Whey Protein Suspensions Research Articles

Characterising the influence of milk fat towards an application for extrusion-based 3D-printing of casein−whey protein suspensions via the pH−temperature-route

This study presents the design and characterisation of casein−whey protein suspensions (8.0/10.0% (w/w) casein and 2.0/2.5% (w/w) whey protein) mixed with dairy fat (1.0, 2.5 and 5.0% (w/w) total fat) processed via the pH−temperature-route in preparation for 3D-printing. Mechanical treatment was applied to significantly decrease the particle size of the milk fat globules and increase surface area, creating small fat globules (<1 μm) covered with proteins, which could act as pseudo protein particles during gelation. Different proteins covered the fat globule surface after mechanical treatment, as a result of differences in the pH adjusted just prior to heating (6.55, 6.9 or 7.1). The protein-fat suspensions appeared similar by transmission electron cryogenic microscopy and the zeta-potential of all particles was unchanged by the heating pH, with a similar charge to the solution (~−20 mV) occurring after acidification (pH 4.8/5.0) at low temperatures (2 °C). A low heating pH (6.55) resulted in increased sol−gel transition temperatures (G՛ = 1 Pa) and a decreased rate of aggregation for protein−fat suspensions. A higher heating pH (6.9 and 7.1) caused an increased rate of aggregation (aggregation rate ≥ 250 Pa/10 K), resulting in materials more promising for application in extrusion-based printing. 3D-printing of formulations into small rectangles, inclusive of a sol−gel transition in a heated nozzle, was conducted to relate the aggregation rate towards printability.

Design and characterization of casein–whey protein suspensions via the pH–temperature-route for application in extrusion-based 3D-Printing

The current interest in individualized food through additive manufacturing has identified a need for more information on the formulation and printability of potential ingredients. Here, the effect of formulation parameters of casein–whey protein suspensions like the pH (4.8–5.4) as well as the casein content (8.0–12.0% (w/w)) mixed with whey protein (2.0–3.0% (w/w)) and the effect of pre-processing parameters including the denaturation of whey proteins (80 °C, 10 min; adjusted pH 6.55, 6.9 and 7.1) on the gel formation via the pH–temperature (T)-route was studied. Rheological measurements showed that the sol–gel transition temperature (G’ = 1 Pa) decreased and the aggregation rate of the casein–whey protein suspensions increased with increasing heating pH value. The aggregation rate was considered to be a key parameter predicting the printability of formulations. By exceeding a certain aggregation rate (250 Pa/10 K), casein–whey protein suspensions were found to be printable resulting in firm and stable gels.

Effect of high power ultrasonic treatment on whey protein foaming quality

SummaryHigh power ultrasonic energy at 20%, 40% and 60% amplitude was applied on whey protein suspension at concentrations of 100, 150 and 200 g kg−1 for 5, 15 and 25 min to improve its foaming quality. Ultrasound‐treated whey protein suspension at 200 g kg−1 showed improvement in terms of increased foaming capacity by 18%, foam stability by 35%, consistency index by 18%, storage modulus by 17%, loss modulus by 26% and viscosity by 21% compared with untreated whey protein. For maximally ultrasound‐treated samples of 60% amplitude treated for 25 min, the improved whey protein foams also had a 46% increase in the number of more evenly distributed fine bubbles which had a size smaller than 0.0025 mm3 as imaged using X‐ray microtomography.

Temperature dependent membrane fouling during filtration of whey and whey proteins

Ultra- and microfiltrations are industrially applied for the concentration and fractionation of whey proteins. Thereby, either high (~50°C) or low (<10°C) processing temperatures can be selected to avoid microbial spoilage of the product. Filtration performance at the two temperature ranges was found to be significantly different. For this reason, this study focusses on the impact of temperature on membrane fouling during both ultra- and microfiltration of whey and whey protein suspensions. We found significantly different deposit layer structures at the two pore sizes investigated. During microfiltration (full whey protein permeation), membrane fouling due to adsorption processes was facilitated at temperatures ≤10°C and >35°C. For filtrations with fully retentive ultrafiltration membranes, an increase in processing temperature resulted in a decrease of specific fouling resistance, while deposit layer solid height increased. In cross-flow mode, fouling resistance was independent of temperature during acid whey microfiltration. A temperature increase during filtration of sweet whey resulted in a sharp increase of membrane fouling for temperatures above 40°C. When increasing temperature, the stronger fouling reaction in neutral pH-range could be attributed to both, the acceleration of thiol/disulfide reaction speed and calcium based protein cross-linking.

