Milk Protein Concentrate Powders Research Articles

Transglutaminase Crosslinked Milk Protein Concentrate and Micellar Casein Concentrate: Impact on the Functionality of Imitation Mozzarella Cheese Manufactured on a Small Scale Using a Rapid Visco Analyzer.

In dairy-based imitation mozzarella cheese (IMC) formulations, intact casein is critical and imparts IMC with a firm and elastic, stringy, melted texture. Rennet casein (RCN) is the desired ingredient to provide intact casein in IMC and is preferred over milk protein concentrate (MPC) and micellar casein concentrate (MCC). Transglutaminase (TGase), a crosslinking enzyme, alters the physical properties of MPC or MCC and may change IMC functionality. The objective of this study was to determine the effect of TGase-crosslinked MPC and MCC powders on the functionality of IMCs. The TGase treatment included TGase at 0.3 (L) and 3.0 (H) units/g of protein and a control (C) with no TGase addition. Each IMC formulation was balanced for constituents and was produced in a Rapid Visco Analyzer (RVA). The MCC or MPC powder with high TGase enzyme in IMC formulation did not form an emulsion. The IMC containing TGase-treated powders had a significantly (p ≤ 0.05) higher RVA-viscosity during manufacture and transition temperature (TT), and a significantly (p ≤ 0.05) lower Schreiber melt test area. The IMC made from MPC (with or without TGase) had lower TT values and Schreiber melt test area as compared with that made from MCC. The TGase-treated MPC and MCC, when used for IMC manufacture, were comparable to IMC manufactured with RCN in texture and some measured melted characteristics. In conclusion, TGase treatment alters the melt characteristics of MCC and MPC in IMC applications.

Impact of non‐thermal plasma generated using air and nitrogen on functional properties of milk protein dispersions

AbstractThis study focuses on improving the functionalities of milk protein concentrate (MPC) using a nonthermal plasma jet and plasma‐activated water (PAW) with atmospheric air and nitrogen as source gases. The 5% and 10% MPC dispersions were directly treated with a plasma jet, and PAW was used to make the MPC dispersions. The dispersions were analyzed for changes in protein structure and functional properties. The treatment altered the secondary structure of MPC protein structure by increasing β‐components and changing the order of random coils. The solubility of the PAW‐treated 5% protein dispersions doubled due to plasma‐induced modification of hydrophilic and covalent bonds of the protein, but this increase was not significant for the 10% dispersions due to less hydration. Emulsifying capacity increases by around 7% for plasma jet and PAW with air, owing to hydrophobicity on the particle surface. The gelation capacity and heat coagulation time rise by almost twice; however, foaming capacity decreases, indicating protein structural modifications and aggregations caused by plasma exposure. The viscosity of the 5% dispersions decreased due to high solubility, while that of the 10% dispersions increased due to less hydration. Principle component analysis was used to correlate the change in functionality with different operating parameters. In conclusion, this study illustrates that the functional properties of MPC can be significantly modified through plasma treatment. The observed changes depend on several factors, including the mode of plasma exposure, the source gas used to generate the plasma, and the concentration of the protein solution.Practical applicationsMilk protein concentrate (MPC) is a promising ingredient in food products such as cheese, cultured dairy items, nutritional goods, infant milk formulas, ice cream, dairy‐based drinks, sports beverages, and a variety of health‐focused products. However, the application is profoundly hindered due to its poor solubility and solubility‐related functional properties. MPC powders lose functionalities during manufacturing and gradually lose them again during processing and storage. This study explores the potential of non‐thermal plasma to improve the functional properties of proteins. This study explores the potential of two different discharges: plasma jet and plasma‐activated water (PAW), using atmospheric air and nitrogen as source gases. The findings of this study would also help to understand the types of plasma discharge (jet vs PAW) and types of sources of gases that can be used in industrial applications. Some optimization parameters of this study can be used for scaling up the plasma processing of milk or dairy products. In addition, PAW is being very well studied to improve food safety, and this study would provide information on the physicochemical properties of MPC. Therefore, it would also help to understand how to apply non‐thermal plasma to achieve both microbial and physical effects.

