Spray-dried Milk Research Articles

Performance Evaluation of Fiber Near-Infrared (NIR) Optic Probes for Quality Control of Curd Hardness in Cheese Produced by Spray-Dried Milk

This study aims to provide the dairy industry with a direct control model focused on milk coagulation by using multifiber probes to determine parameters in the curding process, such as cutting time, at a lower cost. The main objective of the research is to confirm that a multifiber NIR light scattering probe can be used to predict the elastic modulus of curd during milk coagulation in cheese production. Two randomized complete block designs were used with a 3 × 3 factorial arrangement of three protein levels (3%, 3.5% and 4%) and three wavelengths (870 nm, 880 nm and 890 nm). Using a multifiber probe at a wavelength of 880 nm allowed obtaining a better optical response of the sensor during enzymatic milk coagulation than the 870 nm. It showed greater sensitivity to variations in the protein content of the milk and lower variation in the response. The multifiber probe at a wavelength of 880 nm generated a NIR light backscatter profile like those obtained with other systems. The results showed that the prediction model parameters had a variation as a function of the protein content, which opens the possibility of improving the prediction model’s performance substantially. Furthermore, the initial voltage obtained with the probe responded linearly to the different protein levels in milk. This fact would make it possible, at least theoretically, to estimate protein concentration with the same inline probe for G’ determination, facilitating the incorporation of a corrective protein factor in the prediction models using a single instrument.

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.

Effects of supplementing sodium caseinate on rehydration properties of spray-dried milk protein isolates

Poor rehydration properties of spray-dried milk protein isolate (MPI) are one of the major challenges for its applications. In this study, sodium caseinate (NaCas) was added in the MPI dispersions at a total solid concentration of 8 g/100 mL and NaCas:MPI mass ratios of 0:1, 1:9, 3:7, 1:1, and 1:0 for spray-drying. The addition of NaCas improved the static hydration properties of the powders, with the 1:1 treatment being similar to NaCas showing homogeneous dispersions within 60 min. NaCas also improved the dynamic hydration properties of MPI according to the changes of Z-average diameter, protein solubility, total solids solubility, and morphology during stirring for up to 240 min, and the 1:1 treatment was dissolved the fastest, within 10 min. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis and microscopy results showed that the hydration rate was limited by surface micellar casein that was inter-linked and formed a crust layer. The scanning electron microscopy results further indicated that the added NaCas reduced the connection of casein micelles on powder particle surface and therefore accelerated the dissolution of the surface layer and release of interior matters. This study may be significant to improve the hydration and therefore applications of spray-dried milk protein ingredients.

Agglomeration of Spray-Dried Milk Powder in a Spray Fluidized Bed: A Morphological Modeling

The type of solid substrate plays a critical role in determining the kinetics of the spray fluidized bed (SFB) agglomeration process. In the case of porous (also soft) primary particles (PPs), droplet aging is due to imbibition and drying. The surface properties of the substrate also change due to imbibition. The focus of the present work is to simulate the agglomeration of the spray-dried milk powder using the Monte Carlo (MC) method coupled with a drying-imbibition model. In order to extract the morphology of the formed agglomerates, an aggregation model is employed. Further, this aggregation model is employed to predict the number of positions on the PPs (later agglomerates) for droplet deposition; previously, the ‘concept of positions’ was used. The transient growth of different milk powders (whole and skim) is depicted using the enhanced MC model. The enhancement in the droplet deposition model had a prominent influence on the overall kinetics of agglomeration. As expected, this enhanced MC model predicted that the agglomeration rate of skim milk powder is higher than that of whole milk powder.

Improved Flowability and Wettability of Whey Protein-Fortified Skim Milk Powder via Fluidized Bed Agglomeration.

