A methyl esterase from Bifidobacterium longum subsp. longum reshapes the prebiotic properties of apple pectin by triggering differential modulatory capacity in faecal cultures.

Pectin structures have received increasing attention as emergent prebiotics due to their capacity to promote beneficial intestinal bacteria. Yet the collective activity of gut bacterial communities to cooperatively metabolize structural variants of this substrate remains largely unknown. Herein, the characterization of a pectin methylesterase, BpeM, from Bifidobacterium longum subsp. longum, is reported. The purified enzyme was able to remove methyl groups from highly methoxylated apple pectin, and the mathematical modelling of its activity enabled to tightly control the reaction conditions to achieve predefined final degrees of methyl-esterification in the resultant pectin. Demethylated pectin, generated by BpeM, exhibited differential fermentation patterns by gut microbial communities in in vitro mixed faecal cultures, promoting a stronger increase of bacterial genera associated with beneficial effects including Lactobacillus, Bifidobacterium and Collinsella. Our findings demonstrate that controlled pectin demethylation by the action of a B. longum esterase selectively modifies its prebiotic fermentation pattern, producing substrates that promote targeted bacterial groups more efficiently. This opens new possibilities to exploit biotechnological applications of enzymes from gut commensals to programme prebiotic properties.

Pectin from sunflower by-products obtained by ultrasound: Chemical characterization and in vivo evaluation of properties in inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a public health challenge and the use of pectin for symptom amelioration is a promising option. In this work, sunflower pectin has been extracted without (CHP) and with assistance of ultrasound (USP) using sodium citrate as a food-grade extracting agent. At optimal conditions (64 °C, 23 min) the highest yield was obtained with ultrasound application (15.5 vs. 8.1 %). Both pectins were structurally characterized by 1H NMR, HPSEC-ELSD, FT-IR and GC-FID. Unlike CHP, USP showed a lower molecular weight, higher galacturonic acid, lower degree of methyl-esterification and, overall, higher viscosity. These characteristics could affect the anti-inflammatory activity of pectins, evaluated using DSS-induced IBD model mice. So, USP promoted the defence (ICAM-1) and repair of the gastrointestinal mucosa (TFF3, ZO-1) more effectively than CHP. These results demonstrate the potential amelioration of acute colitis in IBD mice through USP supplementation. Taking into account the biomarkers analysed, these results demonstrate, for the first time, the positive impact of sunflower pectin extracted by ultrasound under very soft conditions on inflammatory bowel disease that might open up new possibilities in the treatment of this serious pathology.

New valorization approach of Algerian dates (Phoenix dactylifera L.) by ultrasound pectin extraction: Physicochemical, techno-functional, antioxidant and antidiabetic properties.

To exploit the great fortune of date fruits, the current study aimed to valorize an Algerian common variety by extracting pectins. Response surface methodology (RSM) was applied as process optimization tool to achieve the highest yield using ultrasound-assisted extraction (UAE) as compared to conventional acid extraction (CAE). The experimental yield value (6.7%) was well matched with the predicted one (6.6%) at the optimum conditions (60 °C, 90 min, pH 1.5), confirming the validity of the model. The evaluation of the monomeric composition showed higher content of galacturonic acid and lower of neutral sugars in UAE pectin, as compared to CAE pectin. Conventional treatments decreased the molecular weight (Mw) of the extracted pectins (539 kDa) in a higher extent than ultrasound treatment (800 kDa). Fourier-Transform Infrared Spectroscopy (FT-IR) spectral analysis showed that both samples were low-methoxyl pectins. CAE gave rise to pectins with slightly upper technological samples in terms of water and oil holding capacity (5.2 and 3.8 g/g, respectively), and emulsifying activity (38.5 m2/g). Moreover, date pectins obtained by UAE presented enhanced antioxidant activity (24.3 and 61.0 mg/g DW for DPPH and FRAP assays, respectively), and in vitro antidiabetic properties, showing higher glucose adsorption capacity (4 mmol g-1 at 200 min), as well as α-amylase inhibition (73.7%) and potential capacity to decrease glucose diffusion (1.4 mmol mM g-1 at 150 min), which could improve the ability to retard starch digestion (0.1 mmol mM g-1 at 150 min), providing potential health-promoting properties.

