Molecular and functional modification of hydroxypropylmethylcellulose by high-intensity ultrasound

Low-viscosity hydroxypropyl methylcellulose obtained by electron beam irradiation and its performance in spray drying

Low-viscosity hydroxypropyl methylcellulose (HPMC) was obtained by electron beam irradiation, and its use as an excipient for improving the properties of spray dried pharmaceutical powders was investigated. The minimum molecular weight of HPMC which could maintain the capacity of encapsulation and powder modification was explored. As the irradiation dose was increased from 10 to 200 kGy, the molecular weight and viscosity of HPMC decreased linearly. However, its main structure and degrees of methoxy and hydroxypropyl substitution were not significantly affected. The irradiated HPMC could encapsulate particles during spray drying and, thus, modify powder properties. Furthermore, the water content of spray-dried powders with irradiated HPMC was lower than that with parent HPMC. After the spray-dried powder with irradiated HPMC was prepared into granules, their dissolution rate was also faster. However, in order to achieve high encapsulation, the molecular weight of HPMC should be ensured to be above 7.5 kDa. The designated low-viscosity HPMC obtained by electron beam irradiation is a suitable powder-modification material for use in spray drying, and it shows promise as a superior excipient in medicine, food, paint industries, among others.

Mechanism of ultrasound-induced soybean/egg white composite gelation: Gel properties, morphological structure and co-aggregation kinetics

This study aims to develop ultrasound-assisted acid-induced egg white protein (EWP)-soy protein isolate (SPI) composite gels and to investigate the mechanistic relationship between the co-aggregation behavior of composite proteins and gel properties through aggregation kinetics monitored continuously by turbidity. The results showed that the inclusion of EWP caused the attenuation of gel properties and maximum aggregation (Amax) because EWP could aggregate with SPI at a higher rate (Kapp), which impeded the interaction between SPI and the formation of a continuous gelling network. In the EWP-dominated system, SPI with higher molecular weights also increased the fractal dimension of gels. Ultrasound improved properties of composite gels, especially the SPI-dominated system. After ultrasound treatment, the small, uniform size of co-aggregates and the decrease in potential led to an increase in the aggregation rate and formation of dense particles, consistent with an increase in gelation rate and texture properties. Excessively fast aggregation generated coarse chains and more pores. Still, the exposure of free sulfhydryl groups assisted the gel structure units to form a compact network through disulfide bonding. On the whole, the study could provide theoretical support for a deeper understanding on the interaction mechanism and gelation of composite proteins.

Properties of Active Levan-Bitter Vetch Protein Films for Potential Use in Food Packaging Applications

ζ-potential and Z-average were determined on film-forming solutions of bitter vetch-levan-based films prepared at different ratios in the absence and presence of glycerol as a plasticizer. The casting method was used to obtain manageable films. The results revealed that levan increases the elongation at break of bitter vetch protein films and reduces the tensile strength. The optimal result was obtained through the film that was prepared with the ratio of 50% bitter vetch proteins and 50% levan, in terms of mechanical properties. The surfaces of the prepared films appeared to be more compact and smooth. On increasing the glycerol concentration in the bitter vetch protein-levan films, the oxygen and water vapor permeability increased compared to the control (P < 0.05). Based on the overall results, the reinforcement of bitter vetch proteins with levan at a ratio of 1:1 represents optimal film properties in the presence of a low concentration of glycerol. The proposed film is suggested as an innovative packaging system for beef meat to preserve its quality over time.

Advanced structural characterization and in vitro fermentation prebiotic properties of cell wall polysaccharide from Kluyveromyces marxianus

Through previous study, the three yeast α-mannans (MPS) from various sources of Kluyveromyces marxianus (LZ-MPS, MC-MPS, and G-MPS) were preliminarily characterized. In this study, the advanced structural characterization and the in vitro human fecal fermentation behavior of the three MPS were investigated. According to the results of this study, the polysaccharide molecules of the three MPS were aggregated in solution, supporting their branched chain structure. After in vitro fermentation, the molecular weight and pH of fermentation broth decreased significantly, indicating that the three MPS could be utilized by human gut microbiota. Meanwhile, the production of total short-chain fatty acids (SCFAs) of the three MPS was promoted, especially the production of propionic acid was 45.55, 38.23, and 38.87 mM, respectively. In particular, the three MPS have the ability to alter the composition of human gut microbiota, especially to promote the proliferation of Bacteroidetes, suggesting that the bioactivities of the three MPS can be significantly influenced by intestine Bacteroidetes. In terms of metabolism, all MPS can promote cofactors, vitamins, amino acid metabolism, and glycan biosynthesis and metabolism of bacteria. In consequence, the three MPS were confirmed to regulate the human gut microbiota, increase the level of SCFAs, promote the metabolisms of bacteria on amino acid and glycan, and improve the intestinal health.

