‐esterification of pectin by alkali,plant and fungal pectinmethylesterases and effect on molecular weight

Commercial high methoxyl pectin was de‐esterified using chemical saponification or by pectinmethylesterases. A commercial fungal pectin methyl esterase (PME) (EC 3.1.1.11), free of polygalacturonase, or a citrus Valencia PME was used to de‐esterify pectin enzymatically to a targeted degree of esterification. The apparent molecular weight of pectin did not change by extended times of Valencia PME treatment and ranged from 154100 to 183500. Fungal PME‐modified pectins had moderately increased apparent molecular weight that ranged from 123900 to 169800. The increase in molecular weight was attributed to aggregation. The molecular weight of pectins that were de‐esterified by alkali decreased from about 156200 to 91200. Citrus Valencia or fungal PME modification alters the charge of pectin without loss of high molecular weight. Copyright © 2005 Society of Chemical Industry     

Comparison of Dialysis and Metal Precipitation Effects on Apple Pectins

Metal precipitation as a purification method for pectins was investigated for effects on chemical composition (anhydrogalacturonic acid, methoxyl and degree of esterification and neutral sugars), and molecular properties (molecular weight and intrinsic viscosity) in comparison with dialysis. The Cu(II) ions were used to separate pectins from non-uronide components, and then the Cu(II) ions complexed with pectins were removed by 1% acid alcohol or EDTA treatment. The contaminants were removed more effectively by metal precipitation than dialysis. Acid alcohol did not affect degree of esterification of pectins, whereas it significantly cleaved the neutral sugar side chains. Pectins treated with acid alcohol had lower molecular weights, but larger intrinsic viscosities indicating their more linear nature compared to pectins treated with EDTA.     

Fruit pectins – A suitable tool for screening gelling properties using infrared spectroscopy

Found in higher plants, pectins are natural hydrocolloids whose extraction is controversial as it is condition-dependent. To optimize the methodology for extracting and isolating pectins and verifying the effect on their structural characterization, a factorial 2³ assay was planned, using the following independent variables: pH, duration of heating and nature of alcohol in fruits with different kinds of morphologies. The fruits were grouped into those that produce good jams and jellies (group I), those that have a variable chemical composition and contain fiber (group II), and those that contain starch (group III). The results were compared using variance analysis and Duncan test. The degree of methoxylation (DM) of the pectin isolated from the mesocarp of citrus and guava fruits (whole) was associated linearly with all independent variables. However, the pectin yield was influenced only by pH and duration of heating. The interaction between the nature of alcohol and the duration of heating were shown to be significant, a longer heating time and ethanol being better for the two kinds of fruit. In group I, the pectins isolated showed best DM associated with high yield, whilst group II yield was below the limit for producing jams and jellies, despite high DM. Group I fruits displayed characteristics that favor gel formation, whilst group II and group III proved to be deficient in at least one of the dependent variables. This study has validated as analytical tool for isolating and characterizing the structure of pectins, mainly those naturally occurring in tropical fruits.     

Effect of debranching on the rheological properties of Ca-pectin gels

Water-soluble pectin (WSP) extract was subjected to controlled carrot pectin methylesterase treatment, thereby producing de-esterified pectin (DEP). Both WSP and DEP were incubated with a mixture of endo-arabinanase and α-L-arabinofuranosidase to yield partially debranched pectins (WSP_DBr and DEP_DBr respectively). Pectin samples were characterised in terms of degree of methylesterification (DM), neutral sugar content, and degree of branching (DBr). The characterised pectins were used for the preparation of pectin gels with high and low calcium ion (Ca²⁺) concentrations. The rheological characteristics of the produced gels were evaluated by means of small-amplitude oscillatory tests. These characteristics include network development of the gel, gel strength (G′), gel elastic character and gel type. Partial debranching of pectin resulted in a reduction of the arabinose content (by approximately 50%) and caused a slight decrease in polymer DBr. Gels produced from semi-dilute solutions of partially debranched pectins showed network development profiles similar to those prepared from semi-dilute solutions of the corresponding non-debranched polymers. Yet, the former gels showed lower G′ values, poor gel elastic character and a “weaker” nature as compared to the latter. Next to Ca²⁺ cross-links, the presence of long arabinose-containing side chains is suggested to play an important role in the rheological characteristics of Ca²⁺-pectin gels.     

Characterization of pectin extracted from banana peels of different varieties

Pectins were extracted from banana peels of five different varieties using citric acid solution. The chemical characteristics of banana peel pectins were investigated and compared with citrus peel and apple pomace pectins which were extracted under the same extraction conditions to assess the potential of banana peels as an alternative source of commercial pectin. The yield of banana peel pectins ranged from 15.89 to 24.08%. The extracted banana peel pectins were categorized as high methoxyl pectin with the degree of esterification between 63.15 and 72.03% comparable to those of conventional pectin sources from citrus peel (62.83%) and apple pomace (58.44%). The anhydrouronic acid (AUA) content of banana peel pectins varied from 34.56 to 66.67%. Among various banana varieties being studied, pectin from Kluai Nam Wa variety had the highest AUA content (66.67%) which met the criteria for food additive pectin indicating its commercial significance as an alternative pectin source.     