Use of natural low-methoxyl pectin from sunflower by-products for the formulation of low-sucrose strawberry jams.

BACKGROUND: Due to the increasing incidence of obesity and cardiovascular diseases, consumers are demanding products with lower sugar content. In this sense, the reformulation of traditional foods with improved, safe and tasty ingredients is arousing a huge interest. Jams are conventionally produced with elevated amounts of sucrose, which increase the glycaemic index and must be avoided in certain kinds of consumers. RESULTS: This paper describes for the first time the elaboration of strawberry jams using low-methoxyl pectins from sunflower by-products, which allowed the addition of low amounts of sucrose (10-30%). These jams were compared with best-selling commercial samples. An in-depth physicochemical, compositional, sensorial and rheological characterization was carried out. The obtained jams were safe considering aw and pH values; samples presented enough acidity to avoid microorganism development and syneresis. The stabilizing role of sunflower pectin is noteworthy in terms of colour and other physicochemical characteristics. The organoleptic analysis showed that the taste and sweetness of laboratory samples were highly valued, although the presence of pieces of fruits was disliked some panellists. After knowing the content of added sugar used in each jam, the tasters preferred samples with 20% and 30% of sucrose over commercial samples. CONCLUSIONS: The results show the usefulness of sunflower pectin for the elaboration of jams of low glycaemic index. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Hybrid high-intensity ultrasound and microwave treatment: A review on its effect on quality and bioactivity of foods.

With the growing of consumer's demand for products ready to eat that can be elaborated with greener technologies without affecting to their organoleptic characteristics, the application of ultrasound combined with microwaves has been widely studied on food preservation treatments (drying, frying), extraction of high-value added compounds and enzymatic hydrolysis of proteins. This review presents a complete picture of current knowledge on the ultrasound combined with microwaves including the mechanisms, influencing factors, advantages and drawbacks, emphasising in several synergistic effects observed in different processes of strong importance in the food industry. Recent research has shown that this hybrid technology could not only minimise the disadvantages of power US for drying and frying but also improve the product quality and the efficiency of both cooking processes by lowering the energy consumption. Regarding extraction, current studies have corroborated that the combined method presents higher yields in less time, in comparison with those in the respective ultrasound and microwave separately. Additionally, recent results have indicated that the bioactive compounds extracted by this combined technology exhibit promising antitumor activities as well as antioxidant and hepatoprotective effects. Remarkably, this hybrid technology has been shown as a good pre-treatment since the structural changes that are produced in the molecules facilitate the subsequent action of enzymes. However, the combination of these techniques still requires a proper design to develop and optimized conditions are required to make a scale process, and it may lead to a major step concerning a sustainable development and utilization of bioactive compounds from natural products in real life.

Extraction optimization and structural characterization of pectin from persimmon fruit (Diospyros kaki Thunb. var. Rojo brillante).

In this work we have efficiently extracted and characterized pectin from different tissues of astringent (AS) and non-astringent (NAS) persimmon fruits (peel, pulp, whole fruit) for the first time. The highest pectin extraction (≥7.2%) was carried out at 80 °C, 120 min with 1.5% sodium citrate in peel of both AS and NAS persimmon samples. All persimmon pectins showed a molecular weight and galacturonic acid content upper than 328 kDa and 78%, respectively, indicating their suitability as food ingredient. Pectin extracted from AS pulp and peel tissues exhibited an enriched structure in rhamnose and arabinose, whereas the opposite behavior was observed in NAS persimmon whole fruit samples. Remarkably, both pulp tissues (AS and NAS) presented the highest levels of glucose and mannose, non-pectic carbohydrates. In addition, techno-functional assessment (zeta potential, particle size, apparent viscosity, gelation) showed the suitability of the persimmon pectins for a broad range of industrial applications.