Modification of fermented whey protein concentrates: Impact of sequential ultrasound and TGase cross-linking

This study aimed to examine the impact of fermentation process on whey protein and improve the general properties of fermented whey protein concentrate (FWPC) recovered by a combined ultrafiltration-diafiltration (UF-DF) operation. Impacts of sequential ultrasound (US) pretreatment and transglutaminase (TGase) crosslinking on structural, functional, and physicochemical properties of FWPCs were investigated. Partially denatured and hydrolyzed fermented whey protein could replace heat denaturation prior to the TGase addition to a whey protein system. Sequential treatment increased the molecular weight of FWPCs as exhibited by both SEM and SDS-PAGE, which demonstrates that modification can lead to the polymers and oligomers production. The zeta potential value increased significantly after US treatment and enzyme catalysis, and all the modified FWPCs were strongly negatively charged. Compared with the secondary structure of untreated FWPCs, the percentage of α-helix and random coil in modified FWPCs significantly increased, while the percentage of β-sheet and β-turns reduced. Solubility, free sulfhydryl groups, and surface hydrophobicity of all FWPCs were significantly improved compared to non-fermented WPC (P < 0.05). Sequential treatment induced a substantial impact on the emulsifying activity and stability of modified samples in comparison with untreated FWPCs. Scanning electron microscope pictures confirmed the positive effects of sequential treatments on texture and void size reduction. Therefore, the application of recovering modified FWPCs is fully recommended as a commercially viable approach for enhanced protein production at the industrial scale.

A new methodology to assess the solubility of fatty acids: Impact of food emulsifiers

In food formulations, lipids are normally incorporated as emulsions stabilized by different types of emulsifiers. The emulsifiers can affect fatty acid (FA) solubilization as they can interact with FA. The main purpose of the present work is the development of a methodology to evaluate the FA solubilization in an aqueous medium in the absence and presence of exogenous emulsifiers. To this end, a combination of turbidimetry, oiling off and dynamic light scattering (DLS) was used. The FA solubility, as well as its supramolecular assemblies, were determined by analyzing the changes in the turbidity profile and the corresponding size of particles obtained by DLS. Oleic acid (OA) was used as a model FA and a simulated intestinal fluid (SIF) as the aqueous phase. Emulsifiers of low (Tween 80) and high (protein and polysaccharide) molecular weight were tested. Tween 80 was the only emulsifier that improved OA solubilization, whereas the macromolecules only affected the supramolecular structure that OA adopted, being the structure of these assemblies governed by the emulsifier nature.

Chain conformation and rheological properties of an acid-extracted polysaccharide from peanut sediment of aqueous extraction process

A polysaccharide (PPS) in peanut sediment of aqueous extraction process was obtained at pH4.0, purified via anion-exchange chromatography. The composition, chain conformation and rheological properties were investigated. PPS mainly consisted of arabinose, galacturonic acid, xylose, and rhamnose. The intrinsic viscosity [η] was 0.71 dL/g in 0.1 M NaNO₃ solution. The weight-average molar mass Mw and polydispersity index were 3.77 × 10⁵ g/mol and 1.25, suggesting high homogeneity. The average radius of gyration (R_g), hydrodynamic radius (R_h), R_g/R_h ratio and conformation parameter v were 25.5, 18.2, 1.40 and 0.21, respectively, indicating compact coil chain conformation with branched structure. Molecular morphology revealed that PPS displayed chain shape comprised of spheres with a diameter range of 15-50 nm and apparent length of chains mainly ranged from 100 to 300 nm. The aggregation caused by molecular self-association enhanced with concentration increasing. Additionally, Newtonian behavior was observed at various concentrations. Increase in temperature effectively broke this behavior. 10.0 wt.% PPS possessed activation energy of 21.7 KJ/mol, was structured liquid and almost fitted Cox-Merz rule. These closely related with its conformation and molecular self-association behavior.

Effects and mechanisms of ultrasound- and alkali-assisted enzymolysis on production of water-soluble yeast β-glucan

This study investigated the effects and related mechanisms of ultrasound- and alkali-assisted enzymolysis on production of water-soluble yeast β-glucan (WSYG). Results indicated that ultrasound and alkali pretreatments reduced the particle size of yeast β-glucan (YG) from 8.80 μm to 1.77 and 7.19 μm, respectively. Ultrasound-induced cavitation disrupted YG aggregates to a coarse appearance and exposed internal structure. Alkali penetrated into YG particles and broke the YG aggregates into a flake-like morphology by cleaving the linkages within YG chains. Both pretreatments facilitated enzymolysis by enlarging the YG surface area and increased the WSYG yield to 32.3% and 36.2%, respectively. Meanwhile, the purity of WSYG reached 98.8% after zymoprotein removal by DEAE-Sepharose fast flow column. This work not only provides a green method for producing high-purity and high-yield WSYG, but also reveals the mechanisms of ultrasound and alkali pretreatments for improving enzymolysis efficiency by loosening the YG structure and increasing the surface area.

