Surface Composition Of Powders Research Articles

Milk fat globule membrane regulates the physicochemical properties and surface composition of infant formula powders by improving the stability of the emulsion

The milk fat globules in infant formula (IF) are encapsulated by a component known as milk fat globule membrane (MFGM). However, it is currently unclear whether the improved emulsion stability of MFGM can have a profound effect on the finished IF. Therefore, this study investigated the effects of MFGM on the particle size, stability, rheology, and microstructure of emulsions prepared by dairy ingredients via wet mixing. Further, IF were processed using such emulsions, the physicochemical properties, surface composition of the powders were examined. The results showed that MFGM reduced the particle size of the emulsion, increased the viscosity, and improved the microstructure of the MFGM. Furthermore, MFGM reduced the moisture content of the powder, increased the glass transition temperature, and reduced the presence of surface fat. In conclusion, the addition of MFGM enhance the finished powder stability by improving the emulsion stability prepared during IF manufacturing.

The effect of feed formulation on surface composition of powders and wall deposition during spray drying of acidified dairy products

The effect of feed formulation on surface composition of powders and wall deposition during spray drying of acidified dairy products

Elucidating the physicochemical properties and surface composition of goat milk-based infant formula powders

This study investigated the characteristics of cow milk-based, goat milk-based, and mixed-based (using goat milk and cow whey powder)infant formulas (IF) with different sources of casein and whey protein, aiming to construct the properties of powders prepared using goat milk. Goat milk-based IF have different water activity, color, and glass transition temperature than other IF, whereas the crystallinity and solubility were similar. SDS-PAGE pattern showed that goat milk-based and mixed-based IF contained higher β-casein, while cow milk-based IF contained higher αs1-casein. The differentials of casein affected the powder surface composition and free fat levels. Goat milk-based IF reduces the surface fat content and free fat levels of the particles. Further analysis showed that the surface of the particles was predominantly filled with saturated fatty acids. Our findings revealed that due to the different casein, goat milk-based IF have favorable characteristics and surface composition, thus promoting its particle stability.

Processing of 17Cr7Mn6Ni TRIP Steel Powder by Extrusion at Room Temperature and Pressureless Sintering

Transformation‐induced plasticity (TRIP) steels are known for their outstanding strength and their excellent deformation properties, which are necessary for the improvement of occupant safety elements in air, rail and motor vehicles. One precondition for the realization of the TRIP effect is the creation of a metastable austenitic microstructure through the addition of a number of alloying elements. The great affinity of some alloying elements for oxygen implies the formation of highly stable oxides during thermal processing. In the current study, an extrusion process (derived from the processing of ceramics) with subsequent debinding and pressureless sintering is used to manufacture compact strands from prealloyed and gas‐atomized 17Cr7Mn6Ni TRIP steel powder. The influence of both the debinding temperature and sintering atmosphere on the oxide particle content in the final bulk product are investigated by X‐ray diffraction (XRD) analysis and quantitative metallography. Furthermore, X‐ray photoelectron spectroscopy (XPS) analysis in association with temperature‐programmed reduction (TPR) experiments, thermogravimetric (TG) measurements and mass/infrared spectroscopy (MS/IRS) serve to monitor the changes in the steel powder surface composition and the effectiveness of hydrogen as a reducing agent.

Influence of drying temperatures and storage parameters on the physicochemical properties of spray-dried infant milk formula powders

The influence of spray drier inlet (180 and 200 °C) and outlet (80, 90 and 100 °C) air temperatures and storage parameters (22 and 40 °C, and 11%, 23% and 54% RH, for 6 months) on the characteristics of infant milk formula (IMF) powders was investigated. The combination of inlet–outlet temperatures affected the moisture content, water activity, particle size and glass transition temperature (Tg) in the freshly spray-dried IMF powders, whereas, powder surface composition and morphology were not affected. Powders remained stable for 6 months at 11 and 23% RH at both storage temperatures. Storage at 54% RH (at both storage temperatures) increased the moisture uptake by powders, decreased Tg below storage temperature, induced lactose crystallisation, increased surface fat and caking of powders, and reduced powder solubility. This study shows that inlet–outlet temperature combinations used during spray drying affect the stability of powders during storage by affecting their initial moisture content.

