Milk Droplets Research Articles

Rare earth oxide nanoparticles for superhydrophobic, antifouling and self-cleaning coatings

The widely used rare earth oxides (REOs) have a limited application in antifouling coatings. Here, coatings composited with REOs-1H,1H,2H,2H-perfluorodecytrimeth-oxysilane (REOs-FAS) based on hydrothermal reaction were prepared for study if REOs can be used in marine antifouling coatings. A network consisting of polydimethylsiloxane (PDMS) and REOs-FAS (REOs-FAS/PDMS) (RE = Ce, Pr, Nd) was created by using the blending method and polymerization reaction. The presence of the REOs-FAS imparts to the polymers an amphiphobic structure and disrupts the cell membrane, resulting in excellent antifouling properties and antibacterial performance. The water, coffee, and soya-bean milk droplet state on the Pr6O11-FAS/Sylgard 184 silicone elastomer with the ratio of 4:1 (PFSR-4) and the ink self-cleaning experiment demonstrated that the PFSR-4 has a perfect self-cleaning property. The most suitable surface roughness of PFSR-4 not only empowered the superhydrophobic (the contact angle of water is as high as 157° ± 2° and the sliding angle of water is as low as 5° ± 2°)-oleophobic characteristic (the contact angle of diiodomethane is as high as 132° ± 3°), but also endowed the coating with the anti-diatom (as high as 97.7 %) and anti-mussel adhesive properties. Moreover, the colored PFSR coatings were prepared to do another barrier for the adhesion of large fouling organisms, especially for the white coatings. The anti-mussel attachment ratio of purely whited PDMS was high to 84.6 %. The antibacterial REOs are appropriate for preparing multi-functional coatings. In general, the designed coating has the potential to be a durable, self-cleaning, antibacterial, and antifouling coating and could serve as a foundation for developing innovative super-amphiphobic coatings.

Image-Based Detection of Adulterants in Milk Using Convolutional Neural Network.

Adulteration of milk poses a severe human health hazard. Existing methods for detecting adulterants such as water, urea, ammonium sulfate (AmS), oils, and surfactants in milk are selective, expensive, and often challenging to implement in rural areas. The present work shows the potential of machine learning to detect milk adulterants using patterns of evaporative milk deposits. The final deposit patterns obtained after evaporation of the adulterated milk droplets are used to create an image data set. This data set is used to develop a deep learning model that deploys a convolutional neural network (CNN/ConvNet) to classify the distinct evaporation patterns obtained for different types and concentrations of adulterants. Further, we apply implicit and explicit regularization and compare their accuracies. The models trained with different regularization optimization schemes demonstrate that a CNN can be successfully implemented to detect adulterants in milk. Additionally, we experimentally determine how the type and concentration of milk adulterants, including ammonium sulfate (AmS), urea, oil, and surfactants, affect milk evaporative deposition. Added AmS and urea in milk crystallizes during evaporation to produce recognizable patterns that can be used for their detection. The method is capable of detecting AmS added in excess of 2.4% and urea in excess of 5% in diluted milk (20 wt %) due to the crystallization of AmS and urea, respectively. In the case of milk adulterated with vegetable oil, evaporation leads to the separation and accumulation of oil at the top of the deposit, leading to the detection of oil present in excess of 2% in 20% diluted milk. Furthermore, a minimum individual amount of 5% urea, 2.4% AmS, and 2% oil concentration in diluted milk (20%) is shown to be individually detected by evaporation pattern-based technique when milk is adulterated with all the adulterants (water, urea, AmS, and oil + surfactant) together. When subjected to different regularization optimization schemes, the CNN gives varying degrees of accuracy for successful detection. The use of implicit regularization in the form of data augmentation gives the best results with a testing average accuracy of 98%, showing that a CNN can be successfully deployed to classify and detect adulterants in milk.

