Spray Drying Of Milk Research Articles

Thermodynamic and exergoeconomic analyses of two-stage spray drying plant for skim milk powder production

Spray drying of milk is a highly energy intensive process. In this study, thermodynamic and exergoeconomic analyses of two-stage spray drying plant have been executed. This plant was analyzed on the basis of various parameters such as energy efficiency, exergy efficiency, energy improvement potential, exergy improvement potential, etc. The energy and exergy efficiency of the plant were 72.90 and 35.15%, respectively. The maximum energy improvement potential was for drying whereas maximum exergy improvement potential was for homogenizer. It indicates huge scope in the technical improvement for drying chamber and homogenizer of the plant. The highest cost of processing was for cyclone separator (percentage relative cost difference: 44%) followed by drying chamber (percentage relative cost difference: 40.71%). Highest energy destroyed was calculated for drying chamber (195.83 kJ/kg) followed by VFBD (87.62 kJ/kg). Lowest energy efficiency was calculated for VFBD (34.64%) followed by drying chamber (50.04%). Highest energy improvement potential was estimated for drying chamber (97.86 kJ/kg). Highest relative energy destruction ratio was calculated for drying chamber (52.04%) followed by VFBD (23.30%). Highest energetic factor was calculated for drying chamber (28.22%) followed by homogenizer (16.71%). Based on these analyses, it was realized that performance of the spray drying plant may be substantially improved by some design improvement of drying chamber and homogenizer only.

A new approach for energy optimization in dairy industry

Energy carriers as fuel, are one of the essential needs of various industries. The cost of these carriers persuades us to find solutions to prevent waste of energy consumption. Among the various industries, dairy industry is one of the most energy intensive of them. By considering the importance of energy consumption in the dairy sector, in this study first the types of technologies available in the milk drying industry is discussed and then this technology is investigated economically and its disadvantages and advantages are expressed. This paper's main goal is to optimize energy consumption in the process of milk powder production using pinch technology. Therefore, it provides a brief description of pinch technology and after providing data table consist of streams information, the desired cycle (milk spray dryer) is optimized from a technical and economic point of view by Aspen Energy analyzer (AEA). The modeling assumptions and the desired scenario are also given. Finally, four scenarios about how to apply a connection among heat exchangers and discuss about cost of investment for each scenario is presented. The results show that temperature of pinch point, hot utility and cold utility is 85 °C, 25.3 kW and 66.36 kW respectively and MER-3 networking is chosen as the best option in terms of initial cost (81,304.42 $), number of units (7), area (65.27 m 2 ) and final cost (7.28 × 10 4 $/S) that this amount is close to the target mode but it is not in a good position in terms of the required area, which is a weakness in the desired networking.

Optimization of Spray Dryer Design for Small Scale Drying of Milk Using Computational Fluid Dynamics

Spray drying technology has long been the industry standard for producing quality powdered products such as milk powder, coffee, juice powder, and pharmaceutical products. Spray dryers convert liquid or slurry directly into powdered form with the help of an atomizer and hot drying gas. One of the applications of such technology can be in the milk industry of Nepal. Spray drying of milk can increase the shelf life of milk and significantly reduce its volume, making it easy for storage and transport. This paper is concerned with the design of such a spray dryer for community-based applications. The drying chamber was designed based on previous literature on the topic. Then the analysis and refinement of the initial design were done using the ANSYS Fluent CFD package. An Eulerian-Eulerian framework was utilized to model the problem. The dimensions and thermo-physical properties were optimized for a drying capacity of 400 kg milk in 8 hours. The optimum inlet conditions were found to be 400 K, 0.385 kg/s for hot air inlet, and 318 K, 0.014 kg/s for milk inlet. The length and diameter of the dryer were optimized to 3700 mm and 1790 mm respectively. The airflow pattern at the axial region of the dryer was found to be downward directed, and that at the peripheral region was found to be turbulent with recirculating eddies. According to the observed trend in the transient simulation, the temperature of the milk reaches a value of 385 K at the inlet for a brief period of 0.78 s and then lowers to 365 K and eventually reaches 340 K while exiting the chamber after two seconds of injection. These results are improvements from previous industrial-scale spray dryers as the maximum temperature inside the dryer and the particle-residence-time were reduced. All of this leads to low thermal degradation of milk while drying.