Improvement of Eggless Cake Structure Using Ultrasonically Treated Whey Protein

Ultrasound treatment was applied on whey protein concentrate suspension prior to foaming and being mixed into batter for eggless cake baking. The improvement of batter and baked cake made using ultrasound treated whey protein were measured in terms of aeration, rheological and textural properties. Baked cakes formulated with untreated whey protein suspension at varying concentrations between 10 and 20 % were compared with ultrasound treated whey protein up to 25 min at 60 % amplitude. Visualized images of aerated cake products using x-ray tomography technique supported the findings of improved batter in terms of density decrease by 5 %, and viscosity, consistency index, storage modulus, and loss modulus increase by 31, 57, 33, and 21 %, respectively. For baked cakes, volume increase was 18 %, and density, hardness, and chewiness decrease was 18, 65, and 64 %, respectively, when compared to those made using untreated whey protein. Image analysis presented a higher number of smaller gas cells in the aerated baked cakes structure using ultrasound treated whey protein.

Characterisation of improved foam aeration and rheological properties of ultrasonically treated whey protein suspension

Suspensions of 10, 15 and 20% (w/v) whey protein concentrate (WPC) were treated with 20 kHz ultrasound for 5, 15 and 25 min at an amplitude of 20, 40 or 60%. The treated suspensions were whipped into foam and the aeration and rheological properties were investigated. With increasing ultrasound amplitude and treatment time, whey protein foam at 15% concentration produced the highest foaming capacity, while foam stability, storage modulus, loss modulus, consistency index and viscosity of foam increased with protein concentration. Foam viscosity correlated with foam stability with R2 = 0.7425 and significant at P < 0.001.

A novel method to prepare gluten-free dough using a meso-structured whey protein particle system

This paper presents a novel concept for making an elastic dough using a structured protein suspension. The idea behind it is based on the hypothesis that a number of gluten properties originate from a particle structure present in the gluten network. Three different mesoscopically structured whey protein suspensions were produced: whey protein aggregates, a whey protein cold set gel and whey protein particles. Dough mixtures or batters were prepared by mixing the structured protein particle suspension with starch. Farinograph curves, small and large deformation experiments showed that the presence of a mesoscopic protein structure had a large impact on the properties of gluten-free starch mixtures. The whey protein that was structured into a mesoscopic particle suspension changed the starch mixture from a liquid into a cohesive material, having strain hardening properties.

Optimizing the use of power ultrasound to decrease turbidity in whey protein suspensions

This research employed power ultrasound (US) to decrease the turbidity of whey suspensions. US was applied using a 20 kHz generator and different power levels (3 and 15 W) for different application times (5 and 15 min) at different temperatures (20, 60 °C, and no temperature control [NTC]) to whey suspensions obtained at 4 different steps in a commercial process. The whey suspensions varied from 6.9 to 30.2% solids and 13.5 to 88% protein. This research shows an approximately 90% decrease in turbidity when US was applied to a whey suspension of 28.2% of solids containing 35.6% of protein on a dry basis. The greatest decrease in turbidity was observed when US was applied for 15 min using 15 W of electrical power at 60 °C and NTC conditions. Surprisingly, when US was used in whey suspensions containing 88.0% protein an increase in turbidity of samples was observed.

Influence of pH and Al 2(SO 4) 3 on the stability of whey suspensions

The effects of pH and aluminium sulphate concentration on the stability of whey suspension have been investigated. The particle size and particle size distribution are examined by scanning electron microscopy and granulometric analysis, respectively. The zeta potential and residual turbidity of 0.01 wt% whey suspensions are determined over the pH range of 3–8 with aluminium sulphate as background electrolyte. The results show that the zeta potential of whey suspensions depends on pH and, to a lesser degree, aluminium sulphate concentration. The average particle size of flocs in suspension increases with decreasing zeta potentials which is accompanied by low turbidity. The degree of flocculation of whey suspension is linked to the zeta potential. The DLVO calculations are in good agreement with the observed trends indicating that the classical DLVO theory can be used to predict colloidal stability of the whey protein suspensions in the presence of higher strength electrolyte and varying pHs.

