Ultra Whey 99: a whey protein isolate case study

A case history of the manufacture and use of whey protein isolate is presented and particular attention is paid to the nutritional and processing characteristics of Ultra Whey 99, a whey protein isolate manufactured by Volac International Ltd. The growth of the nutritional bar market in the USA is used to demonstrate the increasing demand for specialist products such as whey protein.     

Stability of oil‐in‐water emulsions as influenced by thermal treatment of whey protein dispersions or emulsions

Properties of whey protein concentrate stabilised emulsions were modified by protein and emulsion heat treatment (60–90 °C). All liquid emulsions were flocculated and the particle sizes showed bimodal size distributions. The state and surface properties of proteins and coexisting protein/aggregates in the system strongly determined the stability of heat‐modified whey protein concentrate stabilised emulsions. The whey protein particles of 122–342 nm that formed on protein heating enhanced the stability of highly concentrated emulsions. These particles stabilised protein‐heated emulsions in the way that is typical for Pickering emulsions. The emulsions heated at 80 and 90 °C gelled due to the aggregation of the protein‐coated oil droplets.     

Highly automated and fast determination of raffinose family oligosaccharides in Lupinus seeds using pressurized liquid extraction and high‐performance anion‐exchange chromatography with pulsed amperometric detection

BACKGROUND: Taking into account several requirements for the determination of raffinose family oligosaccharides (RFOs) from Lupinus seeds—e.g., conducting plant breeding projects or food product development—a reasonable combination of efficient automated sample preparation and reliable analysis need to be developed and validated. RESULTS: In this regard pressurized liquid extraction was applied to extract the RFOs from ground and defatted lupin flour. Compared to many other publications, no further pretreatment, such as protein precipitation, was necessary to obtain satisfactory results applying ion chromatography with pulsed amperometric detection. The oligosaccharide content for the examined Lupinus albus samples were in the range 5.19–9.25 g kg⁻¹ and for Lupinus angustifolius RFOs 3.49–4.75 g kg⁻¹. Stachyose has always been the main component followed by raffinose and verbascose. CONCLUSION: The developed sample preparation and analytical method is suited to quantify raffinose, stachyose, verbascose and the disaccharide sucrose and, owing to a high degree of automation for sample preparation and relatively short analysis times by pretty peak separation, particularly high sample numbers can be accomplished. Copyright © 2008 Society of Chemical Industry     

Size classification of precipitated calcium phosphate using hydrocyclone technology for the recovery of minerals from deproteinised acid whey

Acid whey is generated during the manufacture of acidified dairy products, such as soft cheeses, acid casein ingredients and strained yoghurts. Examples of these whey‐based by‐products include Cottage cheese acid whey and Greek yoghurt acid whey. Alkalisation of acid whey at elevated temperatures (60 °C) precipitates calcium phosphate, which can be recovered and used as an ingredient. The novel application of a liquid–solid hydrocyclone in the size classification of calcium phosphate from heated and neutralised acid whey was investigated in this study. Factors influencing hydrocyclone performance were tested, and the technology was integrated into a membrane filtration‐based process for the production of milk mineral powders.     

Comparison of bioethanol and beta‐galactosidase production by Kluyveromyces and Saccharomyces strains grown in cheese whey

The production of ethanol and beta‐galactosidase by Kluyveromyces marxianus and Saccharomyces fragilis strains grown in cheese whey was evaluated. The conditions for fermentation in 50 g/L (3.3% lactose) and 150 g/L (8.8% lactose) cheese whey were 100 rpm for 24 h at 30, 35 and 40 °C. Saccharomyces fragilis IZ 275 in 8.8% lactose at 40 °C resulted in 3.90% ethanol. Kluyveromyces marxianus CCT 3172 showed higher beta‐galactosidase, 1.10 U/mg, at 30 °C. Therefore, the choice of cultivation conditions and the most suitable species is important for obtaining high yields of the products of interest.     