Development of spray dried functional milk protein concentrate containing whey proteins as fibrils

Fibrillated milk protein concentrate (MPC) was produced by selective fibrillation of whey proteins and spray dried to extend shelf life. The fibrillated MPC powder was characterized for whey protein fibrils and functionality. Observations from Thioflavin T fluorescence value, transmission electron microscopy, gel electrophoresis, rheology, and turbidity confirmed the presence of fibrils in fibrillated MPC. However, fibrils in reconstituted fibrillated MPC were thinner compared with the fibrils before spray drying. Aggregation of fibrils was also seen in fibrillated MPC dispersions. Further, rheological analysis of reconstituted fibrillated MPC at different total solids levels showed that reconstituted fibrillated MPC has significantly higher viscosity, consistency index, and shear thinning behavior compared with control. Reconstituted fibrillated MPC also showed significantly lower surface tension and interfacial tension, with higher emulsification capacity, foaming capacity, and foam stability. Fibrillated MPC powder can be used as a functional ingredient in dairy and food formulations.

Developing New High-Protein-Content Traditional-Type Greek Yoghurts Based on Jersey Cow Milk

In the past few years, Jersey cow milk has been considered an effective commodity for the production of dairy products, such as cheese and yoghurts, due to its high nutrient density. Initially, the microbial safety and physicochemical properties of pasteurized milk from Jersey cows raised in Evrofarma S.A. dairy facilities were monitored and compared to Holstein Friesian milk over a six-month period. Subsequently, a new traditional-type Greek yoghurt was prepared using Jersey cow milk andthe physicochemical, microbiological and sensory properties were monitored throughout its shelf time and compared to commercially available traditional-type Greek yoghurts made with Milk Protein Concentrate powder (MPC)-fortified Holstein Friesian milk. Our study confirmed the significantly higher fat (29.41%), protein (20.6%) and calcium content (19.9%) compared to Holstein Friesian milk. The new yoghurt demonstrated several technological advantages and shared similar physicochemical properties with the commercially available products. Importantly, high protein concentration (4.03 g/100 g) was documented without the addition of MPC. Finally, the new yoghurt was accepted during the preliminary sensory evaluation, while similar scores with the commercially available products were noted during the texture, flavour, aroma and overall quality assessment.

Influence of Bulk Nanobubbles Generated by Acoustic Cavitation on Powder Microstructure and Rehydration Characteristics of Spray-Dried Milk Protein Concentrate Powders

Bulk nanobubbles (BNBs) have widespread applications in various fields of science due to numerous peculiar characteristics. Despite significant applications, only limited investigations are available on the application of BNBs in food processing. In the present study, a continuous acoustic cavitation technique was used to generate bulk nanobubbles (BNBs). The aim of this study was to evaluate the influence of BNB incorporation on the processability and spray drying of milk protein concentrate (MPC) dispersions. MPC powders were reconstituted to the desired total solids and incorporated with BNBs using acoustic cavitation as per the experimental design. The control MPC (C-MPC) and BNB-incorporated MPC (BNB-MPC) dispersions were analyzed for rheological, functional, and microstructural properties. The viscosity significantly decreased (p < 0.05) at all the amplitudes studied. The microscopic observations of BNB-MPC dispersions showed less aggregated microstructures and greater structural differences compared with C-MPC dispersions, therefore lowering the viscosity. The viscosity of BNB incorporated (90% amplitude) MPC dispersions at 19% total solids at a shear rate of 100 s-1 significantly decreased to 15.43 mPa·s (C-MPC: 201 mPa·s), a net decrease in viscosity by ~90% with the BNB treatment. The control and BNB incorporated MPC dispersions were spray-dried, and the resultant powders were characterized in terms of powder microstructure and rehydration characteristics. Focused beam reflectance measurement of the BNB-MPC powders indicated higher counts of fine particles (<10 μm) during dissolution, signifying that BNB-MPC powders exhibited better rehydration properties than the C-MPC powders. The enhanced powder rehydration with the BNB incorporation was attributed to the powder microstructure. Overall, reducing the viscosity of feed by BNB incorporation can enhance the performance of the evaporator. This study, therefore, recommends the possibility of using BNB treatment for more efficient drying while improving the functional properties of the resultant MPC powders.

