Characterization and acid-induced gelation of butter oil emulsions produced from heated whey protein dispersions

Whey protein isolate was dispersed at 4% or 8% (w/v) and heated at neutral pH to produce protein polymers. Butter oil, up to 20%, was homogenized in heated whey protein dispersions at pressure ranging from 10 to 120 MPa. Emulsion gelation was induced by acidification with glucono-δ-lactone. Whey protein polymers produced finely dispersed emulsions with fat droplet diameter ranging from 340 to 900 nm. Homogenization pressure was the main factor influencing droplet size. At low fat volume fraction, the emulsions exhibited Newtonian behaviour. As fat content increased, shear thinning behaviour developed as a result of depletion flocculation. Emulsion consistency index increased with protein and fat concentrations. Increasing homogenization pressure had no effect on Newtonian emulsions but promoted flocculation and significantly increased the consistency of high fat emulsions. Protein concentration was the main factor explaining emulsion gel hardness and syneresis. Syneresis decreased with increasing fat content in the gel.     

Viscoelastic properties and physicochemical characteristics of pressurized ostrich-meat emulsions containing gum additives

Minced-ostrich meat was blended and chopped with various proportions of gum powder in terms of carboxymethyl cellulose (CMC), locust bean gum (LBG) and xanthan gum (XAN) and other ingredients such as sodium chloride, sodium tripolyphosphate, linseed oil and ice. The mixed batters were then pressurized at 600 MPa and 50 °C for 40 min. Subsequently, their viscoelastic and physicochemical properties were assessed in terms of their dynamic oscillatory moduli, their resultant creep behavior, water-holding capacity and electrophoretic profiles. The results showed that the addition of individual gums and composite gum mixtures influenced both viscoelastic behavior and water-holding capacity of resulting pressurized ostrich-meat emulsions. The most elastic system (greatest G′ or smallest J₀ with 4.21 × 10^− 5 1/Pa) was the meat emulsion with 1% LBG added, while the least were those formed by adding 1% XAN or 0.5% XAN plus 0.5% CMC (J₀ with 10 × 10^− 5 and 20.3 × 10^− 5 1/Pa, respectively). Subsequent electrophoritic profiles and the measurement of the water-holding capacity of the materials suggested an evidence of ionic interaction between the basic ostrich-meat protein matrix and XAN or XAN plus CMC.Industrial relevanceOstrich meat emulsions containing composite gums were set by combined pressure and temperature. Subsequently, the pressurized gels were characterized by dynamic oscillatory, creep and other physicochemical measurements. In particular, the viscoelastic measuring system is a promising tool for ensuring quality of food biopolymers. Therefore, this methodology is relevant in the area of controlling quality or developing new products where difficulty exists in solubilising the samples.     

Heat processed whey-protein food emulsions and growth of shear-induced cracks during cooling

When high fat (40 g oil /100 g) food dressings emulsified by whey protein were heat-filled (80°C) into plastic-bottles, large visible cracks developed in the dressings after cooling. The occurrence of cracks was dependent on the length of the heat treatment, pH and protein concentration. Heating (2 h at 80°C), low pH (pH 3) and high protein concentrations (1.5 g/100 g) increased the number of cracks. Dressings with cracks were more viscous and had a broader particle size distribution than dressings devoid of cracks. During heating at 80°C the complex modulus (G¹) measured at low deformation increased sharply, signifying the formation of a three-dimensional network as a result of aggregation of whey protein bridging the fat-droplets. Confocal laser scanning microscopy revealed differences in microstructure dependent on cooling rate and pH. At slow cooling and pH 3 the network structure was inhomogeneous with large voids, while at pH 4, closer to the isoelectrical point, the structure was more compact aggregated and homogeneous. The gels at pH 3 were strain sensitive and seemed more prone to localized fracture. A strong (r=0.86) relationship between a visible quality defect called cracks and the gel properties of the emulsion was found. Avoiding cracks called for a strict control of protein concentration, pH and holding time at higher temperatures.     