Structure and physical properties of pectins with block-wise distribution of carboxylic acid groups

The physical and the interfacial properties of pectins de-esterified by a specific block-wise enzymatic procedure were investigated. Two major types of block-wise de-esterified pectins with different internal distribution of carboxylic acid on the pectin chains were explored. Type C and type U pectins with the same degree of methylesterification are different and a more block-wise intramolecular distribution in comparison to commercial native apple pectin. The most ordered pectin (U63 pectin, 63% methylesterified pectin) has the highest electrophoretic mobility (ζ-potential). It reveals more pronounced intermolecular interactions since it exhibited, at low pH, the lowest circular dichroism intensity at shorter wavelength. U63 pectin (at acidic pH, without calcium addition) has a higher viscosity and formed a stronger gel compared to the less ordered C63 pectin and/or native apple pectin. X-ray patterns show that powdered U63 pectin is more crystalline than C63 pectin, while apple pectin is mostly amorphous. The modified pectin also, most effectively, reduced the surface tension (55 mN/m) and the interfacial tension (5.6 mN/m), probably due to the preferred surface orientation of the carboxylic groups at the water/air or water/oil interfaces.     

Thermodynamic compatibility of sodium caseinate with different pectins. Influence of the milieu conditions and pectin modifications

Combinations of pectins and caseins are ingredients of many food products. Therefore the thermodynamic compatibility of both components was examined to investigate the influences of environmental factors as well as of the structure of the pectin. High‐methoxyl pectin was demethoxylated and amidated, respectively, and tested for the compatibility with sodium caseinate under varying conditions of pH and ionic strength. The compatibility increased with increasing pH and decreasing ionic strength. Demethoxylated pectins were more and amidated pectins less compatible with the caseinate. Changes in the pectin hydrophilicity, solubility and molecular weight and possibly local interactions such as electrostatic attraction, hydrogen bonding and calcium bridges are involved in the compatibility of the components. The type and degree of the pectin modifications as well as the type, composition and properties of the protein were found to be of great importance for the thermodynamic compatibility.     

Extraction and Charcterization of Pectins from Sugar Beet Pulp

Conditions (pH, temperature, time) for the extraction of sugar beet pulp pectins were studied on a laboratory scale and transposed into a pilot plant. Good yields (～ 14%) of pectins are obtained if the pulp is treated at pH 1.0, 85°C for 1 hr. The characteristics of the pilot extracted pectins are very close to those of the laboratory ones, except for a lower molecular weight (～30,000 daltons). Their physicochemical properties confirm their poor gelling ability.     

OPTIMIZING STABILITY OF ORANGE JUICE FORTIFIED WITH WHEY PROTEIN AT LOW pH VALUES

Abstract The influence of temperature, heating time and pH on the stability of whey protein-fortified Valencia orange juice was determined by uronic acid content, degree of esterification (DE), % transmission measurements (%T) and capillary electrophoretic analysis of the juice-protein supernatants. Uronic acid content and charge of pectins showed no significant change in heat-treated samples with added proteins. The %T decreased with decreasing pH and increasing temperature and heating time for α-lactalbumin (α-lac), β-lactoglobulin (β-lg) and whey protein isolate (WPI). The lowest transmission values were shown at pH 3.0 and 85C. Capillary electropherograms confirmed more extensive juice-protein interactions in WPI and β-lg added juices than in those containing α-lac, especially at low pH, resulting in more stable juice-protein mixtures.     

Characterisation of pectins extracted from banana peels (Musa AAA) under different conditions using an experimental design

An experimental design was used to study the influence of pH (1.5 and 2.0), temperature (80 and 90 °C) and time (1 and 4 h) on extraction of pectin from banana peels (Musa AAA). Yield of extracted pectins, their composition (neutral sugars, galacturonic acid, and degree of esterification) and some macromolecular characteristics (average molecular weight, intrinsic viscosity) were determined. It was found that extraction pH was the most important parameter influencing yield and pectin chemical composition. Lower pH values negatively affected the galacturonic acid content of pectin, but increased the pectin yield. The values of degree of methylation decreased significantly with increasing temperature and time of extraction. The average molecular weight ranged widely from 87 to 248 kDa and was mainly influenced by pH and extraction time.     

Cell wall polysaccharides of bush butter (Dacryodes edulis (G Don) HJ Lam) fruit pulp and their evolution during ripening

Cell wall material was isolated as alcohol‐insoluble solids (AIS) from bush butter endocarp tissue at different stages of ripeness. AIS were then extracted with 0.05 M CDTA followed by increasing concentrations of KOH (0.05, 1 and 4 M respectively). The chemical extractions solubilised a total of 51.6–60.6% of AIS, the yields of CDTA extracts accounting for approximately 9.6–12.2% of AIS. The extracts as well as the residues were analysed for their sugar composition and protein and starch contents. CDTA extracted the bulk of uronic acid in AIS, but the uronic acid content (after dialysis) of these extracts showed a significant decrease as the fruits ripened (from 439 to 252 mg g^?1 between the first and the last degree of ripeness). Analysis of the CDTA extracts by anion exchange and size exclusion chromatography showed a gradual appearance of new pectic populations at low degrees of methylation and low molecular weights, indicating that CDTA‐soluble pectins are demethylated and depolymerised during ripening. The dilute alkali (0.05 M KOH) extracts were essentially composed of proteins in addition to a minor quantity of pectin. The 1 M KOH and principally 4 M KOH treatments led to the extraction of hemicelluloses, mainly xyloglucan‐like and mannan‐like polymers. These extracts also contained substantial amounts of protein and starch. No variation related to the degree of ripeness was visible in the sugar composition of the alkali extracts. The molecular weight distribution of the hemicelluloses did not change with the degree of ripeness. The final residues accounted for 21.4–27.3% of AIS and were mostly composed of glucose (827–908 mg g^?1). All these results suggested that only CDTA‐soluble pectins were involved in bush butter fruit softening. © 2001 Society of Chemical Industry