Use of micellar casein concentrate and milk protein concentrate treated with transglutaminase in imitation cheese products—Unmelted texture

The amount of intact casein provided by dairy ingredients is a critical parameter in dairy-based imitation mozzarella cheese (IMC) formulation because it has a significant effect on unmelted textural parameters such as hardness. From a functionality perspective, rennet casein (RCN) is the preferred ingredient. Milk protein concentrate (MPC) and micellar casein concentrate (MCC) cannot provide the required functionality due to the higher steric stability of casein micelle. However, the use of transglutaminase (TGase) has the potential to modify the surface properties of MPC and MCC and may improve their functionality in IMC. The objective of this study was to determine the effect of TGase-treated MPC and MCC powders on the unmelted textural properties of IMC and compare them with IMC made using commercially available RCN. Additionally, we studied the degree of crosslinking by TGase in MPC and MCC retentates using capillary gel electrophoresis. Three lots of MCC and MPC retentate were produced from pasteurized skim milk via microfiltration and ultrafiltration, respectively, and randomly assigned to 1 of 3 treatments: no TGase (control); low TGase: 0.3 units/g of protein; and high TGase: 3.0 units/g of protein, followed by inactivation of enzyme (72°C for 10 min), and spray drying. Each MCC, MPC, and RCN was then used to formulate IMC that was standardized to 21% fat, 1% salt, 48% moisture, and 20% protein. The IMC were manufactured by blending, mixing, and heating ingredients (4.0 kg) in a twin-screw cooker. The capillary gel electrophoresis analysis showed extensive inter- and intramolecular crosslinking. The IMC formulation using the highest TGase level in MCC or MPC did not form an emulsion because of extensive crosslinking. In MPC with a high level of TGase, whey protein and casein crosslinking were observed. In contrast, crosslinking and hydrolysis of proteins were observed in MCC. The IMC made from MCC powder had significantly higher texture profile analysis hardness compared with the corresponding MPC powder. Further, many-to-one (multiple) comparisons using the Dunnett test showed no significant differences between IMC made using RCN and treatment powders in hardness. Our results demonstrated that TGase treatment causes crosslinking hydrolysis of MCC and MPC at higher TGase levels, and MPC and MCC have the potential to be used as ingredients in IMC applications.

Use of micellar casein concentrate and milk protein concentrate treated with transglutaminase in imitation cheese products—Melt and stretch properties

Melt and stretch properties in dairy-based imitation mozzarella cheese (IMC) are affected by the amount of intact casein provided by dairy ingredients in the formulation. Rennet casein (RCN) is the preferred ingredient to provide intact casein in a formulation. Ingredients produced using membrane technology, such as milk protein concentrate (MPC) and micellar casein concentrate (MCC), are unable to provide the required functionality. However, the use of transglutaminase (TGase) has potential to modify the physical properties of MPC or MCC and may improve their functionality in IMC. The objective of this study was to determine the effect of TGase-treated MPC and MCC retentates on melt and stretch properties when they are used in IMC and to compare them with IMC made using RCN. The MCC and MPC retentates were produced using 3 different lots of pasteurized skim milk and treated with 3 levels of TGase enzyme: no TGase (control), low TGase: 0.3 units/g of protein, and high TGase: 3.0 units/g of protein. Each of the MCC and MPC treatments was heated to 72°C for 10 min to inactivate TGase and then spray dried. Each MCC, MPC, and RCN powder was then used in an IMC formulation that was standardized to 48% moisture, 21% fat, 20% protein, and 1% salt. The IMC were manufactured in a twin-screw cooker by blending, mixing, and heating various ingredients (4.0 kg). Due to extensive crosslinking, the IMC formulation with the highest TGase level (MCC or MPC) did not form an emulsion. The IMC made from MCC treatments had significantly higher stretchability on pizza compared with their respective MPC treatments. The IMC made from TGase-treated MCC and MPC had significantly lower melt area and significantly higher transition temperature (TT) and stretchability compared with their respective controls. Comparison of IMC made using TGase-treated MCC and MPC to the RCN IMC indicated no difference in TT or texture profile analysis-stretchability; however, the Schreiber melt test area was significantly lower. Our results demonstrated that TGase treatment modifies the melt and stretch characteristics of MCC and MPC in IMC applications, and TGase-treated MPC and MCC can be used to replace RCN in IMC formulations.

