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.     

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.     

ATTRITION EVALUATION FOR SELECTED AGGLOMERATED FOOD POWDERS: THE EFFECT OF AGGLOMERATE SIZE AND WATER ACTIVITY

Investigation of the attrition of agglomerates is very important for assessing the agglomerate strength, compaction characteristics, and quality control. A one‐term exponential attrition index model and the Hausner ratio were used to study the effects of agglomerate size and water activity on the attrition kinetics of some selected agglomerated food powders. It was found that the agglomerate size and water activity played significant roles in affecting the attrition: the larger the agglomerate size and the higher the water activity, the higher the attrition index under the same tap number. The Hausner ratio was well correlated with the attrition index at high tap numbers and might be used as a simple index to evaluate attrition severity for agglomerates. Knowing the effects of agglomerate size and water activity is very useful to minimize the attrition phenomenon during the handling and processing of agglomerated powders.     

Effect of particle size on droplet infiltration into hydrophobic porous media as a model of water repellent soil

The wettability of soil is of great importance for plants and soil biota, and in determining the risk for preferential flow, surface runoff, flooding,and soil erosion. The molarity of ethanol droplet (MED) test is widely used for quantifying the severity of water repellency in soils that show reduced wettability and is assumed to be independent of soil particle size. The minimum ethanol concentration at which droplet penetration occurs within a short time (≤ 10 s) provides an estimate of the initial advancing contact angle at which spontaneous wetting is expected. In this study, we test the assumption of particle size independence using a simple model of soil, represented by layers of small (~0.2-2 mm) diameter beads that predict the effect of changing bead radius in the top layer on capillary driven imbibition. Experimental results using a three-layer bead system show broad agreement with the model and demonstrate a dependence of the MED test on particle size. The results show that the critical initial advancing contact angle for penetration can be considerably less than 90° and varies with particle size, demonstrating that a key assumption currently used in the MED testing of soil is not necessarily valid.     

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.     

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.     

Measurement of diffusion coefficient of water and ethanol in aqueous maltodextrin solution

Capillary cell and absorption-desorption methods were used to measure the diffusion coefficients of water and ethanol in aqueous maltodextrin solution over a wide range of water content. The diffusion coefficients showed a surprisingly large dependence on water content, particularly at low water content, as reported by other workers. Free volume theory was applied to correlate the diffusion coefficients. It was found that this theory was adequate to explain their large dependence on water content. Furthermore, experimental results on ethanol retention in drying an aqueous maltodextrin droplet could be predicted well, using the present experimental results for the diffusion coefficients of water and ethanol.     

Glass Transition Behavior of Spray Dried Orange Juice Powder Measured by Differential Scanning Calorimetry (DSC) and Thermal Mechanical Compression Test (TMCT)

Spray drying behavior of orange juice concentrate with various levels of maltodextrin (DE 6) was studied. Five combinations of orange juice concentrate and maltodextrin (25:75, 30:70, 35:65, 40:60, and 50:50) were spray dried at 160 and 65°C inlet and outlet temperatures, respectively. The product recovered with 50% maltodextrin concentration was sticky and only 20% powder was recovered. The recovery of orange juice powder increased as the amount of maltodextrin in powders increased. The particle size and bulk density remained almost the same in all except in 50% maltodextrin powder which was slightly larger and more dense. The moisture content of spray dried powders was high and desiccated before measuring glass transition temperature. The anhydrous spray dried powders showed increased T_g values with increasing maltodextrin concentration, from 66°C in 50% maltodextrin to 97°C in 75% maltodextrin containing powders. The glass rubber transition (T_g-r) values of all the products measured using novel Thermal Mechanical Compression Test (TMCT) were higher than T_g values measured by DSC; the difference in values increased with increase in maltodextrin concentration.     

