Lactose Crystallization Research Articles

A comparative analysis of ten milk samples with differential scanning calorimetry and Fourier transform infrared spectroscopy

Milk proteins occupy a prominent place in the nutrition of adults and children. Generally, some commercial dairy contains proteins, lactose, other sugar derivatives, and additives. The proportions of the components that make up the milk are different in commercial milk. For this reason, analyzing milk correctly is essential for determining these contents. In this research, analyses of the milk were made by taking differential scanning calorimetry measurements (DSC), and Fourier transform infrared spectrophotometer (FTIR) measurements. Specific heat values and specific values of temperature peaks were examined for ten kinds of milk. DSC curves revealed triacylglycerol dissolution, lactose crystallization, and protein denaturation peaks. Wide variations were observed with the same fat content from 10 milk powders. Most characteristic peaks were not observed when the samples were re-measured after a year at -20°C. The powder samples were compared in terms of protein, fat, lactose content, whey protein casein, and caseinate contents according to differences in FTIR spectra. The FTIR results confirm the DSC curves for most of the analyzed milk types.

Lactose Mother Liquor Stream Valorisation Using an Effective Electrodialytic Process.

The integrated electrodialysis (ED) process supports valorisation of a lactose-rich side stream from the dairy industry, creating an important source of milk sugar used in various branches of the industry. This work focuses on the optimization of the downstream processes before the crystallization of lactose. The process line includes a pre-treatment and desalination by ED of the industrial waste solution of the lactose mother liquor (LML). The LML was diluted to 25% total solids to overcome hydraulic issues with the ED desalination process. Two different levels of electrical conductivity reduction (70% and 90%) of the LML solutions were applied to decrease the mineral components and organic acids of the LML samples. The ED performance parameters such as ash transfer rate (J), the specific capacity (CF) of the ED and specific electric energy consumption (E) were determined and the influence of the LML solution on the monopolar ion-exchange membranes has been investigated. A higher degree of desalination is associated with higher electric energy consumption (by 50%) and lower specific capacity (by 40%). A noticeable decrease (by 12.8%) in the resistance of the anion exchange membranes was measured after the trials whereas the resistance of the cation exchange membranes remained practically unchanged. Any deposition of the alkaline earth metals on the membrane surface was not observed.

Lactose crystallization and Maillard reaction in simulated milk powder based on the change in water activity.

Maillard reaction (MR) and lactose crystallization (LC) are important reactions in the storage of milk powder. In this study, three models with different proteins based on skimmed milk powder were established to investigate the relationship between MR and LC at different water activities (aw ). Moisture sorption isotherm, glass transition temperature (Tg ), and glycation products were evaluated, and the protein structure and lactose crystallinity were determined. The results indicated that MR product content, browning, and LC subsequently enhanced with the increase in aw . The Tg value dropped lower than 0 at aw 0.43 in whey protein isolate-lactose (WP-Lac) model and at aw 0.54 in casein-whey protein isolate-lactose (CN-WP-Lac) model and casein-lactose (CN-Lac) model. The crystallinity of α-lactose monohydrate and anhydrous β-lactose in WP-Lac model was more significant than CN-WP-Lac and CN-Lac models (p<0.05). The molecular band of whey protein gradually blurred in the Sodium dodecyl-sulfate polyacrylamide gel electrophoresis image, and the content of α-helix of WP-Lac model increased by 45.15% from aw 0.33 to 0.53 (p<0.05), while that of CN-WP-Lac model increased by only 3.95% (p<0.05). With the increase in aw , WP-Lac model formed more browning and crystallization products than CN-WP-Lac model, indicating that the presence of micelle macromolecules and the interaction between casein and whey proteins limited the browning and crystallization in CN-WP-Lac model. Practical Application Maillard reaction and lactose crystallization are important reactions in the storage of milk powder, and the result will provide theoretical guidance for the development of milk powder in the food industry.

