Influence of processing conditions on attrition of NaCl crystals

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.

Breakage Characteristics of Granulated Food Products for Prediction of Attrition during Lean-Phase Pneumatic Conveying

Pneumatic conveying is utilised in a variety of industries to convey food products exhibiting diverse handling characteristics. Attrition of particles caused by this conveying process can result in a number of undesirable outcomes such as loss in product quality or issues in subsequent handling processes. The ability to predict the breakage behaviour of particulate materials is desirable in both new system design and resolving issues in existing plants. This work considers two different particulate materials (Salt and Golden Breadcrumbs) across a range of particle sizes, and quantifies their breakage behaviour under varying impact conditions. Narrow size fractions of each material were degraded; material retained on 250 µm and 355 µm sieves for Salt, and 500 µm, 710 µm and 1,000 µm sieves for Golden Breadcrumbs. Velocity was found to be the most influential factor with respect to particle attrition. The results from the narrow size fraction tests were superimposed to form a simulated full size distribution breakage behaviour, which was then compared to the experimentally determined behaviour. A good agreement was found, however the proportion of material predicted for size fractions smaller than 355 µm for Golden Breadcrumbs and 180 µm for Salt was under-predicted. Recommendations for increasing accuracy of the prediction method are given.

Compression characteristics of agglomerated food powders: Effect of agglomerate size and water activity Características de la compresión de alimentos en polvo: Efecto del tamaño del aglomerado y del contenido de humedad

The stability of food agglomerates is very important for keeping optimal instant properties as well as flow characteristics. Compression tests have been proven not only to be useful tools in char acterizing attrition, but also excellent descriptors for powder flowability. The purpose of this work was to study the effects of particle size and water activity ( a w) on the compression characteristics of selected agglomerated food powders, and then to identify suitable mathematical models by using a non-linear regression program for predicting the compression characteristics of food agglomerates when partial attrition takes place. Three agglomerated food powders - non-fat milk, low fat milk and instant coffee - were classified by size into five or six fractions with a set of RX-29 sieve screens. Each fraction was conditioned at three aw levels, placed in a cylindrical compression cell, and compressed with a piston attached to the crosshead of a TA-XT2 texture analyser. The crosshead speed was 1 mm/s in all tests and the maximum force applied was 245 N. Particle size was found to play a significant role in compression tests in that the greater the particle size, the greater the volume reduction. It was easier to compress the low aw samples, but in all tests changing aw did not significantly affect compression characteristics. Sone's two- parameter model accurately described the combination of compaction and attrition when compres sion pressure did not exceed a certain level, while Peleg's double-exponential model with four parameters best fitted the compression data.