Influence of micro- and nano-bubble treatment on morphological characteristics and flow properties of spray-dried milk protein concentrate powders

This study investigated the morphological and bulk handling properties of milk protein concentrate (MPC) powders manufactured from incorporating micro- and nano-bubbles (MNB) before spray drying. Control MPC powders (C-MPC; no MNB treatment) and MNB-treated MPC powders (MNB-MPC; MPC dispersions passed through the MNB system and subsequently spray dried) were characterized in terms of particle size, shape factors, stability, variable flow rate, shear cell tests, compressibility, and wall friction. The MPC powders produced after the MNB injection process had better flowability and lower basic flow energy. Shear tests showed that C-MPC powders were more cohesive than MNB-MPC powders. The MNB-MPC powders had lower flow rate index values, lower wall friction angles, more rounded shape, and significant differences in powder compressibility compared with C-MPC powders. Overall, the results demonstrated that MNB incorporation during spray drying can produce ingredients with comparable morphological characteristics while improving the bulk powder properties.

Application of micro- and nano-bubbles in spray drying of milk protein concentrates

Micro- and nano-bubbles (MNB) have unique properties and have attracted great attention in the past 2 decades, offering prospective applications in various disciplines. The first objective of this study was to investigate whether venturi-style MNB generation is capable of producing sufficient bulk MNB. A nanoparticle tracking system was used to measure the bubble concentration and particle size of MNB-treated deionized water. The MNB-treated deionized water had a bubble concentration of 3.76 × 108 particles/mL (∼350 million bubbles/mL more compared with control) and a mean particle size of 249.8 nm. The second objective of this study was to investigate the effects of MNB treatment on the microstructure and functional properties of milk protein concentrate (MPC) dispersions. Reconstituted MPC dispersions (21%, wt/wt) without air injection were considered as control (C-MPC), and MPC dispersions passed through the MNB system were considered as MNB-treated (MNB-MPC) dispersions. Control and MNB-MPC dispersions were evaluated in terms of rheological behavior and microstructure. The microscopic observations of MNB-MPC dispersions showed less aggregated microstructures and greater structural differences compared with C-MPC dispersions, therefore lowering the viscosity. The viscosity of MNB-MPC at a shear rate of 100 s-1 significantly decreased to 57.58 mPa·s (C-MPC: 162.40 mPa·s), a net decrease in viscosity by ∼65% after MNB treatment. Additionally, MPC dispersions were spray dried after the MNB treatment, and the resultant MNB-MPC powders were characterized and compared with the control MPC in terms of rehydration characteristics and microstructure. Focused beam reflectance measurement of the MNB-MPC powders indicated lower counts of large particles (150-300 μm) during dissolution, signifying that MNB-MPC powders exhibited better rehydration properties than the C-MPC powders. This study, therefore, recommends the possibility of using MNB treatment for more efficient drying while improving the functional properties of the resultant MPC powders.

