Effect of Agglomeration on Flowability of Baby Food Powders

Abstract: The aim of this study was to investigate the influence of the wet agglomeration in a fluidized bed on flowability of agglomerated products, such as baby food powders. The agglomeration process was performed in the fluidized bed. The wetting liquid used to the process was: water, 2% lecithin solution, and 50% sugar solution. Food powders flowability was expressed as: Hausner Ratio, pouring time, angles of sliding and of repose and flow function. The composition of materials, used to prepare mixtures, has a significant influence on tested properties. The higher milk powder of the mixtures caused decreasing of their flowability. Wet agglomeration of baby food powders caused an increase in the mean diameter of particles, which made it possible to receive agglomerates with good flowability and decreased bulk density. The increase of milk powder content from 0 to 73% in the mixture before the agglomeration contributed to improve its flowability. Wet agglomeration with 2% lecithin solution and 50% sugar solution reduced particle size and bulk density, improved flowability of received agglomerates in relation to agglomerates received with water as a wetting liquid. Practical Application: Agglomeration of baby food powders increases particle size of received agglomerates with a tendency to reduce their bulk density. Agglomerates flowability determined by using practical tests (Hausner ratio, pouring time, angles of sliding and of repose) is not sufficient for a comprehensive assessment of powdered deposit. For complex flow behavior, like that of agglomerated baby food powders, the Jenike shear test only remains as an acceptable test of flowability.     

COMPACTION CHARACTERISTICS OF AGGLOMERATED COFFEE DURING TAPPING

Three brands of instant coffee were used as model agglomerated powders. They were exposed to compaction in a tap density tester. Experiments were done confining samples of instant coffee in graduated cylinders with several diameters, i.e., 1.6, 2.0 and 2.4 cm; and different product heights, i.e., 3.2, 6.3, and 12.5 cm. Increased attrition was noticed with the number of tappings, which ranged from 0 to 10,000 taps. Changes in bulk density were fitted to two-parameter models used for compaction of food powders, using nonlinear regression. New three and four-parameter models were proposed, and their fit to experimental data was also examined. The fit of these new models was better than that of previous ones, indicating that the combined effect of attrition and compaction cannot be properly described by models containing less than three parameters. The container diameter, product height, and particle size were found to affect the parameters' estimates for the models examined.     

Water vapour adsorption properties of agglomerated baby food powders

This paper presents an analysis of the physical properties of materials in powder and agglomerate form and their sorption characteristics on the basis of the shape of the water vapour adsorption isotherms and kinetics. The observed changes that led to a decrease in the vapour adsorption ability of the investigated powdered baby foods depended mainly on their milk powder content and to a lesser extent on the structure of the powders. This was related to the process of agglomeration and the type of wetting liquid used in that process. Wet agglomeration of the baby food powders investigated in this study influenced growth of particle size and increased wettability regardless of the type of wetting liquid used and the components of the powders. The agglomerates obtained using 2% lecithin solution or 50% sugar solution as the wetting liquids presented a decrease in their rate of water adsorption compared to the agglomerates obtained using water.     

Changes in the physical properties of honey powder during storage

Honey powders produced by spray drying with the addition of Arabic gum and sodium caseinate were characterised in terms of the influence of storage time on the following physical properties: particle size, moisture content, water activity, bulk density, flowability and hygroscopicity. The storage affected those properties; after 12 weeks of storage, particle size decreased (except Arabic gum powder treated as a control sample), moisture content and water activity increased, hygroscopicity decreased. Changes in bulk density, particle size and moisture content caused the rise of Hausner ratio value; however, the powders were still characterised by a very good flow properties and low cohesiveness. The colour of reconstituted powders was also affected by storage; in most of samples, the darkening, reduction in redness and yellowness were observed. Colour parameters were the most stable in powders obtained with the addition of 2% w/w of sodium caseinate.     