Mechanism for improving the in vitro digestive properties of coconut milk by modifying the structure and properties of coconut proteins with monosodium glutamate

In this paper, the effect of monosodium glutamate (MSG) on coconut protein (CP) solubility, surface hydrophobicity, emulsification activity, ultraviolet spectroscopy and fluorescence spectroscopy was investigated. Meanwhile, the changes in the in vitro digestive properties of coconut milk were also further analyzed. MSG treatment altered the solubility and surface hydrophobicity of CP, thereby improving protein digestibility. Molecular docking showed that CP bound to pepsin and trypsin mainly through hydrogen bonds and salt bridges. And MSG increased the cleavable sites of pepsin and trypsin on CP, thus further improving the protein digestibility. In addition, MSG increased the Na+ concentration in coconut milk, promoted flocculation and aggregation between coconut milk droplets, which prevented the binding of lipase and oil droplets and inhibited lipid digestion. These findings may provide new ideas and insights to improve the digestive properties of plant-based milk.

Comparing different single milk droplet drying process with spray drying process

Spray drying is currently the main method of industrial milk production because of its high drying speed and high process control accuracy. By controlling the parameters of spray drying process to control the characteristics of the milk powder is well researched. However, the drying mechanism in spray dryer is still not very clear. Methods of measuring single droplet drying kinetics are widely used instead of directly modelling spray drying kinetics. In this study, single droplet drying methods including sessile drying, filament hanging drying, and levitator drying in room temperature are used to compare and simulate the drying kinetics in spray dryer. Experiments show that the droplets in levitator are more spherical, but the final dry particles tend to be more donut-like due to the compression of the upper and bottom sides by the ultrasonic waves. In the filament hanging drying, the droplets are only suspended on the filament by friction. Due to gravity, the shape of the droplets and dried particles is non-sphere droplet shape. In sessile drying, the droplet is half-sphere shape, and the contact area is not changing because of capillary force. By comparison, the final particle morphologies of these are significantly different from those in the spray dryer, therefore, explore the characteristics of spray-dried droplets by monitoring the drying characteristics of single droplets may not suitable on some situation especially on multi-component materials.

An integrated and automated digital microfluidic device for dairy milk droplet actuation

An integrated and automated digital microfluidic device for dairy milk droplet actuation

Evaporation dynamics of a sessile milk droplet placed on a hydrophobic surface

A colloidal droplet is an integral part of spray-drying based applications such as food, pharmaceuticals, drug delivery, etc. The complex physico-chemical dynamics determine the final structures obtained in the process. Therefore, a complete understanding of the different forces involved and the evaluation of the governing parameters is crucial to control the final morphologies as desired. The evaporation-induced dynamics are studied in milk droplets placed on hydrophobic substrates under natural drying condition. Experiments were performed systematically by varying the initial concentration of protein (BSA) in the droplets. The results were analyzed using energy-based models. Capillary forces and inter-particle interaction are found to have dominating effects upon the particle deposition in the evaporating droplets. Furthermore, inclusion of protein beyond a threshold initial concentration leads to buckling instability which produces cavitated structures. Maintenance of hydrophobicity for a sufficient amount of time is an important criterion to initiate the buckling instability. Our study provides physical insights into the dynamics involved in desiccating droplets, including the buckling dynamics. These insights have far-reaching implications in spray-based industries.

Lock-In Amplified Fluorescence Spectroscopy in a Digital Microfluidic Configuration for Antibiotic Detection of Ciprofloxacin in Milk

Antibiotic detection in dairy is crucial, as introduction of antibiotics in food can lead to antibiotic resistance and cause allergic reactions in consumers. Dairy farmers risk monetary fines for shipping contaminated milk. Microfluidics is an appealing technology, as it is portable, can be implemented on-site, and is highly automated. This work presents a digital microfluidic dairy device for antibiotic detection. The digital microfluidic dairy device explores integration of a lock-in amplifier with droplet-based microfluidic techniques, being electrowetting actuation and droplet control. The lock-in amplifier setup is initially demonstrated for the fluorescent dye rhodamine B, to establish baseline operation. Ultimately, the lock-in amplifier setup is demonstrated for detection of ciprofloxacin in milk. The limit of detection is significantly lowered through the integration of the lock-in amplifier technology. Actuation of milk and water samples is shown, demonstrating full two dimensional control over the position of water and milk droplets, to enable a complete lab-on-a-chip system. The results show promise for modern dairy testing of antibiotic signatures. [2022-0120]

