Study on the structural characteristics and emulsifying properties of chickpea protein isolate-citrus pectin conjugates prepared by Maillard reaction.

Chickpea protein isolate (CPI) typically exhibits limited emulsifying properties under various food processing conditions, including pH variations, different salt concentrations, and elevated temperatures, which limits its applications in the food industry. In this study, CPI-citrus pectin (CP) conjugates were prepared through the Maillard reaction to investigate the influence of various CP concentrations on the structural and emulsifying properties of CPI. With the CPI/CP ratio of 1:2, the degree of graft reached 35.54 %, indicating the successful covalent binding between CPI and CP. FT-IR and intrinsic fluorescence spectroscopy analyses revealed alterations in the secondary and tertiary structures of CPI after glycosylation modification. The solubility of CPI increased from 81.39 % to 89.59 % after glycosylation. Moreover, freshly prepared CPI emulsions showed an increase in interfacial protein adsorption (70.33 % to 92.71 %), a reduction in particle size (5.33 µm to 1.49 µm), and a decrease in zeta-potential (-34.9 mV to -52.5 mV). Simultaneously, the long-term stability of the emulsions was assessed by employing a LUMiSizer stability analyzer. Furthermore, emulsions prepared with CPI:CP 1:2 exhibited excellent stability under various environmental stressors. In conclusion, the results of this study demonstrate that the glycosylation is a valuable approach to improve the emulsifying properties of CPI.

Structuring vegetable oils through enzymatic glycerolysis for water-in-oil emulsions.

Enzymatic glycerolysis is a biotechnological process for structuring vegetable oils. This study investigates the kinetics of glycerolysis of peanut oil and explores the potential of the resulting structured oil to enhance the physical stability of water-in-oil emulsions. Using a 1:1 glycerol-to-oil molar ratio and 4 % lipase B from Candida antarctica as a catalyst, the reaction was conducted at 65 °C with stirring at 400 rpm. Acylglyceride fractions changes were quantified through NMR and DSC. Fat crystal formation was observed using scanning electron microscopy. The results revealed a first-order decay pattern, converting triglycerides into monoacylglycerides and diacylglycerides in less than 16 h. Subsequently, water-in-oil emulsions prepared with glycerolized oil showed augmented stability through multiple light scattering techniques and visual assessment. The structured oils effectively delayed phase separation, highlighting the potential of glycerolysis in developing vegetable oil-based emulsions with improved functional properties and reduced saturated fatty acid content.

Effects of extraction methods on the physicochemical properties and functionalities of pectic polysaccharides from burdock (Arctium lappa L.).

In this work, the effects of four different extraction methods, acid (HCl), alkali (NaOH), enzymes (cellulase/pectinase), and buffer (pH 7.0) on the physicochemical properties and functionalities of burdock pectin were systematically investigated and compared. Buffer extraction gave a low yield (2.8 %) and is therefore limited in its application. The acid treatment hydrolyzed the neutral sidechains and gave a homogalacturonan content of 72.6 %. By contrast, alkali and enzymes preserved the sidechains while degrading the polygalacturonan backbone, creating a rhamnogalacturonan-I dominant structure. The branched structure, low molecular weight, and high degree of methylation (42.3 %) contributed to the interfacial adsorption, emulsifying capacity, and cellular antioxidant activity of the enzyme-extracted product. For the acid-extracted product, the strong intramolecular electrostatic repulsion restricted the formation of a contact interface to prevent coalescence of the emulsion. In addition, they did not have sufficient reducing ends to scavenge free radicals. Although a high branching size (5.0) was adopted, the low degree of methylation (19.5 %) affected the emulsifying capacity of the alkali-extracted products. These results provide useful information for pectic polysaccharides production with tailored properties.

Extraction of pectins from renewable grapefruit (Citrus paradisi) peels using deep eutectic solvents and analysis of their structural and physicochemical properties.

