Investigation of the composite system of β-lactoglobulin and pectin in aqueous solutions

The compatibility in aqueous systems of β-lactoglobulin (β-lg) with low and high esterified-sodium polypectates (LMP and HMP) was investigated. The mixture did not separate into two co-existing liquid phases in any case studied. At pH above the isoelectric point (IP) of β-lg, the behavior of LMP and HMP was similar when mixing with β-lg. Pectins and β-lg were co-soluble was around a particular ionic strength (μ) (0.07 M for HMP and 0.3 M for LMP). In these circumstances, the flow behavior of pectin was hardly affected by the addition of β-1g . At all other μ, the mixture formed a liquid phase containing both β-lg and pectin and a small amount of β-lg precipitates. Here, the viscosity of the liquid phase was slightly higher than the viscosity of a solution containing the same concentration of pectin. At pH 3.5, i.e. pH⩽IP of β-lg, the behavior of LMP and HMP was different when mixing with β-lg. LMP formed insoluble complexes with β-lg at low μ (⩽0.25 M), but precipitation was suppressed at high μ (0.5 M). The composite system of β-lg/HMP formed a white, homogeneous and stable dispersion at low μ (0.07 M). The viscosity of this dispersion was much higher than the additive viscosity of individual solutions would be. Probably, the oppositely charged β-lg and HMP formed soluble complexes, which further associated into large aggregates. This complexation was also suppressed at high μ (0.5 M).     

Effect of polysaccharide charge on formation and properties of biopolymer nanoparticles created by heat treatment of β-lactoglobulin–pectin complexes

Biopolymer nanoparticles can be formed by heating globular protein/polysaccharide mixtures above the thermal denaturation temperature of the protein under pH conditions where the two biopolymers are weakly electrically attracted to each other. In this study, the influence of polysaccharide linear charge density on the formation and properties of these biopolymer nanoparticles was examined. Mixed solutions of globular proteins (β-lactoglobulin) and anionic polysaccharides (high and low methoxyl pectin) were prepared. Micro-electrophoresis, dynamic light scattering, turbidity and atomic force microscopy (AFM) measurements were used to determine the influence of protein-to-polysaccharide mass ratio (r), solution pH, and heat treatment on biopolymer particle formation. Biopolymer nanoparticles (d < 500 nm) could be formed by heating protein–polysaccharide complexes at 83 °C for 15 min at pH 4.75 and r = 2:1 in the absence of added salt. The biopolymer particles formed were then subjected to pH and salt adjustment to determine their stability. The pH stability was greater for β-lactoglobulin-HMP complexes than for β-lactoglobulin-LMP complexes. The addition of 200 mM sodium chloride to heated complexes greatly improved the pH stability of HMP complexes, but decreased the pH stability of LMP complexes. The biopolymer particles formed consisted primarily of β-lactoglobulin, which was probably surrounded by a pectin coating at low pH values. AFM measurements indicated that the biopolymer nanoparticles formed were spheroid in shape. These biopolymer particles may be useful as delivery systems or fat mimetics.     

The effects of γ irradiation on the structure of apple pectin

The effects of γ irradiation on the mol. wts, viscosities and methoxyl contents of apple pectins were investigated at doses of 0–10 kGy. The apple pectins investigated were samples isolated in the laboratory before and after irradiation and an industrially purified apple pectin. No changes in mol. wts of the pectins were observed when whole apples were irradiated but decreases in viscosity and methoxyl content were observed at doses of 1 kGy. When isolated pectins were irradiated, reductions also in mol. wt were detected, at the same doses.     

