Degree Of Pectin Esterification Research Articles

Pectin Ultra-degradation Decreases the Force Required to Detach Ripe Fruit from the Calyx in Tabasco Pepper

Pectin metabolism was analyzed in tabasco pepper (Capsicum frutescens L.) to determine the metabolic process associated with the ease of fruit detachment from the calyx. The ease of fruit detachment (deciduous fruit) is a desirable trait in peppers that facilitates mechanical harvest. Two genotypes that differ in the fruit detachment force were used: `Easy Pick' (EZ), which requires a low force, and `Hard Pick' (HP), which requires higher force. Pectin dissolution in water from fresh-ripe EZ tissue was 20 times higher than from HP tissue. EDTA-soluble uronide from inactivated EZ cell wall, however, was only 1.8 times higher. Pectin dissolution was inversely correlated to the fruit detachment force and followed a sigmoidal curve during fruit ripening. Size-exclusion chromatography of EDTA-soluble polyuronides indicated that pectin was degraded in ripe fruit tissue from both genotypes. The degree of depolymerization, however, was more extensive in EZ fruit. Consequently, the ease of fruit detachment was attributed to pectin ultra-degradation. Total pectin content in dry tissue and ethanol/acetone-extracted cell wall was similar in both genotypes. Pectin content in dry tissue was maintained throughout ripening, while extracted cell wall pectin increased slightly. In contrast, the degree of pectin esterification of extracted cell wall decreased only in ripe EZ fruit. These results suggest that pectin de-esterification may have a role in the enhanced pectin depolymerization and consequently in the ease of fruit detachment of the EZ genotype.

Effect of polysaccharides on the stability and renaturation of soybean trypsin (Kunitz) inhibitor

Thermal denaturation and renaturation of soybean trypsin (Kunitz) inhibitor (STI) were studied by high-sensitivity differential scanning calorimetry in the presence of polysaccharides (dextran, and κ-carrageenans, gum arabic, pectins and dextran sulfate). This study was carried out under conditions of both thermodynamic incompatibility and complex formation of STI and polysaccharides. The presence of polysaccharides did neither influence the denaturation temperature nor the denaturation enthalpy of STI under conditions of their incompatibility with the protein. No polysaccharide (except gum arabic) affected the ability of STI to renature and recover its inhibitory activity after thermal denaturation. At acidic pH values, the protein was shown to form electrostatic complexes with pectins and dextran sulfate. Substantial destabilisation of STI bound to dextran sulfate was observed. In the case of STI/pectin complexes, either a decrease or increase in the stability of STI was observed depending on the complex composition and esterification degree of pectin. The mechanism behind the changes in stability of STI bound to the polysaccharide matrix is discussed. Thermal denaturation of STI in complexes with dextran sulfate and pectin was completely irreversible. This observation indicates a possibility of suppressing antinutritional activities of trypsin inhibitors in soy products.

Interactions and compatibility of ribuloso-1,5-bisphosphate carboxylase/oxygenase from alfalfa with pectin in aqueous medium

HPLC, dynamic light scattering, CD- and fluorescent spectroscopy, and phase analysis methods are used to study the effect of Coulomb and non-Coulomb interactions between alfalfa rubisco and pectin on their thermodynamic compatibility. In the acid region of pH, water insoluble interpolymer complexes stabilized by both the Coulomb and non-Coulomb bonds are formed. In the neutral and alkaline regions, the complexes soluble in water are formed via non-Coulomb bonds, due to both the hydrophobic interaction involving the ester groups of pectin and the hydrogen bonding between dissimilar molecules. The compatibility of these biopolymers is sensitive to the esterification degree of pectin. With the latter increasing, compatability increases at neutral pH, but decreases considerably in the acidic region.

Determination of pectin degree of esterification by diffuse reflectance Fourier transform infrared spectroscopy

A diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) method was developed to measure the degree of esterification (DE) of commercial pectin samples. The relationship between infrared spectroscopy data and titrimetrically determined DE values was investigated. The ester carbonyl band area (CO) occurring at a mean frequency of 1756 cm −1 had the highest correlation ( R 2=0.822) with the mean DE of the bands observed. The DE values of pectin samples calculated from the line fit equation were comparable to those obtained from the titrimetric method. Mean DE values obtained were within 3.23% for DE 71.6, 2.9% for DE 62, and less than 1% for DE 55.3 of values obtained by titrimetric method. Spectral variations due to sample source have to be considered in developing prediction equations using FTIR. DRIFTS can be a rapid, alternative method to titrimetric analysis of pectin DE.