The Simulation of Fluid Flow with a Vortex Generator 35° toward the Y-axis to Heat Transfer in Spray Dryer

The Spray Dryer is a spray drying machine to change liquid into dry powder. The spray drying machine can be defined by the drying process in a cylinder, utilizing air heated in the heater and flowing through a blower connected to a vortex generator with an angle of 35° to the Y-axis. The vortex generator causes the formation of turbulence of airflow. Heat transfer occurs between the hot air flow and the milk droplets so that the liquid milk becomes a dry powder. This research aims to see the vortex phenomenon, namely the turbulence intensity, airflow velocity, heat flux, and temperature distribution in a cylinder, compared with an experiment that used four conditions of temperature inlet. There is 80°C, 90°C, 100°C and 110°C. The liquid used in this research is dairy cow’s milk mixed with water and maltodextrin, which has a density value of 1056 kg/m3 and a specific heat value of 3930 J/kg K. The machine’s cylinder has a diameter of 0.5 m with a wall thickness of 1 x 10−3 m and a height of 2 m with a capacity of 1.27 l/hour with a drying time of 80 minutes. The speed airflow of this machine into the cylinder has 16 m/s with a cross-sectional diameter of 9,5 x 10−2 m and a thickness of 1 x 10−3 m which has a debit of 0.11 m3/s. In addition, the injector used has a diameter of 2 x 10−4 m and a speed of 13,54 m/s with a flow rate of 4,5 x 10−4 kg/s with a spray angle of 45° u. Besides that, the analysis results show that the airflow turbulence area is in the form of a vortex so that the drying process of heat transfer that occurs between the product material and the airflow becomes faster.

Physicochemical stability and in vitro digestibility of goat milk affected by freeze-thaw cycles

Freezing and thawing are widely used in dairy processing to ensure the continuous supply of raw milk. In virtue of this, the influences of freeze-thaw cycles on physicochemical stability and in vitro digestibility of goat milk were evaluated. Experimental results showed that repeated freeze-thaw cycles led to the increase of acidity and medium-short chain free fatty acids of goat milk, and the significant decrease of fat and apparent viscosity. Furthermore, the degree of protein oxidation was enhanced, and the secondary structure changed to random coil. The particle size distribution and microstructure all showed the aggregation of goat milk droplets, resulting in the decrease of physical stability. Nevertheless, repeated freeze-thaw cycles could enhance the simulated in vitro digestibility and antioxidant capacity of digested products. These results are helpful to evaluate the quality characteristics of raw goat milk and provide theoretical reference for the industrial production of goat milk products.

Numerical model to study the statistics of whole milk spray drying

Using a numerical model, this study investigates the spray drying process of whole milk by providing statistics on droplet conditions at exit and first impact with the surfaces of the chamber. A comprehensive four-stage droplet evaporation model was validated against an experiment and then coupled to an Euler–Lagrange model for simulating the milk droplet trajectories inside a dryer. Results show that larger droplets remain for a shorter time in the chamber and contain more moisture on exiting. Higher injection angles result in longer residence times, which leads to lower moisture content for the droplets. By increasing the injection velocity of droplets, their relative velocity compared to the airflow increases, raising the rate of evaporation, and consequently more droplets exit the chamber as fully dried. Furthermore, decreasing the airflow rate and humidity, as well as increasing the airflow inlet temperature, results in a lower moisture content in the final powder. When the droplets impacted the wall of the chamber for the first time, nearly 67% of them were fully dried, and 55% had a velocity magnitude less than 1 m/s. A considerable portion of droplets (close to 52%) impacted the wall at an angle of less than 8°. • A modelling approach to better understand the drying of milk droplets in spray dryers is presented. • This approach includes modelling the flow, particle tracking, and a comprehensive drying model. • The validate drying model captures temperature and moisture content distribution. • This model is then used to extract statistical information about the drying state of milk droplet. • The statistical study provides insight into the effects of key operating parameters.

