Whey Protein Concentrate Powder Research Articles

Effects of spray drying and freeze drying on the protein profile of whey protein concentrate.

Whey protein concentrate (WPC) is consumed for its high protein content. The structure and biological functionality of whey proteins in WPC powders may be affected by the drying technique applied. However, the specific impact of spray drying and freeze drying on the overall protein profile of whey protein derived from sweet whey streams at scale is unknown. Herein, we examine the effects of commercial-scale freeze drying and spray drying on WPC to determine which method better preserves bioactive whey proteins, with the goal of helping the dairy industry create high-value products that meet the growing consumer demand for functional dairy products. WPCs were produced from pasteurized liquid whey using either a commercial spray dryer or freeze dryer. A variety of analytical techniques, including enzyme-linked immunosorbent assay, polyacrylamide gel electrophoresis, and bottom-up proteomics using liquid chromatography-tandem mass spectroscopy were used to identify, quantify, and compare the retention of bioactive proteins in WPC before and after spray drying and freeze drying. In addition, the extent of denaturation was studied via solubility testing, differential scanning calorimetry, and hydrophobicity assessment. There was little to no difference in the retention or denaturation of key bioactive proteins between spray-dried and freeze-dried WPC powders. There was a higher percentage of select Maillard modifications in freeze-dried and spray-dried powders than in the control. The lack of significant differences between spray drying and freeze drying identified herein indicates that freeze drying does not meaningfully improve retention of bioactive proteins compared with spray drying when performed after multiple pasteurization steps. PRACTICAL APPLICATION: This study aimed to provide insight into the impacts of spray drying versus freeze drying on whey proteins. Overall, our results indicate that for commercial dairy processing that involves multiple rounds of pasteurization, freeze drying does not meaningfully improve the retention of bioactive proteins compared with spray drying. These findings may help the food and dairy industry make informed decisions regarding the processing of its whey protein products to optimize nutritional value.

Physical, reconstitution and phenolic properties of instant drink mix prepared with Moringa oleifera leaf, raw banana and whey protein concentrate

The formulation of instant drink mix with nutritional enhancement and optimum physical properties is a challenging task. The present study was undertaken to formulate instant drink formulation (IDF) mix using the ingredients green unripe mature banana powder (GMBP), Moringa oleifera leaf powder (MLP) and whey protein concentrate powder (WPCP) as main ingredients. Different combinations of these ingredients were mixed to formulate nine different variants (treatments) of composition mixes. The developed treatments were evaluated for physical and reconstitution properties of color characteristics, water activity, bulk density, tapped density, flowability, angle of repose, foaming capacity, swelling index, hygroscopicity, water absorption capacity (WAC), water solubility index (WSI), dispersibility, and wettability. The samples were evaluated for phenolic composition and antioxidant potential. Water activity, bulk and tapped density among the samples was ranging between 0.245–0.254 aw, 0.35–0.43 g/cm3 and 0.67–0.77 g/cm3, respectively. The flowability characteristics of Carr index (CI), Hausner ratio (HR) and angle of repose were ranging between 26.20–55.51, 1.36–2.34 and 27.51–48.33, respectively, with T1 treatment having the highest values for these characteristics. Foaming capacity, swelling index and hygroscopicity was found to be 21.83–51.17 %, 3.55–10.16 % and 24.53–36.67 %, respectively. The WAC and WSI was observed to be highest in the T1 treatment with 2.55 and 76.27, respectively. Whereas, the dispersibility and wettability was found to be between 49.75–87.93 (%) and 14.15–22.46 (s), respectively. Total phenolic content (TPC), total flavonoid content (TFC) and total anthocyanin content (TAC) in the analyzed samples were ranging between 26.86 and 1740.00 mg GAE/100 g, 12.33–1880.50 mg RE/100 g and 0.27–448.83 μg C3G/g, respectively. For the antioxidant assays, the DPPH, ABTS and FRAP assay were recorded with 10.30–8.36 % inhibition, 11.85–88.07 % inhibition and 0.36–22.72 μM Fe2+/100g, respectively. Polyphenol profile and enzyme inhibition activity was analyzed among the formulated compositions.