This study presents an innovative attempt to extract high-quality pectins from grapefruit (Citrus paradisi) peels by using deep eutectic solvents (DESs) as extraction agents. The maximum yield of betaine-citric acid (BC)-extracted pectin (BC-P) reached 36.47 % under the optimum process conditions: an L/S ratio of 25 mL/g, a pH of 2.0, and a temperature of 85 °C for 120 min. The yield of BC-P was significantly higher than HCl-extracted pectin (HCl-P, 8.76 %) under a pH of 2.0. In addition, the structural, physicochemical, and emulsifying properties of the purified pectins (BC-P and HCl-P) and commercial pectin (CP) were comparatively analyzed. Results showed that BC-P exhibited higher RG-I value, more arabinan side-chains, bigger Mw and Mn value than HCl-P. Moreover, the viscosity, G' and G'' of BC-P were significantly higher than those of HCl-P and CP. More importantly, BC-P demonstrated better emulsifying activity and stability compared to HCl-P and CP. When the concentration of BC-P was increased to 1.50 %, a stable emulsion containing a 50 % soybean oil fraction could be obtained. Our results confirmed that DESs can be considered as high-effective agents for pectin extraction. Pectins extracted from grapefruit peels can be as a promising natural emulsifiers that can be used in the food industry.

Effect of pectin concentration on emulsifying properties of black soldier fly (Hermetia illucens) larvae albumin modified by pH-shifting and ultrasonication.

The effect of pectin concentration on the structural and emulsifying properties of black soldier fly larvae albumin (BSFLA) modified by pH-shifting (pH12) and ultrasound (US) was studied. The results (intrinsic fluorescence, surface hydrophobicity, Fourier transform infrared spectrum, and disulfide bonds) showed that modified BSFLA samples, especially pH12-US, were more likely to bind to pectin through hydrogen bonding, electrostatic interactions, and hydrophobic interactions due to the unfolding of BSFLA, the collapse of disulfide bonds and exposure of hydrophobic groups. Thus, a BSFLA-pectin complex with smaller particle size, more negative charges, and a relatively loose structure was formed. The emulsifying activity (EAI) and stability index (ESI) of pH12-US modified BSFLA were significantly enhanced by the addition of pectin, reaching the highest values (associated with 174.41 % and 643.22 % increase, respectively) at pectin concentration of 1.0 %. Furthermore, the interface modulus of the emulsion prepared by the modified BSFLA was mainly viscous, and had higher apparent viscosity, smaller particle size and droplet size, contributing to higher EAI and ESI. The study findings suggest the addition of pectin to pH12-US treated BSFLA could be used in industry to prepare BSFLA-pectin emulsion with exceptional/desirable properties.

Pectin-rich dragon fruit peel extracts: An environmentally friendly emulsifier of natural origin.

Pectin extraction is generally an energy-intensive industrial process, while on the other hand their extraction methods vary from different sources. Starting with that perspective, pectin (WSP) containing ultra-low degree of methylation (31.08 ± 1.27%) from dragon fruit peel (DFP) was extracted by using pure water at room temperature. WSP, dominant in DFP (17.13 ± 1.01%), showed both a high molecular weight and a wide molecular weight distribution, while the yield of the rest acid-soluble pectin (HAP) from DFP residue was only 5.22 ± 0.76%. Furthermore, WSP can stabilize emulsions over a wide range of concentrations and oil phases, especially HIPE. Therefore, the hypothesis was verified that the pectin-rich extract from dragon fruit peel with excellent emulsifying properties could be simply extracted by pure water. This environmentally-friendly and energy-saving extraction method provides a new insight to increase the additional value of dragon fruit peel produced in food processing.

Valorizing protein-polysaccharide conjugates from sugar beet pulp as an emulsifier.

