Maltodextrin Conjugates Research Articles

Ultrasound-Assisted Maillard Conjugation of Yeast Protein Hydrolysate with Polysaccharides for Encapsulating the Anthocyanins from Aronia.

Valorisation of food by-products, like spent brewer's yeast and fruit pomaces, represents an important strategy for contributing to sustainable food production. The aims of this study were to obtain Maillard conjugates based on spent yeast protein hydrolysate (SYH) with dextran (D) or maltodextrin (MD) by means of ultrasound treatment and to use them for developing encapsulation systems for the anthocyanins from aronia pomace. The ultrasound-assisted Maillard conjugation promoted the increase of antioxidant activity by about 50% compared to conventional heating and SYH, and was not dependent on the polysaccharide type. The ability of the conjugates to act as wall material for encapsulating various biologically active compounds was tested via a freeze-drying method. The retention efficiency ranged between 58.25 ± 0.38%-65.25 ± 2.21%, while encapsulation efficiency varied from 67.09 ± 2.26% to 88.72 ± 0.33%, indicating the strong effect of the carrier material used for encapsulation. The addition of the hydrolysed yeast cell wall played a positive effect on the encapsulation efficiency of anthocyanins when used in combination with the SYH:MD conjugates. On the other hand, the stability of anthocyanins during storage, as well as their bioavailability during gastrointestinal digestion, were higher when using the SYH:D conjugate. The study showed that hydrolysis combined with the ultrasound-assisted Maillard reaction has a great potential for the valorisation of spent brewer's yeast as delivery material for the encapsulation of bioactive compounds.

Formation of casein and maltodextrin conjugates using shear and their effect on the stability of total nutrient emulsion based on homogenization

This study aimed to explore the desirable properties of casein and maltodextrin conjugates (PPCs) with simultaneously increased stability of total nutrient emulsion (TNE). Molecular interaction, stability, rheology and microstructure were analyzed. The results exhibited that the D[4,3] of PPCs increased by 169.34% at the shear time of 12 min and zeta-potential increased to 22.56 mV when the shear time was 4 min. The fluorescence spectrum and Raman spectrum analysis showed that the maximum emission wavelength of casein shifted from 347 nm to 336 nm, and the I760 value showed a decreasing trend (0.93–0.41), indicating that the molecular structure of casein stretches and opens under the influence of the shear force, and the hydrophobic groups inside casein are released into the polar environment. Furthermore, the stability index TSI decreases from 1.3 to 0.7, the change rate of backscattered light decreases to 0.6%, and the local particle concentration decreases, suggesting that the stability of the TNE enhanced with the increase of homogenization pressure in a suitable range. Meanwhile, the droplet particles are obviously smaller and there is no cluster phenomenon. After 28 days of storage, the homogeneous pressure of 80 MPa and 100 MPa makes the TNE have smaller TBARS values. This work provides a comprehensive explanation for preparing TNE based on shear and homogenization treatments.

Maillard reaction-based conjugation of Spirulina protein with maltodextrin using wet-heating route and characterisation of conjugates

Spirulina protein concentrate (SPC) was extracted from Spirulina biomass and its structure and technofunctional properties were modified through Maillard reaction with maltodextrin (MD). Wet-heating route was adapted and Maillard reaction was controlled within initial to intermediate stage by avoiding or minimising the formation of melanoidins. A glycation degree of up to 29.1 % was achieved after reaction between SPC and MD, and molecular weight of the SPC increased accordingly. The solubility of SPC was improved only in the pH range around its isoelectric point after conjugation. The antioxidative property of the SPC–MD conjugate was also improved as the DPPH radical scavenging activity increased 19.7 to 30.2 %. Oil-in-water emulsion stabilised by SPC-MD conjugate produced at 6 h had significantly reduced droplet size, increased surface charge, and higher physical stability in temperature range 25–60 °C. The outcome of this research will help broaden the application of SPC in food as emulsifier and encapsulating shell material.