Antioxidant properties of Maillard reaction products obtained by gamma-irradiation of whey proteins

Abstract The radiation processing of sugar–amino acid solutions results in formation of Maillard reaction products (MRPs). In the present study, the efficacy of gamma-irradiation in the formation of MRPs from whey protein powder was investigated. The formation of MRPs in whey protein suspension was studied by monitoring spectrophotometeric and chemical changes. A dose-dependent increase in UV absorbance and development of fluorescence was observed. Formation of brown pigments was established by increased A420 nm and Hunter colour upon irradiation. These MRPs exhibited antioxidant activity as measured by 1,1-diphenyl-2-picrylhydrazyl and β-carotene bleaching assays. Reducing power and iron-chelating abilities of MRPs also increased upon irradiation. These MRPs were able to scavenge hydroxyl and superoxide anion radicals under in vitro conditions. Dose-dependent decrease in free amino groups and lactose suggested the formation of glycated proteins upon irradiation treatment. SDS–PAGE analyses indicated formation of crosslinked proteins upon irradiation.

Effect of ultrasound treatment on solubility and foaming properties of whey protein suspensions

The aim of this study was to observe the effect of ultrasound and sonication on whey proteins in order to improve their functional properties. Effect of ultrasound treatment on physicochemical and functional properties was examined by pH, conductivity and solubility measurements and foaming properties. In this work, low-intensity ultrasound (500 kHz) and the high-intensity ultrasound (20 kHz probe and 40 kHz bath) were used. 10 wt.% protein model suspensions of whey protein isolate (WPI); whey protein concentrate (WPC-60); and whey protein hydrolysate (HWP) were treated with ultrasound probe (20 kHz for 15 and 30 min) and ultrasound baths (40 kHz and 500 kHz for 15 and 30 min). pH did not change significantly upon ultrasound treatments. Ultrasound affected functional properties (using 20 kHz probe) of whey proteins like solubility and foaming ability by sample exposure at high temperatures caused by sonication. Using ultrasound of 40 kHz frequency had less effect on protein properties and better results were obtained with 15 min treatment than with 30 min treatment. Ultrasound treatment with 500 kHz bath did not had effect on foaming properties of whey protein model solutions. Conductivity decreased for ultrasound treatments with 40 kHz and 500 kHz bath for all samples. Temperature of protein model solutions increased after all ultrasound treatments.

Effect of carbohydrates on the emulsifying, foaming and freezing properties of whey protein suspensions

The aim of this study was to examine interactions between whey proteins (whey protein isolate (WPI), whey protein concentrate (WPC) and β-lactoglobulin) and carbohydrates (glucose, sucrose, starch and inulin) on some physical and functional properties of whey proteins and carbohydrates suspensions (10% dry matter (w/v)). Model systems were therefore investigated related to their foam expansion and foam stability. Carbohydrate addition in model suspensions of whey proteins resulted in significantly ( P < 0.05) enhanced foam stability of protein suspensions (FSI; MFS). Model systems were also analyzed for emulsion activity index (EAI) and emulsion stability index (ESI) by the turbidometric technique. EAI and ESI values increased significantly ( P < 0.05) in model suspensions prepared with WPI and β-lactoglobulin in combination with mono and disaccharides, while significant decrease ( P < 0.05) were remarked in model suspensions prepared with inulin and starch addition. The phase-transition temperatures of investigated model systems were determined using differential thermal analysis with continuous scanning. In all model suspensions, significant lowering ( P < 0.05) of initial freezing temperature has occurred.