Preparation of nanoparticles from denatured whey protein by pH-cycling treatment

Low temperature cross-linking of denatured whey protein through pH-cycling is proposed to develop nanoparticles with controlled size and properties. Soluble polymers were produced by heating whey protein dispersions at low ionic strength and neutral pH. Nanoparticulation was induced by acidification of diluted polymer dispersions followed by pH neutralization. The effect of aggregation conditions on the physicochemical characteristics and stability of nanoparticles was studied. Nanoparticles with a diameter ranging from 100 to 300 nm were produced depending on the pH of aggregation (5.0, 5.5, 6.0), the added calcium concentration (0, 2.5, 5 mM) and the ageing time at the aggregation pH (0–75 h). The size and the turbidity of nanoparticle dispersions increased with increasing ageing time and calcium concentration. Nanoparticle voluminosity decreased with increasing calcium concentration during pH-cycling, suggesting a more compact and less porous internal structure. The stability of nanoparticles in the presence of different dissociating buffers (EDTA, urea, SDS and DTT) was evaluated and the results showed that whey protein nanoparticles were covalently cross-linked by disulphide bonds.     

Iron‐encapsulated cold‐set whey protein isolate gel powder – Part 1: Optimisation of preparation conditions and in vitro evaluation

A central composite design with a quadratic model was used to investigate the effects of three independent variables involved in the synthesis of iron‐encapsulated cold‐set whey protein isolate gel (WPI) on encapsulation efficiency (EE) and L*, a*, b* colour characteristics. The optimal conditions for maximum EE with minimum colour alteration were determined as 6.8% WPI, 18.8 mM iron and pH 7. In an in vitro gastrointestinal assay, only about 28% of the encapsulated iron was released in the gastric condition (with pepsin at pH 1.2), compared to 95% in the intestinal condition (with pancreatin at pH 7.5).     

Adjustment of vat milk treatment to optimize whey protein transfer into semi-hard cheese: A case study

The influence of heat treatment combined with microfiltration on the protein transfer from milk to cheese was investigated. Small-scale laboratory cheese-making experiments (10 L vat) showed that, upon adjusting coagulant and CaCl₂ addition, curd-making was possible as long as β-lactoglobulin denaturation was below 40%. It was also possible to compensate the negative effect of heating on rennet gel formation by protein enrichment through microfiltration. Depending on heat treatment intensity, the protein yield in curd increased to approximately 6%. Using Gouda cheese technology, pilot-scale experiments (500 L vat) showed that, depending on heat treatment intensity (up to 85 °C/60 s) and concentration (up to a concentration factor 2.0), it was possible to reduce the amount of protein which is lost in permeate and whey by 15–30%. Dry matter and crude protein of cheeses were significantly affected by heat treatment and microfiltration of milk, and proteolysis during maturation was delayed.     

Production of bacteriocin‐like inhibitory substances (BLIS) by Bifidobacterium lactis using whey as a substrate

The objective of this work was to evaluate the production of bacteriocin‐like inhibitory substances (BLIS) by Bifidobacterium animalis subsp. lactis in whey supplemented with yeast extract, inulin, Tween‐80 or l ‐cysteine. Cell growth, acidification, glucose and lactose consumption as well as BLIS production were measured during fermentations carried out in shake flasks. The best additive for both cell growth and BLIS production was shown to be yeast extract, which gave the highest concentrations of biomass (9.9 log cfu/mL) and BLIS (800 AU/mL). In a bench‐scale fermentor, B. lactis growth and BLIS production were between 6% and 25% higher than in flasks depending on the conditions assayed.     

Enhancement of the functional properties of whey protein by conjugation with maltodextrin under dry‐heating conditions

Conjugation of whey protein isolate (WPI) and maltodextrin (MD, dextrose equivalent of 6) was achieved by dry‐heating at an initial pH of 7.0, at 60 °C and 79% relative humidity, with WPI: MD6 ratio of 1:1, for up to 24 h. Conjugation was achieved with limited development of colour and advanced Maillard products on 24 h of heating. Conjugation increased the protein solubility at pH 4.5, by 7.1–8.5%, compared to the unheated and heated WPI controls. Conjugation of WPI with MD6 enhanced the stability and retention of clarity in protein solutions heated at 85 °C for 10 min with 50 mM added NaCl.     

