Pectins in Processed Fruits and Vegetables: Part II-Structure-Function Relationships

In Vitro Bioaccessibility of Carotenoids and Vitamin E in Rosehip Products and Tomato Paste As Affected by Pectin Contents and Food Processing

Limited bioavailability of antioxidants present in food from fruits and vegetables matrices is determined by their low bioaccessibility due to the physical and chemical interactions of the antioxidants with the indigestible polysaccharides of cell walls. Therefore, this in vitro investigation aimed to assess the bioaccessibility of carotenoids and vitamin E from rosehips as well as from tomato paste and to investigate several aspects of effects of pectin contents and food processing on bioaccessibility. Following the addition of the enzyme mixture Fructozym P6-XL, the bioaccessibility of carotenoids from rosehips as well as from tomato paste significantly increased. The average relative increase in bioaccessibility from rosehips was lower for ( all-E)-β-carotene compared with ( all-E)-lycopene and ( all-E)-rubixanthin. In contrast, increases of bioaccessibility of α-tocopherol were comparable for rosehip samples and tomato paste.

The effect of pectins on survival of probiotic Lactobacillus spp. in gastrointestinal juices is related to their structure and physical properties

Pectins are plant polysaccharides used in food industry as gelling and stabilizing agents. This study investigated the ability of pectins to improve survival of probiotic species Lactobacillus fermentum PCC, L. reuteri RC-14, L. rhamnosus LGG and L. paracasei F-19 in simulated gastric solution in relationship to their structural and physical properties. Electrostatic interactions between pectins and bacteria were evaluated by the Zeta-potential approach. Bacterial survival was assessed by flow cytometry and plate counting. L. fermentum PCC and L. reuteri RC-14 were more resistant to gastric conditions; their survival rate was further improved in the presence of five out of ten tested pectins. Additionally, two of the pectins had a positive effect on viability of the less resistant L. rhamnosus LGG and L. paracasei F-19. The beneficial effect was generally observed for the high-methoxylated pectins, indicating that substituted polygalacturonic acid in the backbone is essential for bacterial protection. Other pectin features associated with improved survival, included less negative Zeta-potential, higher molecular weight, as well as lower values of hydrodynamic sizes, viscosity and degree of branching. The study indicates that pectins have a potential to protect probiotic bacteria through the gastro-intestinal transit and identifies the features linked to their functionality.

Modification of Cell Wall Polysaccharides during Drying Process Affects Texture Properties of Apple Chips

The influences of hot air drying (AD), medium- and short-wave infrared drying (IR), instant controlled pressure drop drying (DIC), and vacuum freeze drying (FD) on cell wall polysaccharide modification were studied, and the relationship between the modifications and texture properties was analyzed. The results showed that the DIC treated apple chips exhibited the highest crispness (92) and excellent honeycomb-like structure among all the dried samples, whereas the FD dried apple chips had low crispness (10), the minimum hardness (17.4 N), and the highest volume ratio (0.76) and rehydration ratio (7.55). Remarkable decreases in the contents of total galacturonic acid and the amounts of water extractable pectin (WEP) were found in all the dried apple chips as compared with the fresh materials. The highest retention of WEP fraction (102.7 mg/g AIR) was observed in the FD dried apple chips, which may lead to a low structural rigidity and may be partially responsible for the lower hardness of the FD apple chips. In addition, the crispness of the apple chips obtained by DIC treatment, as well as AD and IR at 90°C, was higher than that of the samples obtained from the other drying processes, which might be due to the severe degradation of pectic polysaccharides, considering the results of the amounts of pectic fractions, the molar mass distribution, and concentrations of the WEP fractions. Overall, the data suggested that the modifications of pectic polysaccharides of apple chips, including the amount of the pectic fractions and their structural characteristics and the extent of degradation, significantly affect the texture of apple chips.