Investigation of breakage behavior and its effects on spray-dried agglomerated whey protein-lactose powders: Effect of protein and lactose contents

Particle breakage of dairy powders occurs easily during many processes, reducing the powder functionality. The characteristics of particles and the applied stress from processing conditions on the particles are 2 main factors that can be manipulated to reduce breakage. In this study, we explored the effect of whey protein and lactose contents on dynamic breakage in agglomerated whey protein-lactose powders to provide useful information, in terms of particle characteristics, for controlling unwanted dairy powder breakage. A series of model agglomerates with different whey protein:lactose ratios were produced under the same spray-drying conditions, through a pilot plant trial. We evaluated physical characteristics, composition, and structure of samples; analyzed dynamic breakage under different mechanical stresses; and investigated the rehydration and water adsorption properties of model powders before and after breakage. The particle size and irregularity of agglomerates with more lactose was significantly higher than of samples that contained more protein. This resulted in higher particle breakage during dynamic breakage for samples with more lactose. The breakage of agglomerates was affected by the moisture content of powders and fatigue, where particle breakage happens when mechanical loads, lower than the strength of particles, occur multiple times. Breakage changed the morphology and surface composition of particles and decreased particle size. It also decreased the dispersibility of powders and increased the wetting time of wettable samples but decreased the wetting time of powders with poor wettability. Breakage accelerated time-dependent crystallization and decreased the crystallization temperature but did not affect the glass transition temperature of samples. Thus, under the same drying conditions, composition of powders significantly affected breakage, mainly by altering the physical properties of their particles, which resulted in deteriorated functionality.     

Comparison of the Compaction Characterisitics of Selected Food Powders by Vibration, Tapping and Mechanical Compression

The compaction characteristics of selected powders in tapping could be described by either Sone's model or by a single term exponential equation. The Hausner ratio, i.e., the ratio between tapped and loose density, calculated by using these models was found to be a sensitive and useful indictor of the compaction mechanism in different types of tapping tests. The latter, especially where particle attrition was evident, could produce distinctly different compaction patterns. No correlation was found between these powders, Hausner's ratio, and their compressibility in mechanical compaction.     

Water droplet spreading and recoiling upon contact with thick-compact maltodextrin agglomerates

BACKGROUND: The food and pharmaceutical industries handle a number of compounds in the form of agglomerates which must be put into contact with water for rehydration purposes. In this work, liquid‐solid interaction between water and maltodextrin thick–compact agglomerates was studied at different constituent particle sizes for two compression forces (75 and 225 MPa). RESULTS: Rapid droplet spreading was observed which was similar in radius to the expected one for ideal, flat surfaces. Contact angle determinations reported oscillations of this parameter throughout the experiments, being indicative of droplet recoiling on top of the agglomerate. Recoiling was more frequent in samples obtained at 225 MPa for agglomerate formation. Agglomerates obtained at 75 MPa exhibited more penetration of the water. Competition between dissolution of maltodextrin and penetration of the water was, probably, the main mechanism involved in droplet recoiling. Micrographs of the wetting marks were characterized by means of image analysis and the measurements suggested more symmetry of the wetting mark at higher compression force. CONCLUSION: Differences found in the evaluated parameters for agglomerates were mainly due to compaction force used. No significant effect of particle size in recoiling, penetration of water into the agglomerate, surface texture and symmetry was observed. Copyright © 2011 Society of Chemical Industry     

Mechanical Attrition Rate Measurements in Agglomerated Instant Coffee

Various size fractions of commercial agglomerated instant coffee were subjected to vertical and horizontal vibration at various frequencies. The resulting size reduction and its rate are described mathematically by a three parameter, two term, exponential decay model and a two parameter, nonexponential, model. The constants of these models were used to quantify the effects of particle size, vibration frequency and filling ratio on the agglomerates' attrition rate. The two models, despite their different mathematical structure, yielded a consistent account of the attrition kinetics.     

