Carrot Pectin Research Articles

Structural and rheological properties of diluted alkali soluble pectin from apple and carrot

Pectin, a complex polysaccharide found in plant cell walls, plays a crucial role in various industries due to its functional properties. The diluted alkali-soluble pectin (DASP) fractions that result from the stepwise extraction of apples and carrots were studied to evaluate their structural and rheological properties. Homogalacturonan and rhamnogalacturonan I, in different proportions, were the main pectin domains that composed DASP from both materials. Atomic force microscopy revealed that the molecules of apple DASP were longer and more branched. A persistence length greater than 40 nm indicated that the pectin molecules deposited on mica behaved as stiff molecules. The weight-averaged molar mass was similar for both samples. Intrinsic viscosity values of 194.91 mL·g−1 and 186.79 mL·g−1 were obtained for apple and carrot DASP, respectively. Rheological measurements showed greater structural strength for apple-extracted pectin, whereas carrot pectin was characterized by a higher linear viscoelasticity limit. This comparison showed that the pectin fractions extracted by diluted alkali are structurally different and have different rheological properties depending on their botanical origin. The acquired insights can enhance the customized use of pectin residue and support further investigations in industries relying on pectin applications.

CHARACTERIZATION AND PHARMACEUTICAL EVALUATION OF DAUCUS CAROTA PECTIN AS A SUSPENDING AGENT IN ORAL DOSAGE FORMS

Background: Suspensions are equilibrated two-phased thermodynamically unstable systems increasingly used in the stability and bioavailability enhancement of a myriad of drug substances. Biodegradable, biocompatible and cost-effective biopolymers such as pectin are becoming popular alternative suspending agents to decrease sedimentation and ensure uniformity and accuracy in drug dosing. Nevertheless, limited commercial pectin sources with ideal gelling properties necessitate the search for novel sources such as carrots, a versatile vegetable. Objectives: The study therefore centred on the characterization and pharmaceutical evaluation of the suspending qualities of Daucus carota (carrot) pectin acquired from the conventional acid extraction procedure. Methodology: Fresh carrots were acquired, authenticated and processed before pectin extraction. The pectin extracted was characterized and evaluated for phytochemical properties such as proximate composition and degree of esterification. Different concentrations (1% and 2%) of carrot pectin and acacia gum (as a standard) were utilized in formulating paracetamol suspensions as suspending agents. Results: The pectin yield was 11.6% and contained glycosides, tannins, saponins, and phenols. FTIR analysis identified all the essential pectin functional groups while other characterization parameters showed quality high methoxyl pectin. Carrot pectin suspensions demonstrated significantly (P < 0.01) lower re-dispersibility and sedimentation rate when compared to acacia. The flow rate and sedimentation volumes were however non-significantly different. Conclusion: The characterization and suspending properties of carrot pectin have been successfully evaluated. Ultimately, acacia gum can be substituted with carrot pectin as a suspending agent.

Structural and emulsion stabilizing properties of pectin rich extracts obtained from different botanical sources

The presented research studied the emulsifying and emulsion stabilizing capacity of pectin samples isolated from different plant origin: apple, carrot, onion and tomato. The acid extracted pectin samples showed distinct structural properties. Specifically, apple pectin showed a high degree of methylesterification (78.41 ± 0.83%), carrot pectin had the lowest concentration of other co-eluted cell wall polymers, onion pectin displayed a bimodal molar mass distribution suggesting two polymer fractions with different molar mass and tomato pectin was characterized by a high protein content (16.48 ± 0.05%). The evaluation of the emulsifying and emulsion stabilizing potential of the pectin samples included investigating their ability to lower the interfacial tension next to a storage stability study of pectin stabilized o/w emulsions. Creaming behavior as well as the evolution of the oil droplet size were thoroughly examined during storage using multiple analytical techniques. Overall, smaller oil droplet sizes were obtained at pH 2.5 compared to pH 6.0 indicating better emulsifying capacity at lower pH. The lowest emulsion stability was observed in emulsions formulated with tomato pectin in which weak flocculation and relatively fast creaming affected emulsion stability. Onion pectin clearly showed the most promising emulsifying and emulsion stabilizing potential. At both pH conditions, emulsions stabilized by the onion pectin sample displayed highly stable oil droplet sizes during the whole storage period. The presence of the two polymer fractions in this sample can play an important role in the observed stability. In future work, it could be evaluated if both fractions contribute to emulsion stability in a synergistic way. In conclusion, this work showed that pectin samples extracted from different plant origin display diverse structural properties resulting in varying emulsifying and emulsion stabilizing potential. Polymer molar mass potentially plays a major role in the structure-function relation.