Recently, protein-fortified milk powders are being widely consumed in Korea to prevent sarcopenia, and the demand for high-protein food powders is continuously increasing in the Korean market. However, spray-dried milk proteins have poor flowability and wettability owing to their fine particle sizes and high inter-particle cohesive forces. Fluidized bed agglomeration is widely used to improve the instant properties of food powders. This study investigated the effect of fluidized bed agglomeration on whey protein isolate (WPI)-fortified skim milk powder (SMP) at different SMP/WPI ratios. The fluidized bed process increased the particle size distribution, and agglomerated particles with grape-like structures were observed in the SEM images. As the size increased, the Carr index (CI) and Hausner ratio (HR) values of the agglomerated WPI-fortified SMP particles exhibited excellent flowability (CI: <15) and low cohesiveness (HR: <1.2). In addition, agglomerated WPI-fortified SMP particles exhibited the faster wetting time than the instant criterion (<20 s). As a result, the rheological and physical properties of the WPI-fortified SMP particles were effectively improved by fluidized bed agglomeration. However, the fluidized bed agglomeration process led to a slight change in the color properties. The CIE L* decreased, and the CIE b* increased because of the Maillard reaction. The apparent viscosity (ηa,10) and consistency index (K) values of the rehydrated solutions (60 g/180 mL water) increased with the increasing WPI ratio. These results may be useful for formulating protein-fortified milk powder with better instant properties.

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.

Improvements in the Physical Properties of Agglomerated Milk Protein Isolate/Skim Milk Powder Mixtures Via Fluidized Bed Agglomeration

Protein-enriched dairy powder is widely consumed to promote muscle synthesis. Recently, in Korea, elderly people have also begun consuming protein powder products to prevent muscle loss. However, these protein-enriched powders have poor flowability and hydration properties because of the fine particles of spray-dried milk protein powder. Therefore, in this study, the fluidized bed agglomeration process was used to solve these problems. The rheological and physical properties of milk protein isolate (MPI)/skim milk powder (SMP) mixtures were effectively improved via fluidized bed agglomeration. The particle size of the MPI/SMP mixtures significantly increased from 35.7–58 μm to 118–136 μm, the flowability level improved from fair (21.4–26.3) to good (15.7–16.3), and the cohesiveness level changed from intermediate (1.27–1.36) to low (1.18–1.19) after fluidized bed agglomeration. In addition, the wetting time of the agglomerated MPI/SMP mixtures was effectively reduced to 4.67–58.3 s by fluidized bed agglomeration. These findings may be useful for manufacturing protein-enriched dairy powders with good instant properties.

Process Modelling, Scale-Up and Characterization of Acetaminophen Spray Dried Milk Powder as Novel Pediatric Dosage Form.

Successful drug therapy in children is contingent upon hassle-free administration of pediatric dosage forms. Pediatric patients suffer from difficulty in swallowing due to weak esophagus muscles in their early age. Considering this challenge liquid formulations are preferred over solid dosage form among pediatric patients to avoid the possibility of choking which can be a serious life-threatening condition in children. The main aim of the present research work was to develop a reconstitutable amorphous acetaminophen spray-dried milk powder (ASDM) as novel pediatric formulation. ASDM was prepared by spray drying process and the spray drying process was optimized using Box-Behnken design to study the effect of spray drying process parameters at X1 [inlet temperature], X2 [aspiration rate] and X3 [feed rate] to Y1 [% yield], Y2 [angle of repose], Y3 [Hausner's Ratio] and Y4 [Carr's Index] as dependent variables of ASDM. In addition, each batch was characterized for particle size by polarized light microscopy and drug entrapment. Predicted parameters from optimized spray drying process model were successfully employed to manufacture a scale up cum validation batch of ASDM, which showed notably improved yield and desirable flow properties. The scale-up validation batch was further characterized using thermal analysis, diffraction studies, spectroscopic analysis, dispersion studies, stability APAP in dispersion formulation and formulation stability studies to confirm the physico-chemical stability of ASDM. Thus, ASDM for oral use can serve as a promising pediatric formulation and the developed prototype formulation can be further extended to future newly discovered drugs with similar characteristics.