Chemical Modifications of Lipids and Proteins by Nonthermal Food Processing Technologies

A range of nonthermal techniques have demonstrated process efficacy in ensuring product safety, extension of shelf life, and in general a retention of key quality attributes. However, various physical, chemical and biochemical effects of nonthermal techniques on macro and micro nutrients are evident, leading to both desirable and undesirable changes in food products. The objective of this review is to outline the effects of nonthermal techniques on food chemistry and the associated degradation mechanisms with the treatment of foods. Oxidation is one of the key mechanisms responsible for undesirable effects induced by nonthermal techniques. Degradation of key macromolecules largely depends on the processing conditions employed. Various extrinsic and intrinsic control parameters of high-pressure processing, pulsed electric field, ultrasound processing, and cold atmospheric plasma on chemistry of processed food are outlined. Proposed mechanisms and associated degradation of macromolecules, i.e., proteins, lipids, and bioactive molecules resulting in food quality changes are also discussed.

Effect of Ultrasound Technology on Food and Nutritional Quality

Ultrasound technology has been successfully demonstrated for several food processing and preservation applications. The majority of food processing applications reported refer to liquid foods. Ultrasound has been applied to solid foods in some niche applications, e.g., tenderization of meat, mass transfer applications, and drying. Similar to any other technology, ultrasound also has some positive and negative effects on food quality depending on the application and processing conditions employed. This chapter outlines various applications of ultrasound to food and its effect on food and nutritional quality.

Ultrasound impact on whey protein concentrate-pectin complexes and in the O/W emulsions with low oil soybean content stabilization

Consumers' preference for products with reduced levels of fat increased in the last years. Proteins and polysaccharides have an important role due to their functional and interaction properties because, when combined in ratios and pH of higher potential for electrostatic interactions they may act as emulsifiers or stabilizers. This study evaluated the ultrasound impact on the electrostatic interaction between pectin (PEC) and whey protein concentrate (WPC) at different WPC:PEC ratios (1:1 to 5:1), and its effect on the emulsification and stability of emulsions formulated with WPC:PEC blends (1:1, 4:1) at low soybean oil contents (5 to 15%). Zeta potential analysis showed greater interactions between biopolymers at pH 3.5, which was proven in FTIR spectra. Rheology and turbidimetry showed that the ultrasound reduced the suspension viscosity and the size of the biopolymer complexes. Suspensions were Newtonian, whereas the emulsions showed shear-thinning behavior with slight increase in apparent viscosity as a function of oil content, and remained stable for seven days, with small droplets (<8 μm) stabilized and entrapped in a pectin network evidenced by confocal laser microscopy. Sonication was successfully applied to emulsion stabilization, improving the functional properties of WPC:PEC blends and enabling their application as low-fat systems, providing healthier products to consumers.

Lactobacillus casei BL23 Produces Microvesicles Carrying Proteins That Have Been Associated with Its Probiotic Effect

Archaea, bacteria, and eukarya secrete membrane microvesicles (MVs) as a mechanism for intercellular communication. We report the isolation and characterization of MVs from the probiotic strain Lactobacillus casei BL23. MVs were characterized using analytical high performance techniques, DLS, AFM and TEM. Similar to what has been described for other Gram-positive bacteria, MVs were on the nanometric size range (30–50 nm). MVs carried cytoplasmic components such as DNA, RNA and proteins. Using a proteomic approach (LC-MS), we identified a total of 103 proteins; 13 exclusively present in the MVs. The MVs content included cell envelope associated and secretory proteins, heat and cold shock proteins, several metabolic enzymes, proteases, structural components of the ribosome, membrane transporters, cell wall-associated hydrolases and phage related proteins. In particular, we identified proteins described as mediators of Lactobacillus’ probiotic effects such as p40, p75 and the product of LCABL_31160, annotated as an adhesion protein. The presence of these proteins suggests a role for the MVs in the bacteria-gastrointestinal cells interface. The expression and further encapsulation of proteins into MVs of GRAS (Generally Recognized as Safe) bacteria could represent a scientific novelty, with applications in food, nutraceuticals and clinical therapies.

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.