Pulsed electric field and mild thermal processing affect the cooking behaviour of carrot tissues (Daucus carota) and the degree of methylesterification of carrot pectin

For the first time, the effect of pulsed electric field (PEF) and mild thermal processing on the texture of cortex and vascular carrot tissue during subsequent thermal processing (i.e. cooking behaviour) was compared and the degree of methylesterification (DM) of pectin from the pretreated tissues was investigated. The PEF and mild thermal pretreatment slowed down the cooking behaviour of the carrot tissues, especially when the pretreatments were combined. The DM of pectin from vascular tissue was lowered after both types of pretreatments, the effect being most pronounced in the case of the combination of the PEF and mild thermal pretreatment. In contrast, the DM of cortex pectin only decreased after the mild thermal pretreatment and after the combination pretreatment. This study demonstrates that besides mild thermal pretreatments also PEF pretreatments can be considered in the context of texture preservation of thermally processed fruits and vegetables.

Carrot pectin enriched fraction as a functional additive: Antioxidant and gelling effects in a model spreadable chia oil-in-water emulsion

An orange-colored pectin-enriched fraction previously obtained from discarded carrots (CPEF; 42%-methylated, 14%-acetylated, 50% uronic acids) through high-power-ultrasound and bacterial hemicellulase, carrying carotenes, lutein, and α-tocopherol, was evaluated as a food additive for its capacity to stabilize a model spreadable 20:80 w/w chia-oil-in-water emulsion. The optimal formulation for physical stability after 45 days at 25 °C was first determined through a Box-Behnken design with three independent variables (CPEF and Tween 80 concentrations, and ultrasound-emulsifying time). The optimized CPEF emulsion constituted a calcium-crosslinked “weak-gel type” network formed by the contribution of oil droplets. During storage, its elastic modulus increased probably by CPEF adsorption at the interface. In the optimized emulsion, CPEF prevented oil-phase oxidation by the air-oxygen entrapped, through the 45 day storage (peroxide index: 7.6meq/kg oil-phase; TBARS: 6.0 mg MDA eq/kg oil-phase), based on the differential partition of antioxidants between the interior of the oil droplets (apolar carotenes) and the oil-water interface (more polar tocopherol), the latter formed by the nonionic Tween 80 emulsifier. Despite unfavorable conditions for the preservation of food systems (water activity = 0.979; pH 5.4; air-oxygen; 25 °C), the emulsion orange-color was highly stable during storage due to the stability of carotenoids. CPEF is thus a useful functional additive for food preservation.

Safety assessment of rhamnogalacturonan-enriched carrot pectin fraction: 90-Day oral toxicity study in rats and in vitro genotoxicity studies

The dietary fibre product examined is a pectic polysaccharide extract from carrot (Daucus carota), enriched for pectin fragments comprising mainly rhamnogalacturonan-I (RG-I) (abbreviated product name cRG-I). To assess the safety of cRG-I for use as food ingredient, repeated-dose oral toxicity and in vitro genotoxicity studies were conducted. In the subchronic toxicity study (OECD test guideline 408), Wistar Hannover rats received cRG-I at dietary levels (w/w) of 0%, 2.5%, 5% and 10% for 13 weeks. cRG-I induced no adverse effects in this study. The NOAEL was 10% in the diet (equivalent to 6.9 and 7.8 g cRG-I/kg body weight/day in male and female rats, respectively). A package of three in vitro genotoxicity tests (Ames, mouse lymphoma and micronucleus assay in human peripheral blood lymphocytes) was negative for induction of point mutation and chromosome damage. An initial Ames test showed a weak positive response in Salmonella typhimurium strain (TA1537). This response was non-reproducible and attributed to microbial contamination as subsequent tests with an irradiated batch of cRG-I including a repeat Ames test were negative. cRG-I was therefore considered to be non-mutagenic.