An investigation of four commercial galactomannans on their emulsion and rheological properties

Four types of galactomannans, namely fenugreek gum (FG), guar gum (GG), tara gum (TG) and locust bean gum (LBG), were investigated in the present study on their emulsion and rheological properties. The M/G ratios of the four galactomannans were 1.2, 1.7, 3.0 and 3.7, respectively. The results revealed that the M/G ratio, along with molecular weight and intrinsic viscosity, played an essential role on emulsion and rheological properties. Surface activity followed the trend: FG > GG > LBG > TG. Emulsion capacity and stability followed the trend: GG > FG > TG > LBG. Storage modulus (G′) followed the same order as intrinsic viscosity, which was: GG > FG > TG > LBG. By fitting the shear-thinning region of the flow curves into the Power law model, power law index (n) increased with increased concentration. Zero shear viscosity (η_sp)₀ was derived by fitting the Newtonian regions of the flow curves into Cross model, and followed the same order with viscosity based molecular weight (M_v), which is: FG > GG > TG > LBG. Exponents of the four gums were generated from Master curves (log (η_sp)₀ versus log C), which were 4.57, 3.92, 4.31 and 4.19 for FG, GG, TG and LBG, respectively.     

Sensory profile,acceptability, and their relationship for diabetic/reduced calorie chocolates

The purpose of this study was to determine the sensory properties and acceptability of lab developed prototypes of conventional, diabetic (with no sugar), and diabetic/reduced calorie milk chocolates (no sugar and 25% calorie reduction) with high-intensity sweeteners, sucralose and stevioside, and partial fat replacement with whey protein concentrate (WPC). PLS was performed in order to relate sensory properties and consumer acceptability and to determine drivers of liking and disliking. There was no difference between conventional, diabetic and diabetic/reduced calorie milk chocolates for brightness, cocoa aroma, cocoa butter aroma, and cocoa flavor (p > 0.05). Acceptability was higher for sucrose substitution by sucralose than by stevioside and partial fat replacement reduced acceptability of flavor even more (p ? 0.05). Crucial attributes which determine consumer acceptability in samples are sweet aroma, melting rate, and sweetness, whereas bitterness, bitter aftertaste, adherence, and sandiness were drivers of disliking.     

Fat mimetic capacity of Chlorella vulgaris biomass in oil-in-water food emulsions stabilized by pea protein

Vegetable proteins proved to be good emulsifiers for food emulsions with dietetic advantages. The use of these emulsions as carriers for healthy ingredients, such as colourings, with antioxidant and other beneficial properties, is an interesting subject.In this work, the capacity of the biomass of the microalga Chlorella vulgaris (which has been widely used as a food supplement) as a fat mimetic, and its emulsifier ability, was evaluated. Pea protein emulsions with C. vulgaris addition (both green and orange – carotenogenic) were prepared at different protein and oil contents. The rheological properties of the respective food emulsions were measured in terms of the viscoelastic properties and steady state flow behaviour and texture properties. It was observed that the two microalgal forms evidenced a fat mimetic capacity in these emulsions, the performance of the green stage of this C. vulgaris organism was significantly (p < 0.05) better than the orange stage.     

Ability of conventional and nutritionally-modified whey protein concentrates to stabilize oil-in-water emulsions

The ability of a modified whey protein concentrate (MWPC), which contains relatively high proportions of phospholipid and high molecular weight protein fractions, to form and stabilize 10 wt% corn oil-in-water emulsions (pH 7.0, 5 mM phosphate buffer) was compared with that of a conventional whey protein concentrate (CWPC). The MWPC stabilized emulsions required less protein to prepare stable emulsions with monomodal particle size distributions and small mean droplet diameters (d₄₃ ≈ 0.3 μm at [WPC] ⩾ 0.5 wt%) than CWPC stabilized emulsions (d₄₃ ≈ 0.4 μm at [WPC] ⩾ 0.9 wt%) under similar homogenization conditions (5 passes at 5000 psi). In addition, the emulsions stabilized by 0.9 wt% MWPC were more stable to high salt concentration (NaCl ⩽ 200 mM), thermal processing (30–90 °C for 30 min) and pH (3, 6 and 7) than those stabilized by the same concentration of CWPC, which was attributed to polymeric steric repulsion rather than electrostatic repulsion. This study has important implications for the wide application of WPC as a natural emulsifier in food products.     