Influence of pectin structure on texture of pectin–calcium gels

A library of pectins with varying degree and pattern of methoxylation was produced by demethoxylating a parent pectin by use of NaOH or pectinmethylesterase from plant or fungal origin. Additionally, pectin was chemically depolymerised by a heat treatment. The resulting pectins were characterised in terms of degree and pattern of methoxylation (“(absolute) degree of blockiness”) and the extent of depolymerisation. Pectin–calcium gels were prepared and their texture was studied by performing compression tests. From the resulting force vs. distance curves, the modulus of elasticity under low strain and the fracture stress and strain were determined. The modulus of elasticity under low strain increased with decreasing degree of methoxylation. At very low degree of methoxylation, gels were brittle, resulting in low fracture stress. Both modulus of elasticity and fracture stress correlated more with degree of blockiness and absolute degree of blockiness as compared to degree of methoxylation. Gel strength increased with increasing Ca²⁺ or pectin concentration. Depolymerisation of pectin resulted in formation of brittle gels.Industrial relevancePectin with low degree of methoxylation can form a gel in presence of calcium. Therefore, it is widely used in the food industry. In addition, pectin-calcium interactions are of importance for the texture of fruits and vegetables, since crosslinked pectin in the cell wall provides cell-cell adhesion and mechanical strength of tissues. This research is focused on textural characteristics of pectin-calcium gels. It is shown that pectin structural properties influence texture of gels. As a result, control of pectin structure allows fine-tuning of functional properties.     

Effect of pectin, starch, and locust bean gum on the interfacial activity of monostearin and β-lactoglobulin

The behavior of some hydrocolloids widely used as stabilizers of low-oil-content water emulsions (starch, pectins, and a locust bean gum-pectin blend) at the air-water and model oil-water interface is analyzed. Their influence on the surface and interface activity of typical food emulsifiers, such as β-lactoglobulin and monostearin, is also considered. It is demonstrated that the greatest interfacial activity is provided by one of the commercial pectins studied. It is capable of modifying the characteristics of monostearin and β-lactoglobulin interfacial films in a different way depending on both the nature of the oil phase and the type of surfactant used. PRACTICAL APPLICATION: This research may contribute not only to enhance the final-consumer life quality by optimizing low-oil-content food emulsion formulations which contain "natural" stabilizers, but also to increase the added value of by-products of some fruit juices as well as of sugar factories since pectin can be manufactured not only from citrus and apple peels but also from sugar beet pulps.     

Influence of ι-carrageenan, pectin, and gelatin on the physicochemical properties and stability of milk protein-stabilized emulsions

This study evaluated the stability of bilayer emulsions as a function of secondary layer composition and pH. Primary emulsions were formulated with 5% soybean oil, 1% protein from nonfat dry milk (NDM) powder as emulsifier and ι-carrageenan (ι-carr), low-methoxyl pectin (LMp), high-methoxyl pectin (HMp), or gelatin as secondary layers. ζ-Potential values increased for each emulsion as the pH decreased, with ι-carr emulsions being consistently more negatively charged than primary emulsions and significantly more stable. ζ-Potential values were not always correlated to emulsion stability. Gelatin secondary emulsions at pH 3 and HMp secondary emulsions at pH 7 were unstable due to the presence of depletion flocculation. In addition, LMp secondary emulsions stability at pH 7 might be due to calcium bridging, which increased the emulsion's viscosity. Overall, the stability of NDM emulsions was improved when ι-carr and LMp were used as secondary layers at pH 7 and 5, and when ι-carr and HMp were used as secondary layers at pH 3. Increased stability of these systems can be attributed to a second homogenization step used to formulate the secondary emulsions and to the presence of Ca(+2) in the NDM. Results from this research show that the stability of bilayer emulsions is driven by the presence of depletion flocculation, droplet charge, droplet size and distribution and viscosity. PRACTICAL APPLICATION: The use of everyday ingredients (nonfat dry milk powder, gelatin, pectin, and carrageenan), which are understood and accepted by the average consumer, creates label-friendly products that are the wave of the future. Stable emulsions can be formed using these ingredients at various pH. Understanding the stability and how the pH impacts the physicochemical characteristics and stability of these emulsions will enable manufactures to use ordinary ingredients to create healthier products (for example, low-fat dressings, sauces, dips, and beverages).     

Anti-homogalacturonan antibodies: A way to explore the effect of processing on pectin in fruits and vegetables?