Impacts of glucosamine/oligochitosan glycation and cross‐linking by transglutaminase on the structure and in vitro antigenicity of whey proteins

With the fixed and selected conditions, whey protein concentrate (WPC) was glucosamine‐/oligochitosan‐glycated and cross‐linked by transglutaminase, resulting in glucosamine conjugation of 4.18–5.88 g/kg. Electrophoretic analysis showed cross‐linking and glycation of whey proteins, while circular dichroism analysis indicated that the two reactions contributed less ordered secondary structure to the two products. Enzyme‐linked immunosorbent assay results showed that the two products lost 64–95% antigenic responses of WPC, and oligochitosan was more powerful than glucosamine to reduce the responses. Rocket immuno‐electrophoretic analysis also evidenced antigenicity loss. This applied treatment is efficient to modify the structure and to decrease the allergenicity of whey proteins.     

Purification of lactulose syrup by using nanofiltration in a diafiltration mode

In this study, the retention behaviours of disaccharides (lactulose and lactose) and catalysts (NaCl and H₃BO₃) in the prepared lactulose syrup were investigated in a pilot scale test of nanofiltration. Their retentions in the syrup by the applied membrane, ranked from high to low, were: disaccharides (94.7-98.5%) > NaCl (9.0-20.0%) > H₃BO₃ (−19.9-0.0%)_. These differences in retention were significant, which made it possible to carry out their separation in syrup. In addition, a model was utilized to simulate the purity and yield of disaccharide during the continuous diafiltration process. According to the simulation, 25.0 bar was chosen as the optimum operating pressure for a continuous diafiltration process. Based on the experimental results, it was found that more than 96.5% of NaCl and H₃BO₃ were removed from lactulose syrup with only a small loss (11.0%) of disaccharides when the V_c/V_f (multiple of dilution) was 5.0 for the membrane used.     

Influence of whey peptides on the surface activity of κ‐casein and β‐lactoglobulin A

Whey protein hydrolysate (WPH) was fractionated by reverse‐phase chromatography to obtain fractions of varying surface‐hydrophobicities. A model oil–water interface (MI) was pre‐coated with the WPH or fractions thereof. Contact angle (θ) of sessile drops of κ‐casein (κ‐CN) or β‐lactoglobulin A (β‐LGA) were measured on the MI. Pre‐coating of MI with un‐fractionated WPH decreased θ, that is, increased surface activity, of both κ‐CN (35–8.3°) and β‐LGA (38–21.3°). Conversely, pre‐coating of MI with the fractions significantly increased θ of both proteins as a function of hydrophobicity. Data provide insight into variability of whey protein functionality in food applications.     

Comparison of milk‐derived whey protein concentrates containing various levels of casein

Milk permeate was obtained from microfiltration (MF) and concentrated to produce milk‐derived whey protein concentrate (MWPC); MF at low temperatures yielded permeate with caseins (MWPC‐HC), and at higher MF temperatures, low concentrations of caseins were present (MWPC‐LC). MWPC samples were compared to whey protein concentrates (WPCs). Solutions of MWPC were less turbid and produced larger foam overruns and more stable foams than WPC. MWPC‐HC solutions produced the most stable foams. MWPC contained fewer types and lower relative quantities of volatile compounds than WPC before and after storage. Compared with WPC, MWPC have superior sensory, foaming and storage properties.     

Iron‐encapsulated cold‐set whey protein isolate gel powder ‐ Part 2: Effect of iron fortification on sensory and storage qualities of Yoghurt

Iron was incorporated at 20–60 mg/kg of yoghurt using iron‐encapsulated cold‐set whey protein isolate gel powder (WPI‐Fe) and by direct addition of ferrous sulphate solution. The changes in physicochemical and sensory qualities of the yoghurt samples were determined over 14 days of storage. Quality attributes of the yoghurt fortified using WPI‐Fe particles at up to 60 mg iron/kg were similar to those of unfortified control samples, especially in terms of colour and flavour, while the samples fortified by direct addition of ferrous sulphate exhibited noticeable adverse effects even at 20 mg iron/kg.     