Ultrasound enhances calcium absorption of jujube fruit by regulating the cellular calcium distribution and metabolism of cell wall polysaccharides

BACKGROUND

Ultrasound has been applied in fruit pre-washing processes. However, it is not sufficient to protect fruit from pathogenic infection throughout the entire storage period, and sometimes ultrasound causes tissue damage. The goal of this study was to investigate the effects of calcium chloride (CaCl₂ , 10 g L^-1 ) and ultrasound (350 W at 40 kHz), separately and in combination, on jujube fruit quality, antioxidant status, tissue Ca²⁺ content and distribution along with cell wall metabolism at 20 °C for 6 days.

RESULTS

All three treatments significantly maintained fruit firmness and peel color, reduced respiration rate, decay incidence, superoxide anion, hydrogen peroxide and malondialdehyde and preserved higher enzymatic (superoxide dismutase, catalase and peroxidase) and non-enzymatic (ascorbic acid and glutathione) antioxidants compared with the control. Moreover, the combined treatment was more effective in increasing tissue Ca²⁺ content and distribution, inhibiting the generation of water-soluble and CDTA-soluble pectin fractions, delaying the solubilization of Na₂ CO₃ -soluble pectin and having lower activities of cell wall-modifying enzymes (polygalacturonase and pectate lyase) during storage.

CONCLUSION

These results demonstrated that the combination of CaCl₂ and ultrasound has potential commercial application to extend the shelf life of jujube fruit by facilitating Ca²⁺ absorption and stabilizing the cell wall structure. © 2017 Society of Chemical Industry.

Characterization and Degradation of Pectic Polysaccharides in Cocoa Pulp

Microbial fermentation of the viscous pulp surrounding cocoa beans is a crucial step in chocolate production. During this process, the pulp is degraded, after which the beans are dried and shipped to factories for further processing. Despite its central role in chocolate production, pulp degradation, which is assumed to be a result of pectin breakdown, has not been thoroughly investigated. Therefore, this study provides a comprehensive physicochemical analysis of cocoa pulp, focusing on pectic polysaccharides, and the factors influencing its degradation. Detailed analysis reveals that pectin in cocoa pulp largely consists of weakly bound substances, and that both temperature and enzyme activity play a role in its degradation. Furthermore, this study shows that pulp degradation by an indigenous yeast fully relies on the presence of a single gene (PGU1), encoding for an endopolygalacturonase. Apart from their basic scientific value, these new insights could propel the selection of microbial starter cultures for more efficient pulp degradation.

Gastroprotective effects and structural characterization of a pectic fraction isolated from Artemisia campestris subsp maritima

The aim of this study was to investigate the chemical structure and biological activity of a pectic fraction isolated from the aerial parts of A. campestris L. subsp. maritima Arcangeli. The chemical and spectroscopic analyses of the pectic fraction (ACP-E10) demonstrated that ACP-E10 was composed of homogalacturonan (HG) (60%) and rhamnogalacturonan-I (RG-I) (29%) regions. Side chains of the RG-I included mainly branched arabinans and type II arabinogalactans (AG-II). The molar mass of ACP-E10 determined by HPSEC-MALLS was 16,600g/mol. ACP-E10 was evaluated for its gastroprotective effect against ethanol-induced gastric lesions in rats. Oral pretreatment of animals with ACP-E10 (0.3, 3 and 30mg/kg) significantly reduced gastric lesions by 77±7.9%, 55±11.1% and 65±11.8%. ACP-E10 also maintained mucus and glutathione (GSH) contents in the gastric mucosa. In addition, ACP-E10 demonstrated antioxidant activity in vitro by the DPPH assay. These results demonstrated that the pectin from A. campestris had significant gastroprotective effects in vivo, which were likely attributable to their capacity to increase the protective defenses of gastric mucosa.