Drop impact of non-Newtonian dairy-based solutions

Vertical drop impacts of dairy-based solutions on to smooth stainless steel surfaces have been experimentally studied using high-speed photography. Seven test fluids were prepared using infant formula, whole milk, and whey protein powders, reconstituted at 10–45% total solids content in water. Their shear-thinning rheology yielded Herschel-Bulkley consistency indices up to 385 (mPa s) n with a flow index of n = 0.67. Impacts covered ranges of drop diameters (1.75–3.15 mm) and impact velocities (0.90–3.50 m s −1 ) producing Weber numbers between 35 and 605. Observed outcomes for different fluids were dominated by differences in rheology, and shear-thinning was evident when comparing maximum spread of the two most viscous solutions. To describe the normalised maximum spreading diameter ( β max ), a model which interpolates between capillary and viscous regimes, and which was developed for Newtonian fluids, was successfully adapted for shear-thinning drops. The time taken to reach maximum spread ( t s ) was best described using power-law models in which the dimensional time is proportional to either the Reynolds or Ohnesorge number raised by an exponent. This research should assist with understanding spray-drying of milk, and will be more broadly applicable to processes involving spraying and impact of shear-thinning droplets. • A detailed study of dairy-based liquid drop impacts using high-speed photography. • The fluids with high solids concentrations are non-Newtonian (shear-thinning). • Outcomes for different fluids are dominated by differences in rheology. • Appropriate models are identified for the extent and timing of maximum spread. • The study has broad relevance for food processing using stainless-steel surfaces.

Quantifying the Responses of Three Bacillus cereus Strains in Isothermal Conditions and During Spray Drying of Different Carrier Agents.

Spray drying is a widely used method for producing milk powder. This process is not aimed to cause microbial inactivation, thus sporeforming bacteria may be abundant in the microbiota of milk powder. The first aim of this study was to determine the inactivation kinetics parameters in capillary tubes of three Bacillus cereus strains (436, B63, 540) in three menstrua (whole milk, phosphate buffer, and talc suspension) at 90, 100, and 110°C. D-values for B. cereus in the three menstrua were not significantly different at the highest tested temperature (p > 0.05). Thus, talc was chosen as a carrier agent to allow the recovery of B. cereus from spray dried materials given its low interference on inactivation kinetics. B. cereus spores were also inoculated in whole milk and skim milk following spray drying at 95, 105, and 110°C (outlet temperature). After the spray drying runs, B. cereus spores were counted and the number of decimal reductions (γ) calculated. A correlation between the small diameter of the particles with the survival of spores of three B. cereus strains was found, and B. cereus 436 presented consistently the lowest γ no matter temperature and a carrier agent. The highest γ was found when talc powder was used, which suggest that this carrier agent does not protect B. cereus spores during spray drying. Spray drying of milk can lead to up to 4 γ (strain 540) of B. cereus spores but depending on the strain less than one γ (strain 436) could be observed. This study contributes to the knowledge on the microbiology of low water activity foods by providing novel findings regarding the fate of three B. cereus strains to different spray drying conditions. Acknowledging the variability of inactivation of B. cereus during spray drying is key in the current context of food safety in which the quantification of effects of unit operations must be known for the validation of processes and development of more robust formulations.

Single droplet drying of milk in air and superheated steam: Particle formation and wettability

ABSTRACTSuperheated steam drying has been receiving research attention in recent years due to its increasing industry prevalence in the food and agricultural sector. There is however a gap of knowledge in superheated steam spray drying involving the drying of droplets with dissolved solids as most application to date are solely on solid materials. With this constraint, it is vital to understand and study the effect of superheated steam on the particle formation process as well as on the final particle. The aim of this work is to explore the potential of superheated steam in the spray drying of milk. Specifically, this report examines how superheated steam influences the migration of fats, protein, and lactose in milk during the particle formation process. Studies were conducted by drying fresh milk, using a single droplet drying technique in a superheated steam environment and a hot air environment at a fixed temperature of 110°C. The wettability of the dried single particle was examined using contact angle measurements. The surface of superheated steam-dried milk particles revealed a relatively higher wettability when compared to air-dried milk particles. This suggests that superheated steam promoted the presence of hydrophilic components such as lactose on the exterior surface of the particle. These results have therefore shown the possibility of using superheated steam to control component relocation in multicomponent solutions based on the component hydrophilicity. By recognizing the potential of application of superheated steam in spray drying, engineered multicomponent particles with specific features can be produced.