Topographical changes in high-protein, milk powders as a function of moisture sorption using amplitude-modulation atomic force microscopy

This study aimed to examine how microscopic morphological developments, such as lactose crystallisation, swelling of particles and changes in surface roughness, occur as a function of moisture sorption in skimmed-milk (SMP), milk protein concentrate (MPC) and whey protein isolate (WPI) powders. Atomic force microscopy (AFM) has the potential to identify high-resolution, microstructural changes in high-protein, milk powder particles. A sample preparation technique was developed, which allowed a single-layer of uniformly distributed powder particles to be applied to a mica surface for subsequent AFM analysis. An amplitude modulation (AM)-AFM technique was used, and analysis showed that equilibration of powders under conditions of increasing relative humidity (RH) causes changes in topography and increased surface roughness. In SMP, significant surface changes were observed due to the development of lactose crystallisation and eventual stacking of crystal layers with increased moisture sorption. MPC, however, showed characteristic ‘dimples and folds', which may have been due to shrinkage and compaction of surfaces. With higher moisture content, the number of surface-folds and height-ranges increased, with MPC powders, held at 85% RH appearing highly jagged. The surfaces of WPI powders were smooth but were characterised by the presence of broken powder fragments. Such fragments were absent in SMP and MPC powders, suggesting that WPI powders were the most friable. WPI powders appeared not to change as a function of moisture sorption. AM-AFM was used to provide high-resolution, three-dimensional images of HPMP particles at nano- and micrometre length scales.

Rehydration characteristics of milk protein concentrate powders monitored by electrical resistance tomography

Electrical resistance tomography (ERT) is a robust and low-cost method offering real-time visualization of processes. In this work, we developed an ERT-based method to characterize the rehydration behavior of milk protein concentrate (MPC) powders. Circular-type and linear configurations were used to achieve high resolution in the radial and axial directions, respectively. To evaluate the rehydration profile, MPC powders were reconstituted to 2.5% (wt/wt) total solids at room temperature, and the rehydration behavior of the MPC powders [MPC with 85% protein (MPC85) and milk protein isolate with 90% protein (MPI90)] was monitored for a dissolution time of 30 min using the ERT system. The MPC powders were characterized in terms of overall mean conductivity, area under the mean conductivity curve, slope at a dissolution time of 3 min, and the relative dissolution index. Additionally, the focus beam reflectance measurement (FBRM) was used as a reference method to follow rehydration characteristics. Particle count changes from the FBRM measurements showed that MPI90 had higher larger particle counts and more resistance to dispersing in water. As the dissolution time proceeded, mineral ions and proteins were released and consequently increased the overall conductivity, confirming the transfer of water into MPC particles. At lower protein contents, the particle dispersion rate was higher and an increase in overall mean conductivity was observed, indicating better powder dissolution. Both configurations were able to effectively monitor differences in the dissolution behavior of MPC powders. In the ERT circular configuration, MPC85 and MPI90 showed maximum conductivity of 0.201 ± 0.006 and 0.162 ± 0.001 mS/cm, respectively. In the linear probe configuration, MPC85 and MPI90 showed maximum conductivity of 0.161 ± 0.001 and 0.136 ± 0.001 mS/cm, respectively, suggesting increasingly inhibited water transfer as the protein content of the powder increased. In this study, we demonstrated the capability of ERT using the circular and linear probe configurations to offer, in addition to qualitative tomographic images, reliable quantitative data by which to characterize the dissolution behavior of high-protein dairy powders.

Rehydration properties of regular and agglomerated milk protein concentrate powders produced using nitrogen gas injection prior to spray drying

This study evaluated the effect of high-pressure nitrogen (N2) gas injection prior to spray drying on the subsequent rehydration properties of regular and agglomerated milk protein concentrate (MPC) powders. Conductivity measurements demonstrated a slower release of ions for powders produced using N2 injection (NI) as they took longer to wet and sink due to their lower density. However, analysis of particle size distribution on reconstitution at both 23 and 50 °C showed an improvement in powder dispersion with NI. Powder solubility, when measured at 23 °C, was higher for the NI powders, while agglomeration negatively impacted solubility. Confocal laser scanning microscopy analysis showed a faster diffusion of dye into MPC powder particles produced using NI. The improvement in powder dissolution with NI was attributed to higher porosity and the presence of air voids which facilitated increased water transfer and accelerated the breakdown of primary powder particles.