The effect of induced crystallization of lactose on dulce de leche properties

The effect of induced crystallization of lactose on dulce de leche properties

Assessment of the development of Staphylococcus aureus during the production of soro on a laboratory scale

The aim of this study was to evaluate the multiplication of S. aureus during whey powder production in laboratory scale. Whey was inoculated with 106 CFU∙ mL-1 of the S. aureus mixed culture at the beginning of the processing and the persistence of the microorganism after pasteurization, vacuum evaporation and drying was evaluated. The recontamination of whey by biofilms was also evaluated. Population of 102 CFU∙mL-1 of S. aureus was found after vacuum evaporation. The microorganism was able to multiply in concentrated whey during the crystallization of lactose, which infers that it is possible to form a biofilm during this stage. Confocal microscopy analysis confirmed the presence of adhered cells after 4 h of process (103 CFU∙cm2). After 12 h of incubation, the number of adhered cells was approximately 105 CFU∙cm2. Sessile cells of S. aureus in stainless steel were able to return to the planktonic phase. After spray drying, it was verified that the S. aureus population in the powder was 103 CFU∙g-1. The results obtained in laboratory scale points to the need of quality assurance systems to control the steps of industrial whey powder production.

Corrigendum to “Cooling crystallization of lactose in the presence of whey protein and lactic acid impurities” [J. Food Eng. 311 (2021)110729

Corrigendum to “Cooling crystallization of lactose in the presence of whey protein and lactic acid impurities” [J. Food Eng. 311 (2021)110729

Preparation and Characterization of Inhalable Ivermectin Powders as a Potential COVID-19 Therapy.

Background: Ivermectin has received worldwide attention as a potential COVID-19 treatment after showing antiviral activity against SARS-CoV-2 in vitro. However, the pharmacokinetic limitations associated with oral administration have been postulated as limiting factors to its bioavailability and efficacy. These limitations can be overcome by targeted delivery to the lungs. In this study, inhalable dry powders of ivermectin and lactose crystals were prepared and characterized for the potential treatment of COVID-19. Methods: Ivermectin was co-spray dried with lactose monohydrate crystals and conditioned by storage at two different relative humidity points (43% and 58% RH) for a week. The in vitro dispersion performance of the stored powders was examined using a medium-high resistance Osmohaler connecting to a next-generation impactor at 60 L/min flow rate. The solid-state characteristics including particle size distribution and morphology, crystallinity, and moisture sorption profiles of raw and spray-dried ivermectin samples were assessed by laser diffraction, scanning electron microscopy, Raman spectroscopy, X-ray powder diffraction, thermogravimetric analysis, differential scanning calorimetry, and dynamic vapor sorption. Results: All the freshly spray-dried formulation (T0) and the conditioned samples could achieve the anticipated therapeutic dose with fine particle dose of 300 μg, FPFrecovered of 70%, and FPFemitted of 83%. In addition, the formulations showed a similar volume median diameter of 4.3 μm and span of 1.9. The spray-dried formulations were stable even after conditioning and exposing to different RH points as ivermectin remained amorphous with predominantly crystalline lactose. Conclusion: An inhalable and stable dry powder of ivermectin and lactose crystals was successfully formulated. This powder inhaler ivermectin candidate therapy appears to be able to deliver doses that could be safe and effective to treat the SARS-COV-2 infection. Further development of this therapy is warranted.

Crystallization of Lactose-Protein Solutions in the Presence of Flavonoids.

Lactose is commonly crystallized in the presence of whey proteins, forming co-crystals of lactose and proteins. This work hypothesized that flavonoids such as rutin or epigallocatechin-3-gallate (EGCG) could be incorporated into the lactose and protein co-crystal structure since flavonoids may interact with both lactose and proteins. The interactions between whey proteins and flavonoids were first studied. Then, lactose-protein solutions were crystallized with and without flavonoids, measuring the kinetic parameters of crystallization and characterizing the resulting crystals. The incorporation of flavonoids in lactose-protein co-crystals depended on the hydrophilic nature of flavonoids. The hydrophilic EGCG was scarcely enclosed in the crystal lattice of lactose and avoided the inclusion of whey proteins in the crystals. In contrast, the less water-soluble rutin interacted with whey proteins and lactose, leading to the formation of co-crystals containing lactose, protein, and a large concentration of rutin (3.468 ± 0.392 mg per 100 mg of crystals).

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.