Physicochemical properties of spray-dried model infant milk formula powders: Influence of whey protein-to-casein ratio

The effect of whey protein-to-casein ratio (60:40, 50:50 and 40:60) on the physicochemical properties of model infant milk formula (IMF) wet-mixes and powders prepared therefrom was studied. A lower whey protein-to-casein ratio lowered the zeta potential and apparent viscosity of wet-mixes and increased the particle size after evaporation. Particle size and water activity of powders decreased with decreasing whey protein-to-casein ratio. Glass transition temperature, crystallinity, surface free fat content and solubility of the powders were similar and unaffected by protein composition. Surface composition of powders was substantially different from their bulk composition irrespective of the protein ratios, with fat representing more of the powders surface (∼42–44%) followed by protein (∼30–32%) and lactose (∼24–26%). Overall, IMF powders can be prepared by varying the whey protein-to-casein ratio without affecting the physicochemical properties of the feed and the spray-dried powders.

Effect of lactose-to-maltodextrin ratio on emulsion stability and physicochemical properties of spray-dried infant milk formula powders

This study was conducted to investigate the effects of lactose-to-maltodextrin ratio (L:M 100:0, 85:15 and 70:30) on emulsion stability and the physicochemical properties of spray-dried infant milk formula. Lactose-to-maltodextrin ratio did not affect the emulsion particle size, but increasing the proportion of maltodextrin increased the apparent viscosity after evaporation and decreased the zeta potential of emulsions. Most importantly, increasing maltodextrin proportion increased the glass transition temperature (by 4 and 8 °C at 15% and 30% maltodextrin, respectively) and decreased the crystallinity and yellowness of the powders. Surface composition of powders was different to that of their bulk composition, where fat was over-represented on the powders surface (∼41–44%), followed by protein (∼30–33%) and carbohydrate (∼24–26%). This study concludes that maltodextrin can be successfully included in infant formula blends without affecting emulsion stability in a wet mix and allows controlled modifications of certain properties in corresponding spray-dried powders.

Milk powder quality degradation detection using chitosan film based sensor

Chitosan based milk powder quality degradation sensors have been successfully fabricated by combining electrochemical deposition and photolithography techniques. The aim of this paper is to discuss the potential of chitosan thin film sensors for detecting milk powder quality degradation. The milk powder quality may be decreased upon storage. Milk powder surface composition changes during storage due to increasing in moisture content. Electrical testing of chitosan thin film properties to fresh milk powder and milk powder exposed to air for 1, 2, 3 and 4 weeks has been done at room temperature. The results show that the chitosan-based milk powder quality degradation sensors have good performance demonstrated by very good response, stability, recovery, repeatability and selectivity. The simple, easy and inexpensive technique is required to monitor the milk powder quality degradation.

Chemical components distribution and morphology of microcapsules of paprika oleoresin by microscopy and spectroscopy

Microencapsulates containing oleoresin of paprika (OP) and blends of soy protein isolate (SPI), maltodextrin (MD) and gum arabic (GA) as wall materials, were analysed to evaluate the components distribution developed during the encapsulation process. Encapsulation efficiency, glass transition temperature, flowability and physical properties were also assessed. Focused ion beam coupled to scanning electron microscopy (FIB-SEM), confocal laser scanning microscopy (CLSM), X-ray dispersion spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) allowed identifying the effects of OP into microcapsules, chemical components distribution, and morphology. In microencapsulated OP, the hollow capsules ranged from 8 to 23% and Tgs (near to 83 °C and 98 °C). The protein concentration on particle surface (18.08%–68.48%) was evaluated by XPS and the surface composition of powders was identified. The best encapsulation efficiency (88.4%) was exhibited by the formulation OP-0.10% SPI-10.45% MD-9.45% GA; the capsules showed the lowest wall thickness and the maximum nitrogen reduction (%) on the particle surface. As a conclusion, OP reduces the presence of hollow capsules and increases the Tg; the soy protein may be responsible for the folds with wide crests on the particle surface, giving a soft and active surface. Although the stability of oleoresin of paprika microencapsulated is associated with the low values of moisture content, aw, and glass transition temperature, the OP on the external surface, could reduce the protective capacity of any wall material.