Advanced insight into the emulsifying and emulsion stabilizing capacity of carrot pectin subdomains

Insight in the emulsifying and emulsion stabilizing potential of carrot pectin subdomains was established in the present study. For this purpose, (i) carrot pectin fractions enriched in linear homogalacturonan (HG) and branched rhamnogalacturonan (RG) regions were produced, (ii) specific structural and physicochemical properties of the isolated pectin fractions were analyzed and (iii) stability studies of emulsions where the different isolated pectin fractions were used as the sole emulsifier were performed.Firstly, structural characterization confirmed the successful isolation of the subdomains from the original acid extracted carrot pectin generating three structurally diverse carrot pectin samples: acid extracted pectin (NA), HG rich pectin fraction (NA-HG) and RG rich pectin fraction (NA-RG). The main structural differences among these pectin samples were degree of methylesterification, linearity and molar mass. Analysis of the interfacial tension after pectin adsorption onto an oil droplet, demonstrated surface activity of all pectin samples, except for NA-RG at pH 2.5. Overall, carrot pectin created more stable emulsions at pH 2.5 compared to pH 6.0. Additionally, emulsions stabilized by the more complex NA are less susceptible to creaming than emulsions stabilized by NA-HG or NA-RG. Flocculation was identified as the main destabilization phenomenon in the emulsions stabilized by NA-HG and NA-RG at pH 6.0. NA stabilized emulsions remained relatively stable during 14 days of refrigerated storage. Therefore, it can be stated that the presence of both linear and branched regions in the pectin structure result in more stable emulsions as compared to the individual subdomains.

The Role of Pectin in Pb Binding by Carrot Peel Biosorbents: Isoterm Adsorption Study

Cheaply and abundantly biosorption available materials such as carrot peels can be a cost-efficient method for removing heavy metals from wastewater. To investigate the role pectin plays in metal binding by carrot peels, commerce pectin was compared. FTIR spectra confirmed the presence of carboxyl and hydroxyl groups in commerce pectin and carrot pectin. Isoterm experiments showed that all materials could remove Pb (II) ion. All of materials binding Pb (II) follow Freundlich models adsorption. The commerce pectin bindsPb (II) by involving energy 16.6 KJ/mole whereas pectin from carrot peel involves energy 21.09 KJ/mole. It indicates that commerce pectin binds the Pb (II) by physics adsorption whereas pectin from carrot peel by physics and chemical adsorption.

Interactions between citrus pectin and Zn2+ or Ca2+ and associated in vitro Zn2+ bioaccessibility as affected by degree of methylesterification and blockiness

Insight into the effect of the degree and pattern of methylesterification of citrus pectin on the Ca2+ and Zn2+ adsorption capacity and the associated Zn2+ bioaccessibility was established. Pectins with comparable methylesterification degrees (DM) but different patterns of methylester distribution (blockwise or random) were generated. Blockwise distributions of methylesters were produced through controlled enzymatic means (using carrot pectin methylesterase) while random patterns were obtained through alkaline demethylesterification (using NaOH). The pattern of methylesterification was estimated as the absolute degree of blockiness (DBabs), which is the ratio of non-methylesterified units present in blocks to the total number of galacturonic acid units. Determination and modeling (based on the Langmuir adsorption model) of the adsorption isotherms of these structurally modified pectins for Zn2+ or Ca2+ allowed quantification of their maximum cation binding capacity and interaction energy. Decreasing pectin DM and increasing DBabs were shown to promote the Zn2+ or Ca2+ binding capacity of pectin, with the maximum binding capacity being mainly determined by the DM and interaction energy by DBabs. The influence of cation type was evident, with higher maximum binding capacities and interaction energies exhibited for Zn2+ compared to Ca2+, mainly due to the higher electronegativity of the former. Increased Zn2+ binding to pectin was associated with lower Zn2+ bioaccessibility and no influence of low levels of added Ca2+ was observed. However, enzymes and bile salts added during in vitro simulated digestion were shown to bind substantial amounts of Zn2+ ions.