Continuous lactose recovery from acid whey by mixed suspension mixed product removal (MSMPR) crystallizer in the presence of impurities

The continuous crystallization approach provides the opportunity to intensify production and improve the quality of crystals manufacturing. This study examined the effect of impurities on lactose crystallization in the continuous mixed suspension mixed product removal (MSMPR) crystallizer. Two impurities usually present in acid whey, protein and lactic acid, were examined. The continuous process was evaluated based on the time required to reach a steady state operation, particle size distribution (PSD), purity, and yield. Impurities increased the time for the continuous system to achieve a steady state condition. This effect was more pronounced in the presence of protein (>13 residence time). In the acidic environment, lactose crystals tended to promote caking and agglomeration during the filtration process, resulting in the formation of larger crystals and a wider PSD. The protein incorporation in the continuous process was 1.5 times higher than in the batch process due to the inefficiency of the filtration stage caused by the aggregated denatured protein particles, which entrapped the mother liquor between the void area of the agglomerated crystals. Understanding impurity effects on lactose crystals in continuous crystallization can be used as a fundamental study to intensify the process and improve the quality of the crystals.

Principles of lactose crystallization and rheology of milk protein concentrate

Milk protein concentrate (MPC) is a commercial designation for dairy ingredients with higher protein and lower lactose content than conventional skim milk powder. Lactose in its amorphous form is found in several spray-dried dairy powders. Amorphous lactose is thermodynamically unstable and can mobilize and crystallize over time under adequate temperature and moisture content. Moisture sorption from the air precedes crystallization, enhancing MPC cohesiveness and caking. This increased humidity results in poor rehydration and dispersibility, lower yield during drying, operation problems, difficulties in handling and storage. Moreover, lactose crystallization in MPC can cause Maillard browning reaction and fat oxidation. To avoid this problem, it is necessary to pre-crystallize lactose as alpha-lactose monohydrate, which is non-hygroscopic, before spray drying. Such a procedure is essential in preventing deterioration of MPC resulting from lactose crystallization or chemical reactions. Additionally, the control of this step is important to obtain specified and reproducible powder, in terms of size and crystallization level. There are various reports on the rheology of milk-based products; however, there is a lack of investigation on concentrated systems. Consequently, the objective of the present work is to review basic concepts of lactose crystallization and rheology of milk protein concentrate.

Raman spectroscopic evaluation of crystallinity, chemical composition and stability of pharmaceutical powder aerosols

Raman spectroscopy was used to evaluate the effects of temperature and humidity on the physicochemical stability of inhalable spray-dried (SD) powders containing budesonide (BUD) and crystalline or amorphous lactose. Powders prepared by spray drying of BUD-lactose solution or suspension containing lactose crystals in BUD solution were stored for 0, 1 and 7 days at 25 °C/60 RH or 40 °C/75 RH. Bulk powders along with the large and small particle size fractions collected on stages 2 and 5, respectively, of the Next Generation Impactor (NGI) were chemically characterised. SD powder from solution contained BUD and lactose in amorphous form and both components were homogeneously distributed in bulk and in the particles collected from the two NGI stages. In contrast, SD powder from suspension showed heterogeneous distribution of lactose and drug in the particles containing crystalline lactose. After 1 day of storage at either condition, recrystallisation and changes in the chemical composition of the particles for the SD powder from solution occurred. The number of drug-only particles increased by 70 on stage 5, whereas most particles on stage 2 still contained both drug and lactose. These changes were not observed in the SD powder from suspension after storage, confirming superior stability of the SD powder obtained from suspension.

Cooling crystallization of lactose in the presence of whey protein and lactic acid impurities

Whey protein and lactic acid are two main impurities affecting the crystallization recovery of lactose from acid whey solutions. This study systematically examined the individual and combined effect of whey protein and lactic acid on the purity of the recovered lactose. From batch cooling stirred tank crystallization experiments, whey protein affected the purity by co-precipitation from the denaturation of protein. In contrast, lactic acid affected the purity by incorporation into the lactose crystal structure. This was primarily due to the similarity in the molecular structure between lactic acid and lactose. The presence of both impurities led to an undesired synergistic effect, which led to a significant increase in the impurity level. The low acidity and enhanced aggregation of protein were the main cause of this undesired synergistic effect. This study highlights the importance of the effective separation of whey protein in acidic whey solutions prior to the recovery of lactose by crystallization. • Denaturation of protein at high temperature was co-precipitated with lactose. • Denatured protein at pH of 4.5 resulted in a larger particle size distribution due to aggregation. • The combination of protein and lactic acid yielded the lowest purity.