Effect of heating temperature on physical, functional, and digestibility properties of Whey Protein Concentrate (WPC)

Whey protein is a substance that is derived from the production of cheese. In its native form, whey protein has problems in its application in food products because it can cause a hard texture that affects sensory acceptance. It is necessary to modify the functional properties of whey protein so that it can be used more widely in the food industry. One of the modifications of whey protein is the heating treatment. The process was carried out by preheating at 70, 80, and 90°C. Then centrifuged for 15 minutes at 6000 rpm, then dried the solids using an oven vacuum at 50°C with a pressure of 25 inHg. The functional properties tested in this study were microstructure morphology, solubility, gel texture, voluminosity, and protein digestibility. The morphology of WPC powder produced significant differences between native and heating treatment. The microstructure results using TEM showed that the shape of native WPC was spherical and porous, while the heating treatment was flake-shaped. In terms of particle size distribution, native WPC and 80°C treatment have a bimodal pattern, while 70 and 90°C treatment have a unimodal pattern. As the heating temperature increases, the protein solubility will be getting lower. The lowest solubility was obtained at 90°C (16.04 ± 0.74%). Hardness produced in the gel with heating temperature significantly different than the native with the decreasing pH, the hardness produced will be higher. The fastest acidification rate produced until the final pH of 4.4 was at 80 and 90°C (270 minutes), which was faster than native (295 minutes). The heating treatment increase significantly differently in voluminosity than the native. Protein digestibility resulted in a significant difference between native and 80°C, where at 80°C (30.76 ± 0.07%), protein digestibility was higher than native (27.38 ± 0.09%).

Optimization of spray drying process for recovery of onion-stevia leaf hot water extract powder using response surface methodology.

It is important to optimize the drying process, along with the concentration of drying aid and the inlet air temperature, in order to obtain products with better physicochemical properties. Onion-stevia leaf hot extract powders were prepared using gum arabic (GA) and whey protein concentrate (WPC). Inlet air temperature and carrier concentrations were optimized using response surface methodology. The drying yield of powdered extracts was 14.39-74.32%, L*- value was 52.66-66.98, bulk density was 0.36-0.75 (g/cm3), moisture content was 2.40-11.57%, water solubility index was 30.32%-97.46%, and mean particle size D[4,3] was 9.13-88.01 (μm). For both GA- and WPC-based powders, optimal inlet air temperatures and carrier concentrations were 148.81 and 144.62°C, and 11.58 and 12.03% (w/v), respectively. GA powders had a higher glass transition temperature (76.49°C) as compared to WPC powders (48.12°C) or maltodextrin as control (55.49°C). Sweetness (5.0/7.0) and overall acceptability (4.3/7.0) scores were higher for GA powders as compared to WPC powders (3.7/7.0 and 3.4/7.0), respectively. Conclusively, GA is a better carrier than whey protein for preparing spray-dried onion-stevia powder that can be used as a natural sweetener.

Effect of pH and heat treatment on physicochemical and functional properties of spray-dried whey protein concentrate powder

Effects of pH and heating on deamidation of whey protein concentrate (WPC) solution and functional properties of resultant spray-dried WPC powder were investigated. Temperature and heating time affected deamidation rates with the highest reactivities for WPC solutions heated at 120 °C for 15 min and 145 °C for 120 s. Deamidation sites were pH dependent: pH 3 induced more glutamine deamidation; pH 10 induced more asparagine deamidation. The functional properties of spray-dried WPC powders were also pH dependent. WPC solution adjusted to pH 3 and heated at 145 °C for 120 s (prior to spray drying) exhibited a reduction in solubility and foamability, but markedly improved foam stability of the resultant powders; meanwhile, the properties of powders were not significantly impacted by pH adjustment to 10.0 and heating at 145 °C for 120 s. However, pH 3 and 10 with and without heating significantly improved emulsifying properties of spray-dried WPC.