Pectin from carrot pomace: Optimization of extraction and physicochemical properties

In this study, the central composite design for four variables in five levels was applied to determine the effects of pH (0.5–2.5), temperature (50–90°C), heating time (30–150min) and liquid/solid ratio (10–50v/w) on the yield and degree of esterification (DE) of carrot pomace pectin. The results showed that the pectin yield ranged from 5.0 to 15.2% and also, this pectin is classified as low methoxyl pectin (DE of 22.1–51.8%). The pH of 1.3, temperature of 90°C, time of 79.8min and liquid/solid ratio of 23.3v/w were determined as optimal conditions with a maximum yield of 15.6±0.5%, which was close to the predicted values (16.0%). Under the optimal extraction conditions, the galacturonic acid content and emulsifying activity were 75.5 and 60.3% respectively; moreover, the emulsions had a high stability at two different storage temperatures (4 and 23°C). Furthermore, carrot pectin solutions exhibited viscous and pseudoplastic behavior at 1% w/v.

Pectin nanostructure influences pectin-cation interactions and in vitro-bioaccessibility of Ca2+, Zn2+, Fe2+ and Mg2+-ions in model systems

This study explores the effect of pectin structure on mineral bioaccessibility in model systems. Commercial citrus and sugar beet pectin (CP and SBP, respectively) were demethylesterified by the action of carrot pectin methylesterase and characterisation of the resulting samples revealed different degrees of methylesterification (DM). Additionally, SBP exhibited a higher protein content, degree of acetylation, degree of feruloylation, degree of branching and molar mass compared to CP. In vitro-simulated digestion (stomach and small intestine phases) of mineral-enriched pectin solutions showed that decreasing pectin DM results in a decrease in mineral-bioaccessibility due to pronounced cation-pectin interactions. For a given DM, SBP digests exhibited higher mineral-bioaccessibilities than CP digests possibly due to structural differences of pectin in these sources. Furthermore, increasing the mineral-enrichment prior to in vitro-digestion resulted in a higher mineral-bioaccessibility while increasing the pectin concentration decreased the mineral-bioaccessibility. Generally, Mg2+-ions were the most bioaccessible followed by Ca2+, Zn2+, then Fe2+-ions.

Evaluation of cation-facilitated pectin-gel properties: Cryo-SEM visualisation and rheological properties

To provide more insight into the cation facilitated pectin-gel structure-function relationship, the microstructure of pectin-gels was explored using cryo-scanning electron microscopy (Cryo-SEM) in combination with physiochemical and rheological analysis. Pectin with different degrees of methylesterification, DM, was obtained from commercial citrus pectin (CP) and sugar beet pectin (SBP) by action of carrot pectin methylesterase. Pectin characterisation confirmed that pectin properties other than DM were unaltered and pectin from the two sources exhibited different structures. Cryo-SEM visualisation of pectin-gels prepared with different cations revealed that the network density increased with decreasing DM and increasing pH, pectin and cation-concentration. At a given DM, the more linear and less acetylated pectin (CP) exhibited a more intertwined fibrous network compared to the highly branched and more acetylated pectin (SBP). Furthermore, gel-microstructure was influenced by type of cation with Zn2+, Fe2+ and Ca2+-pectin gels showing a more intertwined network compared to Mg2+-pectin gels. Finally, rheological properties of gels complementing Cryo-SEM observations showed that as the network density increased, the gel-stiffness (G′) increased.

The Effect of Endogenous Pectinases on the Consistency of Tomato–Carrot Purée Mixes

Tomato and carrot were subjected to a split-stream process designed to produce a tomato–carrot suspension with reduced consistency. Raw tomatoes, containing pectinmethylesterase and endo-polygalacturonase, were mixed with thermally pretreated (blanched versus cooked) carrots containing different levels of solubilized pectin. After mixing the vegetables, tomato pectinases were shown to act on both tomato and carrot pectin in case an incubation step at medium temperature level (30 min, 40 °C), to allow enzyme action, was performed. Carrot pectin, when present in a mix of tomato and blanched (5 min, 95 °C) carrot, was solubilized as well as depolymerized, whereas depolymerization of the thermo-solubilized carrot pectin by the tomato pectinases was observed in the tomato–carrot puree containing cooked (30 min, 95 °C) carrots. The final serum pectin properties were however similar for both puree types. Carrot contributed more to the consistency of the puree mix compared with tomato but by stimulating the action of the tomato pectinases at mild temperature (30 min, 40 °C), this contribution was lost which resulted in a consistency reduction of the puree mix. This puree liquefaction was larger for the tomato–carrot puree containing blanched instead of cooked carrots. Based on the results, it is suggested that the liquefying effect is related to solubilization and degradation of pectin that is counteracted by a reduction in particle size. The puree mix containing cooked carrot showed in this respect smaller particle sizes than the mix containing blanched carrot.