Influence of sodium dodecyl sulfate on the thermal stability of bovine serum albumin stabilized oil-in-water emulsions

The influence of an anionic surfactant (sodium dodecyl sulfate, SDS) on the thermal stability of emulsions stabilized by a globular protein (bovine serum albumin, BSA) was examined. 1 wt% n-hexadecane oil-in-water emulsions (0.5 wt% BSA, 100 mM NaCl, 20 mM imidizole, pH 7.0) were held isothermally at temperatures from 30 to 90 °C for 30 min. Extensive droplet flocculation was only observed in emulsions held at 90 °C, which lead to rapid creaming instability. The thermal stability of emulsions heated at 90 °C could be greatly improved by adding SDS at surfactant-to-protein molar ratios (R) greater than 5 (∼0.01 wt% SDS). On the other hand, adding surfactant (0<R<600) to the emulsions after heating could not prevent extensive droplet aggregation. Adding SDS to emulsions prior to heating may have improved their thermal stability by increasing the electrostatic repulsion between the lipid droplets or by increasing the denaturation temperature of the adsorbed proteins. These results may have important applications in the development of heat-stable emulsions.     

Comparison of properties of oil-in-water emulsions stabilized by coconut cream proteins with those stabilized by whey protein isolate

Coconut cream protein (CCP) fractions were isolated from coconuts using two different isolation procedures: isoelectric precipitation (CCP1-fraction) and freeze–thaw treatment (CCP2-fraction). The ability of these protein fractions to form and stabilize oil-in-water emulsions was compared with that of whey protein isolate (WPI). Protein solubility was a minimum at ∼pH 4, 4.5 and 5 for CCP1, CCP2, and WPI, respectively, and decreased with increasing salt concentration (0–200 mM NaCl) for the coconut proteins. All of the proteins studied were surface active, but WPI was more surface active than the two coconut cream proteins. The two coconut cream proteins were used to prepare 10 wt% corn oil-in-water emulsions (pH 6.2, 5 mM phosphate buffer). CCP2 emulsions had smaller mean droplet diameters (d₃₂ ≈ 2 μm) than CCP1 emulsions (d₃₂ ≈ 5 μm). Corn oil-in-water emulsions (10 wt%) stabilized by 0.2 wt% CCP2 and WPI were prepared with different pH values (3–8), salt concentrations (0–500 mM NaCl) and thermal treatments (50–90 °C for 30 min). Considerable droplet flocculation occurred in the emulsions near the isoelectric point of the proteins: CCP2 (pH ∼ 4.3); WPI (pH ∼ 4.8). Emulsions with monomodal particle size distributions, small mean droplet diameters, and good creaming stability could be produced at pH 7 for WPI, but CCP2 produced bimodal distributions at this pH. The CCP2 and WPI emulsions remained relatively stable to droplet aggregation and creaming at NaCl concentrations ⩽50 and ⩽100 mM, respectively. In the absence of salt, both CCP2 and WPI emulsions were quite stable to thermal treatments (50–90 °C for 30 min).     

The increased viability of probiotic Lactobacillus salivarius NRRL B-30514 encapsulated in emulsions with multiple lipid-protein-pectin layers

Probiotics have demonstrated various health benefits but have poor stability to sustain food processing and storage conditions, as well as after ingestion. Biopolymer beads are commonly studied to encapsulate probiotic cells to improve their stability, but the millimeter-dimension of these beads may not meet the quality requirement of food products. The aim of this study was to enhance the viability of Lactobacillus salivarius NRRL B-30514 by encapsulation in emulsion droplets with multiple lipid-protein-pectin layers. Spray-dried L. salivarius was suspended in melted anhydrous milk fat that was then emulsified in a neutral aqueous phase with whey protein isolate or sodium caseinate to prepare primary solid/oil/water (S/O/W) emulsions. Subsequently, pectin was electrostatically deposited onto the droplet surface at pH 3.0 to form secondary emulsions. The encapsulation efficiency was up to 90%. After 20-day storage at 4 °C, the viable cell counts of bacteria in secondary emulsions at pH 3.0 and primary emulsions at 7.0 were 3 log higher than the respective free cell controls. After heating at 63 °C for 30 min, free L. salivarius was inactivated to be undetectable, while about 2.0 log CFU/mL was observed for primary (at pH 7.0) and secondary (at pH 3.0) emulsion treatments. Additionally, a 5 log-CFU/g-powder reduction was observed after spray drying free L. salivarius, while a 2 log CFU/g reduction was observed for emulsion treatments with capsules smaller than 20 μm. Furthermore, cross-linking the secondary emulsion with calcium enhanced the viability of L. salivarius after the simulated gastric and intestinal digestions. Therefore, the studied S/O/W emulsion systems may be used to improve the viability of probiotics during processing, storage, and gastrointestinal digestion.     