The potential of the anti-homogalacturonan(HG) antibodies JIM5, JIM7, LM7, LM18, LM19, LM20 and PAM1 for investigating the effect of processing on pectin in fruit and vegetable tissues was screened in this study. In this respect, the specificity of the antibodies towards pectin and methoxylated polygalacturonic acid with defined degrees and patterns of methylesterification was elaborated, leading to a substantial extension of the information already available in literature. Based on the obtained specificities, the distribution of pectin methylesterification in carrot and broccoli tissue was mapped. It was established that pectin with a low degree of esterification (DE) and a more blockwise distribution of the methylesters is, both in carrot and in broccoli, preferentially located at the tricellular junctions between adjacent cells. This cell wall region, however, is also likely to contain other structural pectic domains. The inner face of the cell wall adjacent to the plasma membrane seems to contain pectin with a medium DE. To evaluate the potential of the anti-HG antibodies to detect changes in degree and pattern of methylesterification caused by processing, carrot and broccoli were subjected to a thermal treatment aimed to stimulate the endogenous pectinmethylesterase (PME) activity. It was revealed that process-induced de-esterification by endogenous PME mainly tends to take place at discrete regions of the inner face of the cell wall adjacent to the plasma membrane for carrot and in tricellular junctions and the middle lamella for broccoli.     

Impact of whey protein – Beet pectin conjugation on the physicochemical stability of β-carotene emulsions

The aim of the present study was to investigate the impact of whey protein isolate (WPI)-beet pectin conjugation on the physical and chemical properties of oil-in-water emulsions incorporating β-carotene within the oil droplets. Covalent coupling of WPI to beet pectin was achieved by dry heating of WPI-beet pectin mixtures of different weight ratios at 80, 90, 100 °C and 79% relative humidity for incubation times ranging from 1 to 9 h. It was confirmed by SDS-polyacrylamide gel electrophoresis that WPI covalently linked to beet pectin. The physical and chemical stability of β-carotene emulsions was characterized by droplet size and distribution, transmission profiles using novel centrifugal sedimentation technique, microstructure and β-carotene degradation during the storage. Compared with those stabilized by WPI alone and unheated WPI-beet pectin mixtures, β-carotene emulsions stabilized by WPI-beet pectin conjugates had much smaller droplet sizes, more homogenous droplet size distribution, less change in centrifugal transmission profiles and obviously improved freeze–thaw stability, indicating a very substantial improvement in the physical stability. Rheological analysis exhibited that emulsions stabilized by WPI-beet pectin conjugates changed from a shear thinning to more like Newtonian liquid compared those with WPI alone and unheated WPI-beet pectin mixtures. Degradation of β-carotene in emulsion during storage was more obviously retarded by WPI-beet pectin conjugate than WPI and unheated WPI-beet pectin mixture, probably due to a thicker and denser interfacial layer in emulsion droplets. These results implied that protein–polysaccharide conjugates were able to improve the physical stability of β-carotene emulsion and inhibit the deterioration of β-carotene in oil-in-water emulsions.     

Spray drying behaviour and functionality of emulsions with β-lactoglobulin/pectin interfacial complexes

Aim of the present study was to investigate the impact of atomization and drying on the functionality of emulsions with a bilayered oil–water interface consisting of a globular protein (β-lactoglobulin, bLG) and anionic polysaccharides (pectins with varying degree of methoxylation). With regard to the atomization process, the emulsion spray droplet size generally decreased with increasing atomization energy. The spray droplet size distribution was narrower with rotary atomization compared to two-fluid nozzle atomization. The single droplet drying behaviour of the differently stabilized emulsions was similar as examined by acoustic levitation. With more than 95%, microencapsulation efficiency was high in all spray-dried particles. However, a shift in oil droplet size upon reconstitution indicated that oil droplet coalescence occurred within the process which was less pronounced in bilayer emulsions compared to the bLG-stabilised single layer emulsion. Data from interfacial viscoelasticity measurements showed distinct differences, which may explain oil droplet coalescence. The oxidative stability of encapsulated oil was influenced by both the physical state of the emulsions and the different constituents at the o/w-interface with bLG and low methoxylated pectin giving the best protection of the oil.     