Cocoa powder surface composition during aging: A focus on fat

The surface of 11wt.% fat cocoa particles was thoroughly investigated during a 2-month storage at 20 and 40°C and at aw=0.2. Surface fat migration was evidenced only for powders stored at 40°C by X-ray Photoelectron Spectroscopy. This was confirmed by ToF-SIMS, which allowed visualizing bigger fat patches at the surface of 40°C-stored powders. These observations emphasize that fat need to be under a melted form to move toward the surface during storage. However, an increase in the free fat content was observed at both 20°C and 40°C. These results suggest rearrangements of particle structure during storage; free fat being more accessible to solvents at both temperatures. Confirmation was done by Scanning and Transmission Electron Microscopy images. Free and encapsulated fat were also extracted and analyzed during storage and no significant difference in fatty acids distribution (C16, C18, C18:1, C18:2) was observed by gas chromatography.

Impact of Spray-Drying Process Parameters on Dairy Powder Surface Composition and Properties

To design dairy powder properties according to their future use, it is necessary to know how to identify the main process parameters that influence the drying mechanisms and to optimize them on the basis of the desired powder properties. The impacts of atomization process parameters on powder physicochemical properties and surface composition were investigated and correlated. The analytical results permitted us to sort the produced powders into groups according to their dependency to process parameters. This study shows the feasibility of developing a model for the prediction of the physicochemical properties of dairy powders via a reverse engineering approach.

Changes in the surface chemistry of chromium-alloyed powder metallurgical steel during delubrication and their impact on sintering

Changes induced in the surface chemistry of metal powder during the delubrication stage affect the subsequent sintering process and hence the final properties of the sintered compacts. The different stages during delubrication were characterized by means of in situ visual observation of components made by compacting chromium-alloyed water-atomized steel powder with lubricant additions. A strong correlation is found between this visual observation of changes of the compact appearance during the delubrication and the component chemistry depicted via the monitoring of the exhaust gases composition (CO2, O2 and H2O), thermogravimetric analysis, and changes in powder surface composition (X-ray photoelectron spectroscopy combined with scanning electron microscopy and energy dispersive X-ray analysis). The compacts were delubricated at different conditions and the effect of different parameters was studied, including temperature (300, 450 and 900°C) and processing gas (N2 or air). Delubricated compacts were further sintered at 1120°C in N2/3%H2 mix to evaluate the effect of delubrication on the properties of the sintered components. The mechanical properties, chemistry and microstructure obtained after sintering show a strong relation to the surface changes induced during delubrication. The results indicate that delubrication at 450°C in dry N2 preserves the original surface condition of the powder and upon sintering the compacts exhibit optimum properties. Sintered compacts delubricated at 450°C in air and at 900°C in N2 exhibited inferior properties. In the former case, this was related to the growth of Fe-oxide on the powder surfaces. In the latter case, the initial thin Fe-oxide layer, covering most of the powder surfaces, was reduced and oxygen made available was transferred into stable Cr–Mn–Si-rich oxide particles. Delubrication at 300°C resulted in insufficient lubricant removal along with soot formation contributing to inferior mechanical properties after sintering as well.

Effect of protein content on the physical stability and microstructure of a model infant formula

The effect of protein content (6.68–11.88 g protein 100 g−1 powder) on the microstructure and physical stability of dry infant formula was investigated at relative humidities (RH) of 0 and 54.4%. Time-dependent lactose crystallisation of powders occurred at lower water contents as protein level decreased. Surface composition of powders stored at 0% RH were significantly (P < 0.05) different to their bulk composition, with fat extensively covering the surface of powder particles. Increasing RH to 54.4% increased surface lactose levels due to lactose crystallisation. Reducing protein level increased levels of free fat in powders stored at 0% RH for 14 days. Glass transition temperatures of powders decreased only at the lowest protein level studied (6.68 g 100 g−1). Reducing the protein content of infant formulae resulted in altered powder particle surface composition, free fat levels and time-dependent lactose crystallisation properties.