两种酪蛋白磷酸肽混合物的钙结合能力及物化性质比较

本研究探讨了两款市售酪蛋白磷酸肽产品在物化性质、钙离子结合能力的差异。钙乙醇法结果显示两款CPP产品的纯度具有较大差异（p<0.05）,CPP2的纯度是CPP1的1.36倍。体外钙离子螯合方法结果显示CPP1、CPP2的钙离子结合量分别是107.15 mg/g和142.56 mg/g,CPP2显著高于CPP1（p<0.05）。CPP1和CPP2的轻敲密度、Hausner比值和Carr''s指数指标结果存在显著差异（p<0.05）,CPP1的Hausner比值（1.52）显著高于CPP2（1.36）（p<0.05）,CPP1的Carr''s指数（34.40）显著高于CPP2（26.51）（p<0.05）。Hausner比值和Carr''s指数可以用来表示粉体的可压缩性和流动性,两种指标结果分析表明CPP2的流动性优于CPP1。CPP1、CPP2的休止角均高于40°,说明CPP1、CPP2都存在一定黏聚性,CPP2的休止角数值低于CPP1,结果表明CPP2的流动性略好于CPP1,与Hausner比值和Carr''s指数结果一致。30%乙醇溶解性结果表明CPP1（93.49%）和CPP2（7.46%）在30%乙醇溶解性存在极显著差异,两款CPP产品两款CPP在物质组成上有一定差异。两种CPP产品的纯度和钙结合能力成正比。两者粉末都存在一定黏聚性,流动性一般,CPP2强于CPP1。30%乙醇溶解性存在极显著差异,可能是影响钙片质量的主要因素。本研究为CPP作为食品添加剂的应用情况提供科学依据。     

Effect of composition on the mechanical response of agglomerates of infant formulae

The objective of this paper is to investigate the relationship between the compositions of four typical infant formulae, the evolution of key quality characteristics during pneumatic conveying and the mechanical properties of individual agglomerates. Conveying experiments were conducted using a lab-scale rig. Four quality characteristics were measured before and after conveying: bulk density, volume mean diameter, wettability and percentage free fat. Relative breakages were calculated from particle size distributions. Uniaxial compression experiments were performed on individual agglomerates, giving forces and strains at failure and agglomerate stiffnesses. Coefficients of restitution of the agglomerates were obtained by video analyses of drop tests. The data indicate that bulk densities before conveying and the force and the strain of individual agglomerates at failure were related to the protein content. The force at failure and agglomerate stiffness were strongly correlated, and generally increased with increasing protein to fat ratio while the strain at failure decreased.     

Effects of hot air and freeze drying methods on physicochemical properties of citrus ‘hallabong’ powders

Citrus ‘Hallabong’ powders were prepared using hot air and freeze drying methods, and their physicochemical and flow properties were measured. The yields of the powders from whole fruit and pressed cake by hot air drying method were 17.5 and 22.0%, while those by freeze drying method were 20.0 and 22.5%, respectively. Vitamin C was high in freeze-dried whole fruit powders (220.8–364.7 mg/100 g) compared with those in hot air-dried ones (80.1–114.6 mg/100 g). Browning index of freeze-dried powders was significantly lower than those of hot air-dried ones. Bulk densities, compaction densities, and Hausner ratios of the powders were significantly higher in freeze drying method compared with hot air drying method. Water solubilities and hygroscopicities of freeze-dried powders were higher than those of hot air-dried ones. In conclusion, ‘Hallabong’ powders can be made using freeze drying method with high quality in terms of vitamin C content, color, and water solubility.     