Effect of debranching on the rheological properties of Ca 2+–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 (Ca 2+) 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 Ca 2+ cross-links, the presence of long arabinose-containing side chains is suggested to play an important role in the rheological characteristics of Ca 2+–pectin gels.

Effect of de-methylesterification on network development and nature of Ca 2+-pectin gels: Towards understanding structure–function relations of pectin

Pectins of varying degree and pattern of methylesterification were produced through controlled de-esterification of highly esterified citrus pectin, using carrot pectin methylesterase (PME) (P-pectins), Aspergillus aculeatus PME (F-pectins) or sodium hydroxide saponification (C-pectins). Estimation of the degree of methylesterification (DM) and quantification of the pattern of methylester distribution in terms of absolute degree of blockiness (DB abs) enabled the characterisation of pectins. Characterised pectins were used for the preparation of Ca 2+-pectin gels with varying calcium ion (Ca 2+) concentration. The rheological characteristics of produced gels were evaluated by means of small-amplitude oscillatory tests. During gel formation, gel strength was monitored so as to allow assessment of network development. Based on the evaluation of mechanical spectra, the nature of the cured gels was established. Depending on Ca 2+ concentration as well as DM and DB abs, gels prepared from specific C-pectins (48 ≥ DM ≥ 26%; 9 ≤ DB abs ≤ 37%) and F-pectins (64 ≥ DM ≥ 29%; 9 ≤ DB abs ≤ 50%) showed a striking decrease of the gel strength with time, while gel networks produced from other pectins either displayed a continuous increase of the gel strength or verged towards pseudo-equilibrium within the observation time of 5 h. Furthermore, the DM, DB abs and Ca 2+ concentration influenced the evolution of Ca 2+-pectin networks from “structured liquids” to “strong gels”. Based on the experimental results, specific mechanisms of Ca 2+ interactions with pectins were (also) considered.

Beneficial effects of carrot pectin against lead intoxication in Wistar rats

The aim of the present study was to investigate the beneficial action, in vivo, of pectin against subacute lead acetate (350 mg/l) intoxication. The adverse effects of lead on the haematological disturbances that concerned, more precisely, the decrease of red blood corpuscle life duration and on the appearance of ever granulated basophilic haematites by inhibiting an enzyme responsible for haeme synthesis have been demonstrated after 1 month of oral lead administration to female Wistar rats. Also, this caused an elevation of the blood lead level as compared with the control group. The introduction of carrot pectin to a level of 3% in the feeding of intoxicated rats has shown a chelating and correcting effect on haematological disturbances caused by lead toxicity, which is reflected by a significant decrease (P<0.05) of blood lead (from 117 to 65 to 19 μg/l), zinc protoporphyrine (portophyrine-zinc from 7.7 to 5.1 to 3.5 μg/g of Hb), increase in haemoglobin to 27% (from 5.09 to 6.05 to 7.79%) and iron to 8% (from 1.34 to 0.9 to 0.5%) of the treated rats by pectin as compared with the untreated groups. Differences in blood lead were significant between the control diet and the addition of pectin therefore suggesting that pectin fibre ingestion in diets decreases the risk of lead poisoning. Key words: Blood lead, carrot pectin, haemoglobin, lead acetate, ZPP