Modifying whey protein concentrate/isolate by heating in the presence of cysteine

Heating whey protein concentrate (WPC) or isolate (WPI) solutions at 63 °C and in the presence of cysteine (CYS) denatured α-lactalbumin. The denaturation of α-lactalbumin was described as a first order reaction, with the rate constant increasing linearly with the log of the CYS concentration. Acidifying the WPC/WPI solutions that were heated in the presence of CYS produced a precipitate of denatured α-lactalbumin and a serum containing the native whey proteins. These precipitates/serums could be separated (centrifugation or ultrafiltration/microfiltration) and dried to produce WPC and WPI powders that were either enriched in β-lactoglobulin/depleted in α-lactalbumin or enriched in denatured α-lactalbumin/depleted in β-lactoglobulin, although the latter was difficult to dry. When added to skim milk before heating and acidification, β-lactoglobulin-enriched WPC markedly increased the stiffness of the acid gels; β-lactoglobulin-enriched WPI slightly increased the stiffness of the gels. The powder enriched in denatured α-lactalbumin decreased the stiffness of the acid gels.

The effect of agglomerate integrity and blending formulation on the mechanical properties of whey protein concentrate powder tablets

In this work, the strength of tablets made from mixtures of whey protein concentrate (WPC) powder and different types of sugar was investigated. The agglomerated WPC powder was pneumatically conveyed (lean phase) at three different air speeds of 10, 20 or 30 m/s to simulate the effects of industrial powder transport, resulting in agglomerates with reduced integrity. Conveyed and control WPC powder, and sugar of three different particle size distributions (i.e., granulated, GS; caster, CS and icing sugar, IS) were analysed for microstructure, particle size, moisture, and flowability. Tensile strength of tablets from WPC powder alone or blended with 0.5–10% sugar was tested. Conveying of WPC powder led to a significant increase in tablet strength, (i.e., from failure strength of 1.67 N/mm2 for control tablets to 2.33, 2.11 and 2.11 N/mm2 after conveying at 10, 20 or 30 m/s, respectively), suggesting that the generation of smaller powder particles led to increased mechanical strength of tablets. The addition of sugar also resulted in a significant increase in tablet strength (e.g., failure strength of 2.34, 2.12 and 2.47 N/mm2 at 1.5% addition level of GS, CS and IS, respectively) and strongest tablets were obtained at 1.5–3% sugar addition and by blending with icing sugar. This study demonstrated, for the first time, that conveying and dry blending of whey protein and sugar powders significantly influenced the rheological properties of resultant tablets.

Development of Synbiotic Litchi Juice Drink and its Physiochemical, Viability and Sensory Analysis

The study was carried out to evaluate the viability, physicochemical analysis and sensory analysis using fuzzy logic of synbiotic litchi juice drink containing probiotic L. casei 359 microencapsulated by spray drying using whey protein concentrate powder (WPCP) as wall material along with prebiotics inulin, gum acacia and oligofructose. The viable cell counts showed promising results for WPCP in combination with inulin, although, the cell count was higher than 106 cfu/ml for all the juice drink samples. The microcapsules showed similar morphologies with partially collapsed spherical shape with concavities but no surface fissures. There was reduction in pH for the sample containing gum acacia as prebiotic. Rheological properties showed a non-Newtonian behaviour and Herschel-Buckley model was fitted best. Fuzzy analysis showed higher acceptance for the sample containing inulin as prebiotic based on the parameters of color, taste, aroma and mouthfeel.

Production and stability of nisin in whey protein concentrate

The objective of this research was to manufacture nisin-containing whey protein concentrate (WPC) and study its stability during storage. Pasteurized reconstituted (6% w/v) sweet whey powder was used before or after ultrafiltration (UF) as a growth medium for nisin-producing strains of Lactococcus lactis subsp. lactis (ATCC 7962 or BS10). The fermented medium was freeze-dried, stored in polyethylene bags protected from light at 4 °C or 30 °C for 3 months. There was no difference in nisin yields by both strains between the regular and UF whey. Yeast extract supplementation resulted in an increase in nisin activity in UF whey fermented with BS10 and ATCC 7962 from 183 to 167 IU/ml to 1617 and 1667 IU/ml respectively. During storage at 4 °C for 1 month, the freeze dried WPC powder lost 55–60% of the nisin activity. At 30 °C for the same period, a 65–70% reduction in nisin activity was observed. Samples reconstituted at pH 2 and then boiled for 5 min increased nisin activity (P < 0.05). The present study presents WPC as an attractive, clean label ingredient with antimicrobial activities.