ANALYSIS OF SURIMI GEL PROPERTIES BY COMPRESSION AND PENETRATION TESTS

Gel properties of surimi of different quality were analyzed using compression and penetration tests. Parameters used to vary the surimi quality were species, freshness, freeze-abuse and added ingredients. Compressive force at failure was more discriminative than penetration force. The result of a failure response analysis suggests that the compression test is useful in assessing the cohesive property, while the penetration test is better for assessing density and compactness. Good correlations between compression and penetration force values were seen in surimi gels prepared from the same species with and without ingredients, while poor correlations were observed in the surimi which either underwent freeze-abuse or was prepared from different species.     

超声与高压微射流处理对大豆分离蛋白微细化的影响

研究超声功率与时间和高压微射流操作压力与次数件对乳液温升、加权平均粒径和粒度分布等的影响,以寻找适合不同工艺需求的大豆分离蛋白物理改性方法。结果表明,经超声处理SPI乳液粒径呈现双峰分布,经高压微射流处理SPI乳液粒径呈单峰分布,说明高压微射流比超声处理的乳化均匀一致性好。超声(1200 W)能够提高SPI乳液的均匀一致性和乳化稳定性,但SPI微团尺寸缩减能力有限,处理时间过长则乳液发生再凝聚,出现SPI微团尺寸增大的现象。当乳液粒径较大(10~(-4) m级)时,瞬时(10~(-6) s级)高压微射流(35 MPa以上)处理形成高能量密度能够达到较好的微细化结果,加权平均粒径D_([3,2])和D_([4,3])显著减小。     

Encapsulation efficiency and oxidative stability of flaxseed oil microencapsulated by spray drying using different combinations of wall materials

This study aimed at evaluating the potential of maltodextrin combination with different wall materials in the microencapsulation of flaxseed oil by spray drying, in order to maximize encapsulation efficiency and minimize lipid oxidation. Maltodextrin (MD) was mixed with gum Arabic (GA), whey protein concentrate (WPC) or two types of modified starch (Hi-Cap 100^TM and Capsul TA®) at a 25:75 ratio. The feed emulsions used for particle production were characterized for stability, viscosity and droplet size. The best encapsulation efficiency was obtained for MD:Hi-Cap followed by the MD:Capsul combination, while the lowest encapsulation efficiency was obtained for MD:WPC, which also showed poorer emulsion stability. Particles were hollow, with the active material embedded in the wall material matrix, and had no apparent cracks or fissures. During the oxidative stability study, MD:WPC combination was the wall material that best protected the active material against lipid oxidation.     

A MICRO-SCALE METHOD FOR MEASURING THE HARDNESS OF HEAT-INDUCED PROTEIN GELS

A micro-scale penetrometry method for testing the hardness of heat-induced whey protein gels was developed. The hardness of gels could be determined quantitatively on sample volumes as small as 20 μl. A needle with an outside diameter of 1.06 mm (18 gauge) weighted with a water reservoir was used to measure the force which was necessary to penetrate a gel contained within a capillary tube. In parallel, the Instron was used for compression testing of protein gels. There was a high correlation between the values obtained using an Instron (70% compression) and those obtained using a micro-penetrometer for bovine β -lactoglobulin gels prepared at concentrations over a range of 10-13%. Similarly, there was a high degree of correlation for hardness measurements between both methods for gels made from either whey protein isolate or bovine serum albumin. Based upon standard curves of Instron force versus penetration force, the penetration force of whey protein gels as measured by micro-scale penetrometry could be converted into relative Instron force units.     