Berry fruits as source of pectin: Conventional and non-conventional extraction techniques.

Three non-conventional extraction techniques (enzyme-assisted with cellulase, citric acid ultrasound-assisted and enzyme-ultrasound-assisted treatment) and conventional citric acid extraction were applied to obtain pectin from raspberry, blueberry, strawberry and redcurrant, and were compared in terms of extraction yields and physicochemical properties of the extracted pectins. Except for pectin from raspberry, conventional citric acid extraction led to the highest extraction yield (~8%) and, for the same berries, the lowest pectin recovery was found for the extraction with cellulase (~4%). Regarding the structural characteristics of pectins, enzymatically extracted pectins from redcurrant and strawberry exhibited the highest levels of galacturonic acid (≥73%) whereas, in general, this monosaccharide was found from 51 to 69% in the rest of samples. Although, ultrasound-assisted extraction did not improve pectin yield, it minimized the levels of "non-pectic" components leading to the obtainment of purer pectin. The different monomeric composition and the wide range of molecular weight of the obtained pectins pointed out their usefulness in different potential food applications (e.g., thickening, gelling ingredients) and biological activities. This has been evidenced by the differences found in their physicochemical and techno-functional characteristics. Finally, it can be considered that the berries here studied are efficient sources of pectin.

Apple pomaces derived from mono-varietal Asturian ciders production are potential source of pectins with appealing functional properties.

Comprehensive chemical characterization of nine mono-varietal apple pomaces obtained from the production of ciders with PDO is described. They were rich in essential minerals, fibers (35-52.9 %), and polyphenols. High levels in GalA (11.8-21.6 %), revealed the suitability of these apple pomaces as efficient sources of pectins. Extracted pectins showed high variability in monomer composition, with degrees of methylesterification, strongly associated with pectins functional properties, ranging from 58 to 88 %. For a subset of apple pomace varieties, pectin extraction was accomplished by conventional acid heat treatment or ultrasound. Despite ultrasound-assisted extraction did not improve pectin yield, it minimized levels of "non-pectin" components as revealed by the low content of Glc/Man, leading to the obtainment of high-purity pectin. Our work highlights the key role played by the selection of the apple variety to streamline the potential food applications (gelling/thickening agents or prebiotics) of the extracted pectins that largely depend on their structural features.

Application of sunflower pectin gels with low glycemic index in the coating of fresh strawberries stored in modified atmospheres.

BACKGROUND: This study reports the use of low glycemic sunflower pectin gel, elaborated with calcium and without or with sweeteners (sucrose, stevia and saccharin) as an edible coating and its possible combination with two modified atmosphere packaging (MAP), in order to extend shelf life, maintaining the quality, of strawberries during the storage at 4 °C. RESULTS: This pectin coating, formed with only calcium and/or stevia or saccharin, extended the shelf life of strawberries with respect to uncoating fruits, up to 12 days, keeping the microbial load constant, the firmness and less weight loss. With the same edible coatings, the shelf life of strawberries was extended up to 23 days when they were combined with MAP [10% carbon dioxide (CO2 ), 85% nitrogen (N2 ) and 5% oxygen (O2 )], maintaining the quality of strawberries, while the other MAP, with a higher CO2 concentration (20% CO2 , 75% N2 and 5% O2 ), had no effect. CONCLUSIONS: These results highlight the suitability of the combination of edible pectin coating combined with MAP to obtain an important shelf life extension, maintaining the good quality of the fruit. © 2021 Society of Chemical Industry.

Role of pectin in the current trends towards low-glycaemic food consumption.

