Physicochemical characterisation of the lactoperoxidase system powders: comparison of two drying techniques (original) (raw)
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Dairy Science & Technology, 2010
Our previous work demonstrated that the powder flowability of a cohesive lactose sample can be improved substantially using a dry coating technique. Our study reported here aims to investigate the influence of host particle size on the modification of powder flowability following dry coating process. Four commercial lactose monohydrate powders with different particle sizes were coated by an intensive mechanical process or mixed using a conventional tumbling process, both with magnesium stearate. All four untreated lactose samples showed a relatively poor powder flow. After dry coating, poured and tapped densities of all the lactose samples increased, while Carr indices and Hausner ratios decreased substantially. The angle of repose values were reduced to a notable extent only for particles with a median size larger than about 7 μm after dry coating. Both specific energy (SE) and cohesion values of lactose samples, measured by a powder rheometer system, decreased substantially after coating. In contrast, no apparent changes in powder flow were evident for conventionally mixed batches, except that in the dynamic powder rheometry measurement, a relatively small change in SE was observed. This study demonstrated that for the finer particles examined, cohesive forces were more influential in the powder bed after the surface treatment and resulted in a relatively poor flow. However, for the larger powders studied, the cohesive inter-particle forces could be overcome after this dry coating, whereby satisfactory flow could be obtained. This study indicated that the host particle size was a critical factor in influencing the modification of cohesive powder flowability.
Effect of surface composition on the flowability of industrial spray-dried dairy powders
Colloids and Surfaces B: Biointerfaces, 2005
The surface composition of four industrial spray-dried dairy powders (skim milk powder, whole milk powder, cream powder and whey protein concentrate) was estimated by electron spectroscopy for chemical analysis (ESCA), and its influence on powder flowability was studied. It was found that skim milk powder flows well compared to the other powders because the surface is made of lactose and protein with a small amount of fat, whereas the high surface fat composition inhibits the flow of whole milk, cream and whey protein powders. However, the poor flowability of the powders with high surface fat coverage was drastically improved by removal of fat present on the surface through a brief wash with petroleum ether. The results obtained indicate that, although there are several parameters including particle size, which influence the flowability of powders, the flowability of powders is strongly influenced by the surface composition of powders, particularly for fat-containing powders.
Exploring drying kinetics and morphology of commercial dairy powders
Journal of Food Engineering, 2015
Understanding the effect of the initial composition of a liquid feed on the spray drying process and morphology of powders is important in order to reduce the time and costs for process design, and ensure the desired properties of the final product. In this work, seven commercial dairy products with different fat content were selected. The effect of initial composition on drying time during single drop experiments was studied. The morphology of powder particles and the influence of morphology changes on the drying rate were investigated in order to assess the effect of fat content on the effective diffusivity of water in dairy products. Results show that fat content influences drying time and morphology of powder particles. The higher the fat content the longer the drying time and particles appear to be less shrivelled. Changes in morphology and the drying rate seem to be related. Two falling drying periods were observed for most of the products. During the first period the drops shrink spherically, while during the second period shrivelling occurs. The effective diffusivity of water shows that high fat contents lead to a lower diffusivity of water in the products.
Effect of composition and storage conditions on the flowability of dairy powders
International Dairy Journal, 2007
This work investigated the influence of composition (moisture, fat, lactose and protein content) and storage conditions (temperature, time and moisture sorption from air) on the flowability of dairy powders. This was undertaken by measuring the flow properties of eight different commercial dairy powders using shear testing techniques and by measuring how temperature and exposure to moisture in air affected their flowability. Differential scanning calorimetry was used to measure phase and state transitions. The dominant compositional factors affecting the cohesiveness of dairy powders were moisture, amorphous lactose and fat content. All powders had a tendency to absorb moisture from air when in intimate contact with air, however the powders with greater amounts of amorphous lactose were more sensitive to absorbing moisture, giving rise to lumping and caking problems. Fat content had a major influence on powder cohesiveness, with greater particle surface fat content resulting in greater cohesiveness. r
Impact of Spray Drying Parameters on Lactose-Free Milk Powder Properties and Composition
Journal of Agricultural Studies
Lactose-free milk powders are an interesting topic, as the industry still struggles with the enhanced stickiness of the material. To better understand this topic, an industrial scale spray-dryer was used to assess the influence of process parameters on the powder properties of lactose-free milk. A simple design of experiments was conducted varying the inlet temperature in combination with the atomization flow rate. The intention was to set different driving forces for drying in combination with the different surfaces are for mass transport. Yield is typically the process bottleneck, but from results, high inlet temperature combined with small droplet size resulted in a 50.73% yield. Powder's moisture contents were between 0.53% and 5%, and water activity between 0.21 and 0.43, being all values within a safety threshold for storage. From bulk and tap density results, all powders revealed to be cohesive with the Hausner ratio above 1.5. Color measurements revealed off white sample...