Investigation of the influence of powder characteristics on the breakage of dairy powders

Dairy powder breakage occurs in many processes and deteriorates powder properties and functionalities. This study investigated the influence of powder and particle characteristics on the dynamic breakage of dairy powders during the dispersion and conveying in a powder venturi feeder to provide information on assessing and reducing powder breakage during production and transportation. Four kinds of dairy powders (fifteen samples) were analysed: lactose crystals, agglomerates, commercial and lab-scale non-agglomerates. During the dispersion and conveying, breakage degree increased with increasing particle size and decreasing particle structural strength. Considering particle structure, the strength of crystals was the highest, followed by the continuum solids, followed by particles with numerous small holes throughout the particle, followed by particles with a small number of randomly distributed internal holes, followed by the hollow sphere particle with a very thin shell. The breakage behaviour of crystals during conveying was different from the other powders due to the difference in particle structures. Besides, the fat in particles might decrease the breakage of powders.

Investigation of Crystallization Process of Lactose in Milk Serum Permeate

One of the main factors determining physicochemical and structural properties of the dry permeate of spray drying is lactose which is present in permeate as a basic phase. If lactose is in the β-form in a dry powder, the powder easily absorbs moisture from the atmosphere during storage, causing agglutination, clumping, and caking of the product. Prevention of negative consequences associated with increased hygroscopicity, is ensured by the directed crystallization of lactose in a condensed product before spray drying. The purpose of this investigation was to study the crystallization process of lactose in permeate under industrial conditions when using various seed materials. Results of the studies showed that the type of a crystal forming agentdoes not affect the size and shape of lactose crystals and the level of lactose crystallization. Seed material is of critical significance as it will ensure both a high level of crystallization and homogenous crystals which, in general, leads to an increase in melting temperature, due to a decrease in the proportion of amorphous lactose, as well as improves the drying process.

Effect of feeding type and artisanal process in microstructural and physicochemical parameters of fresh and ripened goat cheese

The objective of the present work was to determine the influence of feeding type and artisanal process on microstructural and physicochemical parameters of goat cheeses. The cheeses were made with goat's milk from goats which were fed with different forages: (1) reed (Cissu verticillata) and King grass (Saccharum sinense), (2) mulberry (Morus alba) leaves and orange (Citrus sinensis) peels, (3) alfalfa (Medicago sativa) and corn (Zea mays) stover, and (4) bellota (Quercus ilex) and Kikuyu grass (Pennisetum clandestinum). Fresh and ripened artisanal cheeses were analysed by scanning electron microscopy and image analysis. Results showed that goat’s milk of goats fed with mulberry leaves and orange peels generated larger conglomerates of fat in both types of cheeses, while the microstructure of the rest of the cheeses presented protein networks. A low pH and moisture content contributed to the formation of lactose crystals which ended in a compact microstructure, propitiating, reduction of the number of pores, porosity, and increase in the breakability of ripened cheeses. Pores of elongated shapes with irregular edges characterised the microstructure of both kinds of cheeses. Through discriminant analysis, it was found that the effect of the type of cheese and type of goat feeding influenced the microstructural and physicochemical parameters such as pore number, porosity, pore size, pore perimeter, roundness, FF, AR, SOL, tortuosity, INP-DI, PAZ, fat, moisture, and pH.

Characterizing Maillard reaction kinetics and rheological changes in white chocolate over extended heating.