Quality Characteristics of Seolgiddeok added with Whey Protein Concentrate (WPC) Powder

Abstract The effects of substituting whey protein concentrate (WPC) powder for rice flour in the preparation of seolgiddeok were determined by objective and subjective tests. Milk whey is drained from milk curd as a by-product of the cheese manufactureing process. Whey protein is known as a good nutritional source and is a functional material for many processed foods. WPC contains more than 80% whey protein. The moisture content decreased gradually during storage and the decrease in moisture was less in the control than in the WPC powder substituted groups. The color lightness (L) decreased significantly as the amount of WPC powder increased, wherease redness (a) and yellowness (b) both increased. Texture analyses revealed that the hardness, chewiness, gumminess and adhesiveness of seolgiddeok tended to increase in proportion to the amount of WPC powder in the formula. Seolgiddeok gelatinization was investigated by amylographing. Initial pasting temperature, peak viscosity, hot pasting viscosity and breakdown were low in seolgiddeok prepared with WPC powder substituted for rice flour. Setback had the lowest value in the control. Sensory evaluations revealed that, seolgiddeok prepared with 3% WPC powder had the highest overall acceptability score. These results indicated that WPC seolgiddeok with 3% WPC powder has the best quality.Key words: whey protein concentrate, seolgiddeok, texture analyses, sensory evaluation

The effect of bleaching agent on the flavor of liquid whey and whey protein concentrate

The increasing use and demand for whey protein as an ingredient requires a bland-tasting, neutral-colored final product. The bleaching of colored Cheddar whey is necessary to achieve this goal. Currently, hydrogen peroxide (HP) and benzoyl peroxide (BPO) are utilized for bleaching liquid whey before spray drying. There is no current information on the effect of the bleaching process on the flavor of spray-dried whey protein concentrate (WPC). The objective of this study was to characterize the effect of bleaching on the flavor of liquid and spray-dried Cheddar whey. Cheddar cheeses colored with water-soluble annatto were manufactured in duplicate. Four bleaching treatments (HP, 250 and 500mg/kg and BPO, 10 and 20mg/kg) were applied to liquid whey for 1.5h at 60°C followed by cooling to 5°C. A control whey with no bleach was also evaluated. Flavor of the liquid wheys was evaluated by sensory and instrumental volatile analysis. One HP treatment and one BPO treatment were subsequently selected and incorporated into liquid whey along with an unbleached control that was processed into spray-dried WPC. These trials were conducted in triplicate. The WPC were evaluated by sensory and instrumental analyses as well as color and proximate analyses. The HP-bleached liquid whey and WPC contained higher concentrations of oxidation reaction products, including the compounds heptanal, hexanal, octanal, and nonanal, compared with unbleached or BPO-bleached liquid whey or WPC. The HP products were higher in overall oxidation products compared with BPO samples. The HP liquid whey and WPC were higher in fatty and cardboard flavors compared with the control or BPO samples. Hunter CIE Lab color values (L*, a*, b*) of WPC powders were distinct on all 3 color scale parameters, with HP-bleached WPC having the highest L* values. Hydrogen peroxide resulted in a whiter WPC and higher off-flavor intensities; however, there was no difference in norbixin recovery between HP and BPO. These results indicate that the bleaching of liquid whey may affect the flavor of WPC and that the type of bleaching agent used may affect WPC flavor.

Comparison of composition, sensory, and volatile components of thirty-four percent whey protein and milk serum protein concentrates