Stabilization activity of a new protein-carbohydrate complex in sesame paste: rheology, microstructure, and particle size analysis.

Sesame protein concentrate is a by-product of sesame processing with great nutritional and functional value. In the present study, sesame protein concentrate and a conjugated form of the protein with maltodextrin were applied to improve stability and texture of sesame paste. The rheological properties of samples were studied using dynamic measurement, controlled rate and controlled stress rheological analysis, and creep analysis to investigate the sesame paste structure and to illustrate the mechanism of their stability against oil separation. Samples containing the conjugate showed good stability, low average droplet size and uniform microstructure. Creep analyses showed as the conjugate was added to sesame paste, μ0 and μ1 values (corresponding dashpot viscosities) were higher than that of G0 and G1 (shear moduli of Maxwell and Kelvin-Voigt springs). Dynamic shear test exhibited increased storage modulus (G') and loss modulus (G″) by the increase in frequency and elastic structure of sesame paste converted to viscose behavior with the contribution of conjugate. Particle interaction in sesame protein concentrate (SPC)-maltodextrin conjugate (SMC), may be overcome by steric repulsion force. Furthermore, impression of a weak network structure can be observed. These phenomenon could resolve the phase separation problem of traditional sesame paste. © 2022 Society of Chemical Industry.

Influence of the Protein Content on Fiber Morphology and Heat Treatment of Electrospun Potato Protein–Maltodextrin Fibers

The production of ultrafine fibers of proteins and polysaccharides by needleless electrospinning can be performed prior to a thermal treatment to form glycoconjugates via the first stage of the Maillard reaction. The aim was to produce potato protein–maltodextrin conjugates with a varying protein content of 0.05, 0.1, 0.15, and 0.2 g/mL by needleless electrospinning and subsequent thermal treatment (0, 6, 12, 24, and 48 h at 65 °C and 75% relative humidity). The concentrations of the maltodextrins, with a dextrose equivalent of 2 and 21, were kept constant at 0.8 and 0.1 g/mL. The highest fiber production rate was achieved with a protein content of 0.1 g/mL (5.8 ± 0.4 g/h). With increasing protein content, the production rate decreased to 2.8 ± 0.5 g/h. The fibers obtained from the spinning solution containing 0.2 g/mL protein showed the largest average diameter (4.0 ± 1.5 µm) and the broadest fiber diameter distribution. The protein content of the fibers was close to that of the corresponding spinning solution. The browning index after 48 h of heating increased for all samples (9.7–14.7) compared to the unheated samples (1.1–3.3). The results indicate that the protein content has an impact on the yield, the fiber diameter, and the morphology of the fibers.

Influence of sodium caseinate, maltodextrin, pectin and their Maillard conjugate on the stability, in vitro release, anti-oxidant property and cell viability of eugenol-olive oil nanoemulsions

The influence of protein (sodium caseinate-SC), polysaccharide (maltodextrin–MD; pectin-PC) and their Maillard conjugates (sodium caseinate maltodextrin conjugate–SCMDC; sodium caseinate pectin conjugate-SCPCC) were studied on the physico-chemical and biological properties of eugenol nanoemulsions/powder. The chemical composition was optimized using Taguchi design. The particles size of eugenol nanoemulsions with SC, MD, PC, SCMDC and SCPCC were 104.6, 323.5, 1872, 181.7, and 454.4 nm, respectively while their zeta potentials were −31.2, −28.5, −21.4, −40.1 and −25.1 mV, respectively. Turbidity studies revealed higher stability of nanoemulsion prepared with Maillard conjugate (SCMDC) compared to protein or polysaccharides alone. The dispersion of SCMDC eugenol nanoparticles in buffer was prepared to study its stability at different pH (3.0, 5.0, and 7.0) and temperature (4°, 37°, 60 °C) range. In-vitro enzymatic release study showed 31 and 74% release of eugenol after 6 h at pH 2.4 and 7.4, respectively. In vitro antioxidant capacity of SCMDC encapsulated eugenol was higher than native eugenol, as demonstrated by free radical scavenging assays. In comparison to native eugenol, E:SCMDC eugenol showed reduced toxicity. These findings suggested that nanoencapsulated eugenol (E:SCMDC) have a huge potential in nutraceutical and therapeutic applications.