Correlations between the solubility and surface characteristics of milk protein concentrate powder particles

The solubility of high-protein milk protein concentrate (MPC) may decrease significantly during storage, particularly at relatively high temperatures and humidity. The objective of this study was to seek correlations between the solubility loss of MPC during storage and various surface characteristics determined on the basis of simultaneous nanoscale topographical imaging and nanomechanical mapping of MPC particle surfaces using atomic force microscopy. A control MPC and a calcium-depleted MPC were stored at 45°C and 66% relative humidity for up to 60 d. The solubility of the control MPC was 56% at the beginning of the storage and gradually decreased to 10% at the end of the 60-d storage. The calcium-depleted MPC exhibited more rapid decreases from almost 100% at the beginning of the storage to 18% after storage for 45 d, after which we observed no significant difference in solubility between the control and calcium-depleted MPC. Averaged or root mean squared roughness values calculated using topographical images were found to have no correlation with the solubility. Deformation, Derjaguin-Muller-Toropov modulus, and adhesion images revealed the presence of individual casein micelles and larger clusters of aggregated casein micelles at MPC particle surfaces, whereas we observed no correlation between the solubility and averaged values of these nanomechanical properties. Furthermore, Derjaguin-Muller-Toropov modulus and adhesion images showed that the peripheral edges of individual casein micelles and their clusters had significantly higher values of the corresponding nanomechanical properties than other regions in the images, indicating the occurrence of the fusion of casein micelles. The surface area coverage or the percent area of the fused regions in an image revealed significant negative linear correlations with the solubility for both the control and calcium-depleted MPC. The present results support the hypothesis that the fusion of casein micelles at MPC powder particle surfaces is a causative factor for the solubility loss of MPC during storage and in turn suggest that the solubility loss may be alleviated by inhibiting the formation of a crust or skin on powder particle surfaces.

Production and characterization of cow milk based low-protein milk protein concentrate (MPC) powders.

Ultrafiltration and Diafiltration processes are used to concentrate proteins present in defatted milk in order to manufacture milk protein concentrate (MPC) powders. Selective passage of the water-soluble components causes retention as well as concentration of colloidal milk components in these processes. Increase in calcium and casein contents decreases the stability of milk proteins present in ultrafiltered retentates and negatively influence properties of manufactured MPC powders. Homogenization, diafiltration and disodium phosphate induced changes in properties of low-protein MPC powders were targeted in this study. Applied treatments significantly (P < 0.05) improved foaming and emulsification, solubility, viscosity, heat stability, dispersibility, specific surface area and buffer index of resultant MPC powders over control. Fresh, treated low-protein MPC powders showed significantly higher (< 0.05) solubility values over control sample, which remains higher even after 60days of storage at 25 ± 1°C. The rheological behaviour of reconstituted low-protein MPC solutions was also studied. It was best explained as Herschel-Bulkley rheological behaviour. Low-protein MPC powders with improved functional properties may find better use as a protein ingredient in different dairy and food applications.

Effect of sodium triphosphate and sodium hexametaphosphate on properties of buffalo milk protein concentrate 60 (BMPC60) powder.

Milk protein concentrate (MPC) powders are high-protein, innovative dairy ingredients. Buffalo milk naturally contains higher concentrations of casein and calcium, which have adverse effect on solubility of MPC powders. Therefore, this study was undertaken to investigate the effect of Sodium triphosphate (STP) and Sodium hexametaphosphate (SHMP) addition in ultrafiltered retentate on physicochemical, functional and reconstitution properties, morphological characteristics and rheological behaviour of the resultant powder. Pasteurized buffalo skim milk (PBSM) was concentrated by ultrafiltration (UF) process to obtain 2.53 × UF retentate (2.53 × UFR) with 0.61 protein to total solids (TS) ratio. Compared to PBSM, ultrafiltration significantly increased (p < 0.05) calcium, protein and TS contents of 2.53 × UFR, but significantly decreased (p < 0.05) its heat stability. Addition of STP-SHMP mixture in 2.53 × UFR noticeably improved the solubility, flowability, water binding, oil binding, foaming capacity, foam and thermal stability and, viscosity of treated MPC60 powder over control powder. The DeBroukere (D43) mean, d50, specific surface area, span and water activity values of treated MPC60 powder were 94.96 ± 0.05, 78.33 ± 0.04µm, 715.93 ± 0.29m2 kg-1, 1.97 ± 0.01 and, 0.26 ± 0.01, respectively. Scanning electron micrograph showed the presence of different size powder particles without clustering. Rheological modelling of the reconstituted solution of treated MPC60 was very well described by Herschel-Bulkley model. Overall, this study established that addition of STP-SHMP salts mixer in 2.53 × UFR could improve the solubility of resultant buffalo milk based MPC60 powder.