Molten white chocolate held at high temperatures for extended periods of time undergoes thickening and nonenzymatic browning reactions. Lactose and milk proteins participate in Maillard browning, which occurs more rapidly at higher temperatures. Crystallization of amorphous lactose and high temperature contribute to rheological changes over heating. In the present study, five white chocolates of varied compositions were sampled over time at different temperatures. White chocolates containing amorphous lactose showed increases in complex viscosity, while chocolates with crystalline or no lactose showed no change in rheological properties. Maillard browning was measured through both colorimetry and spectrophotometric analysis of brown pigments. Both markers showed the greatest browning for Nonfat dry milk (NFDM)-containing systems. Chocolates containing no NFDM (milk protein isolate, MPI, or crystalline lactose) showed no change in absorbance after clarification, but some browning in colorimetry results, likely due to residual amorphous lactose in the MPI or increased mobility of lactose from crystals at high temperatures. The evolution of fluorescent intermediates was visualized using fluorescence spectroscopy, revealing that these intermediates were formed prior to colored end stage products and were consumed as the reaction approaches completion. An excess of lactose in the system meant reducing sugar declines were relatively small throughout. Kinetic models were created to determine the influence of chocolate composition and temperature on thickening as related to complex viscosity (first order) and browning via colorimetry and absorbance (pseudo-zero order). Both thickening rate and Maillard reaction rates were faster in chocolates with greater levels of amorphous lactose and when held at higher temperatures. PRACTICAL APPLICATION: So-called "golden chocolate" is white chocolate that has been held at warm temperatures for a period of time to undergo Maillard browning. However, thickening of the chocolate during heating can cause processing problems. In this study, viscosity changes are correlated with Maillard browning kinetics to help chocolate manufacturers find optimal conditions for creating new products.

Lactose mother liquor stream valorisation using electrodialysis

To increase lactose yield, crystallisation of lactose from lactose mother liquor (LML; a by-product containing high amounts of lactose, proteins and minerals) can be applied, but inorganic ions and organic acids inhibit crystallisation and so reduce final product yield. Electrodialysis is proposed for desalting LML before crystallisation to increase lactose yield. Basic parameters of the electrodialysis process for removal of inorganic ions and organic acids as well as changes in membrane properties during electrodialysis are presented. Electrodialysis provided high removal of inorganic ions coming from LML (64 ± 5%), while lactose content did not decrease (11.7 ± 0.2 g L−1 in desalted LML). Furthermore, titratable acidity decreased 2-fold (from 25 ± 2 to 13 ± 2 °SH), thus ensuring more efficient crystallisation process of lactose from desalted LML, when coupled with electrodialysis. The cation-exchange membranes after ED showed increased specific resistivity and permselectivity, while the opposite effect was observed for the anion-exchange membranes.

A sub-zero crystallization process for the recovery of lactose

In industry, lactose is generally produced by concentrating whey permeate by evaporation followed by a slow cooling process where lactose is crystallized. Here, an alternative method is presented whereby the concentration and crystallization steps are combined at sub-zero temperatures, so-called eutectic freeze crystallization. It was discovered that simultaneous crystallization of lactose and water (ice) is possible. The obtained lactose crystals had an average size of 10 μm and a thin triangular or tomahawk morphology. The process was analyzed in detail in two steps: freeze concentration and lactose crystallization at sub-zero temperatures. Freeze concentration experiments showed that concentrating to supersaturation was possible without excessive lactose crystallization. In the second step, lactose was crystallized at temperatures below zero from a 30 wt% lactose solution, without observation of significant primary or secondary nucleation. The amount of seed material had a large influence on the final yield, crystal size and morphology. The optimum seed amount was found to be at 0.08% of the total lactose; the resulting crystals had an average size of 26 μm and a tomahawk morphology. Although highly supersaturated conditions are present in the sub-zero crystallization of lactose, crystal growth is found to be the predominant process rather than nucleation.

Fabrication of Agglomerated Lactose Using Fluidized Bed for Good Compressibility

In this work, a fluidized bed agglomeration process was used to produce agglomerated lactose with good compressibility. In the fluidized bed agglomeration, large lactose crystals were used as the core materials, fine-milled lactose particles were bound to the surface of large lactose cores, and lactose solution was used as the binder. A suspension of lactose solution is sprayed onto the fluidized lactose particles, forming liquid bridges among the large and small lactose particles to form agglomerated lactose. Good hardness of 75-88 N was achieved for the agglomerated lactose. The particle size and bulk density can be controlled. The effects of agglomeration parameters, including solution concentration and temperature, atomizing pressure, peristalsis speed, and material temperature, were investigated for the agglomeration result and the characteristics of the agglomerated lactose. The result also shows that high solution temperature and high solution concentration can improve fluidized bed agglomeration efficiency.