Structure and acid-induced gelation properties of soy protein isolate–maltodextrin glycation conjugates with ultrasonic pretreatment

Glycated conjugates were prepared by heating aqueous dispersions of soy protein isolate (SPI) and maltodextrin (MD) after ultrasonic treatment (138 W/cm2, 20 kHz) for 5, 15, and 25 min. The effect of the ultrasonic pretreatment on the structure, physicochemical characteristics, and acid-induced gelation properties of the resulting SPI–MD conjugates was investigated. The analyses of free amino groups, degree of graft, intermediates, and browning intensity confirmed the formation of SPI–MD conjugates. The ultrasonic treatment promoted the glycation reaction, which led to the increase in the β-type ordered secondary structure and less compact tertiary conformation of conjugates. The ultrasonic treatment for 5 min increased the isoelectric point, surface hydrophobicity (H0), free sulfhydryl (-SH) groups, and particle size of the conjugates. These changes in the structural and physicochemical properties of the conjugates affected their acid-induced gelation. Glucono-δ-lactone was used to form acid gels at 25 °C. Although the glycation with MD deteriorated the acid-induced gelation properties of SPI, the 5 min ultrasonic conjugates formed gels faster than the untreated conjugate, and their gels exhibited higher storage modulus (G′), gel strength, and water holding capacity (WHC), as well as denser microstructure, than the untreated conjugate gels. However, prolonged ultrasonic treatment (15 or 25 min) weakened the gelation properties of the conjugates by promoting the glycation reaction and reducing the H0. Thus, an optimum ultrasonic pretreatment can be used to modify the structure of soy protein glycation conjugates to control their gelation properties.

The Effect of Eugenol and Chitosan Concentration on the Encapsulation of Eugenol Using Whey Protein–Maltodextrin Conjugates

Eugenol has many functional properties for food and pharmaceutical purposes, especially as an antimicrobial agent. However, its use is constrained by its volatility and shelf life because it is easily degraded due to temperature, oxidation, and light. Research on encapsulation technology using biopolymers is still required to obtain the appropriate formulation in a eugenol delivery system. The aims of this research were to develop a new formulation of protein and polysaccharides in eugenol encapsulation and to determine the effect of eugenol and chitosan concentration on the characteristics of the emulsions and spray-dried powder produced. In this study, eugenol was encapsulated in whey protein–maltodextrin conjugates and chitosan through the double layer encapsulation method. The emulsions which were prepared with 2.0% eugenol were relatively more stable than those of 1.0% eugenol based on the polydispersity index and zeta potential values. Spray-dried powder which was prepared using an emulsion of 2.0% w/w eugenol and 0.33% w/w chitosan had the highest eugenol loading. The presence of chitosan resulted in more stable emulsions based on their zeta potential values, improved thermal stability of eugenol, increased eugenol loading to become twice as much as the loading obtained without chitosan, and modified release profile of eugenol from the spray-dried powders.

Formation of Whey Protein Isolate (WPI)-Maltodextrin Conjugates in Fibers Produced by Needleless Electrospinning.

Glycation of proteins via the first stage of the Maillard reaction is capable of improving their stability but not economically feasible yet. This work reports the glycation of whey protein isolate (WPI) with maltodextrin at a high yield after heating electrospun fibers made from the reactants. Glycoconjugates were characterized by Fourier transform infrared spectroscopy (FTIR) and SDS-PAGE. The binding ratio between WPI and maltodextrin was assessed via the free amino groups. The molecular weight of the conjugates and the reaction yield were studied by size exclusion chromatography. The impact of different mass ratios between WPI and maltodextrin in the fibers (5:95, 10:90, 20:80, and 25:75 w/w) was investigated. With increasing WPI content, the binding ratio of maltodextrin decreased from ∼2.1 to ∼1.2. Preferably small polysaccharides (2-13 kDa) from the maltodextrin reacted. Protein specific reaction yields of up to 44.52 ± 7.46% w/w were demonstrated in all WPI-maltodextrin fibers after heating.