Improving rehydration properties of spray-dried milk protein isolates by supplementing soluble caseins

Spray-dried milk protein isolates (MPIs) are important dairy ingredients but may not have desirable rehydration properties for industrial applications. In the present study, rehydration properties of MPIs were improved by spray-drying MPI dispersions containing different amounts of soluble caseins in the form of derivatized MPI (dMPI). dMPI was prepared by alkalizing MPI dispersions to pH 11.0 and subsequently acidifying to pH 6.8 (the pH-cycle). All the spray-dried MPIs had the similar bulk density (around 0.33 g/cm−3), composition, size distribution (1–100 µm), and SEM morphology. However, the decrease of hydrodynamic diameter, dissolution of total solids and proteins, and disruption of particles during the dynamic rehydration were accelerated as the dMPI content increased, indicating the improved rehydration properties. The improvement in rehydration properties was not due to the wettability that decreased as the dMPI:MPI mass ratio changed from 0:8 to 8:0, but resulted from the reduced cross-linking of casein micelles on powder surface and the increased surface porosity during the hydration as observed for partially hydrated samples. The present work may assist industrial applications of spray-dried MPIs.

Particle surface design for enhanced reconstitution of fat-based food powders

Spray-dried milk powders are characterized by an underrepresentation of hydrophilic compounds on the particle surface compared to the bulk, which renders reconstitution unfavourable. To overcome this issue, in the present study we instigated the coating of whole milk powder with two types of micronized lactose: crystalline and amorphous.We demonstrate that deposition of micronized lactose on the surface of whole milk powder leads to an increase in the reconstitution rate at 21 °C, correlated with a decrease in the apparent contact angle of the material. We also show that the physical solid state of micronized lactose is an important factor influencing the reconstitution performance of coated whole milk powder; If micronized lactose is amorphous, increasing the coating concentration beyond a certain point has little or no further effect on the reconstitution kinetics, which could be explained by viscosity build-up effects that hamper capillary penetration and sinking.

Investigation of alterations in phospholipids during the production chain of infant formulas via HILIC-QTOF-MS and multivariate data analysis

Phospholipids play a key role in infant nutrition and cognitive function. In this study, hydrophilic interaction liquid chromatography coupled to quadrupole time-of-flight mass spectrometry method was firstly developed to analyze the composition of phospholipids. Then we characterized and quantified phospholipids extracted from raw, pasteurized, homogenized, and spray-dried milk to investigate the effect of the technological process on the composition of the phospholipids. Results indicate that the composition of the phospholipids underwent minor changes after pasteurization, while the concentration of phospholipids was significantly affected by the spray-drying process, especially phosphatidylethanolamine and phosphatidylinositol. Multivariate data analysis further verified the results and indicated that phospholipids containing polyunsaturated fatty acids had undergone significant changes during the production chain, especially in spray-drying. This work reveals the changes of phospholipids composition during the production chain of infant formulas and serve as a reference for the subsequent optimization of infant formulas to meet nutritional need of infants.

Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder.