Unsaturated oligogalacturonic acids are generated by in vitro treatment of pectin with human faecal flora

Pectins with a degree of esterification (DE) of 95, 66, 34 and 0%, respectively, were incubated in vitro with human faecal flora (pH 7.8). The concentration and composition of oligogalacturonic acids (oligoGalA) generated were determined using high-performance thin-layer chromatography (HPTLC) with UV and colorimetric detection. In the first period of the anaerobic degradation, the pectin macromolecules were fragmented into unsaturated oligoGalA as intermediate products by the action of bacterial pectate lyases. Depending on the incubation time and the DE of pectin, the amount of unsaturated oligoGalA having different degrees of polymerization changed continuously. These oligoGalA were present in the cultures for some hours. Mixtures of unsaturated di-, tri- and tetraGalA were the end products of a pectate lyase action. Later, the oligoGalA disappear as a result of their further fermentation by the gastrointestinal microflora under formation of short-chain fatty acids (SCFA). Low-esterified pectins were depolymerized and fermented faster than the highly esterified by the human faecal flora in vitro. Furthermore, a mixture of unsaturated oligoGalA prepared from pectic acid by the action of pectate lyase from Erwinia carotovora was completely fermented by human faecal flora.

Thermal and Calcium Pretreatment Affects Texture, Pectinesterase and Pectic Substances of Frozen Sweet Cherries

ABSTRACTFreezing causes loss of turgidity and firmness in sweet cherries. Thermal pretreatment at 50°C for 10 min followed by immersion in 100 mM CaCl2 and thermal pretreatment at 70°C/2 min with or without immersion in 100 mM CaCl2 prevented freezing‐induced loss of firmness. Thermal pretreatments increased the pectin fraction soluble in EDTA, reduced the degree of pectin esterification, and increased both the concentration of divalent cations in the cell wall and the pectinesterase activity bounded to the cell wall. Immersion in CaCl2 increased the concentration of Ca2+ cations in the cell wall and enhanced the effect of thermal pretreatments on pectinesterase activity.

Effect of the structural features of pectins and alginates on their thermodynamic compatibility with gelatin in aqueous media

Thermodynamic compatibility and phase equilibria were studied in aqueous systems containing gelatin with pectin or with sodium alginate. Pectins with various degrees of esterification, block and statistical distribution of free carboxyl and ester groups as well as alginates of various block-structures were used. It was found that at high ionic strength ( μ) of ≳0.2 the systems studied separated into two phases. The compatibility of macromolecular components was increased with an increase in esterification degree of pectin, local concentration of its ester groups and with a decrease in temperature and pH. An increase in the content of mixed MG-blocks in alginates increased their compatibility with gelatin. At low μ ( <0.15) and pH above isoelectric point of the protein the above systems exhibit a single-phase behavior. It is suggested that the dominant mechanism controlling compatibility of gelatin with anionic polysaccharides involves the creation of weakly bound complexes of various origins, which destruct at increased salt concentrations and temperatures.

Microbiological, Chemical, and Sensory Changes in Irradiated Pica De Gallo

ABSTRACTThe effects of gamma processing (1 kGy) and refrigerated storage (2°C) on microbiological, sensory, and chemical quality of pico de gullo was studied. Color, flavor, texture, odor, and heat sensory attributes were not affected by radiation treatment. The treatment decreased populations of aerobic mesophilic, heterofermentative, and total lactic microflora during storage. L‐ascorbic acid content declined 50% in response to gamma processing, but levels were similar in irradiated and nonirradiated samples after 6 wk. Pectin solubility was affected by radiation treatment. Gamma processing caused a reduction in pectin degree of esterification, and conversion of chelator soluble to dilute alkali soluble and nonextractable pectins.