Physico-chemical and antimicrobial properties of d-limonene oil nanoemulsion stabilized by whey protein-maltodextrin conjugates.

In the present investigation d-limonene oil (4-isopropenyl-1-methylcyclohexene) was encapsulated by ultra-sonication method using whey protein (WP)-maltodextrin (MD) conjugates as coating material and their characterization was done with respect to physico-chemical and antimicrobial properties. Antimicrobial activity of limonene oil (LO) nanoemulsion and bulk LO dissolved in dimethyl sulphoxide (DMSO) were assessed by agar well diffusion method. Stable formulation of d-limonene oil nanoemulsion [5.0% LO + 9.0% WP-MD (1:2 w/w) conjugate] had shown mean particle size, zeta potential and poly dispersity index of 116.60 ± 5.30nm, - 19.64 ± 0.23mV and 0.205 ± 0.02 respectively. LO nanoemulsion were stable to different food processing conditions like heat treatments, ionic strength (0.1-1.0M) and pH (3.0-7.0). LO nanoemulsion was stable for 15days at 25°C and it had shown particle size of 332.20 ± 5.40nm at 15th day. It was observed that minimum inhibitory concentration (MIC) of both LO nanoemulsion and bulk LO dissolved in DMSO were at 12.50µl/ml against Bacillus cereus (ATCC 14459), Escherichia coli (ATCC 25922), Enterococcus faecalis (NCDC 115) and Salmonella typhi (NCDC 6017). Since d-limonene has been considered to be a safer alternative compared to synthetic antimicrobial food additives, the present investigation will be helpful in developing a more effective antimicrobial system for the production and preservation of foods.

Insignificant impact of the presence of lactose impurity on formation and colloid stabilising properties of whey protein–maltodextrin conjugates prepared via Maillard reactions

Abstract We investigate the sensitivity of steric stabilising properties of protein–polysaccharide conjugates, prepared via the Maillard reactions, to the presence of sugar impurity during synthesis. The sugar can also react with protein, thus rendering potential sites on protein unavailable for linkage with polysaccharide and severely reducing the efficiency of producing these types of food dispersants. We demonstrate that despite the presence of a relatively high molar ratio of lactose contaminant to maltodextrin (10:1), the covalent complexes between maltodextrin DE19 (MD19) and Whey Protein Isolate (WPI) are still formed and continue to show superior emulsifying and colloid stabilising properties compared to native protein. The improvement was particularly marked under unfavourable environmental conditions, such as pH ∼ pI of protein, up to a storage time of 21 days. In contrast, the covalent complexes of lactose + WPI were found to have rather poor emulsion stabilising characteristics, under the same conditions. We also confirm this result by performing theoretical Self Consistent Field type calculations. The stability of emulsions was monitored using a variety of measures including the average droplet size (ADS), droplet-size distribution (DSD), rheological flow behaviours and confocal laser imaging microscopy. The suggestion that the WPI-MD19 (1:2, w/w) system is quite tolerant to the presence of lactose is of significance in future large scale industrial manufacturing of such food dispersants, due to less stringent requirements for the purity of raw material (WPI).

Improved thermal stability of whey protein–maltodextrin conjugates at pH 5.0 by d-Glucose, sucrose, d-cellobiose, and lactose