小桐子油及其生物柴油在旋流喷嘴中雾化特性数值模拟

为了掌握入射压力对生物质燃油在旋流喷嘴中雾化特性的影响规律,在不同入射压力条件下,采用Fluent数值模拟的方法对小桐子油和小桐子生物柴油进行雾化过程模拟仿真研究。结果表明:使用的旋流雾化喷嘴比普通喷嘴对索特平均直径(D32)有更好的优化效果,内螺旋结构增强了雾化的湍流强度,使得气液两相混合及对雾化液滴的破碎效果更好;在等温条件下,不同入射压力对D32、雾化总表面积、雾化速度、雾化贯穿距影响较大。入射压力越大,D32越小;入射压力越大,雾化总表面积、雾化速度、雾化贯穿距越大。入射压力对D32的影响存在临界值,即小桐子油雾化入射压力达到0.8 MPa、小桐子生物柴油雾化入射压力达到0.7 MPa后,D32趋于稳定,不会随入射压力的增大继续减小;通过曲线拟合及雾滴粒径数量密度分析,得到了不同入射压力距离喷嘴不同位置处轴向D32变化的拟合方程及雾化液滴不同粒径数量密度分布情况。     

Influence of homogenisation conditions and drying method on physicochemical properties of dehydrated emulsions containing different solid components

Dehydrated o/w emulsions containing sodium caseinate and lactose (sample 1), and gelatine, sucrose and maltodextrin (DE 10) (sample 2) were used to study the influence of homogenisation conditions – homogenisation pressure (15 and 70 MPa) and number of passes (1 and 2) – and the drying method – spray‐drying vs. freeze‐drying – on physicochemical parameters, including oil microencapsulation efficiency (ME), oil droplet size in reconstituted emulsions, water activity, glass transition temperature, powder bulk density and time for emulsion reconstitution in water. Results showed that small and uniform oil droplets attained with increased homogenisation pressure were not sufficient for high oil encapsulation. The permeability of the solid wall to the extraction solvent appeared to be the dominant factor, and this may increase with homogenisation pressure. With the exception of oil droplet size in sample 1 and ME in sample 2, the drying method exerted larger changes in the physicochemical parameters studied than the homogenisation pressure. For sample 2, significant changes in the ME were not observed between the freeze‐dried and spray‐dried samples, even though a great emulsion destabilisation was observed in the reconstituted emulsion of the latter.     

Adiabatic compression heating coefficients for high-pressure processing of water,propylene-glycol and mixtures – A combined experimental and numerical approach

The compression heating of water and water/propylene-glycol mixtures during high-pressure processing was studied using a purpose-designed experimental setup allowing for near-adiabatic conditions. The fluids were pressurised in a Stansted ISO-LAB FPG11501 HPP 3 L unit up to 750 MPa. Pressure/temperature profiles at varying initial temperatures (5–90 °C) were recorded and numerically evaluated to obtain pressure and temperature dependent compression heating properties of water/glycol mixtures at 0%, 25%, 50%, 75% and 100% glycol concentration. A further step was implemented in the numerical routine to derive the compression heating properties as function of pressure, temperature and glycol concentration.     

Storage of spinach juice agglomerates: Physical,flow, structural,and thermal properties

The objective of this study was to investigate how the various storage temperatures affected the physical properties, flow characteristics, microstructure, and glass transition temperature of spinach juice agglomerates. For this purpose, spray-dried spinach juice powders were processed to agglomerates by using a modified fluidized bed dryer (1.6 m/s airflow rate, 60°C drying air temperature, 20 min processing time, and with different binder solutions containing agents as maltodextrin, gum Arabic, and whey powder isolate). The analyses were carried out every month throughout 6 months while the spinach juice agglomerates were stored at temperatures of 4, 20, and 35°C. The results revealed that over the storage time, the moisture content and water activity values of the agglomerates were generally under 11% and 0.6, respectively. The color values generally showed a decreasing trend depending on the storage time. The solubility times of the samples stored at 4°C were longer than those of stored at other storage temperatures. The SJA-GA had the lowest HR and CI values and thus the best flowability properties during all storage times. There was no detectable change in the structures of SJA stored at 20°C according to the storage time. Throughout the storage time, it was discovered that the glass transition temperature of all spinach juice agglomerates was remarkably similar. Overall, the investigation revealed that storage at 35°C for 6 months might be suitable because it delivered the intended outcomes such as greater flowability and cohesiveness, and shorter wettability and solubility times.     