Some Salmonella enterica strains survive well in low-water activity (low-aw) foods and cause frequent salmonellosis outbreaks in these products. Methods are needed to overcome such desiccation-resistant Salmonella and to improve the safety of low-aw foods. Building on a recent finding, we hypothesized that natural antimicrobial food additives, which are active against cytoplasmic membrane, could overcome this desiccation resistance phenomenon, and thus, sensitize the pathogen to drying and mild processing. Food additives were screened for the ability to cause leakage of intracellular potassium ions; retention of these ions is vital for protecting Salmonella against desiccation. Two antimicrobial food additives, carvacrol and thymol, caused considerable potassium leakage from the desiccation-resistant S. enterica serovars, Tennessee and Livingstone. Thus, carvacrol and thymol were investigated for their ability to sensitize the desiccation-adapted S. enterica to heat treatment. The combined use of food additives, at their minimum inhibitory concentrations, with heat treatment at 55 °C for 15 min caused 3.1 ± 0.21 to more than 5.5 log colony forming unit (CFU)/mL reduction in desiccation-adapted S. enterica, compared to 2.4 ± 0.53–3.2 ± 0.11 log CFU/mL reduction by sole heat treatment. Carvacrol was the additive that caused the greatest potassium leakage and sensitization of Salmonella to heat; hence, the application of this compound was investigated in a food model against Salmonella Typhimurium ASD200. Addition of carvacrol at 200 or 500 ppm into liquid milk followed by spray-drying reduced the strain’s population by 0.9 ± 0.02 and 1.3 ± 0.1 log CFU/g, respectively, compared to 0.6 ± 0.02 log CFU/g reduction for non-treated spray-dried milk. Additionally, freeze-drying of milk treated with high levels of carvacrol (5000 ppm) reduced the population of Salmonella Typhimurium ASD200 by more than 4.5 log CFU/g, compared to 1.1 ± 0.4 log CFU/g reduction for the freeze-dried untreated milk. These findings suggest that carvacrol can combat desiccation-resistant S. enterica, and thus, potentially improve the safety of low-aw foods.

Investigation of caprine milk serum proteome and glycated proteome changes during heat treatment using robust ion mobility time-of-flight proteomic techniques

For microbial safety, thermal processing is applied during caprine milk processing, which affects the stability of proteins, specially the whey proteins. Therefore, this study evaluated the changes of glycated serum proteome in caprine milk products using a robust ion mobility time-of-flight proteomic technique, without glycated peptides enrichment. In total, 302 proteins were identified in whey and 41 lactosylation sites from 16 proteins. The number of identified whey proteins decreased from 202 to 194, 178 and 186 in pasteurised milk (PM), spray-dried milk (SDM) and ultra-high temperature (UHT) milk serum, respectively, as the heating intensity increased. Nevertheless, lactosylation sites increased 16 in raw milk to 20 in PM, 25 in UHT and 27 in SDM serum. Moreover, major whey proteins contained the highest number of lactosylation sites as expected. The results of this study may contribute to measurement of the quality of caprine milk after industrial processing.

Effects of feed composition, protein denaturation and storage of milk serum protein/lactose powders on rehydration properties

Whey powder rehydration is expected to be closely linked to both denaturation and lactosylation of the proteins. This study investigated the relation between the forced imbibition rate of spray-dried milk serum protein/lactose powders and the particle morphology and how it is related to the insoluble and lactosylated protein fraction, respectively. Despite extensive variation in protein denaturation, aggregation and lactosylation, only comparably small effects on the forced imbibition rate of the powders and the particle morphology could be observed. A possible explanation for this rather limited effect on the rehydration properties and particle morphology might be that the surface composition of the powder particles is rather similar and dominated by native proteins. These insights have relevance for the formulation of whey powders with improved rehydration properties.

Impact of formulation on reconstitution and flowability of spray-dried milk powders

The present study focuses on the impact of lipid content (1.5, 13.8, and 26 % (w/w)) and pretreatment of dairy concentrates (air incorporation by whipping prior to spray-drying) on the physicochemical and technofunctional characteristics of dairy powders. Spray-drying was performed according to the following conditions: 200 °C inlet air temperature and 85 °C outlet air temperature. Physicochemical properties (particle size distribution, shape factors, moisture content, water activity, and surface composition) of spray-dried powders were characterized in order to explain their reconstitution properties and flowability.The first part of the study revealed that changing the lipid content induced no significant difference of powder reconstitution. It was evidenced that median particle size of fatty powders was higher, thus counteracting the negative effect of powder surface hydrophobicity on its reconstitution behavior. Air incorporation in feed dairy concentrates did not significantly affect powder reconstitution properties, even if surface lipid content and median particle size were both decreased. Standard wettability and dispersibility tests were not relevant to evaluate the reconstitutability of investigated powders and all studied powders were classified as non-wettable and poorly dispersible.The second part of the study revealed that changing the lipid content induced a decrease in powder flowability both in unconfined conditions and under high normal stress. Powders were cohesive due to their low median particle size and their surface lipid coverage, nevertheless feed concentrates aeration induced an improvement of powder flowability by the decrease in surface lipid content. The bulk density (BD) and the compressed bulk density (CBD) both decreased with the lipid content, and the aeration of feed concentrates did not impact the BD but led to a decrease in CBD. Last, the compressibility increased with the lipid content and the aeration of feed concentrates, as the former increased particle cohesion and the latter induced the formation of smaller particles.