The objectives of this study were to identify and compare the composition, flavor, and volatile components of serum protein concentrate (SPC) and whey protein concentrate (WPC) containing about 34% protein made from the same milk to each other and to commercial 34% WPC from 6 different factories. The SPC and WPC were manufactured in triplicate with each pair of serum and traditional whey protein manufactured from the same lot of milk. At each replication, SPC and WPC were spray dried (SD) and freeze dried (FD) to determine the effect of the heat used in spray drying on sensory properties. A trained sensory panel documented the sensory profiles of rehydrated SD or FD powders. Volatile components were extracted by solid-phase microextraction (SPME) and solvent extraction followed by solvent-assisted flavor evaporation (SAFE) with gas chromatography-mass spectrometry and gas chromatography-olfactometry. Whey protein concentrates had higher fat content, calcium, and glycomacropeptide content than SPC. Color differences (Hunter L, a, b) were not evident between SPC and WPC powders, but when rehydrated, SPC solutions were clear, whereas WPC solutions were cloudy. No consistent differences were documented in sensory profiles of SD and FD SPC and WPC. The SD WPC had low but distinct buttery (diacetyl) and cardboard flavors, whereas the SD SPC did not. Sensory profiles of both rehydrated SD products were bland and lower in overall aroma and cardboard flavor compared with the commercial WPC. Twenty-nine aroma impact compounds were identified in the SPC and WPC. Lipid and protein oxidation products were present in both products. The SPC and WPC manufactured in this study had lower total volatiles and lower concentrations of many lipid oxidation compounds when compared with commercial WPC. Our results suggest that when SPC and WPC are manufactured under controlled conditions in a similar manner from the same milk using the same ultrafiltration equipment, there are few sensory differences but distinct compositional and physical property differences that may influence functionality. Furthermore, flavor (sensory and instrumental) properties of both pilot-scale manufactured protein powders were different from commercial powders suggesting the role of other influencing factors (e.g., milk supply, processing equipment, sanitation).

Heat-Induced Whey Protein Gels: Protein−Protein Interactions and Functional Properties

Heat-induced gelation (80 degrees C for 30 min or 85 degrees C for 60 min) of whey protein concentrate (WPC) solutions was studied using small deformation dynamic rheology, small and large deformation compression, and polyacrylamide gel electrophoresis (PAGE). The WPC solutions (15% w/w, pH 6.9) were prepared by dispersing WPC powder in water (control), 1% (w/w) sodium dodecyl sulfate (SDS) solution, and N-ethylmaleimide (NEM) solution at a protein/NEM molar ratio of 1:1 or in 10 mM dithiothreitol (DTT) solution. PAGE analyses showed that the heat treatment of control solutions contained both disulfide and non-covalent linkages between denatured protein molecules. Only disulfide linkages were formed in heated SDS-WPC solutions, whereas only non-covalent linkages were formed in DTT-WPC and NEM-WPC solutions during heating. In heated NEM-WPC solutions, the pre-existing disulfide linkages remained unaltered. Small deformation rheology measurements showed that the storage modulus (G') values, compared with those of the control WPC gels (approximately 14000 Pa), were 3 times less for the SDS-WPC gels (approximately 4000 Pa), double for the NEM-WPC gels (approximately 24000 Pa), and even higher for the DTT-WPC gels (approximately 30000 Pa). Compression tests suggested that the rubberiness (fracture strain) of the WPC gels increased as the degree of disulfide linkages within the gels increased, whereas the stiffness (modulus) of the gels increased as the degree of non-covalent associations among the denatured protein molecules increased.

Effect of whey protein concentrate addition on the physical properties of homogenized sweetened dairy creams

The influence on their whipping properties of homogenization at first and second stage pressures of 3.5/1.5 MPa and addition of whey protein concentrate (WPC) powder at three different (0.7, 1.4, and 2.1 wt percentage) concentrations to sweetened and homogenized creams was studied. Homogenization of cream significantly decreased maximum overrun and made the foam microstructure less open, while increasing whipping time, cream and foam lightness (Hunter L‐value) and apparent viscosity. It also resulted in a less elastic foam structure with an increased drainage. Addition of WPC decreased the amount of maximum overrun, foam drainage and its lightness in parallel with developing a more compact microstructure. It increased the whipping time, apparent viscosity of unwhipped creams and foams, and resulted in a less elastic foam structure. The apparent viscosity of whipped cream with 2.1 wt percentage WPC, however, was lower than that of whipped cream with 1.4 wt percentage WPC, due most probably to the start up of gel formation at 2.1% WPC concentration in sweetened cream when it was sheared. Fresh foam whipped from sweetened cream with 2.1 wt percentage WPC also tended to have a slightly but not statistically significant lower elastic modulus (G′) than fresh foam whipped from sweetened cream with 1.4 wt percentage WPC. This concentration can be considered as the critical value for gel formation in sweetened creams enriched by whey proteins when sheared. This study indicated the potential of WPC powder for reducing foam drainage from whipped homogenized sweetened cream.