Effect of microbial transglutaminase treatment on thermal stability and pH-solubility of heat-shocked whey protein isolate

Whey protein isolate (WPI) dispersions (5% protein, pH 7.0) were subjected to heat-shock at 70 °C for 1, 5 and 10 min. The heat-shocked WPI dispersions were treated with microbial transglutaminase (MTGase) enzyme, and thermal properties and pH-solubility of the treated proteins were investigated. Heat-shocking of WPI for 10 min at 70 °C increased the thermal denaturation temperature (T_d) of β-lactoglobulin in WPI by about 1.5 °C. MTGase treatment (30 h, 37 °C) of the heat-shocked WPI significantly increased the T_d of β-lactoglobulin by about 6.3–7.3 °C when compared with heat-shocked only WPI at pH 7.0. The T_d increased by about 13–15 °C following pH adjustment to 2.5; however, the T_d of heat-shocked WPI was not substantially different from heat-shocked and MTGase-treated WPI at pH 2.5. Both the heat-shocked and the heat-shocked-MTGase-treated WPI exhibited U-shaped pH-solubility profiles with minimum solubility at pH 4.0–5.0. However, the extent of precipitation of MTGase-treated WPI samples at pH 4.0–5.0 was much greater than all heat-shocked and native WPI samples. The study revealed that while MTGase cross-linking significantly enhanced the thermal stability of β-lactoglobulin in heat-shocked WPI, it caused pronounced precipitation at pH 4.0–5.0 via decreasing the hydrophilic/hydrophobic ratio of the water-accessible protein surface.     

Physicochemical properties of High‐Protein‐Set Yoghurts obtained with the addition of whey protein preparations

The aim of the paper was to investigate the effects of the addition of whey protein isolate (WPI) and whey protein concentrate (WPC80) on physicochemical properties of high‐protein yoghurts. Changes in storage, loss moduli, phase angle values, flow behaviour and textural parameters were determined. Surface properties (roughness, contact angles) were also estimated. The properties of yoghurts depended on the preparation type and their concentration. The application of WPI resulted in accelerated gel formation in comparison with the yoghurts produced with WPC80. This technology is addressed to particular consumers who search for new foods to meet their daily protein requirements.     

Effect of thermal treatment on whey protein polymerization by transglutaminase: Implications for functionality in processed dairy foods

The effect of thermal treatment of whey proteins (50 g/100 g) at 75, 80, 85, 90 and 95 ^°C before enzymatic treatment with microbial transglutaminase was evaluated by rheological measurements. Thermal denaturation of whey proteins was determined by differential scanning calorimetry (DSC); and the gel point and turbidity were also evaluated after addition of transglutaminase at different pH values in protein solutions. A significant (p < 0.05) interaction was observed between transglutaminase and thermal treatments. At temperatures higher than 85 ^°C the apparent viscosity measurements of whey protein solutions with transglutaminase were significantly higher than those of the control samples. DSC analysis showed that thermal denaturation occurred at temperatures close to 82 ^°C, and the enzymatic reaction was enhanced at higher temperatures. The gel point of whey proteins decreased with transglutaminase addition. This decrease became greater as a function of reaction time due to the formation of high weight protein polymers catalyzed by transglutaminase, which was also observed in the turbidity analysis.     

The effectiveness of butylated hydroxyanisole and α‐tocopherol in inhibiting oxidant‐induced chemical and structural changes of whey protein

The objective of the study was to investigate the role of butylated hydroxyanisole (BHA) and α‐tocopherol in protecting whey protein isolate (WPI) from oxidative modification. The results showed that oxidation increased protein carbonyls and decreased total sulfhydryls, and led to higher dityrosine and surface hydrophobicity (P < 0.05) than nonoxidised WPI. The presence of BHA and α‐tocopherol significantly reduced (P < 0.05) the extent of WPI oxidation, thus limiting the oxidation‐induced protein aggregates and structural changes. Therefore, BHA and α‐tocopherol may be used as potential antioxidants in WPI and WPI‐containing foods.