Thermal aggregation of whey proteins is a challenge for applications in clear food products with acidity around their isoelectric points (∼pH 5.0). Glycating whey proteins with sufficient maltodextrins by the Maillard reaction effectively prevents thermal aggregation but produces undesirable color and byproducts. Co-solutes improve heat stability of whey proteins at neutral pH but have not been studied at pH 5.0. In this work, mono- and di-saccharides were studied for heat stability improvements of whey protein–maltodextrin conjugates at pH 5.0. The saccharides increased the viscosity of the continuous phase and the stability of conjugates against denaturation (increased denaturation temperature and reduced enthalpy change), corresponding to smaller aggregates and improved heat stability. Sucrose was more effective in improving thermal stability than d-cellobiose, lactose and d-glucose and was interpreted by the stronger preferential interactions with conjugates. During heating, co-solutes preferentially accumulate around conjugate molecules to minimize the contact with water molecules and therefore conjugate aggregation, which was verified using atomic force microscopy. Therefore, the saccharides can be used to stabilize conjugates during heating so that milder conjugation conditions can be adopted to reduce the color and byproduct formation during the Maillard reaction.

Effect of Maillard reaction conditions on the degree of glycation and functional properties of whey protein isolate – Maltodextrin conjugates

The Maillard reaction has been used as a natural alternative to improve protein functionality by covalent coupling with saccharides. However, if reaction conditions are not properly selected, glycation can lead to a loss in functional properties. The objective of our research was to study the effect of temperature, time, water activity and reactants molar ratio on the degree of glycation and color development in whey protein isolate conjugated with maltodextrins. Three different levels of glycation (low, medium and high) were selected to investigate functional properties. The extent of glycation was assessed by quantifying the loss of amino groups using the o-phthaldialdehyde technique. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to evaluate the molecular weight of the glycoproteins. Color changes were determined using a Minolta colorimeter and calculating the browning index. Functional properties evaluated were solubility, rheological behavior, foam overrun and foam stability. Temperature and water activity were the most influential factors determining the degree of glycation and color change. The correlation coefficient between blocked amino groups and color was of 0.743. Whey protein isolate exhibited lower solubility at pH 5 and conjugates at pH 4. Consistency index and foaming properties improved according to the level of glycation achieved.

Properties of whey protein–maltodextrin conjugates as impacted by powder acidity during the Maillard reaction

Heating the powder of whey protein isolate (WPI)-maltodextrin (MD) mixture, the Maillard reaction, improves thermal stability of WPI, but the effects of powder acidity have not been studied. In this work, solutions with WPI and MD were adjusted to pH 4–7 (m-pH) to obtain spray-dried powder that was glycated at 80 °C and 65% relative humidity for 1–4 h. The conjugates were evaluated for physicochemical properties. A higher m-pH and a longer glycation resulted in a darker color. The m-pH 6 treatment had the highest degree of glycation, lowest surface hydrophobicity, lowest isoelectric point, and highest denaturation temperature, which contributed to the best heat stability evaluated at 5% protein, pH 4–7 and 0–150 mM NaCl by heating at 138 °C for 1 min. The results indicate that adjusting WPI-MD mixture solution to pH 6.0 to prepare powder for glycation can reduce the color of protein ingredients while providing heat stability for transparent beverage applications.

Effect of ultrasound treatment on the wet heating Maillard reaction between β-conglycinin and maltodextrin and on the emulsifying properties of conjugates

Soy β-conglycinin (7S) was grafted with maltodextrin (MD) by combined ultrasound treatment and wet heating Maillard reaction in this work. The physicochemical and emulsifying properties of 7S–MDH (classical wet heating) and 7S–MDUH (ultrasound-assisted wet heating grafting) have been investigated. Ultrasound treatment could speed up the conjugation process and obtain a protein–polysaccharide conjugate that exhibits superior functionality compared with the one obtained simply by wet heat treatment. The degree of grafting of 32.73 % was obtained in 30 min by ultrasound-assisted wet heating , whereas classical wet heating required 60 min. SDS-PAGE analysis indicated that 7S globulin had become complex with MD to form conjugates of higher molecular weight. Reduction in the contents of lysine and arginine during the graft reaction indicated that these two amino acid residues had the covalent linkage between 7S and MD. The results of secondary structure showed that grafted 7S had decreased α-helix level and increased β-sheet and unordered coil levels. In addition, ultrasound-assisted treatment significantly changes in surface hydrophobicity (H 0), emulsifying activity index and emulsifying stability index of 7S (p < 0.05). Moreover, the emulsions of 7S–MDUH were stable under unfavorable conditions, such as extreme pH, ionic strength and heat treatment temperature, which is mainly due to changes in surface hydrophobicity (H 0) and secondary structure, resulting in a reduction in protein molecular steric hindrance in an increase in molecular flexibility. This study demonstrated that combined ultrasound treatment and wet heating Maillard reaction could potentially be applied as a method to prepare 7S–MD conjugates.