An assessment of various powdered baby formulas by conventional methods (DSC) or FT-IR spectroscopy

Milk components are assumed to be uniformly distributed in a concentrate whilst it is being dried. During milk powder production, these components are redistributed in the drying droplets and the powder surface composition is significantly different from that of the bulk of it. The objective of this article was to analyze and compare phase transitions of powdered baby formulas as well as to make a study of their FT-IR spectra. Food powders of different composition were tested by a differential scanning calorimeter (DSC, TA Instruments Q 200) with a normal pressure cell and a System 2000 spectrophotometer. Significant differences were observed in the shape of curves of the mixtures and the agglomerates. The observed phase transitions in powders depended on fat content. Characteristic peaks of melting lactose were observed in the curves of the powdered baby formulas. The IR spectra proved to be useful in determining adulteration of baby formulas. Both methods were complimentary during a thorough evaluation of these food powders.

How surface composition of high milk proteins powders is influenced by spray-drying temperature

High milk proteins powders are common ingredients in many food products. The surface composition of these powders is expected to play an essential role during their storage, handling and/or final application. Therefore, an eventual control of the surface composition by modifying the spray-drying temperature could be very useful in the improvement of powder quality and the development of new applications. For this purpose, the influence of five spray-drying temperatures upon the surface composition of the powders was investigated by X-ray photoelectron spectroscopy. The major milk proteins were studied: native micellar casein and native whey, both more or less enriched in lactose. The results show a surface enrichment in lipids for all the powders and in proteins for many powders. Whatever the drying temperature, lipids and proteins are preferentially located near the surface whereas lactose is found in the core. This surface enrichment is also highly affected by the spray-drying temperature. More lipids, more proteins and less lactose are systematically observed at the surface of powders spray-dried at lower outlet air temperatures. The nature of proteins is also found essential; surface enrichment in lipids being much stronger for whey proteins containing powders than for casein containing powders. Additionally, we found a direct correlation between the lipids surface concentration and the wetting ability for the 25 powders studied.

Surface composition of industrial spray-dried milk powders. 3. Changes in the surface composition during long-term storage

The changes in the surface composition of industrial spray-dried milk powders (skim milk powder, whole milk powder and cream powder) during long-term storage were investigated. The powders were stored in the conditions, which are more likely for commercial circumstances, for 6 months and the surface composition of the powders was analyzed before and after storage using electron spectroscopy for chemical analysis (ESCA). For the fat-containing powders (whole milk powder and cream powder), the various milk fat fractions (surface free-fat, inner free-fat and encapsulated fat) were also extracted before and after storage, and analyzed for their fatty acid and triglyceride compositions to evaluate whether there was a release of fat onto the powder surface during storage and if this causes changes in the melting characteristics of the fat present on the powder surface. The structure of the powders and the physical state of the lactose present in the powder were studied before and after storage by scanning electron microscopy (SEM) and X-ray diffractometer (XRD), respectively. The results showed that the lactose present in the powders remained in the amorphous state over the storage, and therefore no significant changes in structure and surface composition of the powders occurred. However, a release of encapsulated low-melting triglycerides towards the surface of powder during storage was observed in the fat-containing powders, thereby the melting points of the surface free-fat and the inner free-fat were lowered. This phenomenon was observed in both whole milk powder and cream powder, but more significant changes were observed in CP.

Surface composition of industrial spray-dried milk powders. 2. Effects of spray drying conditions on the surface composition

The effects of various spray drying conditions (feed solids content, drying temperature, degree of homogenization and initial droplet size) on the surface composition of industrial spray-dried milk powders (skim milk powder and whole milk powder) were investigated. Experiments were performed in a laboratory-scale spray drier and the surface compositions of the powders were measured using electron spectroscopy for chemical analysis (ESCA). For whole milk powder, the amount of surface free-fat was also measured as a complement to the surface composition estimated using ESCA. For both skim milk powder and whole milk powder, the surface composition of the powders was found to be determined to a large extent by the spray drying conditions employed. At higher feed solids content or drying temperature, less fat and protein appeared on the surface of the powders. Less redistribution of components seemed to occur within the drying droplet because of high viscosity and rapid crust formation. Increasing the number of homogenization passes reduced the fat globule size and consequently the amount of fat present on the powder surface. The initial droplet size did not have a significant effect on the range of particle sizes studied in this work. Strong interaction effects between the spray drying conditions were also found. The results suggest that a combination of spray drying conditions is necessary to control the surface composition of milk powders. Possible mechanisms behind the formation of the surface composition of industrial spray-dried milk powders were proposed based on the findings in this work and theoretical considerations.

