The segregation of binary mixtures of non-food wheat bran and vegetables at different levels of dryness was studied by simulating different stages of the atmospheric freeze drying by immersion in an adsorbent material (AFD IAM) process. It was characterized using a new set of four indices, which allows to evaluate not only the segregation level, but also the segregation pattern. The mixing performance was evaluated in a fluidized bed (considering also the effect of air superficial velocity) as well as in a spout-fluid bed, and peas, carrot discs, and potato slabs were used as food products. In general, it was found that food material segregates towards the bed bottom during the firsts stages of the drying process in fluidized beds, which translates in a poor contact product-adsorbent. On the contrary, uniform mixing patterns were observed in the spout-fluid bed, for the beginning and final stages of the process. On the other hand, despite the very low cost of non-food wheat bran and its compatibility with food materials, it presents a channeling fluidization as a consequence of the cohesive properties of its particles. This behavior was also characterized by means of video analysis in two different fluidized beds. A channel generation and collapse general cycle was highlighted, whose frequency and channel characteristics depend on the air superficial velocity. In addition, three main types of food particle transport were identified: passive (downward), active (upward), and particle blocking effects. These findings allowed to explain segregation phenomena in these kinds of binary mixtures.
|Titolo:||Mixing and segregation of wheat bran and vegetables pieces binary mixtures in fluidized and fluid-spout beds for atomospheric freeze-drying|
|Data di pubblicazione:||2017|
|Digital Object Identifier (DOI):||10.1080/07373937.2016.1230741|
|Appare nelle tipologie:||1.1 Articolo in rivista|
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