Freeze-Thaw Stability of Oil-in-Water Prepared with Soy Protein Isolate-Maltodextrin Conjugates

The objective of the study was to investigate the impact of soy protein isolate (SPI)-maltodextrin conjugates on the freeze-thaw stability of oil-in-water emulsions. Covalent coupling of maltodextrin to SPI was achieved by wet heating of SPI- maltodextrin mixtures of different weight ratios and different protein contents at 70,80,90,100°C for 1 to 5 h. The freeze-thaw stability was characterized by measurements of creaming index and oiling off after isothermal storage at -20 °C for 24 h and further thawing. Compared with those stabilized by SPI alone, o/w emulsions stabilized by SPI-maltodextrin conjugates showed a higher stability against freeze-thaw treatment, exhibiting a lower creaming index and oiling off.

Sodium caseinate–maltodextrin conjugate stabilized double emulsions: Encapsulation and stability

The potential food applications of water-in-oil-in-water (W1/O/W2) double emulsions are great, including the encapsulation of flavours or active ingredients. However, the stability of these emulsions restricts their applications in food systems. Sodium caseinate (NaCN)–maltodextrin (Md40 or Md100) conjugates were investigated for their potential to improve the stability of W1/O/W2 double emulsions compared to NaCN. NaCN–Md40 and NaCN–Md100 conjugates were prepared by a Maillard-type reaction by dry heat treatment of mixtures of NaCN–Md40 or NaCN–Md100 at 60 °C and 79% relative humidity for 4 days. Water-in-oil-in-water (W1/O/W2) double emulsions with NaCN, NaCN–Md40 or NaCN–Md100 as outer aqueous phase containing emulsifier were prepared using a two-step emulsification process. General emulsion stability was characterised by determining the droplet size distribution, viscosity characteristics and by confocal microscopy of the W1/O/W2 double emulsions on formation and after their storage under accelerated shelf life testing conditions at 45 °C for up to 7 days. Inner phase encapsulation and stability were characterised by monitoring the level of entrapped Vitamin B12 in the inner aqueous phase on formation of the double emulsions and after storage at 45 °C for up to 7 days. Conjugate stabilized emulsions were more generally stable than NaCN stabilized emulsions. In comparison to NaCN stabilized emulsions, conjugate stabilized emulsions showed improved Vitamin B12 encapsulation efficiency in the inner aqueous phase on emulsion formation and improved encapsulation stability following storage of the emulsions.

Heat stability and freeze–thaw stability of oil-in-water emulsions stabilised by sodium caseinate–maltodextrin conjugates

Abstract A sodium caseinate (NaCN)–maltodextrin (Md100) conjugate was prepared by a Maillard-type reaction by dry heat treatment of a NaCN–Md100 mixture at 60 °C and 79% relative humidity for 4 days. Conjugation resulted in a 35.7% loss of available amino groups in the NaCN and a 25.9% loss of available reducing groups in the Md100. The crude conjugate was purified by batch anion exchange chromatography to remove non-conjugated Md100. Purification reduced the available reducing groups in the conjugate from 74.1% to 23.7% and increased the protein content from 45.6% to 83.9%. The emulsifying properties of the conjugates were assessed in oil-in-water (o/w) emulsions; crude and purified conjugate stabilised emulsions had improved storage stability and freeze–thaw stability when compared to NaCN stabilised emulsions. Purified conjugate stabilised emulsions had better thermal stability than NaCN, NaCN–Md mixture and non-purified conjugate stabilised emulsions. These results indicate a potential for these NaCN–Md conjugates as speciality functional food ingredients.