A comparison of drying operations on the rheological properties of whey protein thickening ingredients

SummaryAn existing procedure for the alteration of whey proteins into a cold‐set thickening agent was modified by developing a spray‐drying operation to replace the prohibitively expensive freeze‐drying step. The original and the modified derivatization procedures were used with a commercial whey protein concentrate (WPC). The freeze‐dried and spray‐dried derivatized WPC powders, along with polysaccharide thickeners, were reconstituted in water and evaluated by using a range of rheological studies. The effects of temperature, concentration, and shear on viscosity as well as the mechanical spectra were assessed to characterize the ability of the powders to function in food systems. Rheological characterization revealed the modified derivatization procedure yielded an ingredient having the same cold‐set thickening and gelling ability as the original derivatized powder. The modified whey proteins were also able to achieve, at higher usage levels, textural properties similar to several polysaccharide thickeners. Use of a spray‐drying technique created a more economical process for the production of a whey protein ingredient that was suitable for contributing viscosity and texture to a wide range of food systems.

The roles of disulphide and non-covalent bonding in the functional properties of heat-induced whey protein gels.

Heat-induced gelation (80 degrees C, 30 min or 85 degrees C, 60 min) of whey protein concentrate (WPC) solutions was studied using transmission electron microscopy (TEM), dynamic rheology and polyacrylamide gel electrophoresis (PAGE). The WPC solutions (150 g/kg, pH 6.9) were prepared by dispersing WPC powder in water (control), 10 g/kg sodium dodecyl sulphate (SDS) solution or 10 mM-dithiothreitol (DTT) solution. The WPC gels containing SDS were more translucent than the control gels, which were slightly more translucent than the gels containing DTT. TEM analyses showed that the SDS-gels had finer aggregate structure (approximately equal to 10 nm) than the control gels (approximately equal to 100 nm), whereas the DTT-gels had a more particulate structure (approximately equal to 200 to 300 nm). Dynamic rheology measurements showed that the control WPC gels had storage modulus (G) values (approximately equal to 13,500 Pa) that were approximately equal to 25 times higher than those of the SDS-gels (approximately equal to 550 Pa) and less than half those of the DTT-gels after cooling. Compression tests showed that the DTT-gels were more rigid and more brittle than the control gels, whereas the SDS-gels were softer and more rubbery than either the control gels or the DTT-gels. PAGE analyses of WPC gel samples revealed that the control WPC solutions heated at 85 degrees C for 10 min contained both disulphide bonds and non-covalent linkages. In both the SDS-solutions and the DTT-solutions, the denatured whey protein molecules were in the form of monomers or small aggregates. It is likely that, on more extended heating, more disulphide linkages were formed in the SDS-gels whereas more hydrophobic aggregates were formed in the DTT-gels. These results demonstrate that the properties of heat-induced WPC gels are strongly influenced by non-covalent bonding. Intermolecular disulphide bonds appeared to give the rubbery nature of heat-induced WPC gels whereas non-covalent bonds their rigidity and brittle texture.

Functional properties of ovine whey protein concentrates produced by membrane technology after clarification of cheese manufacture by-products

Functionality (solubility, emulsifying and foaming properties) of ovine cheese whey and deproteinized whey ( Sorelho) protein concentrates was evaluated. Both by-products of ovine cheese manufacture were clarified by thermocalcic precipitation and microfiltration using two pore size membranes (0.65 and 0.20 μm). Next, they were ultrafiltrated/diafiltrated, and then, the liophilization of the corresponding retentates was carried out. The functionality of these powders, as well as that of untreated ultrafiltrated whey protein concentrate (WPC) and microfiltration retentates powders, was evaluated. The clarification treatment increased solubility of the WPC produced from ovine whey and deproteinized ovine whey. Moreover, these products had foaming properties, whereas conventional WPC and microfiltration retentate powders (MFRP) were unable to produce foams. The whey product obtained after clarification using a 0.65 μm microfiltration membrane had the best foaming properties. The clarification treatment did not significantly increase emulsifying activity and stability, except for the Sorelho product obtained using a 0.65 μm membrane. MFRP from ovine whey and Sorelho, the by-products of the clarification procedure, showed similar solubility and higher emulsifying activity than conventional WPC, although their emulsion stability was lower. The clarification procedure studied, particularly when a 0.65 μm microfiltration membrane was used, improved some functional properties of the whey and Sorelho protein concentrates, and also generated microfiltration retentates for potential use in food manufacturing.