Beneficial effects of carrot pectin against lead intoxication in Wistar rats

Beneficial effects of carrot pectin against lead intoxication in Wistar rats

Improving the hardness of thermally processed carrots by selective pretreatments

Abstract The aim of this study was to improve the texture of thermally processed carrots by selective pretreatments modifying plant-intrinsic properties. Pretreatments were a combination of a thermal or high-pressure (HP) treatment followed by a 1 h soak in a specific solution. Lowering the degree of methyl-esterification (DM) of the carrot pectin was confirmed to be one strategy to reduce texture degradation. The thermal or HP pretreatment resulted in pectin with a lower DM which is less susceptible to β-eliminative depolymerization. A subsequent Ca2+ soak resulted in an even better texture by enhancing the amount of pectin cross-links within the cell wall. Lowering the pH of the carrots was proven to be another strategy. A thermal or HP pretreatment followed by soaking carrots in solutions of low pH proved to be effective in lowering the internal carrot pH, hereby retarding β-elimination and consequently texture degradation. The composition of the low pH solution was shown to be of importance; soak solutions containing cations and/or Ca2+ complexing agents have to be avoided. Ferulic acid proved to be a good acidifying candidate. In conclusion, for texture improvement of thermally processed carrots, lowering the susceptibility for β-elimination and enhancing cell wall cross-links are two main targets which both can be reached by manipulating different plant-intrinsic properties.

Size Exclusion Chromatography To Gain Insight into the Complex Formation of Carrot Pectin Methylesterase and Its Inhibitor from Kiwi Fruit As Influenced by Thermal and High-Pressure Processing

A size exclusion chromatography (HPSEC) method was implemented to study complex formation between carrot pectin methylesterase (PME) and its inhibitor (PMEI) from kiwi fruit in the context of traditional thermal and novel high-pressure processing. Evidence was gained that both thermal and high-pressure treatments of PME give rise to two distinct enzyme subpopulations: a catalytically active population, eluting from the size exclusion column, and an inactive population, aggregated and excluded from the column. When mixing a partly denatured PME sample with a fixed amount of PMEI, a PME-PMEI complex peak was observed on HPSEC, of which the peak area was highly correlated with the residual enzyme activity of the corresponding PME sample. This observation indicates complex formation to be restricted to the active PME fraction. When an equimolar mixture of PME and PMEI was subjected to either a thermal or a high-pressure treatment, marked differences were observed. At elevated temperature, enzyme and inhibitor remained united and aggregated as a whole, thus gradually disappearing from the elution profile. Conversely, elevated pressure caused the dissociation of the PME-PMEI complexes, followed by a separate action of pressure on enzyme and inhibitor. Remarkably, PMEI appeared to be pressure-resistant when compressed at acidic pH (ca. 4).

Carrot pectin methylesterase and its inhibitor from kiwi fruit: Study of activity, stability and inhibition

Abstract Carrot pectin methylesterase (PME) and its inhibitor (PMEI) from kiwi fruit were successfully purified by affinity chromatography. Enzyme and inhibitor activity and stability and PME–PMEI complex formation, as influenced by intrinsic product factors (pH and NaCl) and extrinsic process factors (temperature and pressure), were studied. The effect of temperature- or pressure-induced denaturation of PME and PMEI on their respective activities was assessed by estimating inactivation kinetic parameters. PME inactivation obeyed first-order kinetics. The enzyme was rather heat-labile but pressure-stable. PMEI inactivation was best described by a model taking into account a processing-stable PMEI intermediate. The behavior of PME and the PME–PMEI complex at elevated temperature or pressure in the presence of pectin was explored by following methanol formation as a function of treatment time. PME catalytic activity was stimulated up to a certain temperature or pressure level before declining. No conclusive evidence was obtained for a temperature-induced dissociation of the PME–PMEI complex, whereas high pressure exposure caused the complex to separate. Industrial relevance PME activity control is a major point of interest in the quest of obtaining high quality plant-derived food products. The current study demonstrates that both traditional thermal processing and novel high hydrostatic pressure processing allow stimulation as well as inactivation of PME and, hence, directing the PME-catalyzed pectin hydrolysis. An alternative or additional approach to control endogenous PME activity (e.g. to obtain cloud-stable juices) is through enzyme inhibition using kiwi PMEI. In this context, pH and NaCl boundaries for application were established, the existence of a temperature- and pressure-stable PMEI intermediate was shown and the PME–PMEI complex was proven not to be dissociated at mild temperature and pressure levels. These observations endorse the possibility of inhibiting undesirable PME activity remaining after mild processing.