Spray-drying of milk for oxygen evolution electrocatalyst and solar water splitting

The development of efficient and robust electrocatalyst has been the central of the solar water splitting-based hydrogen fuel acquisition. In this work, we reported the use of cow milk, with addition of tetraethyl orthosilicate (TEOS) and melamine, for the synthesis of nitrogen-doped mesoporous carbon microspheres. Due to the large surface and enhanced charge transport behavior, the obtained samples enabled low overpotentials and a small Tafel slope toward oxygen evolution reaction, which were close or comparable to the best OER catalysts of carbon materials reported previously. Further incorporation of this catalyst and a Pt wire to a commercial solar cell, the direct solar-to-hydrogen conversion was realized, with a stability of over 30h.

Thermo-economic optimisation of industrial milk spray dryer exhaust to inlet air heat recovery

This study reports a thermo-economic design optimisation of an industrial milk spray dryer liquid coupled loop exhaust heat recovery system. Incorporated into the analysis is the ability to predict the level of milk powder fouling over time and its impacts on heat transfer and pressure drop. Focus is given to a finned round tube, a bare round tube and a bare elliptical tube. Modelling results show that spray exhaust heat recovery is economically viable for the considered industrial case study. Based on the results, the best liquid coupled loop heat exchange system uses a finned tube heat exchanger to recover heat from the exhaust air with a face velocity of 4 m/s and 14 tube rows, which gives a net present value of NZ$2.9 million and an internal rate of return of 71%. The developed thermo-economic assessment method has the ability to cater to site specific needs that affect the utility savings and the capital cost for implementing exhaust heat recovery.

A Simple Methodology Based on the Pittsburgh Coal Method for Assessing Specific Explosion Risks in Dust-Generated Explosive Atmospheres: A Case Study from Galicia (NW Spain)

Hazardous explosive atmospheres caused by dust may occur when powdered combustible material is present in an enclosed area. In general, dust explosions take place when high enough concentrations of combustible powdered dust particles are present in the atmosphere with another suitable gaseous medium such as oxygen. Because the manipulation of these substances in industrial activities entails a risk that could have devastating consequences (including serious injuries or loss of life, as well as significant damage in installations), the risk assessment to eliminate or control the risk of explosive atmospheres in the workplace is a challenging task. In European countries the assessment of these risks is evaluated using the ATEX Directives as per European legislation. However, using this legislation to assess the risk of explosion in powder atmospheres presents difficulties due to the variety and complexity of possible explosive atmospheres and the extremely high variety of ignition sources involved. Therefore, risk evaluation becomes a difficult and time-consuming task.In the present article, a simple empirical method for detecting and making an initial assessment of dust-generated ATEX atmospheres is presented. The force of possible explosions was estimated using the explosion index, which was obtained from other indices: explosion severity and ignition sensitivity. For a specific dust, both of these factorial indices were calculated on the basis of their explosive characteristics in relation to those of Pittsburgh coal (employed as a standard). The proposed methodology was applied to a real case study of an explosion in a milk spray dryer in Lugo (northwestern Spain). Taking into consideration the explosive characteristics of the products treated in this type of installation, the ATEX zones, the probability of the explosion, and the severity of the consequences (determined in accordance with the proposed Pittsburgh coal method), the risk assessment performed according to the methodology developed here provided results that agreed with the real accident in terms of probability and severity of the explosion as well as damages incurred.