DRY BEAN (PHASEOLUS VULGARIS) HARDENING and the CONSEQUENCES of PECTIN METHYLESTERASE ACTIVITY IN STORAGE

Pectin methylesterase (PME) activities (degree of pectin esterification) and hardness (Kramer shear force) of decorticated Malawi bean varieties (Phaseolus vulgaris) were evaluated at 4 and 8 months storage at 0.55 a w and 0.85 a w , and 16˚C and 35˚C. PME activities were significantly higher at 4 and 8 months than in controls (2˚C, 0.30 a w ) and at 8 versus 4 months, irrespective of a w . Hardening increased with storage time, temperature and a w . Varieties showed significant hardness differences. PME activity influence on hardness was not clearly revealed during the 8 month storage period in the current study

Enzyme activities in soft rot pathogenesis of potato tubers: Effects of calcium, pH, and degree of pectin esterification on the activities of polygalacturonase and pectate lyase

The activities of cell wall degrading enzymes were monitored during the maceration of potato tuber tissue by Erwinia carotovora subsp. atroseptica. Pectin-methylesterase activity was present in uninoculated tuber tissues. Polygalacturonase (PG), pectate lyase (PL), cellulase, protease, and xylanase activities appeared in a sequential manner 10, 14, 16, 19, and 22 h, respectively after inoculation. The pH of crude tissue extracts made over this time period changed from pH 6·3 to 6·7. The depolymerizing pectic enzymes produced in the tissues exhibited different characteristics. PG activity was inhibited by the divalent cations Ca 2+, Sr 2+, Ba 2+, Mg 2+ and its optimum pH was around 6·0. PL activity was enhanced by Ca 2+ and Sr 2+, but not by Mg 2+ and Ba 2+ and its optimum pH was around 8·5. At their optimal pHs both PG and PL enzymes attacked polygalacturonic acid in preference to pectin, but at pH 6·5 PL activity was greater on pectin. Both PGs and PLs generated a series of reaction products including galacturonic acid suggesting both exo- and endo-activity. At the beginning of the maceration process, between 12 and 14 h after inoculation, PG played the dominant role but thereafter the increasing levels of calcium and pH reduced activity. By 22 h after inoculation the pH and free Ca 2+ levels in the macerate enhanced PL activity. At pH 6·5 both a high level of free Ca 2+ and pectin, favoured PL activity. Thirty hours after inoculation six multiple forms of PL were detected in macerated tissues, with pIs between 8·0 and 10·7. PLs 2, 5, and 6 were the first formed of the PL isozymes during tissue maceration. Only PLs 1, 2, and 5 were detected in cultures of E. carotovora subsp. atroseptica.

Calcium content and cell wall polygalacturonans in potato tubers of cultivars with different susceptibilities to Erwinia carotovora subsp. atroseptica

The cell wall content of polygalacturonans and cell wall calcium in medullary tissues of six potato cultivars with different susceptibility to Erwinia carotovora subsp. atroseptica were investigated over a period of 3 years to determine parameters which correlated with soft rot resistance. The cell walls were isolated by discontinuous Percoll-gradients. A high correlation between cell wall content and the level of resistance was found. However the calcium content of the tissue, the polygalacturonan content of the cell walls and the degree of pectin esterification showed only a slight correlation with resistance. Total and non-esterified pectin in the medullary tissues correlated with resistance, but the amount of esterified pectin did not. In 1984 when tubers of the cultivar Atika were highly susceptible they had a high degree of pectin esterification and in consequence a low amount of non-esterified pectin. In contrast, in 1985 and 1986 the tubers of cv. Atika were less susceptible and the cell walls had a lower degree of esterification and high amounts of non-esterified pectin. In vitro experiments showed that the cell walls of low susceptible cultivars bound more calcium than the cell walls of highly susceptible cultivars.

Complexation of poly(Lys-Ala) and poly(Lys-Ala-Ala-Ala) with pectins and potassium oligogalacturonates

The selected model polypeptides poly(Lys-Ala) and poly(Lys-Ala-Ala-Ala) underwent a helix-forming interaction with potassium pectates and pectinates of various esterification degree (E) and with some potassium oligogalacturonates (n = 2-5, 9, 13). Formation of the complex quantitatively monitored by a circular dichroic measurement showed that the specific band distribution of charged side chains of lysine units at the surface of helical structure does not constitute grounds for the local mode of interaction. Potassium pectinate of esterification degree E 57%, corresponding to polypeptides by charge density, does not reveal enhanced complexation values. The complex-forming efficacy continuously decreases with the increase of the esterification degree of pectin. Saturation of charges of the polypeptide was achieved predominantly by the spatial action of the superhelical structure of D-galacturonate chains.