Nudging product choices: The effect of position change on snack bar choice

The influence of product position in a row of three similar snacks with varying calorie contents was examined in a sample of 120 students (equal numbers of males and females). Three equally sized, real cereal snack bars were arranged on a vendor’s tray in three identical boxes. Two conditions were used. In the control condition, the three boxes of snack bars were positioned from left to right in ascending order of calorie content (apple/lowest calorie content = left position; apple-chocolate/high calorie content = middle position; coco-chocolate/highest calorie content = right position). In the experimental condition (nudged group), the left and middle box positions were exchanged (apple-chocolate/high calorie content = left position; apple/lowest calorie content = middle position; and coco-chocolate/highest calorie content = right position). There was a significant effect of position on participants’ snack bar selections (χ²₍₂₎ = 14.953, p = 0.001). When the apple bar was positioned on the left, it was selected 13.3% of the time (8/60), and when it was positioned in the middle, it was selected 36.3% of the time (22/60). There was no gender effect (χ²₍₂₎ = 0.713, p = 0.70). The apple bar with lowest calorie content was selected almost three times more often when it was placed in the middle than when it was placed on the left. Changing the physical placement of the snack improved snack choices. Rearranging snacks on shelves and checkout counters in grocery stores or vending machines in schools might be an easy, inexpensive and effective intervention measure to improve consumers’ snack choices.     

Enhancement of the nutritional status and quality of fresh pork sausages following the addition of linseed oil,fish oil and natural antioxidants

Fresh pork sausages (pork shoulder, pork back fat, water, rusk and seasoning) were manufactured where 15% of the pork back fat was substituted with linseed oil (LO) or fish oil (FO). Green tea catechins (GTC) and green coffee antioxidant (GCA) were added to both LO (LGTC 200 and LGCA 200) and FO (FGTC 200 and FGCA 200) substituted sausages at a level of 200 mg/kg. Raw and cooked pork sausages were either over-wrapped with oxygen permeable film (aerobic storage) or stored in modified atmosphere packages (MAP) containing 80% O₂:20% CO₂ or 70% N₂:30% CO₂, respectively for 7 days at 4 °C. Effects on fatty acid profiles, lipid oxidation, colour and sensorial properties were investigated. α-Linolenic acid increased from 1.34% (control) to 8.91% (LO) and up to 11.2% (LGTC 200 and LGCA 200). Addition of fish oil increased levels of EPA from 0.05% (control) to 2.83% (FO), 3.02% (FGTC 200) and 2.87% (FGCA 200) and DHA levels increased from 0.04% (control) to a maximum of 1.93% (FGTC 200). Lipid oxidation was low in raw and cooked linseed oil containing sausages. GTC (200 mg/kg) significantly (P < 0.05) reduced lipid oxidation in raw fish oil containing sausages after 7 days of storage. Colour parameters in raw pork sausages were unaffected by the packaging atmosphere. L¹ lightness values were lower (P < 0.05) in LGTC 200 and a¹ redness values lower (P < 0.05) in LGTC 200 and FGTC 200 after 7 days of storage. Sensory scores of cooked pork sausages were unaffected by linseed oil addition. Flavour and overall acceptability scores in cooked fish oil containing sausages were improved by GTC addition. Results obtained demonstrate potential for the production of nutritionally enhanced fresh pork sausages.     