Extraction and chemical characterization of rye arabinoxylan and the effect of β-glucan on the mechanical and barrier properties of cast arabinoxylan films

Water-extractable hemicellulose (WEH) fractions, containing approximately 65% arabinoxylans (WE-AX) and 20% mixed-linkage β-glucans were isolated from rye bran. In addition, water-extractable mixed-linkage β-glucans (BG) were isolated from oat bran as a reference material. The β-glucan content of the rye hemicellulose isolate was reduced to less than 5% by a selective lichenase treatment. Rye hemicelluloses, WEH and WE-AX had arabinose-to-xylose ratios of 0.54 and 0.57 and weight-average molecular weights (M_w) of 270 000 and 232 000 g/mol respectively. The M_w of BG was higher at 386 000 g/mol. The material properties of films prepared from the rye hemicellulose isolate and WE-AX as such, or with varying amounts of added BG (20:80; 50:50; 80:20 ratios) were studied. Prior removal of β-glucan from the isolate decreased the tensile strength of the films significantly as well as the elongation at break. Addition of BG to the purified WE-AX resulted in an increase in the tensile strength and elongation at break of the films. In contrast, the presence of BG had no clear effect on the oxygen permeability of the films. Both pure rye WE-AX and pure BG films showed excellent oxygen barrier properties (between 0.9 and 1.0 cm³ μm/m² d kPa). However, the water vapor permeability increased with addition of increasing amounts of BG to WE-AX. To our knowledge, this is the first study on the effect of β-glucans on the material and permeability properties of arabinoxylan-based films.     

A Review on the Fermentation of Foods and the Residues of Pesticides—Biotransformation of Pesticides and Effects on Fermentation and Food Quality

Residues of pesticides in food are influenced by processing such as fermentation. Reviewing the extensive literature showed that in most cases, this step leads to large reductions in original residue levels in the fermented food, with the formation of new pesticide by-products. The behavior of residues in fermentation can be rationalized in terms of the physical-chemical properties of the pesticide and the nature of the process. In addition, the presence of pesticides decrease the growth rate of fermentative microbiota (yeasts and bacterias), which provokes stuck and sluggish fermentations. These changes have in consequence repercussions on several aspects of food sensory quality (physical-chemical properties, polyphenolic content, and aromatic profile) of fermented food. The main aim of this review is to deal with all these topics to propose challenging needs in science-based quality management of pesticides residues in food.     

Effects of the addition of sucrose and cellulose on the compression behaviour of ϰ-carrageenan gels

Influence of the concentration of sucrose and cellulose pulp on the compression behaviour of ϰ-carrageenan-based gels is studied. Composition of samples was established by using a second-order central composite design. Carrageenan concentrations used were between 0.5 and 1.25%, sucrose concentrations between 0 and 30% and cellulose fibre contents between 0 and 0.5%. Uniaxial compression behaviour was analysed by evaluating two parameters: maximum rupture strength (F_max) and apparent Young's modulus (E_ap). Results obtained showed that addition of sucrose increased both F_max and E_ap values while the effect of cellulose depended on the concentration of the other components.     