The emulsion flocculation stability of protein–carbohydrate diblock copolymers

The effect of the steric layer thickness on the flocculation stability of β-lactoglobulin–carbohydrate diblock copolymers was assessed. The diblock copolymers were created by conjugating β-lactoglobulin to maltose or a series of different M n maltodextrins using the Maillard reaction. The thickness and spatial arrangement of the interfacial layers were assessed via latex adsorption and selective enzymatic digestion studies. An increase in the molecular weight of the maltodextrin (900, 1900 and 3800 Da) increased the interfacial thickness (1.1, 2.5 and 7.3 nm, respectively). No detectable change to interfacial thickness was observed upon the attachment of maltose. The increase in the interfacial layer thickness scaled with the hydrodynamic size of the carbohydrate. The β-lactoglobulin–maltodextrin conjugates were found to have a diblock architecture, with the protein anchored at the surface and the carbohydrate protruding into the aqueous continuous phase. The stability of oil-in-water emulsions formed using the conjugates was assessed by exposing them to salt (150 mM NaCl or 0–20 mM CaCl 2), heat alone or heat in the presence of 150 mM NaCl. Conjugation of a 900 Da maltodextrin provided sufficient steric stabilization to prevent flocculation in high salt environments. The effect of the (number) density of the steric layer was also assessed by controlling the average number of maltodextrins attached per β-lactoglobulin molecule. The steric layer density at which emulsions became unstable was a function of carbohydrate M n . Emulsions made from the 900 Da maltodextrin conjugate became unstable below a steric layer density of one tail per 7.5 nm 2, whilst emulsions made from the 1900 Da maltodextrin were unstable below a steric layer density of one tail per 9.5 nm 2. This trend was expected and can be explained by the stronger van der Waals attraction that arises from the closer interdroplet separations that are permissible with the shorter maltodextrins. The excellent flocculation stability of Maillard conjugate emulsions is thought to arise from the combined effects of weak electrostatic repulsion from the screened protein surface charge and steric repulsion from the attached carbohydrate layer. This means that attachment of a relatively thin steric layer is enough to stabilize the emulsions against flocculation. These findings have important implications for the development of commercial processes to manufacture protein–carbohydrate Maillard conjugate emulsifiers. Furthermore the work provides a greater empirical understanding of the relationship between interfacial architecture and colloidal stability, and may provide the means for greater theoretical understanding of biopolymer stabilization of interfaces.

Whey protein–maltodextrin conjugates as emulsifying agents: An alternative to gum arabic

The emulsifying properties of covalent complexes of maltodextrin (MD) with whey protein (WP) isolate have been investigated under both acidic and high electrolyte concentration conditions in systems containing medium-chain triglyceride oil or orange oil. Covalent coupling of protein to polysaccharide was achieved by dry-heat treatment of a protein+polysaccharide mixture for up to 2 h. It was confirmed by SDS-polyacrylamide gel electrophoresis that the WP does become directly linked to the MD. Analysis of droplet-size distributions has shown that this covalent linking of MD to WP leads to a very substantial enhancement in the protein emulsifying behaviour under both acidic and neutral conditions. Analogous dry-heating treatment of MD with soy protein does not have this positive effect. A whey protein–MD conjugate WP–MD19, made from MD (DE=19) of intermediate mean molecular weight (8.7 kDa), has been found to be capable of producing fine emulsion droplets (0.5–1 μm) with either triglyceride oil or orange oil. Optimized WP–MD19 conjugates can produce fine stable emulsions (20 vol% oil) at 2 wt% emulsifier content, whereas the equivalent emulsion made with gum arabic requires a 20–30 wt% level of emulsifier. A WP–MD19 conjugate of protein/polysaccharide ratio 1:2 or 1:3 is effective in stabilizing low-pH emulsions of a commercial flavour oil (containing a weighting agent) over a storage period of several weeks, with no visible precipitation or phase separation when mixed with colouring agents, either before or after extensive emulsion dilution.