Complex coacervation between lysozyme and pectin: Effect of pH, salt, and biopolymer ratio

The complexation between lysozyme and pectin was studied by acidification using zeta potential, turbidity measurements and calorimetry titration. The complexes were analyzed in various NaCl concentrations with different ratios. At ratio 1:1 with 0.01M NaCl, is worth mentioning that the insoluble complexes were formed between pH 2.0 and 7.0, which represents a great range to apply this complex to different food matrices. When the ratio was increased from 1:1 to 3:1, the pH range between the pH_φ1 and pH_φ2 increased even more. When the NaCl concentration was increased from 0.01M to 0.2M, a progressive reduction of turbidity was observed. At 0.4M NaCl, there was total suppression of complex formation at ratio ≤ 3:1. The process of complex coacervate formation occurred in two different steps, presenting favorable enthalpic as well as entropic contributions. The positive entropy change is a strong indication that water molecules have been released from the complex surface, however the positive sign of TΔS suggests that hydrophobic interactions were involved in the interaction between lysozyme and pectin. Microscopy images of the samples revealed that the complexes presented a spheroid-like appearance which may contribute to possible future applications.

Stabilization of milk proteins in acidic conditions by pectic polysaccharides extracted from soy flour

Pectic polysaccharides were extracted from soy flour at either room temperature (SPRT) or 121°C (SPH), and their abilities to stabilize milk proteins in acidic conditions were evaluated. Both SPRT and SPH were found to contain proteinaceous components that were difficult to dissociate from polysaccharide components using size exclusion chromatography, whereas the molar mass of the former was approximately twice that of the latter. Due to the higher molar mass, SPRT was expected to provide stronger steric effects to prevent aggregation between milk proteins in acidic conditions than SPH. Alkaline treatment of SPRT for breaking O-linkages between AA and monosaccharide residues decreased its molar mass by approximately 160 kDa, indicating that they contained naturally occurring conjugates of pectic and proteinaceous moieties. Particle size distributions in simulated acidified milk drink samples containing 0.2% SPRT or SPH showed monomodal distributions with median diameters of around 1.2 μm at pH 4. The presence of large protein aggregates (∼5 μm) was detected at 0.2% SPRT and pH 3.2, 0.6 to 0.8% SPRT and pH 4, or 0.2% SPH and pH 3.4. The presence of excess polysaccharide molecules unbound to proteins was detected at 0.2% SPRT and pH 3.2 to 3.4, 0.4 to 0.8% SPRT and pH 4, 0.2% SPH and pH 3.4 to 3.6, and 0.4 to 0.8% SPH and pH 4. The present results suggest that molecular characteristics of pectic polysaccharides vary depending on extraction conditions and hence their functional behavior.

Changes in pectin characteristics during the ripening of jujube fruit

BACKGROUND

Pectin is related to fruit maturation and loss of flesh firmness. In this research, changes in pectin characteristics, including pectin content, neutral sugar composition, molecular weight (M_w ) distribution and degree of methylesterification (DM), in six different growth stages (S1 to S6) of jujube fruit were assessed.

RESULTS

The growth of jujube fruit corresponded to an increase in water-soluble pectin (WSP) and a decrease in sodium carbonate-soluble pectin (SSP). The chelate-soluble pectin (CSP) content reached a maximum level at S3 but decreased significantly from S3 to S4. Arabinose proved to be the principal branched neutral monosaccharide in pectin during growth and was lost from WSP, CSP and SSP in S4 to S6. The ratios of (arabinose + galactose)/rhamnose indicated that the branched chains of WSP, CSP and SSP degraded in S2, S3 and S4 respectively. SSP depolymerized from S2 and increased as jujube fruit ripened. By contrast, WSP depolymerized throughout ripening. The DM of pectins ranged from 45.38 to 92.21%. Among the obtained DMs, the lowest was observed in WSP from ripened jujube fruit (S6).

CONCLUSION

The content, neutral sugar composition, DM and M_w distribution of pectins changed markedly as jujube fruit ripened. Jujube fruit could be a promising alternative source of pectins in terms of maturation degree. WSP from S6 and CSP from S1 or S2 could be used as gelling agents in low-sugar-containing products because of their low methoxyl pectin contents. WSP from S1 could also be applied as a thickener or emulsifier owing to its high M_w distribution. © 2017 Society of Chemical Industry.