In Situ De‐esterification of lime pectin

AbstractThe in situ de‐esterification of pectin in lime pulp by the action of pectinesterase (PE) has been investigated. It has been shown that the degree of pectin esterification is reduced to about 20% when the pulp is held at pH 8.5 for 90 min. The rate of de‐esterification by the enzyme in situ is highest when the pH is in the range 7.5–9.0 and the NaCl concentration is 0.1–0.3M. At pH values above 9 chemical de‐esterification becomes important. The activity of extracted lime PE was shown to be almost independent of pH in the range pH 6.0–9.0. It is suggested that the difference between the behaviour of the extracted and the in situ enzyme is due to the fact that the latter needs to be solubilised before it can act on some of the pectin in the pulp. In support of this it is found that the proportion of lime PE which can be extracted from the pulp decreases with decreasing pH and ionic strength, reflecting electrostatic binding to the cell wall.

Binding of lead and chromium(III) cations to pectin

Binding of Pb2+ ions to magnesium pectinates was studied by dialyzation technique in relation to their esterification degree (E) in the interval E = 0 to 84,7%, at an ionic strength I = 0.30. It has been found that the binding of Pb2+ ions to pectinates proceeds according to the theory of multiple equilibria. The values of stability constant K and selectivity coefficient KPbMg evidence the high selectivity of pectinates towards Pb2+ ions. Both those constants are, in contrast with value corresponding to other bivalent cations (e.g.Ca2+, Sr2+), independent on the esterification degree of pectin in the E 50% range. A strong binding of Pb2+ to carboxyl groups takes place also at a high esterification degree of pectin. The exchange of Cr3+ 3 K+ was investigated with a model preparation of potassium pectate crosslinked with epichlorhydrin by a batch method at various pH of equilibrium solutions (I = 0.15). Potassium pectate was shown to be a highly selective ion exchanger towards Cr3+. The binding of Cr3+ to pectate also occured in a sufficient extent at a low pH of equilibrium solutions (pH 3). Due to a very strong binding of Cr3+ to pectate a substantial shift of dissociation equilibrium of carboxyl groups in favour of further binding of Cr3+ ions occured.

TECHNOLOGICAL ASPECTS OF HIGH QUALITY RAW MATERIAL OBTAINING FOR PECTIN PRODUCTION

&#x0D; The article is devoted to the study of the chemical composition, physical and thermal-pfysical characteristics of damp apple pomaces and the identifying patterns of influence of drying temperature the functional composition and gel-forming ability of pectin. The research is aimed at obtaining initial data for the subsequent calculation of the main technological, hydro-mechanical, thermal, structural and economic characteristics of devices for drying the plant raw materials, ensuring the environmental safety and high quality of pectin-containing raw materials, the reducing heat and energy costs. As a result of the study of the thermal characteristics of apple pomaces, the critical points (temperature conductivity – 16.5 x 10-8 m2/s, thermal conductivity – 0.28 W/m K, heat capacity – 1627 j/(kg K)) at a humidity of 56 % are determined, which characterizing the transition from the extraction of weakly bound moisture to the extraction of moisture with strong bonds (colloidal, adsorption). It was found that the pomaces obtained from apples of late ripening have a higher content of solids (21-23 %), soluble pectin and protopectin (2.5-4.5 %). Dried pomaces obtained from apple varieties of late ripening contain up to 25 % pectin, which allow us to recommend them as a source of raw materials for the production of pectin. The optimum modes of preliminary washing of raw materials are offered, allowing to the remove the ballast substances as much as possible. It is established that when the drying temperature increases, the destructive processes are catalyzed: the strength of the pectin jelly and the uronide component and the degree of pectin esterification are reduced. The optimum drying temperature of damp apple pomaces is 80 0C, at which the quality of pectin extracted from the dried raw materials is maintained as much as possible. It is shown that the most effective for the pectin production is a fraction with a particle size of 3-5 mm, which allow us to extract up to 71 % of pectin from raw materials.

Relation of Pectic and Fatty Acid Changes to Respiration Rate During Ripening of Avocado Fruits

SUMMARYThe ripening of a lot of hard mature avocado fruits (Persea americana Miller, CW. MacArthur) was followed at 15°C by measuring respiration rate and softening. The climacteric rise in respiration was accompanied by rapid softening of the flesh, a drop in content of protopectin and in degree of pectin esterification, and a rise in soluble pectin. Eight fatty acids were identified in the oil, but the oil composition did not change significantly, suggesting that the storage oil of the tissue has no major metabolic role in fruit ripening.