Nanostructured sorbents for capture of cadmium species in combustion environments

The pathways of cadmium species to form a submicrometer-sized aerosol in a combustion system exhaust were established. Cadmium oxide was the predominant species formed in the experiments and resulted in particles of a mean size of 26-63 nm with number concentrations in the range of 2-8 x 10(6) cm(-3). Two different nanostructured sorbents, a solid montmorillonite (MMT) and an in situ generated agglomerated silica, were used for capture of the cadmium species. The MMT sorbent was not stable at 1000 degrees C, and structural changes resulted. MMT did not suppress nucleation of cadmium species and partially captured it by weak physisorption as established by the leachability tests. In contrast, the in situ generated silica nanostructured agglomerates had a high surface area, suppressed nucleation of cadmium species vapors, and chemisorbed them effectively resulting in a firm binding, as compared to the MMT sorbent. There is an optimal temperature-time relationship at which the capture process is expected to be most effective. The leaching efficiency under these conditions was less than 3.2%. The nanostructured silica agglomerate size can be tuned for effective capture in existing particle control devices.     

Fractal Analysis to Characterize Ruggedness Changes in Tapped Agglomerated Food Powders

Samples of commercial instant coffee and instant skim milk were exposed to attrition in a tap density tester. Digital images of the projected outlines of individual particles were obtained and the Fractal dimension of their profiles was computed with three different algorithms. Results show that the mean apparent Fractal value of the agglomerates varied with the number of tappings.     

Effect of inlet temperature on the physicochemical properties of spray-dried seed-watermelon seed protein powder

Here, we studied the effects of inlet temperature on the physicochemical properties of the hydrolyzed protein (seed-watermelon seed hydrolyzed protein [SWSP]) powder in seed-watermelon seeds. The inlet temperature of the study was in the range of 150 to 180 °C, and the remaining experimental parameters remained constant, that is, the feed flow rate was 0.2 L/hr, the concentration of maltodextrin was 30%, and the outlet temperature was 80 °C. We studied the water activity and moisture content, bulk density, flowability (Carr index and Hausner ratio), angle of repose, solubility, color, hygroscopicity, powder morphology, particle size, crystallinity, and odor of the sample. Inlet temperature of 170 to 180 °C reduced the moisture content and increased the particle size. It was found that the value of measured water activity was less than 0.5, which helped in maintaining stability of the sample. Powders produced at the temperatures showed smoother particle surfaces, whereas higher inlet temperature showed spherical particles with some shrinkage as analyzed by scanning electron microscope. The inlet temperature affected the color of the sample, thus at high temperature, the sample had a brighter color. The sample was approximately 18% crystalline. At a preparation temperature of 160 °C, the sample showed significant antioxidant activity (P < 0.05).     

Total phenolic content,antioxidant activity,shelf-life and reconstitutability of okra seeds powder: influence of milling and sieving processes

This study aimed at relating phytochemical properties (total phenolic content and antioxidant activity), reconstitutability (water absorption capacity and water solubility index) and preservation ability (water activity) of okra seed powders to physicochemical properties (particle size distribution and moisture content). Okra seed powders were produced at three different milling frequencies, and then, each obtained sample was sieved with 180, 315 and 500 μm sieves. An increased milling frequency resulted in lower median particle size, water activity and moisture content. The maximal water activity and moisture content were 0.583 ± 0.010 and 12.07 ± 0.05% (w/w), respectively, showing the good preservation ability of okra seed powders. Total phenolic content and antioxidant activity were raised at higher milling frequency. Reconstitutability was significantly enhanced at higher milling frequency and/or for smaller median particle size. Thus, the successive milling and sieving process was successful in improving physicochemical and functional properties of okra seed powders, especially for smaller particles.     

The influence of the carrier addition and spray drying temperatures on physicochemical properties of microencapsulated carrot juice powder

The objective of this study was to determinate the influence of carrier addition and spray drying temperatures (160 or 200°C) on physicochemical properties of spray-dried carrot juice powder. As carriers, maltodextrin and gum Arabic in different proportions were used. In powders were determined the following: moisture content, water activity, apparent density, size of particles, colour and carotenoids content. The content of carotenoids in powders prepared from solutions with juice to carrier ratio 2:3 was 324.3–406.6 mg/kg d.m., while in powders with a J:C = 3:2 values ranged from 576.7 to 637.7 mg/kg d.m. The highest content of carotenoids and the most yellow colour were observed in powders with 1:3 gum Arabic to maltodextrin ratio. Powders with the highest amount of gum Arabic have the highest diameter and the lowest water activity. High inlet temperature caused brighter colour of powders, higher dry matter content, lower water activity and apparent density of powders.     