Effects of particle size and aging of milk protein concentrate on the biophysical properties of an intermediate-moisture model food system

This study investigates the effects of particle size (22.4 and 7.5 μm diameters) and aging history (40 °C, 20 days) of milk protein concentrate (MPC) powders on their rehydration properties as well as the biophysical properties including molecular migration, microstructure, and texture of a high-protein nutrition bar (HPNB) made using these MPC powders. It was observed that the rehydration properties (wettability and solubility) of MPC powders decreased with aging but increased with the decrease in the MPC particle sizes. The migration of small molecules (water, glycerol and sorbitol) was slower for HPNB formulated with aged powders of the same sizes but faster for those formulated with small-sized powders of the same aging history. Plasticization of powder particles was lesser for HPNB formulated with aged powders having the same sizes, but greater for those formulated with small-sized powders with the same aging history. The increase in hardness during storage was smaller for HPNB formulated with fresh and small-sized powders, compared to those formulated with aged and large-sized powders. The cohesiveness was higher for HPNB formulated with small-sized powders, compared to those formulated with large-sized powders. These results suggest that the reduction of the MPC powder particle size by manipulating the spray airflow rate offers a potential route to manipulate the textural properties of HPNB.

A novel approach for dynamic in-situ surface characterisation of milk protein concentrate hydration and reconstitution using an environmental scanning electron microscope

Composition and relative humidity (RH) can have a profound impact on the physical (flowability, stickiness) and functional (reconstitution) properties of milk powder (MP) and therefore its quality, storage stability and shelf-life. Conventional microscopic techniques are not capable of dynamically imaging the effect of RH on MP at high magnification. The aim of this study was to develop a novel method to characterise in-situ and in real time the hydration and reconstitution of five spray-dried milk protein concentrates (MPCs) using an Environmental Scanning Electron Microscope (ESEM). ESEM was employed to observe the surface microstructure of MPC powders with varying protein content (38.63%–80.94%, w/w), at various RH values ranging from 35% to over 100%. MPC powders were imaged by an ESEM without any prior preparation, and with minimal physical sample alteration, thus providing fundamental insights into MPC hydration and reconstitution. ESEM surface analysis showed particle swelling in all MPCs, and that with increasing protein content, hydration and reconstitution efficiency decreased. For the first time, dynamic particle surface fusion was observed. Such fusion can result in stickiness and caking over time. ESEM methods developed here may provide mechanistic insights into the effects of RH during storage. Surface re-arrangement was also observed in all MPCs, but was impeded in MPC70 and MPC80 thus indicating that this is the rate limiting step for MPC reconstitution. This work validates the use of an ESEM to dynamically characterise MPC powder hydration and reconstitution in-situ and in real-time, at both high magnification and spatial resolution.

The Influence of Composition and Manufacturing Approach on the Physical and Rehydration Properties of Milk Protein Concentrate Powders.

This study investigated the physical and rehydration properties of milk protein concentrate (MPC) powders with five different protein contents (i.e., 38.9, 53.7, 63.6, 74.1, and 84.7%, w/w) prepared by recombining the ultrafiltration (UF) retentate and UF permeate of skim milk. Powder density and flowability increased, while the powder particle size decreased with decreasing powder protein content. The amount of non-wetting MPC powder decreased with decreasing protein content, demonstrating greater wettability for lower protein powders. At protein contents >65% (w/w), the dispersibility and solubility of the powders decreased significantly, likely due to the greater hydrophobic interactions between casein proteins and a lower concentration of lactose. Therefore, as the protein content of the MPC powders was decreased, their rehydration properties improved. The results obtained in this study provide novel insights into the relationship between the composition of recombined UF retentate and UF permeate streams on the subsequent powder particle size, density, and rehydration properties, and demonstrate that such powders possess similar properties to those prepared using conventional direct membrane filtration.