Inspired by the emulsion stability of sugar beet pulp pectin, the hydrophobic protein fraction in sugar beet pulp (SBP) is expected to feature high interfacial activity. This work retrieved alkaline extracted protein-polysaccharide conjugates (AEC) from partially depectinized SBP by hot alkaline extraction. AEC was protein-rich (57.20 %), and the polysaccharide mainly comprised neutral sugar, which adopted a rhamnogalacturonan-I pectin-like structure. The hydrophobic polypeptide chains tangled as a dense 'core' with polysaccharide chains attached as a hydrated 'shell' (hydrodynamic radius of ~110 nm). AEC could significantly decrease the oil-water interfacial tension (11.58 mN/m), featuring superior emulsification performance than three control emulsifiers, especially the excellent emulsifying stability (10 % oil) as the emulsion droplet size of 0.438 and 0.479 µm for fresh and stored (60 °C, 5 d) emulsions, respectively. The relationship of molecular structure to emulsification was investigated by specific enzymic modification, suggesting the intact macromolecular structure was closely related to emulsifying activity and that the NS fraction contributed greatly to emulsifying stability. Moreover, AEC was highly efficient to stabilize gel-like high internal phase emulsions (oil fraction 0.80) with low concentration (0.2 %) and even high ionic strength (0-1000 mM). Altogether, valorizing AEC as an emulsifier is feasible for high-value utilization of SBP.

Effect of different processing methods of hawthorn on the properties and emulsification performance of hawthorn pectin.

Five types of hawthorns were obtained using hot air drying (HH), vacuum freeze-drying (FH), Parched processing (PH), Charred processing (CH), and blackening (BH). Five types of pectins (HHP, FHP, PHP, CHP, BHP) were extracted and characterized based on a series of characterization methods. The results indicated that the esterification and molecular weight of BHP were the lowest, which were 30.92 % and 73.67 × 103 (g/mol), respectively. FHP had the highest apparent viscosity and molecular weight (464.42 × 103 g/mol). PHP and CHP differ in galacturonic acid, molecular weight, and monosaccharide composition depending on the time of processing. The emulsion of HHP had the best stability, and the emulsification properties of FHP, PHP, and CHP also showed better performance compared to BHP. In conclusion, our results showed that different processing methods of hawthorn affected the physicochemical properties of pectin, and pectin with specific properties could be obtained by choosing the appropriate processing method.

Thermomechanically micronized sugar beet pulp: Dissociation mechanism, physicochemical characteristics, and emulsifying properties.

Sugar beet pulp (SBP), the main by-product of the beet sugar industry, has gained increasing attention due to its potential functional properties as a clean-label food ingredient. The aim of the present work was to optimize a food-grade approach for SBP micronization via harsh thermal pretreatment and ultrasonication, after which the micronized SBP was used as an emulsifier. Harsh thermal pretreatment substantially softened the compact particle structure of SBP, thereby improving breakage efficiency by reducing the ultrasonication time to 10 min (suspension stability of ∼100%). During ultrasonication, the particle size of SBP declined from ∼34 to ∼25 µm, which showed long and tangled morphology as fibers (diameter of 50-300 nm). The increased solubility enlarged the specific surface area of SBP from ∼0.6 to ∼3.5 g/m2, endowing it with a porous structure for improved ultrasonic energy adsorption, thereby preventing the degradation of the dissolved pectic polymers. The dissociation of SBP particles contributed to the enhancement of emulsification and was correlated with an increase in suspension stability. These findings provide a feasible strategy for the high added-value utilization of SBP.

Physicochemical characterization, emulsifying and antioxidant properties of the polysaccharide conjugates from Chin brick tea (Camellia sinensis).