Protein–polysaccharide interactions: Phase behaviour of pectin–soy flour mixture

Biopolymers mixed systems have been widely studied in the past two decades, resulting in advances in knowledge of the key parameters involved in macromolecules–macromolecules interactions. Sound understanding and control of these parameters should enable food scientists to design coating or film with desired functional properties. In this study the phase behaviour of high methoxyl pectin and soy flour at pH 4.6 was investigated. The aim was to investigate the effect of different concentrations of pectin (P) and soy flour (SF) solution and different P/SF ratios on mixture phase behaviour. Pectin suspensions at 16 mg ml⁻¹ and 8 mg ml⁻¹ concentrations and soy flour suspensions at 13 mg ml⁻¹ and 6.5 mg ml⁻¹ concentrations were prepared and mixed together in different ratios (10/90, 25/75, 50/50, 75/25, 90/10). Turbidity and rheological measurements were performed to obtain information on pectin–soy flour interaction in electrostatic compatibility conditions. The experimental data show that soy flour solution is a non-stable system in which complexes may be formed during aging. It becomes insoluble and settles to the bottom of the suspension. By blending charged soy flour, at high concentration, with anionic pectin an associative interaction between biopolymers occurs which stabilizes the protein in solution. The best pectin and soy flour suspension for forming film with a continuous network was at concentrations of 16 mg ml⁻¹ and 13 mg ml⁻¹.     

Preparation of and studies on the functional properties and bactericidal activity of the lysozyme–xanthan gum conjugate

The purpose of this research was to produce a xanthan gum–lysozyme conjugate (Lyz–XM) and to investigate the effect of conjugation on functional properties and antimicrobial properties of the conjugated products. The antimicrobial activity of Lyz is limited to Gram positive bacteria, but its antibacterial spectrum can be extended towards Gram negative bacteria by conjugation with carbohydrate through the Maillard reaction. Lyz was allowed to react with XG under mild Maillard reaction condition (pH 8.5 and 60 °C for 10 days) and conjugation was confirmed by SDS-PAGE, enzyme activity and determination of sugar content of the product. Results showed that under optimal conditions approximately 1.9 mmol XG was attached to one mol Lyz. The Lyz–XG conjugate showed higher solubility at acidic pHs and at different temperatures, increased heat stability with improved emulsion and foaming properties. Additionally, Lyz–XG conjugate showed antioxidant properties and significantly inhibited the growth of Staphylococcus aureus and Escherichia coli in a dose dependent manner. These findings may broaden food applications of Lyz as a functional ingredient with high quality emulsifier, foam producer or natural antibacterial agent in food or pharmaceutical industries.     

Interaction of phosphatidylcholine and α-tocopherol on the oxidation of sunflower oil and content changes of phosphatidylcholine and tocopherol in the emulsion under singlet oxygen

Abstract: Interaction of phosphatidylcholine (PC) and α‐tocopherol (α‐Toc) on the oxidation of oil in the emulsion consisting of sunflower oil and water under singlet oxygen at 25 °C was studied by determining peroxide value (PV) and conjugated dienoic acid (CDA) contents. Singlet oxygen was produced by chlorophyll b under 1700 lux. Single addition of PC or α‐Toc decreased the values of peroxides and CDAs of oil in the emulsion via singlet oxygen quenching. PC and α‐Toc showed simply additive interaction in decreasing the singlet oxygen oxidation of oil in the emulsion. α‐Toc was a physical quencher of singlet oxygen in the emulsion, but PC involved chemical quenching in the antioxidant action. Chlorophyll and PC contents were decreased in the emulsion under singlet oxygen, while α‐Toc was not. α‐Toc protected chlorophyll and PC from degradation, and was a more important component than PC in the oil oxidation under singlet oxygen in the emulsion.     

Elucidating the relative roles of ammonia oxidizing and heterotrophic bacteria during the biotransformation of 17α-Ethinylestradiol and Trimethoprim

The biological fate of 17α-ethinylestradiol (EE2; 500 ng/L to 1 mg/L) and trimethoprim (TMP; 1 μg/L to 1 mg/L) was evaluated with flow through reactors containing an ammonia oxidizing bacterial (AOB) culture, two enriched heterotrophic cultures devoid of nitrifier activity, and nitrifying activated sludge (NAS) cultures. AOBs biotransformed EE2 but not TMP, whereas heterotrophs mineralized EE2, biotransformed TMP, and mineralized EE2-derived metabolites generated by AOBs. Kinetic bioassays showed that AOBs biotransformed EE2 five times faster than heterotrophs. The basal expression of heterotrophic dioxygenase enzymes was sufficient to achieve the high degree of transformation observed at EE2 and TMP concentrations ≤ 1 mg/L, and enhanced enzyme expression was not necessary. The importance of AOBs in removing EE2 and TMP was evaluated further by performing NAS experiments at lower feed concentrations (500-1000 ng/L). EE2 removal slowed markedly after AOBs were inhibited, while TMP removal was not affected by AOB inhibition. Two key EE2 metabolites formed by AOB and heterotrophic laboratory-scale chemostats were also found in independent laboratory-scale mixed culture bioreactors; one of these, sulfo-EE2, was largely resistant to further biodegradation. AOBs and heterotrophs may cooperatively enhance the reliability of treatment systems where efficient removal of EE2 is desired.     