Ultrasonic degradation of sweet potato pectin and its antioxidant activity

The effect of ultrasound factors (time, power, and duty cycle) on sweet potato pectin molecular weight, neutral sugar composition, pectin structure, and antioxidant activity was investigated. Sweet potato pectin dispersions (0.0025, 0.005 and 0.01g/mL) in deionized water were sonolyzed for 5, 10 and 20min to assess effect of sonication time and pectin concentration on sonolysis. For further experiments 0.0025g/mL was sonicated under varying ultrasonic power and duty cycle levels, subsequently the molecular weight, galacturonic acid content, degree of methoxylation and antioxidant activity of sonicated pectin products were investigated. Results showed that ultrasound treatment reduced pectin molecular weight, while polydispersity did not show clear trend which characterized random pectin scission, increasing duty cycle from 20% to 80% resulted in approximately threefold reduction in pectin molecular weight, increased sonication power from 100W to 400W led to significant increase in galacturonic acid content from 72.0±1.2% in native pectin to between 85.0±3.2% and 92.0±2.7%, the degree of methoxylation significantly reduced from 12.0±3.0% to between 5.25% and 6.28%, sonication led to increase in galactose and decrease in rhamnose consistent with debranching of pectin. Moreover, sonication lead to increased antioxidant capacity, both 200W and 400W sonicated pectin having higher ORAC and FRAP values, with highest pectin concentration 4mg/mL in ORAC and 0.8mg/ml in FRAP giving substantially high antioxidant activity than native and 100W treated pectin. The ORAC value of 400W sonicated pectin increased five hold above the native pectin, while it's FRAP value was almost three fold higher than native pectin. However, ultrasound did not alter pectin primary structure as showed by FTIR and HPAEC results. The results indicated that ultrasound offers effective and green process for pectin transformation and creation of antioxidant potent pectin products.

Structural properties and foaming of plant cell wall polysaccharide dispersions

Water suspensions of cellulose nanofibres with xylan, xyloglucan and pectin were studied for foaming and structural properties as a new means for food structuring. The dispersions were analysed with rheological measurements, microscopy and optical coherence tomography. A combination of xylan with TEMPO-oxidized nanocellulose produced a mixture with well-dispersed air bubbles, while the addition of pectin improved the elastic modulus, hardness and toughness of the structures. A similar structure was observed with native nanocellulose, but the elastic modulus was not as high. Shear flow caused cellulose nanofibres to form plate-like flocs in the suspension that accumulated near bubble interfaces. This tendency could be affected by adding laccase to the dispersion, but the effect was opposite for native and TEMPO-oxidized nanocellulose. Nanocellulose type also influenced the interactions between nanofibers and other polysaccharides. For example, xyloglucan interacted strongly with TEMPO-oxidized nanocellulose (high storage modulus) but not with native nanocellulose.

Emerging concepts in the nutraceutical and functional properties of pectin-A Review

Pectin is a structural heteropolysaccharide found ubiquitously in terrestrial plants. It finds diverse food applications such as that of a gelling agent, stabilizer, and fat replacer. In the pharmaceutical arena, pectin exhibits a number of functions, from decreasing blood fat to combating various types of cancers. This review shows the shift of pectin from its conventional roles to its progressive applications. Insights into the advances in the production of pectin, the role it plays as a nutraceutical, possible prebiotic potential and a delivery vehicle for probiotics, and food applications are highlighted. Bioactive and functional properties of pectin are discussed and how the structural built up defines them, is emphasized. As a biopolymer, the applications of pectin in active packaging are also mentioned.