Nanostructures and polymorphisms in protein stabilised lipid nanoparticles,as food bioactive carriers: contribution of particle size and adsorbed materials

Eight oil-in-water emulsions were prepared using melt high-pressure homogenisation (HPH) at 300 or 1200 Bar. The emulsions produced from lipid phase (20%) were composed by palm oil alone or in mixture with α-tocopherol at 4:1 weight ratio, and an aqueous phase containing whey proteins alone or in mixture with phospholipids. The resulting nanoemulsions (fat droplet size ranging from 200-500 nm) presented different stability against aggregation and coalescence, fat crystallinity and polymorphisms in relation to different degrees of α-tocopherol encapsulation and protection against chemical degradation. Protein stabilised emulsions were monomodal, while emulsions stabilised by proteins and lecithins were slightly bimodal. Application of an isothermal treatment (4 °C for 2 hours) to these emulsions showed crystallization peaks located at longer time values in smaller particle size emulsions, while in the presence of added α-tocopherol average particle size values were higher and crystallization was not observed in 2 hours storage. Study of fat polymorphisms performed after 12 hours storage at 4 °C revealed the formation of 2L structures with coexistence of α, β’ and β forms in all of the emulsions. Increasing HPH from 300 to 1200 Bar favoured development of β structure (4.5 A^-1) in α-tocopherol added emulsions, with the presence of one extra peak β structure evolved at 3.9 A^-1 only in emulsions containing lecithins. α-tocopherol addition decreased in 2L structures (by approx. 40-50%). The formation of lipid nanoparticles with decreasing size values (increasing HPH parameters) was accompanied by increased long-term stability against aggregation and coalescence, but increased vitamin degradation (up to 15 wt% for 1200 bar). Degradation of α-tocopherol after 2 months storage at 4 °C was lower for nanoparticles stabilised by whey proteins alone (21 and 33%, respectively) than for nanoparticles stabilised by whey proteins in mixture with phospholipids and presenting higher size values (44 and 52%, respectively), where β polymorphs were more evolved.     

Impact of high pressure treatment and intramuscular fat content on colour changes and protein and lipid oxidation in sliced and vacuum-packaged Iberian dry-cured ham

The effect of high hydrostatic pressure (HHP) (600 MPa) and intramuscular fat content (IMF) on colour parameters and oxidative stability of lipids and proteins in sliced vacuum-packaged Iberian dry-cured ham during refrigerated storage (120 days at 2 °C) was investigated. Several studies have investigated the influence of HHP on lipid oxidation of meat products. However, its effects on protein carbonylation, as also the influence of IMF content on this carbonylation are poorly understood. HHP treatment had a significant effect on lean lightness after 0 and 120 days of storage while IMF content increased lightness and yellowness over time. Regarding oxidative stability, the effect of HHP treatment depended on IMF content samples with a high IMF having greater lipid instability while samples with a low IMF underwent more protein carbonylation.     

Gel-like pea protein Pickering emulsions at pH 3.0 as a potential intestine-targeted and sustained-release delivery system for β-carotene

In recent years, there is increasing interest in the development of food-grade Pickering emulsions as promising delivery systems for bioactive compounds. Our previous work reported that most of the proteins in pea protein isolate (PPI) at pH 3.0, present in the nanoparticle form, can effectively perform as a kind of food-grade Pickering stabilizers for oil-in-water emulsions (LWT, 2014). The purpose of this study was to further report that PPI-stabilized emulsions at pH 3.0 exhibited great potential to act as intestine-targeted and sustained-release delivery systems for β-carotene. The emulsions were produced by microfluidization at a specific protein concentration of 6.0% (w/v) and varying oil fractions (ϕ) of 0.2–0.6. The results indicated that increasing ϕ was favorable for the gel-like network strengthening of these emulsions. The gel formation was largely related to the droplet flocculation as well as inter-floc attractive interactions. The in vitro simulated digestion results showed that the release of β-carotene during the intestinal digestion of these emulsions could be well modulated by altering ϕ. The gel-like emulsion at ϕ = 0.6 exhibited much lower release of β-carotene, but higher stability towards degradation during the digestion, than that at ϕ = 0.3. The findings provide important information not only for the design of novel delivery systems for lipophilic bioactive components, but also for the development of plant protein-based formulations.     