Enzymatic scouring and bleaching of cotton terry fabrics – opportunity of the improvement on some physicochemical and mechanical properties of the fabrics

In the present study, an attempt was made to treat cotton terry fabrics with alkaline pectinase enzyme and observe the effects on the properties including the degree of whiteness, water absorbency, pill formation, weight loss after abrasion, tenacity at maximum load, degree of polymerization (DP), and hand feeling of the fabric. The enzymatic treatment of cotton terry fabrics had a positive influence on some of their properties. The degree of damage of cotton terry fabrics after 20 washings in a domestic washing machine was determined by analyzing the tenacity at maximum load, weight loss after abrasion, fabric hand feeling, and the DP. Enzymatic-scoured fabrics had a higher resistance to abrasion, a lower decrease in the DP, and a higher rating of the fabric hand feeling compared with alkaline-scoured fabrics. Enzymatic processing was accompanied by a significant lower demand of energy and water. Consequently, at these processes arises the lowest amount of effluents and the produced wastewater is biodegradable. This study attempted to introduce enzymatic scouring (ES) and bleaching with peracetic acid (PAA) of the cotton terry fabrics.     

Investigation into the Maillard reaction between ɛ-polylysine and dextran in subcritical water and evaluation of the functional properties of the conjugates

The effects of temperature and pressure on the Maillard reaction between ?-polylysine and dextran in subcritical water were investigated. Browning index was determined at 420 nm, and degree of graft was estimated by O-phthaldialdehyde (OPA) method. The formation of conjugates by Maillard reaction was testified by UV–vis spectrum and SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The emulsifying activity of the conjugates was greatly improved with the rise of temperature. The antimicrobial activity of the conjugates formed below 110 °C remained the same as ?-polylysine, and then decreased obviously when the reaction temperature was above 120 °C. The reaction pressure (0–10 MPa) had no effect on the emulsifying and antimicrobial activities, but higher pressure could effectively inhibit the formation of browning compounds.     

β-Lactoglobulin conformation and mixed sugar beet pectin gel matrix is changed by laccase

Sugar beet pectin (SBP) and β-lactoglobulin (BLG) contain ferulic acid and tyrosine, respectively, potential substrates for laccase. Dispersions of BLG were treated with laccase and/or heat and SBP to assess potential for ferulic acid in SBP to influence laccase conjugation of BLG. Changes were investigated by size exclusion chromatography combined with multi angle laser light scattering (HPSEC-MALLS), refractive index (RI) and UV detector, particle size and ζ-potential analysis. Molecular weight (MW) of BLG decreased from 3.7 × 10⁴ to 2.9 × 10⁴ and root mean square (RMS) decreased from 41 to 36 after laccase treatment. The slope of a conformation plot increased from 0.35 to 0.72, indicating a change in shape in laccase treated BLG to more random coil. While laccase did not affect MW of BLG, MW of BLG increased after sequential heat and laccase treatment to 2.9 × 10⁶ and 4.4 × 10⁶, respectively. Free thiol (SH) increased by heat and laccase treatment of BLG; tyrosine in BLG increased only by heat. An increased MW and decreased ferulic acid in SBP was observed in the presence of BLG and laccase. The increase in MW was attributed to entrapment of BLG in SBP cross-linked matrix catalyzed by laccase.