交联酯化麦芽糊精制备乳状液的稳定性能研究

研究了木薯酯化麦芽糊精(COMD)和木薯交联酯化麦芽糊精(CCOMD)制备的乳状液的稳定特性。随着麦芽糊精用量的增加、取代度的升高,乳状液的稳定性增加。中性或偏碱性条件有助于提高乳状液的稳定性。采用COMD和CCOMD制备的乳状液平均粒径分别为1.46μm和1.13μm,液滴表面带有较强的负电荷。空间位阻和静电排斥是其乳状液稳定的主要机理。     

Characteristics of submicron emulsions prepared by ultra-high pressure homogenisation: Effect of chilled or frozen storage

Model O/W pre-emulsions at an initial temperature of 24 °C and pH 6.3, and containing (w/w) 4.3% whey proteins plus 15, 30 or 45% peanut oil were processed using a ∼15 L/h homogeniser with a high pressure (HP) valve immediately followed by cooling heat exchangers. The effect of ultra-high pressure homogenisation (UHPH) between 100 and 300 MPa (P₁) or of recycling (1–3 homogenisation passes) at 200 MPa was investigated on the droplet size distribution, size indices and viscosity. Fluid temperatures were measured at the inlet (T₁) and outlet (T₂) of the HP-valve, and after immediate cooling downstream of the HP-valve (T₃) as they varied throughout UHPH. Short-life heating phenomena and mechanical energy involved in droplet processing were clearly influenced by emulsion composition. Oil droplet diameters decreased when (P₁) increased from 100 to 300 MPa leading to submicron droplets at ≥200 MPa. Monomodal distributions with droplets well below 0.3 μm were obtained after recycling at 200 MPa for the three oil contents, with a peak at 138 nm (distribution in volume) or 60–70 nm (in number frequency). The emulsion behaviour varied from fluid (and quite Newtonian) to thick (and shear thinning) depending on the droplet size reduction and the oil volume fraction. Emulsions displayed an excellent stability vs. creaming and coalescence after 9 d storage at 5 °C. Freezing followed by 13 d storage at −24 °C then thawing, induced an increase in particle sizes depending both on the oil volume fraction and (P₁). After UHPH at 200–225 MPa (±recycling), the freezing/thawing process maintained most of oil droplet size below 1 μm at 15% (w/w) oil, and induced mainly oil droplet aggregation through SDS-labile interactions at higher oil contents.     

高压均质对天然和热变性大豆蛋白-磷脂水包油型乳状液功能性质的影响

为揭示大豆蛋白和大豆卵磷脂在油-水界面层的交互作用及复合微乳体系的稳定机制,探究了温度(20、60℃)和均质压力(0~80 MPa)的协同作用对蛋白质-磷脂复合乳化体系功能性质的影响。结果显示:相比于天然大豆蛋白与磷脂(native soybean isolate-lecithin,NSI-Lec)形成的乳状液,热变性大豆蛋白与磷脂(denatured soybean isolate-lecithin,DSI-Lec)的乳状液功能性质随均质压力的变化更明显。NSI-Lec乳液在均质压力达到80 MPa时乳化性、乳化稳定性及电位变化不再显著,但DSI-Lec乳液在该条件下功能性质继续提高。当均质压力高于40 MPa时,DSI-Lec乳液的乳层析指数明显下降,说明乳液更加稳定。粒径分布结果表明:NSI-Lec乳液呈双峰粒径分布,DSI-Lec乳液在均质压力高于20 MPa后粒度分布曲线向小粒径方向移动,且当均质压力达到80 MPa时粒径分布呈现单峰。激光共聚焦显微镜结果显示,DSI-Lec乳液随均质压力的提升分布更均匀,乳液连续性较好。