Drying kinetics of skim milk with 50wt.% initial solids

► Experimental determination of droplet drying behavior of 50 wt.% skim milk droplets. ► Important kinetics data for modeling of industrial spray drying processes. ► Extension of the Reaction Engineering Approach (REA) to high solids concentration. ► Behavior of the activation energy at high initial solids concentration. Drying kinetics data are of paramount importance for simulating industrial spray drying operations. This study reports for the first time the drying kinetics of skim milk droplets with 50 wt.% initial solids, as typically encountered in practice. The changes in droplet temperature, moisture content, and diameter were experimentally determined using glass-filament single droplet drying technique. Enhanced effects of drying temperature on droplet shrinkage were observed. Experimental data were correlated using the Reaction Engineering Approach (REA) with the master activation-energy curve providing a good description to the drying histories. Activation energy curves obtained here were compared with previous data from lower initial concentrations, as well as the plot obtained using a preliminary desorption method. The outcomes support the suitability of REA to interpret the drying behavior of skim milk with high initial solids level, which is the norm for practical spray drying of milk with feed concentration of around 50 wt.%.

A Fundamental Model of Particle Deposition Incorporated in CFD Simulations of an Industrial Milk Spray Dryer

Particle deposition is an important, undesirable problem during the operation of spray dryers. A new mathematical model of particle deposition has been developed and implemented in the computational fluid dynamics (CFD) software FLUENT. The pseudo Ohnesorge number Oh* and Weber number We* have been used to formulate the model to the determine possibility of particle deposition. The reentrainment of the particles back into the dryer chamber was determined according to the wall shear stress. The transient multiphase flow process in an industrial spray dryer that produces around 9 tonnes of milk powder per hour was simulated to validate the deposition model. The numerical results show that reentrainment of particles into the dryer chamber is significant at the chamber walls. The deposition intensity has been found to be higher near the adjunctions of the ceiling wall, the vertical wall, and the conical wall because of smaller wall shear stress. The distribution of wall temperature, Oh* and We*, which has important influence on wall deposition, has been obtained from the numerical results. More experimental and computational work is required for future validations.

A Computational Fluid Dynamics Study of a Tall-Form Spray Dryer

Two phase simulations have been performed of a tall-form Delaval skim milk spray dryer in order to evaluate the applicability of current computational fluid dynamics models to this type of simulation, and to examine the characteristics of the flows that exist within these complex devices. The simulations have been performed with and without milk particles included, for a variety of droplet nozzle injection velocities, and for two dryer inlet throat geometries. Limited validation of the results has been achieved by comparing the simulated product moisture contents against data measured in experiments1. It was found that the simulated product moisture contents were of the same magnitude, but generally slightly lower than those found during experiments. It was also found that the behaviour of the dryer is largely determined by the relationship between the initial momentum of the injected particles and the gas fiowfield within the dryer.

Stability of vitamin D 3 during spray-drying of milk

High-performance liquid chromatography was used to evaluate the stability of vitamin D 3 in milk when subjected to spray-drying. Measured losses through the pasteurisation, high-pressure evaporation and drying processes were demonstrated to be statistically insignificant ( P = 0.05). The common practice of overage addition during manufacture of supplemented milk powder formulations is therefore a questionable risk factor to regulatory compliance.

Modelling and control of a spray dryer: a simulation study

This paper presents a new model for predicting the dynamic behaviour of a milk spray dryer, and also develops and evaluates a simple and robust control structure by means of simulations. The new model includes a rigorous energy balance in the gaseous phase, and considers variable droplet size and density. The predicted response of this model differs appreciably from the response of the models found in the literature. The control structure manipulates the inlet liquid flow rate and measures the humidity of exiting gas. With the aim of improving the control system's robustness, a cascade control is proposed, based on periodic off-line measurements of solid water content at the outlet. This system is capable of controlling solid humidity as it leaves the dryer, despite any kind of disturbance.

A COMPARISON BETWEEN TWO METHODS FOR THE RECOVERY OF LISTERIA MONOCYTOGENES IN MILK POWDER REFERENCE SAMPLES

ABSTRACTTwo methods (A and B) for the recovery of Listeria monocytogenes were compared using reference samples based on spray drying of milk containing this pathogen and competitive microflora. For method A, the sample was inoculated in a buffered liquid medium (same as IDF Pre‐enrichment Broth) and then passed to IDF Enrichment Broth plus phosphate buffer. For method B, the sample was inoculated in FDA Enrichment Broth (LEB) and then passed to LEB (subenrichment). The solid selective medium used in both cases was Listeria Selective Agar (Oxford formulation). The sensitivity and specificity of method B was 95.2% and 100% vs. 76.1% and 88.8% for method A, respectively.