Wet-core temperature and concentration profiles in a single skim milk droplet drying process

Spray drying is a commonly used method to rapidly produce dry powder from liquids or slurries. In the dairy industry, this method is preferred for producing milk powder to prolong shelf life as well as to make the product denser for transportation. In the current work, an experiment accompanied by a numerical model is employed to study the drying kinetics of an industrial-scale skim milk droplet. A comprehensive four-stage evaporation model was validated against the experimental results and was then used to study the temperature and solute distribution profiles within the wet-core of the drying droplet. The results showed that the heat diffuses within the wet-core sufficiently quickly (as indicated by the Lewis number of 25.53), such that the uniform wet-core temperature assumption remains valid for this case study despite Biht=0.281. The uniform solute concentration assumption, however, does not appear to be an appropriate assumption (Bimt=77), especially for the later drying stages where the droplet becomes further concentrated and mass diffuses at slower rates. Furthermore, when the milk droplet dries faster under a higher evaporation rate, the solute had insufficient time to redistribute from the surface towards the centre, resulting in an uneven solute concentration profile. For the high evaporation rate presented in this study, a solute mass fraction of approximately 0.5 was calculated in the droplet centre, compared with 0.82 for a lower evaporation rate. Therefore, for obtaining a uniformly distributed solute in the final dried powder, a lower rate of evaporation is recommended.

Deep neural network for generalizing and forecasting on-demand drying kinetics of droplet solutions

Recent trend in consumer preferences toward healthy and on-demand-to-make items has mandated food manufacturers to seek more efficient production processes in order to make their businesses sustainable. For powder producers in particular, the business models are drifting from ‘ready-made’ toward on-the-go items, thus requiring an urgent attention. Here, we present a long short-term memory (LSTM) model for forecasting drying kinetics histories of lactose, low-fat and high fat milk droplet solutions; covering a wide gas-and-material spectrum, utilizing only their initial conditions. Within the examined range, results show that the forecast lactose temperature and mass drying curves have accuracies within 0.9987 and 0.9841 respectively; that improve in the order of training-material-blend/training-data-rows as thus: lactose/3612, lactose-fat/4515, lactose-protein/5317 and lactose-fat-protein/6220. This indicates the impact of data size on the model accuracy and generalization of the trained LSTM network. For low/high fat milk (20–30% total solid), accuracy margins are within 0.0179 and 0.0655 in the range of 1–8 combined test samples. Beyond 8 samples up to 20 combined scenarios, accuracies are capped at 0.9749 for temperature and 0.9000 for mass profiles. Since only the initial conditions are required by the developed model to provide forecasting, this removes cost and time barriers inherent in traditional approaches during new product launch. Future application of deep learning models would integrate the presented LSTM network to consider actual characteristics of material mixing such as colour, texture and taste.

Concept of Busoore Labaniya (Acne Vulgaris) and its Management In Light of Unani System of Medicine