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.

Changes in bioactive milk serum proteins during milk powder processing

This study mainly investigated changes in milk serum proteins by simulating the industrial processing of whole milk powder using a label-free proteomic approach. A total of 391 proteins were identified, 89 of which were quantified in all groups. Compared with raw milk, the milk subjected to the heating pasteurization process showed significantly decreased the serum protein profile, whereas that subjected to vacuum concentration and spray-drying showed minimal changes. The LC-MS/MS results were further confirmed by determining the activity of bioactive xanthine oxidase and retention of lactoferrin and immunoglobulins. The data showed that 70%–85% of lactoferrin and immunoglobulins were retained in vacuum-concentrated or spray-dried milk but were hardly identifiable in heat-pasteurized milk or whole milk powders. These findings indicate the need for improving the current milk powder-manufacturing techniques to allow the retention of active milk proteins.

Microscopy tools for product innovation

Microscopy tools for product innovation

Water sorption and hydration in spray-dried milk protein powders: Selected physicochemical properties

Low and high protein dairy powders are prone to caking and sticking and can also be highly insoluble; with powder storage conditions an important factor responsible for such issues. The aim of this study focused on the bulk and surface properties of anhydrous and humidified spray-dried milk protein concentrate (MPC) powders (protein content ~40, 50, 60, 70 or 80%, w/w). Water sorption isotherms, polarized light and scanning electron micrographs showed crystallized lactose in low protein powders at high water activities. High protein systems demonstrated increased bulk diffusion coefficients compared to low protein systems. Glass transition temperatures, α-relaxation temperatures and structural strength significantly decreased with water uptake. CLSM measurements showed that humidified systems have slower real time water diffusion compared to anhydrous systems. Overall, the rate of water diffusion was higher for low protein powders but high protein powders absorbed higher levels of water under high humidity conditions.

Physical characterization of spray-dried milk powders and their agglomerates with the addition of carob, cinnamon, and ginger powders

The scope of the study is to determine the influence of the addition of different amounts of carob (CP), cinnamon (CNP), and ginger (GP) powders and fluidized bed agglomeration process on the moisture content, water activity and powder properties of milk powders as well as powder yield and the energy consumption of the drying and agglomeration operations. CP, CNP, and GP were directly added to whole milk at different concentrations (1-8 % by weight), mixed for 30min and filtered by crude filter paper. Then, the filtrate was spray dried at the inlet and outlet air temperatures of 160 and 80 °C respectively. The powder yield ranged between 55.57-67.07% for milk powder with CP (MPCP), 45.48-61.04% for milk powder with CNP (MPCNP), and 42.42-46.93% for milk powder with GP (MPGP). The addition of the powders decreased the total drying time and energy consumption of the drying process (p<0.05). The agglomeration process was performed at 1.8 m/s, and 80 °C for 15 min. During this process, water (1:0.1 weight: weight, water: powder) was added to powders as a binder. Agglomerates have higher moisture content (3.45-4.60%, wet basis) and water activity (0.171-0.257) values compared to corresponding powders. The solubility times of powders decreased with the increasing amount of ingredients. Higher bulk (200-259 kg/m3) and tapped (339-400 kg/m3) density values were obtained from MPGP compared to other powders. Agglomeration process improved the flow properties of milk powders and increased the bulk and tapped density values. The long solubility times of milk powders (194-244.5 s) reduced to 10-50 s by means of the applied agglomeration process.