Influence of sodium alginate pretreated by ultrasound on papain properties: Activity, structure, conformation and molecular weight and distribution

The aim of the study was to investigate the impact of sodium alginate (ALG) pretreated by ultrasound on the enzyme activity, structure, conformation and molecular weight and distribution of papain. ALG solutions were pretreated with ultrasound at varying power (0.05, 0.15, 0.25, 0.35, 0.45W/cm(2)), 135kHz, 50°C for 20min. The maximum relative activity of papain increased by 10.53% when mixed with ALG pretreated by ultrasound at 0.25W/cm(2), compared with the untreated ALG. The influence of ultrasound pretreated ALG on the conformation and secondary structure of papain were assessed by fluorescence spectroscopy and circular dichroism spectroscopy. The fluorescence spectra revealed that ultrasound pretreated ALG increased the number of tryptophan on papain surface, especially at 0.25W/cm(2). It indicated that ultrasound pretreatment induced molecular unfolding, causing the exposure of more hydrophobic groups and regions from inside to the outside of the papain molecules. Furthermore, ultrasound pretreated ALG resulted in minor changes in the secondary structure of the papain. The content of α-helix was slightly increased after ultrasound pretreatment and no significant change was observed at different ultrasound powers. ALG pretreated by ultrasound enhanced the stability of the secondary structure of papain, especially at 0.25W/cm(2). The free sulfhydryl (SH) content of papain was slightly increased and then decreased with the increase of ultrasonic power. The maximum content of free SH was observed at 0.25W/cm(2), under which the content of the free SH increased by 6.36% compared with the untreated ALG. Dynamic light scattering showed that the effect of ultrasound treatment was mainly the homogenization of the ALG particles in the mixed dispersion. The gel permeation chromatography coupled with the multi-angle laser light scattering photometer analysis showed that the molecular weight (Mw) of papain/ALG was decreased and then increased with the ultrasonic pretreatment. Results demonstrated that the activity of immobilized papain improved by ultrasonic pretreatment was mainly caused by the variation of the conformation of papain and the effect of interactions between papain and ALG. This study is important to explain the intermolecular interactions of biopolymers and the mechanism of enzyme immobilization treated by ultrasound in improving the enzymatic activity. As expected, ALG pretreated by appropriate ultrasound is promising as a bioactive compound carrier in the field of immobilized enzyme.

Natural emulsifiers - Biosurfactants, phospholipids, biopolymers, and colloidal particles: Molecular and physicochemical basis of functional performance

There is increasing consumer pressure for commercial products that are more natural, sustainable, and environmentally friendly, including foods, cosmetics, detergents, and personal care products. Industry has responded by trying to identify natural alternatives to synthetic functional ingredients within these products. The focus of this review article is on the replacement of synthetic surfactants with natural emulsifiers, such as amphiphilic proteins, polysaccharides, biosurfactants, phospholipids, and bioparticles. In particular, the physicochemical basis of emulsion formation and stabilization by natural emulsifiers is discussed, and the benefits and limitations of different natural emulsifiers are compared. Surface-active polysaccharides typically have to be used at relatively high levels to produce small droplets, but the droplets formed are highly resistant to environmental changes. Conversely, surface-active proteins are typically utilized at low levels, but the droplets formed are highly sensitive to changes in pH, ionic strength, and temperature. Certain phospholipids are capable of producing small oil droplets during homogenization, but again the droplets formed are highly sensitive to changes in environmental conditions. Biosurfactants (saponins) can be utilized at low levels to form fine oil droplets that remain stable over a range of environmental conditions. Some nature-derived nanoparticles (e.g., cellulose, chitosan, and starch) are effective at stabilizing emulsions containing relatively large oil droplets. Future research is encouraged to identify, isolate, purify, and characterize new types of natural emulsifier, and to test their efficacy in food, cosmetic, detergent, personal care, and other products.

Effect of power ultrasound pretreatment on peptidic profiles and angiotensin converting enzyme inhibition of milk protein concentrate hydrolysates

BACKGROUND

The use of power ultrasound as a pretreatment to enhance the hydrolysis of milk protein concentrate (MPC) and subsequent angiotensin converting enzyme (ACE) inhibitory activity has been studied. Liquid chromatography was used to analyse peptide profiles of Neutrase-derived MPC hydrolysates after pretreatment at 0, 1, 3, 5 and 8 min at an ultrasound power level of 800 W.

RESULTS

The peptide profiles indicated an increase in number of peptides when ultrasound pretreatment was applied. There was also an increase in the degree of hydrolysis of MPC hydrolysates. The profiles indicated that new small peptides in ultrasound pretreated samples (1-5 min) which were not present in the control samples and 8 min pretreated samples, could be responsible for increased ACE inhibitory activity. These small peptides were digested in the 8 min pretreated samples.

CONCLUSION

Ultrasound pretreatment of MPC increases the ACE inhibitory activity of the hydrolysates because of the production of new small peptides. This can be used as a means to derive potent ACE inhibitory peptides at industrial scale in complex protein sources.