Acne vulgaris is extremely common dermatological disorder, affecting more than 85% of adolescents and young adults. In western societies, acne vulgaris is a nearly universal skin disease afflicting 79% to 95% of the adolescent population. A recent systematic review of the epidemiology of acne across the world noted acne prevalence estimates ranging from just over 20% to over 95%. The greatest burden of acne globally is between the first and third decade of life and almost certainly causes embarrassment, stigma, shame, guilt, and low self-esteem, which are likely to cause psychosocial problems. It is characterized by both inflammatory (papules, pustules and nodules) and non-inflammatory comedones (open and closed) lesions. In Unani system of medicine, acne vulgaris is termed as busoore labaniya that are whitish eruptions on the nose and face that represent milk droplets or frozen ghee (Roghan zard) due to Ma’dah sadidiyah or pus like morbid matter that is directed towards the skin for expulsion along with ghaleez bukharat. There are mentioned numerous single and compound formulations having Mujaffif and Muhallil properties for the management of Busoore Labaniya. The principle of treatment is aimed to removal of morbid matter, which is the actual culprit for the genesis of pathology leading to development of busoore labaniya. So there is need to explore the Unani concept of dermatoses. Present review paper is an attempt to highlight the possible management and preventive measures of acne vulgaris through Unani medicine.
 Keywords: Busoore labaniya, Acne vulgaris, Unani system of medicine, Mujaffif and Muhallil.

A new approach to account for porosity variations on the solidification of a skim milk droplet

In modeling the drying process of a skim milk droplet subjected to a hot gas flow, ignoring the effect of solid particles in reduction of evaporation surface before the crust formation and porosity variation within the droplet, causes the predicted surface temperature of droplet deviate from the experimental values. In the present study, a new drying model is developed in which the effects of variable porosity within the droplet as well as the reduced area of the evaporation surface due to the presence of solid particles are accounted for. Based on this model, a Finite Volume code is developed to calculate the droplet porosity at all drying stages and also taking into account the effect of solid particles in reducing the evaporation area of the droplet by calculating the diffusion coefficient of porous medium. Using this model leads to a better prediction of droplet temperature with a maximum error of 2% compared to experimental results. This model also has a good prediction of droplet mass reduction with an average error of about 10%. Also, a parametric study is performed to investigate the effect of the principal parameters such as air temperature, air velocity and droplet initial diameter on the drying time and morphology of obtained dry particles. Peclet number is a criterion for determining the morphology of dried particles. Numerical results show that with increasing the hot air velocity and temperature, the Peclet number increases but the initial droplet size does not have much effect on the Peclet number. Based on this observation a new correlation is introduced between the Peclet number and the characteristics of the dryer air flow.

Formation of cheddar cheese analogues using canola oil and ultrasonication – A comparison between single and double emulsion systems

Cheddar cheese analogues were produced from skim milk in which canola oil was emulsified using ultrasound to form either single (O/W) or double emulsions (W1/O/W2). The double emulsion cheese analogues (DECH) had a distinct microstructure and retained small skim milk droplets, dispersed in the fat phase, for more than 7 months of ageing at 4 °C. The single emulsion cheese analogues (SECH), prepared with the same fat content as control cheeses, produced comparable yields of cheese and whey, with similar composition, although the fat droplets were more spherical and showed greater coalescence. The DECH cheese with skim milk encapsulated in the oil droplets was harder, melted less and showed more free fatty acid development over 7 months of aging than the control cheeses. The SECH cheeses were softer than the control and also melted less effectively but did not show greater free fatty acid development.

Physicochemical Properties of African Catfish Mucus and Its Effect on the Stability of Soya Milk Emulsions

Mucus, a waste product produced when African catfish undergoes stress, has lubricating effects and could be a potential emulsifier. Emulsions are thermodynamically unstable; researchers have documented synthetic bio-polymers as emulsifiers, but its sustainability is in question. This research aims to establish some physicochemical properties of African catfish mucus (ACM) and its effect in soya milk emulsions. A Zetasizer and Turbiscan were used to measure stability, morphology was determined with Transmission electron microscopy (TEM), while functional groups in ACM and ACM-stabilized soya milk emulsions were determined using Attenuated Total Reflection Fourier Transform Infra-red spectroscopy. ACM is a stable hydrogel with negatively charged (−36.2 mV) loosely bound electrons with polar and non-polar portions. ACM concentrations of 1, 3, and 5 g w/w stabilized soya milk emulsions after 180 min of storage. The spectra of stabilized emulsion revealed interactions with soya milk droplets. ACM encapsulated the stabilized emulsion and conferred a kind of cohesive interaction and stability. Turbiscan revealed that the mucin formed strong cohesive connections with stabilized emulsions and the mucin exhibited adhesive properties. ACM is an excellent natural emulsifier with mucoadhesive properties as it encapsulates soya milk to enhance stability.