Study of physical and chemical properties of spray drying whey powder
Background Making powder from whey is one of the most challenging parts of whey processing. The present study investigates the performance of a spray dryer for the preparation of whey powder. Its main objective is to categorize unknown samples using analysis of discrimination function between the operating variables and powder properties in two or more naturally occurring groups. In this work, spray drying was performed in a pilot-scale co-current spray dryer. The amount of solid content, inlet, and outlet air temperature was chosen as independent variables. The titratable acidity, PH, EC, TDS, analytical elements, particle size diameter, ingredients, and morphology were the response variables that quantify the powder quality. Results The PH of whey powder with 15 % solid content was lower than the PH of whey powder with 30 % solid content. Furthermore, the PH of the whey dried at inlet (outlet) air temperature of 180 °C (106 °C) was lower than the whey dried at 145 °C (87 °C). Substances with higher acidity had higher electrical conductivity (EC) as well. The mean particle diameters of the powders produced by pilot-plant spray dryer were in the range of 11.26–18.23 lm. SEM picture showed that in pilot-plant spray dryer, there were a few shallow holes on the particle surfaces as well as a few wizened particles. Conclusions It was observed that in the materials with higher acidity, the EC was high and the PH was low. More solid content caused higher viscosities in the feed, which increased the droplet size and consequently, the particle size. By increasing the temperature and heating duration, the amount of PH reduced and the diameter of the particles increased. Moreover, by increasing the percentage of the solid content, the PH increased, while the solid mass carried away by the outlet air decreased. Small particles sprayed by the two-fluid nozzles, led to less amount of TDS. From the morphological point of view, as the industrial samples were exposed to heat longer as compared to pilot-plant samples, they produced spherical and smoother particles.
Powder Technology, 2011
The aim of this study was to evaluate the effect of an intensive dry coating process on the improvement in flow behaviours for fine cohesive lactose powders as a function of size distribution and coating process parameters. Various commercial fine lactose powders with particle size range from approximately 4 to 120 μm were dry coated with magnesium stearate using a recently optimised mechanofusion approach. The bulk densities for all cohesive powders increased and flow behaviours were improved substantially except for the already freeflowing powder of R010 (with VMD approximately 120 μm). Of particular note, the originally non-flowing cohesive powder P450 with VMD approximately 20 μm achieved free-flowing characteristics and was as flowable as R010 after mechanofusion. The improvement in powder flow behaviours was shown to be dependent on coating parameters such as coating speed and coating time duration. At an appropriate coating speed, optimal coating can be achieved after processing for 5 min for P450. This study demonstrated that an optimised mechanofusion process is an efficient and effective approach for substantially improving flow of fine cohesive powders to achieve equivalent flow behaviours of much larger sized powders.
Comparative Evaluation of Flow for Pharmaceutical Powders
2008
The objective of the present work was to carry out a systematic evaluation of flow of pharmaceutical powders and granules using compendial and non-compendial methods. Angle of repose, bulk density, tapped density, Carr’s compressibility index, and Hausner ratios were evaluated. Additionally, flow was characterized using a powder rheometer in which a sensitive force transducer monitors the forces generated as a result of the sample displacement. The critical attributes such as cohesivity index, caking strength, and flow stability were determined for samples. The samples consisted of different grades of magnesium stearate powder including bovine, vegetable, and food grade, physical mixture powder blend consisting of a model formulation, granules prepared by various methods including slugging, high shear granulator, and fluid bed dryer. Lubricant efficiency was also determined for granules lubricated with various concentrations of magnesium stearate. It was observed that the compendial methods were often non-discriminating for minor variations in powder flow. The additional characterization such as cohesivity, and caking strength were helpful in understanding the flow characteristics of pharmaceutical systems. The flow stability test determined that the powders were not affected by the test conditions on the rheometer. The non-compendial tests were discriminating to even minor variations in powder flow.
How surface composition of high milk proteins powders is influenced by spray-drying temperature
Colloids and Surfaces B: Biointerfaces, 2010
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.