The intake of diets rich in carbohydrates with a high-glycaemic load provides excessive energy consumption and low nutritional quality, contributing to cardiovascular diseases, type II diabetes and obesity, among other pathologies. Natural options such as the use of low-methoxyl pectin to develop sugar free formulations is growing since they form gel without sucrose, providing stability and viscosity of numerous foodstuffs. In this paper, we have reviewed the consumer habits of sugar intake and the potential of pectin in the elaboration of low-glycaemic index foods, as well as the structure, applications and sources of pectin. Special attention has been paid on the structure-function relationship of low-methoxyl pectins considering their effects on type I and II diabetes. It has been shown that these pectins reduce the post-prandial glycaemic responses and have an important and recognised potential for the treatment and prevention of diabetes. Rheological behaviour of pectin, impact on intestinal microbiota and on different biomarkers have been postulated as the potential involved mechanisms. As future trends, it is necessary to consider new sources and structures of pectin that present improved functionalities. For this purpose, the obtainment of pectin and derivatives should be placed in a framework of sustainable food systems.

Exploring the Microalga Euglena cantabrica by Pressurized Liquid Extraction to Obtain Bioactive Compounds.

In the present study, the chemical composition of the microalga Euglena cantabrica was investigated. The extraction of bioactive compounds was done using pressurized liquid extraction (PLE) at different temperatures (40-180 °C) and using green solvents (ethanol-water mixtures). A statistical design of experiments was used to optimize the maximum antioxidant capacity of the extracts by response surface methodology. The antioxidant capacity was determined through the inhibition of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, while the chemical analyses of the extracts were carried out using different chromatographic techniques. Chlorophylls and carotenoids were analyzed by high-performance liquid chromatography coupled to a diode array detector and mass spectrometry (HPLC-DAD-MS/MS) and carbohydrates by gas chromatography with flame ionization detection (GC-FID) and high-pressure size-exclusion chromatography coupled to an evaporative light-scattering detector (HPSEC-ELSD). The results showed different possibilities for the extraction conditions, depending on the desired bioactivity or chemical composition. Briefly, (i) mixtures of ethanol-water containing around 40% ethanol at 180 °C gave the best antioxidant capacity, (ii) mixtures containing around 50% ethanol at 110 °C gave the best yield of ß-glucan paramylon, and (iii) the use of pure ethanol at a low temperature (40 °C) is the best choice for the recovery of carotenoids such as diatoxanthin. Summing up, E. cantabrica seems to be a good candidate to be used in biorefinery to obtain different bioactive compounds.

Obtainment and characterisation of pectin from sunflower heads purified by membrane separation techniques.

A pilot-scale extraction of sunflower pectin with 0.74% (w/v) sodium citrate (72 °C, 194 min) and different procedures of purification including alcohol precipitation, ultrafiltration (UFDF) and microfiltration (MFDF) with diafiltration were carried out. Considering the alcohol treatment, the yields were similar at laboratory and pilot-scale (~8.9%), demonstrating the efficiency of the scale-up. With respect to membrane processes, the best results were obtained with UFDF, showing the highest yield (13.3%) and pectin concentration higher than 90%. In all cases, pectins presented very low amount (~1%) of glucose and mannose, monosaccharides not included in the pectin structure. Detailed NMR analysis and functional properties (emulsifying and viscosity) that were also assessed corroborated the good quality of UFDF obtained pectin. These results point out that the obtainment of sunflower pectin of good quality can be achieved at pilot-scale by the extraction with sodium citrate and purification with membrane separation, eco-friendly alternatives to conventional procedures.

Structural characterisation of pectin obtained from cacao pod husk. Comparison of conventional and subcritical water extraction.

Pectin was obtained with citric acid and subcritical water extraction from cacao pod husk with or without a previous step consisting of a supercritical fluid extraction of phenols. By subcritical conditions a higher yield (10.9%) was attained in a time 3-fold shorter than that obtained by conventional extraction (˜8%) and a greater effectiveness in the recovery of pectin with higher molecular weight (750 kDa) was also found. Regarding pectin structure, galacturonic acid and degree of methyl esterification content were similar (˜55 and ˜36%, respectively) in both methods. Moreover, pectin recovered by citric acid presented 2-fold higher amount of impurities as compared to subcritical water extraction. Hardly any effects of a previous supercritical treatment were observed in the structure and composition of pectin, indicating the efficiency of the integrated supercritical carbon dioxide and subcritical water extraction as green processes for the obtainment of phenol and pectin from cacao pod husk.