Numerical simulation of mono-disperse droplet spray dryer: Coupling distinctively different sized chambers

The discrete phase model (DPM) has been widely used in CFD simulations to track discrete particles or droplets in a continuum fluid filed. This powerful technique, however, may face tremendous difficulty in tracking droplets flying through chambers with significantly different sizes. In such cases, it becomes very challenging to develop effective mesh for the big and small chambers together with the transition zone that can ensure solution convergence within reasonable computational time. In this work, a systematic method is introduced to tackle this problem. This method allows simulation of different sized chambers separately to avoid the meshing difficulty. A unique coupling approach offers smooth transition of droplets from one chamber to the other with rigorous conservation of their mass, energy and momentum. The effectiveness of the method is demonstrated through the simulation of skim milk droplet drying in a mono-disperse droplet spray dryer (MDSD), where droplets must pass through a small dispersion chamber before entering the main big drying chamber. For the first time, droplet drying process from exiting nozzle to the arrival at the dryer outlet can be simulated. The new model can be used in the future to optimize the spray drying process.

Prolonged milk provisioning and extended maternal care in the milking spider Toxeus magnus: biological implications and questions unresolved

Prolonged milk provisioning and extended parental care for nutritionally independent offspring, previously considered to only co-occur in long-lived mammals (Clutton-Brock, 1991; Royle et al., 2012), were recently reported in the reproduction of the milking spider, Toxeus magnus (Chen et al. 2018). Newly hatched T. magnus spiderlings require 53 days to develop to maturity, with an average adult body length of 6.6 mm. The mother provides milk droplets to her newly hatched spiderlings until they develop into subadults (~38 days old), during which their body lengths increase from 0.9 mm at birth to 5.3 mm at weaning. Although spiderlings can forage for themselves at around 20 days old, they remain in the breeding nest for weeks after maturity.

Prolonged milk provisioning in a jumping spider.

Lactation is a mammalian attribute, and the few known nonmammal examples have distinctly different modalities. We document here milk provisioning in a jumping spider, which compares functionally and behaviorally to lactation in mammals. The spiderlings ingest nutritious milk droplets secreted from the mother's epigastric furrow until the subadult stage. Milk is indispensable for offspring survival in the early stages and complements their foraging in later stages. Maternal care, as for some long-lived vertebrates, continues after the offspring reach maturity. Furthermore, a female-biased adult sex ratio is acquired only when the mother is present. These findings demonstrate that mammal-like milk provisioning and parental care for sexually mature offspring have also evolved in invertebrates, encouraging a reevaluation of their occurrence across the animal kingdom, especially in invertebrates.

A differential shrinkage approach for evaluating particle formation behavior during drying of sucrose, lactose, mannitol, skim milk, and other solid-containing droplets

Particle formation process during drying of solid-containing droplets exerts profound influence on the property and quality of dried particles. A differential shrinkage approach is proposed to describe the particle formation behavior of different materials, by evaluating how the droplet shrinkage kinetics of the given material(s) deviates from the ideal shrinkage. Sucrose was selected as the reference material to establish ideal shrinkage kinetics, as its shrinkage at 10, 30, and 50 wt.% initial concentrations well followed the ideal shrinkage at all temperatures tested (70, 90, and 110 °C). Comparing the differential shrinkage kinetics of sucrose, lactose, and mannitol showed that mannitol has a strong crust-forming tendency, which could not be explained by the difference in the solubility of the three materials. By establishing a differential shrinkage curve for each material, this approach offers a straightforward and powerful method to evaluate the particle formation property of the material at various initial concentrations.