Surface composition of industrial spray-dried milk powders. 1. Development of surface composition during manufacture

Development of the surface composition of milk powders during manufacture was investigated in three industrial spray-dried milk powders (skim milk powder, whole milk powder and instant whole milk powder). Samples were obtained from commercial production plants and were collected at different manufacturing stages. As the powder properties of milk powder are defined in spray-drying and the subsequent manufacturing processes, the powder samples were collected at the exit of the spray drying chamber and the exit(s) of the fluidized bed(s), and the surface compositions of the powder samples collected were studied using electron spectroscopy for chemical analysis (ESCA). For all three industrial spray-dried milk powders, no significant differences in surface composition were observed between the samples collected at different manufacturing stages, except for a slight increase (3%) in the surface fat coverage for whole milk powder after the fluidized bed drying process. These results indicate that the surface composition of milk powders is determined to a large extent during the spray drying process and that the subsequent fluidized bed drying and handling processes have no or little effect on the surface composition of milk powders, even though these processes affect the final powder quality (e.g. moisture content, particle size). For whole milk powder and instant whole milk powder, no fat appeared to leak out on to the powder surface during the fluidized bed drying process; however, the fat present on the powder surface after the spray-drying process appeared to flow over the particle surfaces, resulting in a slight increase in the surface fat coverage. After lecithin treatment (instantization), because a mixture of lecithin and anhydrous milk fat was sprayed on the powder, a slight increase in the thickness of the surface fat layer was observed.

Surface composition and contact angle relationships for differently prepared solid dispersions

Solid dispersions are promising drug delivery forms which offer the possibility to disperse a hydrophobic drug in a hydrophilic matrix and thereby improve the dissolution behavior and the bioavailability of the drug. One important aspect and a prerequisite in understanding the drug dissolution mechanism from solid dispersions is a better analytical monitoring of the solid dispersion surface properties, such as powder surface composition and water adsorption properties. In this paper, we have considered chemical and structural surface analysis data for solid dispersions processed by spray drying or roto-evaporation and compared these data with information obtained by contact angle measurements. Firstly, we establish the usefulness and suitability of X-ray photoelectron spectroscopy (XPS) for determination of surface chemical composition and scanning electron microscopy (SEM) for determining the structure of solid dispersions composed of different types of carriers, drugs and drug concentrations. Secondly, we measure contact angles of solid dispersions to describe wettability, to finally establish a link between the surface chemical composition, the powder structure and the wetting behavior. These experimental methods offer a rapid screening tool for the selection of carrier, drug concentration and/or process in early development. In addition, they provide a useful tool for investigating structural aspects of solid dispersions which have intrinsic relevance for drug dissolution and stability.

Relationships between Dairy Powder Surface Composition and Wetting Properties during Storage: Importance of Residual Lipids

The relationships between powder surface composition and powder rehydration properties under variable conditions of storage are investigated in this paper. A rheological approach was used to evaluate the modifications induced by storage on the rehydration properties of native phosphocaseinate powder. Concurrently, the powder surface composition (i.e., lactose, proteins, and lipids) was evaluated by X-ray photoelectron spectroscopy (XPS). A strong correlation was found between the powder wetting time lengthening and the migration of lipids on the powder surface during storage. XPS studies indicated also an over-representation of lipids on the powder surface (6%) in comparison with total lipids (0.4%) even on fresh powder before storage. Detailed investigation of powder lipids revealed the presence of high levels of polar lipids (66% compared with <1% in milk lipids). Their amphiphilic nature and their melting points could explain the extensive enrichment of lipids observed at the powder surface during processing and storage.