Structural and technological characterization of pectin extracted with sodium citrate and nitric acid from sunflower heads.

An optimization of temperature, time, and extracting agent concentration of pectin extraction from sunflower heads using sodium citrate and nitric acid (SP-SC and SP-NA) was carried out. At optimal conditions, the yield of extraction with nitric acid (SPO-NA) was twofold greater than the corresponding with sodium citrate (SPO-SC) (14.3 versus 7.7%, respectively). Regarding pectin structure, the galacturonic acid (GalA) content in both, SPO-SC and SPO-NA, was similar (∼85%). However, SPO-NA showed lower molecular weight (Mw) (88.9 kDa) and neutral sugar content (4%) than SPO-SC (464 kDa, 9%), indicating that nitric acid deeply degraded pectin structure. These differences derived into dissimilar behavior in their technological functionality. SPO-SC showed higher viscosity and better emulsifying capacity than SPO-NA, although any of them were able to stabilize the oil/water emulsion. Both sunflower pectins formed gels with Ca2+ (75 mg/g of pectin) at pH 3.0. However, when sucrose was added, the gels formed by SP-SC and 20% sucrose presented the same hardness as those of SP-NA with 40% sucrose. These results suggest that the pectin extracted with sodium citrate, an eco-friendly agent, could be a promising ingredient, with good thickening and gelling properties.

Pectin characterisation using size exclusion chromatography: A comparison of ELS and RI detection.

A high-performance size-exclusion chromatography (HPSEC) method coupled to Evaporative Light Scattering (ELS) and Refractive Index (RI) detectors were evaluated and compared for the molecular mass (Mw) estimation of pectin in a wide range (0.342-805 kDa). Instrumental parameters of the ELSD were optimised by Response Surface Methodology (RSM) being 73 °C the evaporator temperature and 0.9 mL/min the air flow rate. The linear range for the ELSD concentration response was wider (10-2250 mg/L) and better (R2 = 0.985) than RID (10-1500 mg/L; R2 = 0.875). The limits of detection (LOD) and quantitation (LOQ) for all pullulans hardly changed in ELSD (LOD: 1.22-1.99 mg/L; LOQ: 4.07-6.63 mg/L); however, RID showed huge variations (LOD: 0.49-10.41 mg/L; LOQ: 1.64-34.70 mg/L), which increased with the Mw. In general, responses of both detectors were similar for the Mw estimation, although pectin characterisation with HPSEC-ELSD exhibited better results in the lowest Mw compounds.

Modification of citrus and apple pectin by power ultrasound: Effects of acid and enzymatic treatment.

Pectin-derived oligosaccharides are emerging as a new generation of functional ingredients with new or improved technological and/or bioactive properties as compared to pectin. This work addresses the impact of power ultrasound (US) on the structure of citrus and apple pectin under different experimental conditions of power, amplitude and pectin concentration in aqueous and acid media, as well as in the presence of a pectinase. Results indicated that depolymerisation of both pectin increased with time and intensity of US in aqueous media and their polydispersity decreased. In general, a higher depolymerisation was observed in pectin treated by US in the presence of nitric and citric acids than in water, and hardly any difference was detected between both types of acids. Most of the assays gave rise to high-methoxylated pectin with a degree of esterification above 50%, pointing out their suitability for potential gelling agents. Finally, US did not have any impact in assisted enzymatic hydrolysis on the degree and/or rate of depolymerisation at low and medium levels of pectin concentration (0.5 and 2%), whereas a higher diversity of pectin fragments was found at 5% which could be indicative of a more controlled depolymerisation. These findings highlight the importance of the selection of appropriate US processing conditions to diversify the applications of modified pectin, as well as the potential of US as a prospective alternative to currently used depolymerisation techniques.