Tea polysaccharide conjugate fractions (TPCs) with different molecular weights (TPC-40, TPC-60, and TPC-80, MW = 1355 to 204 kDa) were prepared from Chin brick tea using graded alcohol precipitation. The physiochemical and functional properties of TPCs were investigated. Results showed that TPC-80 (204 kDa) had the highest antioxidant activity attributed to its higher phenolic and theabrownin contents. Moreover, this fraction had the highest surface pressure (16.2 ± 0.9 mN/m), but the lowest interfacial dilatational modulus (30.3 ± 2.2 mN/m) than TPC-40 (1355 kDa) and TPC-60 (955 kDa). As a result, TPC-80 had the highest emulsifying activity but the lowest emulsion stabilizing properties due to its fastest adsorption kinetics but the relatively thin interfacial coating on the oil droplets. Overall, our results indicate that the chemical compositions and structural characteristics of TPCs significantly impact their functional attributes. TPCs have the potential to be a novel natural antioxidant emulsifier in food industry.

Effect of glycosylation with apple pectin, citrus pectin, mango pectin and sugar beet pectin on the physicochemical, interfacial and emulsifying properties of coconut protein isolate.

The present study aimed to investigate the effect of glycosylation with four different sources of pectin on the structural, interfacial and emulsifying properties of coconut protein isolate (CPI). The conjugates achieved the degree of graft of 59.11%, 52.80%, 41.39% and 39.26% for apple pectin, citrus pectin, mango pectin and sugar beet pectin, respectively. The covalent bonding of the conjugates was further confirmed by SDS-PAGE gel electrophoresis and FT-IR spectra. In addition, CD spectra exhibited that the conjugates had less α-helix and ß-sheet, and more random coil, resulting in more flexible and loose protein structure. Attributed to glycosylation and the strong steric hindrance effects of pectin, fluorescence intensity of the conjugates decreased significantly. Moreover, the solubility, soluble free sulfhydryl content, surface hydrophobicity, emulsifying activity and emulsifying stability of the conjugates improved significantly after glycosylation. The results of adsorption kinetics showed that glycosylation could increase interfacial pressure, adsorption and rearrangement rates of CPI at the oil-water interface. In summary, the glycosylation between CPI and the four different sources of pectin can significantly improve their emulsifying properties, in particular, citrus pectin and sugar beet pectin have more significant effects.

Extraction of Pectin from Satsuma Mandarin Peel: A Comparison of High Hydrostatic Pressure and Conventional Extractions in Different Acids.

Satsuma mandarin peel pectin was extracted by high hydrostatic pressure-assisted citric acid (HHPCP) or hydrochloric acid (HHPHP), and the physiochemical, structural, rheological and emulsifying characteristics were compared to those from conventional citric acid (CCP) and hydrochloric acid (CHP). Results showed that HHP and citric acid could both increase the pectin yield, and HHPCP had the highest yield (18.99%). Structural characterization, including NMR and FTIR, demonstrated that HHPHP showed higher Mw than the other pectins. The viscosity of the pectin treated with HHP was higher than that obtained with the conventional method, with HHPHP exhibiting significantly higher viscosity. Interestingly, all the pectin emulsions showed small particle mean diameters (D4,3 being 0.2-1.3 µm) and extremely good emulsifying stability with centrifugation and 30-day storage assays, all being 100%. Satsuma mandarin peel could become a highly promising pectin source with good emulsifying properties, and HHP-assisted acid could be a more efficient method for pectin extraction.

Functional and emulsification characteristics of phospholipids and derived o/w emulsions from peony seed meal.

Peony seed phospholipids (PPLs), a kind of multifunctional plant-like phospholipids were extracted from peony seed meal. We investigated the functional properties of PPLs and compared their emulsification performance in corn oil-peony seed oil o/w emulsion systems with that of soy lecithin (DPLs). The PPLs were characterized with the higher content of phosphatidylcholine (PC) (416 ± 28 mg/g) and lyso-phosphatidylcholine (LPC) (43 ± 14 mg/g) fractions, and lower content of phosphatidylethanolamine (PE) (71 ± 13 mg/g). The polyunsaturated fatty acids showed higher content (83.25%), with the highest content of linoleic acid (46.05%) in PPLs. PPLs-emulsions showed smaller average particle size and higher loaded peony seed oil content at pH 5, temperature 50 °C, and about 60% corn oil content. PPLs-emulsions imparted better hydroxyl radical scavenging efficiency and reducing power than DPLs. Our results suggest that PPLs can be used as emulsifiers with improved antioxidant properties.