Encapsulation of bifidobacteria in whey protein-based microcapsules and survival in simulated gastrointestinal conditions and in yoghurt

Abstract Bifidobacterium breve R070 (BB R070) and Bifidobacterium longum R023 (BL R023) were encapsulated as freeze-dried or fresh cultures in water-insoluble food-grade microcapsules produced by emulsion and/or spray-drying, using milk fat and/or denatured whey proteins as immobilization material. The encapsulation yield differed significantly according to the method and the strain used. Dispersion of fresh cells in heat-treated whey protein suspension followed by spray-drying was the least destructive immobilization technique tested, with a survival rate of 25.7±0.1% and 1.4±0.2% for BB R070 and BL R023, respectively. Viable counts of BB R070 cells entrapped in whey protein microcapsules using this method were significantly higher than those of free cells after 28 days in yoghurt stored at 4°C (+2.6 log cycles), and after sequential exposure to simulated gastric and intestinal juices (+2.7 log cycles). In contrast, no protective effect of encapsulation was observed with BL R023. Immobilization of probiotic cultures in whey protein-based microcapsules can increase cell survival when subjected to extreme conditions, making this approach potentially useful for delivery of viable bacteria to the gastrointestinal tract of humans via dairy fermented products. However, technological properties of the strains, and particularly heat resistance, should be taken into consideration for spray-dry encapsulation of sensitive microorganisms.

Effects of flow behaviour on the aggregation of whey protein suspensions, pure or mixed with xanthan

The effects of the flow behaviour at different temperatures on whey protein isolate (WPI) suspensions, pure or mixed with xanthan, have been investigated at pH 5.4. The experiments were performed in a continuous rotor/stator device, on the pilot-scale, using different rotational speeds and rotor geometries. The effects of a defined shear flow in a concentric cylinder system were compared with the shear and elongational flow resulting in a geometry with two scraping blades. The aggregation was studied by means of a phase inverse light microscope and quantified by particle laser diffraction measurements. The suspensions were rheologically analysed by a steady stress sweep. A decrease in aggregate size was found with an increased rotational speed, independent of temperature and rotor geometry. For the pure suspensions, the increase in rotational speed from 100 to 500 rpm, in the absence of scrapers, was accompanied by Taylor vortices. These changes in flow behaviour resulted in a dramatic decrease in aggregate size for the suspensions close to denaturation at 70°C. The rotor geometry also influenced the aggregate size. At 70°C, smaller aggregates were formed in the presence of scrapers compared to in the absence of scrapers, while below denaturation at 50°C, the opposite behaviour was found. The viscosity of the processed suspensions was lower compared to that for an unprocessed sample. The processed sample showed shear thickening behaviour. In the presence of xanthan, the effects of temperature and flow behaviour on the WPI aggregation were similar but less pronounced than those in the pure suspensions. This indicates that xanthan inhibits the effects on the WPI aggregation. When scrapers were attached to the rotor, WPI aggregates with a tendency to a long and rod-like shape were formed. These shaped aggregates were explained in terms of the flow behaviour and the pseudoplastic nature of xanthan. All mixtures showed this pseudoplastic behaviour, independent of process history.

Effect of Casein and β-Casomorphins on Gastrointestinal Motility in Rats

The effect of bovine casein and synthetic beta-casomorphins on the motility of rat gastrointestinal tract was studied by noninvasive techniques using the nonabsorbable marker 141Ce. Casein suspensions (CAS) or whey protein suspensions (WPS) were labeled with 141Ce and fed by gastric tube. Gastric emptying rate (GER) as well as gastrointestinal transit time (GITT) of the tracer were significantly longer with feeding CAS compared to WPS. The differences between the CAS and the WPS groups were partly (GER) or completely (GITT) abolished by pretreating the animals with the specific opiate-receptor antagonist naloxone. It is assumed that opioid peptides released from casein during digestion slowed gastrointestinal motility by direct interaction with gut opiate receptors. To prove whether beta-casomorphins, when given by gastric tube, can affect motility, different synthetic beta-casomorphins in doses between 1 and 10 mg were added to the WPS. The beta-casomorphin-4 (Tyr-Pro-Phe-Pro-NH2) showed no effect on GITT. The D-Ala substituted D-Ala-beta-casomorphin-4 (Tyr-D-Ala-Phe-Pro-NH2) and D-Ala-beta-casomorphin-5 (Tyr-D-Ala-Phe-D-Ala-Tyr-NH2), which are more resistant to proteolytic attack and have higher opioid potency than beta-casomorphin-4, slowed GITT in a dose-dependent manner.