Structure and visco-elastic properties of set yoghurt with altered casein to whey protein ratios

Abstract Set yoghurts with a consistent total protein content were manufactured from milks reconstituted from skim milk powder (SMP), or blends of SMP and whey protein concentrate (WPC) powders with crude protein concentrations between 25% and 80% (w/w) so that the casein to whey protein ratio varied from 4.7:1 to 0.5:1. As the casein to whey protein ratio was decreased the maximum gel strength of the yoghurt increased, the initial gradient of the force–distance curves generally decreased, whey drainage was reduced, and the gels were generally less viscous. Scanning electron microscopy indicated that gels with a lower proportion of casein had a finer structure with numerous small pores and a dense network of crosslinks. When the casein to whey protein ratio was maintained at a constant level, the physical properties of the gels were generally similar, regardless of the protein concentration of the WPC powder that was used. The relationship between the casein to whey protein ratio and the physical properties of the yoghurts is considered in terms of the microstructure of the protein network.

WHEY PROTEIN CONCENTRATE PRODUCTION IN A PILOT SCALE TWO-STAGE DIAFILTRATION PROCESS

A pilot scale two-stage batch diafiltration process for whey protein concentrate (WPC) production is presented in this work. This process has two main advantages: a significant water saving with respect to a single-stage diafiltration process and a membrane surface saving with respect to a continuous multistage process. Every unit operation of the process has been experimented in a pilot scale (ultrafiltration, diafiltration, drying), in order to produce a WPC powder. Lactose content decreased from about 75% (of whey) to 4.5% (calculated as mass of lactose per total solute mass) and proteins increased from 15%to 83% (calculated as mass of proteins per total solute mass), with a water consumption of about 1.5 L/L of whey. Permeability tests enabled the calculation of the main mass-transfer resistances through the membrane: the intrinsic membrane resistance, RM , was 13.8 ± 0.1, the one due to fouling, RF , was 3.68 ± 0.04, and the one due to polarization, RG , was estimated at 2.4 ± 0.4 (at 150 kPa TMP) 109Pa s m-1, at 25°C. These values are in agreement with data reported in the literature. A study performed on the membrane retention properties showed that not only peptides but also two native proteins (β-lactoglobulin and α-lactoalbumin) pass in the permeate during ultrafiltration. Consequently, a significant protein loss takes place during the process. Diafiltration tests performed in a two-stage countercurrent operation demonstrated the water saving with respect to a single-stage process (46%). Furthermore, experimental data have been used in order to evidence the capability of a previously developed mathematical model to predict the components' concentration during diafiltration.

A study of volatile “trapping” in spray dried whey protein concentrate by “crushing” and/or vacuuming, and detection by solid-phase microextraction/gas chromatography/mass spectrometry

Flavour is an important quality aspect of spray dried whey protein concentrate (WPC). A blander flavour of WPC would find greater acceptance in a wide range of other combined foods. The objective of this study was to investigate the extent of physical “trapping” or “binding” of volatiles during powder formation in spray drying. Two simple procedures were used: (1) “crushing” and (2) subjecting WPC powder to vacuuming. Scanning electron microscopy images were used to observe the structure of the “original” WPC and treated WPC particles. Solid-phase microextraction followed by gas chromatography/mass spectrometry, and sensory evaluations of both powder and liquid samples of WPC, were used to demonstrate that although vacuuming and/or “crushing” WPC powder certainly liberate some aroma/odour-impact constituents, indicating a certain degree of volatile trapping by the physical structure, others may require the powder to be “crushed” more effectively, or dissolved in water, before a large percentage of volatiles are liberated. Thus, it appears that flavour volatiles are entrapped (thus supporting the selective diffusion theory) or bound in different ways to WPC, and that some of them are weakly bound, possibly hydrophobically.