Properties of Bacillus cereus spores in reference materials prepared from artificially contaminated spray dried milk

A reference materials for Bacillus cereus was developed based on spray drying of milk artificially contaminated with B. cereus spores. Various properties of the B. cereus spores in the milk powder were determined. The stability of the materials was good with no detectible decrease in the contamination level during 1 1 2 years storage at − 20°C or 4 weeks at 22, 30 or 37°C. The homogeneity of the material was found acceptable for use as a reference material. Heat treatments (10 min at 70 or 80°C) and addition of lysozyme to the enumeration medium did not influence the number of spores counted. The germination of the spores depended on the type of medium in which the milk powder was reconstituted, and on the storage period of the material. The suitability of the material was confirmed in a collaborative study. From the results obtained it was concluded that the material developed meets the general requirements set for reference materials and can therefore be used for, among others, testing laboratory performance.

Direct ‘low‐NOX’ gas combustion heating of a spray drier during milk powder manufacture

Direct gas‐fired heating experiments were carried out during spray drying of milk using a ‘low‐NOx' burner in order to minimize contamination of the drying air by the combustion products in the flue gases from the burner. The burner, model CXA (Urquhart Engineering Co Ltd, England) was of the ‘excess air’ type, and was fuelled by natural gas. There was no significant difference between the mean values of the nitrate content of the skim milk powders produced by direct firing, electrical heating and the factory produced (indirect heating) sample. Only with nitrite content (NO2) was there a significant difference between the direct gas fired (0.811 ppm NO2‐) and the factory (0.460) samples, but the range of values encountered was very small (0.24–1.68). Direct gas‐fired heating using the low NOx burner did not contribute to the levels of N‐nitrosodimethylamine (NDMA) detected in the test powders when compared to the levels found in the control samples (trace‐1.3 μg/kg NDMA).

Influence of sample shape and size on self-ignition of a fat-filled milk powder

A lecithinated, 30% tallow fat-filled, milk-product powder, commercially-manufactured in Ireland, was used as the test material to assess the effect of sample shape and size on self-ignition in a thermostatically-controlled oven. Cubes of edge 25, 38 and 51 mm, spheres of diameter 26, 50, 77 and 102 mm, cylinders with diameter equal to length of 51, 76 and 100 mm and layers of 100 mm diameter and thickness of 10, 15 and 20 mm were tested. The minimum ignition temperature (MIT) varied from 206°C for the thinnest layer to 131°C for the largest sphere. For each shape, the results fitted the linear relationship ln( δ c T 2 r 2 ) = M− (N/T) , with close correlation. However, contrary to theory, the four straight lines did not coincide. Those for the spheres and layers were very close while those for cubes and cylinders had approximately 25% greater values for their slope (N). These results are shown to introduce significant differences when the values of M and N for the two most divergent lines within the test range are used to extrapolate estimates of critical layer thickness for the lower operating temperatures in parts of a milk spray dryer. M and N obtained from spheres gave the lowest estimates while those for cubes gave values up to 2·32 times, and those for cylinders, 2·85 times greater at 50°C. These results could also affect the safe design of silos for the storage of powder in the 40–50°C range to avoid self-ignition and allow the contents to cool to ambient temperature.

Fire and explosion hazards in the spray drying of milk

SummaryRecent reports in the literature indicate that incidents involving fires and explosions in the spray drying of milk products are increasing in number. Whilst milk powder is not highly explosible, the conditions for a dust explosion, apart from the ignition source are almost always present in certain areas of a spray dryer during its normal operation. Self‐ignition of deposits is known to be possible at the high temperatures in a spray dryer. At best, this can cause product degradation and discolouration whilst at worst it can provide the source of ignition for an explosion. This paper is an attempt to draw together recent work on fire and explosion prevention and protection formilk powders.

Effect of Processing upon Concentration and Distribution of Natural and lodophor-Derived Iodine in Milk

Cream removal, pasteurization, and spray-drying of milk did not affect concentration of either natural or iodophor-derived iodine, as measured by both chemical and electrode methods, although electrode results were significantly higher. The use of iodine-131 labeled iodophor showed that only .02% of iodine was lost from milk on boiling and that 3.4% of iodophor-iodine became associated with milk casein.