Effect of the ripening time under vacuum and packaging film permeability on processing and quality characteristics of low-fat fermented sausages

The effect of vacuum ripening of low-fat fermented sausages packaged in films with different permeabilities on their microbiological, physicochemical and sensorial characteristics was studied. High-fat control sausages were produced with 30% initial fat and low-fat sausages with 10% initial fat. The low-fat sausages were separated into: (a) non-packaged (control) and (b) packaged under vacuum on 7th, 12th and 17th day of processing, remaining under vacuum during the ripening period for 21, 16 and 11 days, respectively, in three different oxygen (100, 38 and ⩽ 5 cm³/m²/24 h/1 atm) and water vapour (4.5, <2.5 and 1 g/m² 24 h) permeability plastic bags. Vacuum packaging reduced (p < 0.05) the weight loss, the hardness and extent of lipid oxidation in the sausages, increased (p < 0.05) their lightness, but had no effect (p > 0.05) on the redness, compared to the control sausages. Packaging low-fat fermented sausages under vacuum for the last 11 days of ripening in packaging film with high permeability increased (p < 0.05) the lactic acid bacteria count. The same product packaged in film with medium permeability had a higher (p < 0.05) Micrococcaceae count and the same (p > 0.05) hardness and overall acceptability as the high-fat control sausages. A ripening time of 11 days and the medium packaging film permeability were the most appropriate conditions for the vacuum packaging of low-fat fermented sausages.     

Controlling moisture transport in a cereal porous product by modification of structural or formulation parameters

Equilibrium and dynamic water sorption properties of sponge cakes with varying porosity (86–52%) and fat content (0–0.30 g/g d.b.) were determined using a water vapour sorption microbalance. Contrary to porosity, addition of fat decreased equilibrium moisture contents. The effective moisture diffusivity (D_eff) was identified from a numerical solution of Fick’s second law, taking into account an external mass transfer coefficient and the swelling of the solid matrix. D_eff increased from 1.61 to 8.67 × 10⁻¹⁰ m²/s with moisture content, reached a threshold at moisture content 0.15 g/g d.b. and then decreased until water saturation. D_eff decreased from 8.67 to 2.97 × 10⁻¹⁰ m²/s with decreasing porosity. This effect was attributed to a change of water diffusion mechanism, from predominant vapour to liquid. D_eff decreased from 8.67 to 2.12 × 10⁻¹⁰ m²/s with increasing fat content. Addition of fat had an effect on the water diffusion in two ways, decreasing porosity (sagging of the foam) and increasing tortuosity.     

Physicochemical properties of different thickeners used in infant foods and their relationship with mineral availability during in vitro digestion process

Locust bean gum (LBG) and modified starches are commonly used as thickeners in food products for infants. However, there is no consensus on their possible effects on infant nutrition, especially on mineral availability. The aim of the present work was to characterize the effect of LBG, cross-linked, hydroxypropylated maize starch (Mhdp) and pre-gelatinized rice starch (gRS) on Ca, Fe and Zn availability during a gastric and intestinal in vitro digestion assay in relation to their physicochemical properties in solution (apparent viscosity, solubility, molar mass (M) and conformational properties) through the simulated digestion process. LBG gave the highest decrease in Ca and Fe gastric (17.96% and 17.6% respectively) and intestinal (19.5% and 13.5%) solubility with respect to the reference without thickeners. Ca (11.1% ± 1.1), Fe (2.77% ± 0.3) and Zn (7.78% ± 0.6) dialyzability was also lower than for the reference (23.4% ± 2.9; 19.65% ± 3.53 and 27.74% ± 3.3 respectively). LBG solubility remained stable during gastric digestion, decreasing significantly from a range of 65–69% to 61.1% after intestinal digestion. LBG viscosity remained stable during the digestion process, being these findings attributable to its resistance to enzymes. On the other hand, the addition to Mhdp or gRS slightly affected Ca and Fe solubility or Ca dialyzability, decreasing after gastric digestion and then increasing after intestinal digestion with respect to the reference. These results correlated to the changes in their viscosity enhancing properties, which increased during gastric digestion and decreased after intestinal digestion, being attributable to their digestion by pancreatic enzymes. Gastric digestion resulted in an increase in M for the modified starches (more pronounced for gRS). The increase in mineral solubility and dialyzability after intestinal digestion with respect to the gastric stage was explained by the degradation of starches by intestinal enzymes, which resulted in a decrease in apparent shear viscosity (from 1.2 to 1 Pa s, measured in a shear rate range 0.00–50 s⁻¹) and an increase in solubility (from 3 to 6% to approximately 70%) after intestinal digestion. In conclusion, LBG could be more effective than Mhdp and gRS as thickener, providing higher viscosity and resistance to digestive process. However, its negative effect on mineral solubility and dialyzability should be taken into account. On the contrary, Mhdp and gRS showed to be degraded after intestinal digestion.     