Enzymatic extraction and functional properties of phosphatidylcholine from chicken liver.

An environmentally sustainable method to extract phosphatidylcholine (PC) from chicken liver (PCCL) and its functional properties were studied. The extraction times, enzymatic hydrolysis time, the solid-liquid ratio as well as types of enzymes (protamex proteinase and neutral proteinase) were investigated. Furthermore, the content of PCCL, emulsifying properties and solubilities of PCCL were also determined. The optimum conditions of extracting PCCL were found to be: reaction time of 3.75 h, enzymatic hydrolysis time of 85.22 min, 1: 3.15 (w/v) of solid-liquid ratio, using protamex proteinase, and the yield and concentration of PCCL was 88.92% and 0.89 mg/mL, respectively. Solubility and emulsifying properties of PCCL showed that the HLB value of PCCL was 10, and in ethanol and glycerol, the solubility of PCCL was 0.5850 g/mL and 0.0965 g/mL, respectively, which was shown to have good ethanol solubility and lipophilicity. From the perspective of green production and high-value utilization of by-products, PCCL could be used as a potential new lecithin source, providing ideas for the development and application of PC of animal origin.

Structural and emulsifying properties of soybean protein isolate glycated with glucose based on pH treatment.

BACKGROUNDS: In the present study, a glycosylated soybean protein with glucose was prepared after pH treatment under different conditions (5.0, 6.0 7.0, 8.0, 9.0) and the conformation and emulsifying properties of soybean protein isolate (SPI) and soybean protein isolate-glucose (SPI-G) were investigated. RESULTS: The degree of grafting (37.11%) and browning (39.2%) of SPI-G conjugates were obtained at pH 9.0 (P < 0.05). The results of analysis of polyacrylamide gel electrophoresis, Fourier transform infrared spectroscopy and Endogenous fluorescence spectroscopy showed that the Maillard reaction between the SPI and glucose occurred and the natural rigid structure of test proteins was stretched and became looser, and thus the tertiary conformation was unfolding. Furthermore, the particle size of the all of samples was reduced under different pH conditions, indicating that pH treatment can increase the flexibility of SPI molecules. The proteins exhibited the best surface hydrophobicity, thermal stability and emulsifying activity (EA) of modified products when subjected to a pH treatment of 9.0, whereas they afforded the best emulsion stability (ES) at pH 8.0. There was a good correlation between the molecular flexibility and emulsifying properties of SPI-G [0.963 (F:EA) and 0.879 (F:ES)] (P < 0.05). CONCLUSION: The present study shows that the structural and emulsification characteristics of natural SPI and SPI-G conjugates have been significantly enhanced via pH treatment and these results provide a theoretical guidance for the application of glycosylated SPI in the food industry. © 2022 Society of Chemical Industry.

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.

Characterization and emulsifying properties of aquatic lecithins isolated from processing discard of rainbow trout fish and its eggs.

This study investigates the characterization and emulsifying properties of different type lecithins. Emulsifying properties of lecithins isolated from rainbow trout egg (RL) and trout processing discard (WL) were compared with the soybean (SL) and hen egg yolk (HL) lecithin in sunflower-fish oil O/W emulsion systems. The phospholipid contents of RL and WL were significantly higher than those of HL and SL. The higher phospholipid contents in RL and WL resulted in lower droplet size (18.3-20.5 µm), higher viscosity (2.37-2.51 mPa.s) and higher physical stability (78.11-75.33) of emulsions. The linoleic acid (C18:2) was the most abundant PUFA in terrestrial origin lecithins (HL and SL), whereas DHA and EPA, a valuable omega-3 fatty acid, were the major PUFAs in aquatic origin lecithins (RL and WL). RL and WL formed more stable emulsions than HL and SL. This study provides valuable information for utilization of RL and HL as emulsifier in emulsion systems.