Production of vegetable yoghurt like from lupin milk

The objective of the present study was to produce vegetable milk from lupine seeds as an alternative to natural milk in the yogurt like production. Lupine yoghurt like was made from in-permeate lupine extract fortified with different levels of milk protein concentrate (MPC) powder in comparison with cow-milk yoghurt. Where lupine milk was extracted from soaked legume lupine (Lupinus angustifolius) seeds using milk permeate (1Kg beans / 5 Kg permeate) and divided into 4 equal portions and fortified with MPC powder at level of nil, 1, 2 or 3%. All treatments were converted into yoghurt using 3% bacterial starter culture of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus (1:1). The results showed that, the addition of MPC to lupine extract led to increase in the total solids content of resultant yoghourts like. Also, cow yoghourt had significantly higher fat content than lupine yoghurt like. Adding MPC to the lupine yoghurt milk resulted in lower fat content. Cow yoghurt had lowest protein content while lupine yoghurt with 3% MPC showed the highest protein content. Crude fiber content of lupine yoghurt without MPC was found to be highest than other yoghurt treatments. Values of viscosity were increased more with ascending ratios of MPC in Lupine milk. Hardness and springiness values of all lupine yoghurt treatments were increased during cold storage and the increase in these two texture parameters were positively correlated to the MPC level. Str. theromphillus or Lb. delbrueckii ssp. bulgaricus count in yoghurt made from cow milk showed higher counts than that of lupine-milk yoghurt like. All samples were free from any contamination either with yeast or fungi organism whether when fresh or after 7 days of cold storage while they appeared after 14 days. All yoghurt were sensory acceptable especially that fortified with 3% MPC powder, which helped to beany flavor disappearing.

Effect of change in pH, heat treatment and diafiltration on properties of medium protein buffalo milk protein concentrate.

The demand of milk protein concentrate (MPC) powders is continuously increasing as high protein dairy ingredients. Presence of higher calcium and casein contents; heating, ultrafiltration (UF), diafiltration (DF) and spray drying of buffalo skim milk induces undesirable changes in milk proteins that causes problem of poor solubility in MPC powders. Therefore, this investigation was aimed to study the effect of change in pH (6.8-native, 7.0-neutral), heat treatments (74 ± 1°C/15s, 80 ± 1°C/5min, 85 ± 1°C/5min, 90 ± 1°C/5min) and DF on physicochemical, functional, reconstitution and rheological properties of medium protein buffalo milk protein concentrate (MP-BMPC) powder. Based on maximum ζ-potential and heat stability, UF retentate was selected, diafiltered and spray dried to obtain MP-BMPC powder. Despite having higher protein content, MP-BMPC powder exhibited markedly better functional (solubility, wettability, viscosity and emulsion stability) properties than buffalo milk protein concentrate 60. The interstitial air content, occluded air content, loose bulk density, packed bulk density, particle density and porosity values of MP-BMPC powder were 145.97 and 112.92mL 100g-1 of powder, 0.21gmL-1, 0.30gmL-1, 0.55gmL-1 and 65.09%. Further, its specific surface area; particle size distribution (d10, d50, d90); Sauter (D32) and DeBroukere (D43) mean values were 97.93m2 kg-1; 34.32, 104.42, 218.58µm; 61.27µm and 117.99µm. The storage modulus (G') and loss modulus (G″) crossover temperature of UF and DF retentates were ~ 57.16°C and 55.10°C, respectively. Rheological behaviour of UF, DF retentates and MP-BMPC solution were best explained by Herschel-Bulkley model. Fourier-transform infrared spectroscopy best described amide I, II and III regions in 1700-1400cm-1 and 1350-1200cm-1 wavenumber range.