Physical and oxidative stability of whey protein oil-in-water emulsions produced by conventional and ultra high-pressure homogenization: Effects of pressure and protein concentration on emulsion characteristics

Oil-in-water pre-emulsions (15% sunflower + 5% olive oils) obtained by colloid mill homogenization (CM) at 5000 rpm using whey protein isolate at different levels (1, 2 and 4%) were stabilized by ultra high-pressure homogenization (UHPH, 100 and 200 MPa) and by conventional homogenization (CH, 15 MPa). Emulsions were characterized for their physical properties (droplet size distribution, microstructure, surface protein concentration, emulsifying stability against creaming and coalescence, and viscosity) and oxidative stability (hydroperoxide content and thiobarbituric acid reactive substances, TBARs) under light (2000 lux/m² for 10 days). UHPH produced emulsions with lipid droplets of small size in the sub-micron range (100–200 nm) and low surface protein with unimodal distribution when produced at 4% whey proteins and 200 MPa. All emulsions exhibited Newtonian behavior (n ≈ 1). Long term physical stability against creaming and coalescence was observed in UHPH-emulsions, compared to those obtained by CM and CH. However, CH emulsions were highly stable against creaming (days) in comparison to the CM emulsions (hours). UHPH resulted in emulsions highly stable to oxidation compared to CM and CH treatments, especially when 100 MPa treatment was applied.Industrial relevanceIn the food, cosmetic and pharmaceutical sectors, industrial operators are currently interested in developing encapsulating systems to delivery bioactive compounds, which are generally hydrophobic, unstable and sensitive to light, temperature or/and oxygen. Ultra high-pressure homogenization is capable of producing stable submicron emulsions (< 1 μm) with a narrow size distribution, inducing more significant changes in the interfacial protein layer thus preventing droplet coalescence and also inhibit lipid oxidation. The present study suggests that emulsions produced by whey protein (4%) treated by ultra high-pressure homogenization have a good physical stability to flocculation, coalescence and creaming and also high stability to lipid oxidation, opening a wide range of opportunities in the formulation of emulsions containing bioactive components with lipid nature.     

Effect of germination on the chemical,functional and pasting properties of flour from brown and yellow varieties of tigernut (Cyperus esculentus)

The chemical, functional and pasting properties of flours processed from germinated (0, 24, 48 and 72 h) brown and yellow varieties of tigernut (Cyperus esculentus) seed was studied. Germination decreased carbohydrate (60.50–53.60%) and fat (60.50–53.60%) while protein and ash increased from 8.23% to 12.40% and 3.28% to 4.26%, respectively. In addition, functional properties such as foaming, emulsion, water and oil absorption capacities increased from 7.75% to 12.91%, 14.32–20.25 ml oil/g sample, 2.56–6.97 g water/g sample and 1.14–1.78 g oil/g sample, respectively, with germination. Least gelation of flour samples were improved as a result of germination process. Conversely, bulk density decreased with germination time (0.58–0.50 g/cm³). Trough, peak viscosity, break down, final viscosity, peak time and pasting temperature values were in the range (120.96–203.04 RVU), (145.28–228.11 RVU), (7.85–14.32 RVU), (180.62–324.73 RVU), (5.01.83–6.00 min) and (63.85–65.47 °C), respectively. Our results suggest that the incorporation of germinated tigernut flours may help in enhancing protein calorie delivery with improved functionality in complementary food formulations and baked products.