Fine structure, physicochemical and antioxidant properties of LM-pectins from okra pods dried under different techniques.

This work investigates the effect of drying okra pods by different techniques [freeze-drying (FD), sun-drying (SD), oven-drying (OD) and microwave-drying (MD)] on the molecular structure, physicochemical and antioxidant properties of the subsequently extracted OP. Remarkably, although the degree of methyl esterification (∼41.1 %) remained similar among samples, the content of galacturonic acid (62.67-68.77 %), average number molecular weight (MnI: 758.8-808.5 kDa, MnII: 20.9-24.2 kDa), and to a greater extent the apparent viscosity of an aqueous solution of pectin molecules, water holding capacity (0.21-10.71 g/g) and emulsifying activity (42.3-72.7 %) and stability (38.6-53.5 %), decreased with the drying temperature in the order of FD-OP > SD-OP > OD-OP > MD-OP. On the other hand, only FD-OP presented a higher proportion of galactan and/or arabinan side chains [(Ara + Gal) / Rha = 12.37%] compared to the rest of the samples, with values ranging from 7.79 to 9.17%. FD-OP and SD-OP resulted in lower DPPH and ABTS radical scavenging activities.

Optimization of Pectin Extraction from Sweet Potato Peels Using Citric Acid and its Emulsifying Properties.

BACKGROUND: Pectin is a natural polysaccharide that has been used widely as a stabilizer in food emulsion system. OBJECTIVE: This study aimed to optimize the yield of pectin extracted from sweet potato residue and investigate its emulsifying properties. METHODS: Response surface methodology (RSM) has been utilized to investigate the pectin extracted from sweet potato peels using citric acid as the extracting solvent. Investigation of the effect of different extraction conditions namely temperature (°C), time (min) and solution pH on pectin yield (%) were conducted. A Box-Benhken design with three levels of variation was used to optimize the extraction conditions. RESULTS: The optimal conditions determined were temperature 76°C, time 64 min and pH 1.2 with 65.2% yield of pectin. The degree of esterification (DE) of the sweet potato pectin was determined using Fourier Transform Infrared (FTIR) Spectroscopy. The pectin is high-methoxyl pectin with DE of 58.5%. Emulsifying properties of sweet potato pectin were investigated by measuring the zeta-potential, particle size and creaming index with addition of 0.4 and 1.0 wt % pectin to the emulsion. CONCLUSION: Extraction using citric acid could improve the pectin yield. Improved emulsion stability was observed with the addition of the sweet potato pectin.

Valorization of Flaxseed Oil Cake Residual from Cold-Press Oil Production as a Material for Preparation of Spray-Dried Functional Powders for Food Applications as Emulsion Stabilizers.

Flaxseed oil cake extract (residual from cold-press oil production and rich in proteins and polysaccharides) was evaluated as a potential substrate for the preparation of spray-dried powders with emulsifying activity. Three variants of powders were obtained using different spray-drying process inlet temperatures: 160 °C, 180 °C, and 200 °C. The influence of temperature on physicochemical features (water holding capacity, oil binding capacity, water activity, solubility, color, chemical composition, antioxidant activity, and surface morphology) of the powders was estimated. Additionally, the emulsifying activity of the powders and the stability of oil-in-water emulsions prepared with their various content (0.5%, 1%, and 3%) were determined. Results showed that inlet temperature had significant influence on all physicochemical and functional properties of the powders. Increased inlet temperature decreased solubility and antioxidant activity but increased water-holding capacity, oil-binding capacity, and emulsifying activity. The emulsions prepared with the powder obtained at 200 °C showed the highest stability. SEM images showed the production of relatively spherical particles which were folded or wrinkled with a lot of dentures. This study could open a promising pathway for producing natural and plant-based spray-dried powders for food applications as emulsion stabilizers.