In-line monitoring of durum wheat semolina wet agglomeration by near infrared spectroscopy for different water supply conditions and water addition levels

The aim of this work is (i) to study the ability of near infrared (NIR) spectroscopy to follow in-line the agglomeration process of durum wheat semolina using mechanical mixer according to two different water supply conditions (i.e. high versus low water flow rates) and to four different water addition levels, and (ii) to describe the associated structural changes of agglomerates. The results showed that analyses of spectral variations can be useful to discriminate different agglomeration processes, which are associated to different kinetic changes in terms of agglomerate size distribution and water content per size fraction. Principal component analysis (PCA) has been used to qualitatively describe physical and chemical variations occurring during the wet agglomeration mechanisms and to identify specific kinetics and characteristic times. Whatever the water supply condition, kinetic variations of principal components (PCs) on raw and second derivative NIR spectra are observed. Characteristic times have been identified on PC scores and an attempt to link these times to changes of agglomerates physical and chemical properties have been carried out, mainly based on the analysis of associated loading spectra.     

Characterization of stipe and cap powders of mushroom (Lentinus edodes) prepared by different grinding methods

The effects of micronization methods, mechanical and jet millings, on the physico-chemical properties of mushroom (Lentinus edodes) powder were investigated in contrast to shear pulverization. The powders of dried mushroom cap and stipe were prepared to obtain six powders. Compared to shear pulverization, mechanical and jet millings effectively reduced particle size and brought about a narrow and uniform particle size distribution. With the same material, powders from mechanical and jet millings had higher values in soluble dietary fiber content, surface area, bulk density, water soluble index and nutrient substance solubility, but lower values in the angles of repose and slide, water holding and swelling capacities than shear pulverized powder. These indexes were tightly dependent on particle size with absolute coefficients beyond 0.8330. With the same grinding method, cap powders possessed higher values in water soluble index, swelling capacity, bulk density, protein and soluble dietary fiber than stipe powders.     

Microencapsulation of flax oil with zein using spray and freeze drying

Microencapsulation of flax oil was investigated using zein as the coating material. Central Composite Design - Face Centered was used to optimize the microencapsulation with respect to zein concentration (x₁) and flax oil concentration (x₂) using spray drying. Also, freeze drying was carried out at two zein:oil ratios. The quality of microcapsules was evaluated by determining encapsulation efficiency, flowing properties (Hausner ratio), and evaluating the morphology with scanning electron microscopy. The response surface model for microencapsulation efficiency showed a high coefficient of determination (R² = 0.992) and a non-significant lack of fit (p = 0.256). The maximum microencapsulation efficiencies were 93.26 ± 0.95 and 59.63 ± 0.36% for spray drying and freeze drying, respectively. However, microcapsules prepared by spray and freeze drying had very poor handling properties based on the Hausner ratio. The bulk density decreased with an increase in zein concentration at the same flax oil concentration. The morphology of the flax oil microcapsules depended on the zein:flax oil ratio and the process used for microencapsulation. Flax oil microcapsules prepared by spray drying appeared to be composed of heterogeneous spheres of various sizes at high zein:flax oil ratios. Microcapsules prepared by freeze drying resulted in agglomerated small spheres. These microcapsules might find a niche as functional food ingredients.     

Wetting behaviour of instantized cocoa beverage powders

Summary The aim of this work was the characterization of various instantized cocoa beverage powders with regard to their wetting behaviour in a standardized test. Brand name powders from local superstores were compared to each other and to model powders instantized in the laboratory by steam jet agglomeration. Basic powder properties such as agglomerate size or fines content in a mixture were varied to study possible effects on the wettability of this product group.