Effects of pectin on lipid digestion and possible implications for carotenoid bioavailability during pre-absorptive stages: A review

Pectin, an abundant polysaccharide in the human diet, has structural characteristics and functional properties that are strongly dependent on the food matrix (e.g., origin, type, cultivar/variety, ripening stage, style and intensity of processing). These polysaccharides have a strong effect on lipid digestion, which is required for the liberation of carotenoids from emulsified lipid droplets in the gastrointestinal content and for the formation of micelles, in which the carotenoids must be incorporated before absorption. Only micellarized carotenoids can be absorbed and subsequently exert protective effects on human health. The alteration of lipolysis by pectin can occur through several mechanisms; however, they have not been linked directly to carotenoid micellarization. This paper provides an overview of the effects of the properties of pectin on the ion concentration in the digestive content, the viscosity of the digestive medium, the properties of the lipid droplet surfaces and lipase activity and analyzes the impact of these events on lipid digestion and subsequent carotenoid micellarization.

Stabilization of red fruit-based smoothies by high-pressure processing. Part A. Effects on microbial growth, enzyme activity, antioxidant capacity and physical stability

BACKGROUND

Non-thermal pasteurization by high-pressure processing (HPP) is increasingly replacing thermal processing (TP) to maintain the properties of fresh fruit products. However, most of the research on HPP-fruit products only partially addresses fruit-pressure interaction, which limits its practical interest. The objective of this study was to assess the use of a mild HPP treatment to stabilize red fruit-based smoothies (microbial, enzymatic, oxidative and physical stability).

RESULTS

HPP (350 MPa/10 °C/5 min) was slightly less effective than TP (85 °C/7 min) in inactivating microbes (mesophilic and psychrophilic bacteria, coliforms, yeasts and moulds) in smoothies kept at 4 °C for up to 28 days. The main limitation of using HPP was its low efficacy in inactivating oxidative (polyphenol oxidase and peroxidase) and hydrolytic (pectin methyl esterase) enzymes. Data on antioxidant status, colour parameters, browning index, transmittance, turbidity and viscosity confirmed that the HPP-smoothies have a greater tendency towards oxidation and clarification, which might lead to undesirable sensory and nutritional changes (see Part B).

CONCLUSION

The microbial quality of smoothies was adequately controlled by mild HPP treatment without affecting their physical-chemical characteristics; however, oxidative and hydrolytic enzymes are highly pressure-resistant, which suggests that additional strategies should be used to stabilize smoothies. © 2016 Society of Chemical Industry.

Nanospherical arabinogalactan proteins are a key component of the high-strength adhesive secreted by English ivy

Over 130 y have passed since Charles Darwin first discovered that the adventitious roots of English ivy (Hedera helix) exude a yellowish mucilage that promotes the capacity of this plant to climb vertical surfaces. Unfortunately, little progress has been made in elucidating the adhesion mechanisms underlying this high-strength adhesive. In the previous studies, spherical nanoparticles were observed in the viscous exudate. Here we show that these nanoparticles are predominantly composed of arabinogalactan proteins (AGPs), a superfamily of hydroxyproline-rich glycoproteins present in the extracellular spaces of plant cells. The spheroidal shape of the AGP-rich ivy nanoparticles results in a low viscosity of the ivy adhesive, and thus a favorable wetting behavior on the surface of substrates. Meanwhile, calcium-driven electrostatic interactions among carboxyl groups of the AGPs and the pectic acids give rise to the cross-linking of the exuded adhesive substances, favor subsequent curing (hardening) via formation of an adhesive film, and eventually promote the generation of mechanical interlocking between the adventitious roots of English ivy and the surface of substrates. Inspired by these molecular events, a reconstructed ivy-mimetic adhesive composite was developed by integrating purified AGP-rich ivy nanoparticles with pectic polysaccharides and calcium ions. Information gained from the subsequent tensile tests, in turn, substantiated the proposed adhesion mechanisms underlying the ivy-derived adhesive. Given that AGPs and pectic polysaccharides are also observed in bioadhesives exuded by other climbing plants, the adhesion mechanisms revealed by English ivy may forward the progress toward understanding the general principles underlying diverse botanic adhesives.