Intensification of Starch Processing Using Apparatus with Couette–Taylor Flow

Abstract

Couette-Taylor flow (CTF), which is characterized by the presence of Taylor vortices, ensures effective mixing, fast heat transfer and improved rheological properties of starch slurry. Therefore, this type of flow can be expected to provide favorable conditions for starch processing. In order to check how to intensify the process, starch gelatinization has been studied experimentally and using computer simulation in two CTF apparatuses of different volumes. The results show that, when the volume of apparatus was small, high value of degree of starch gelatinization could be achieved at relatively low temperature or at relatively low rotor rotation frequency. The increase in the apparatus volume ensures higher rate of gelatinized starch production and the reduction in dissipation of mechanical energy connected with rotor rotation, however, it also amplifies the detrimental inlet and gravitation effects. To overcome both of these negative effects, the increase in the rotor frequency is required. PRACTICAL APPLICATIONStarch gelatinization is a process frequently encountered in food industry, e.g., food sterilization or starch hydrolysis. Therefore, a new way of starch processing could be interesting in the context of growing consumer interest in natural food. It is expected that CTF apparatus could enable to process much more concentrated starch slurry than a jet cooker or coil heater typically used in industrial setting. Starch granules should also be less damaged during treatment in CTF apparatus than in an extruder. The results presented in this paper are relevant for process intensification and scale-up of starch gelatinization in CTF apparatus and will be extended to simultaneous starch gelatinization with enzymatic hydrolysis in the future work. bs_bs_banner Journal of Food Process Engineering ISSN 1745-4530 STARCH PROCESSING IN COUETTE-TAYLOR FLOW R. HUBACZ, N. OHMURA and E. DLUSKA

Thermal treatment of starch slurry in Couette-Taylor flow apparatus

“…Meanwhile, both amylose leaching and water absorption favored the increase in dissolved starch concentration (represented by ABS) in the continuous water phase in which starch granules were suspended. On the contrary, at T hj ≥ 85 C gelatinization can be completed (DSG = 1) even for higher values of starch slurry axial flow and values of ω lower than those investigated here (see Hubacz et al, 2013 andMasuda et al, 2013). When gelatinization is completed a pasting process starts and water absorption by starch granules (i.e.…”

“…The results from Hubacz et al (2013) revealed an increase in SGSD with increasing ω for ω < 11.56 rad/s and a reversed tendency for ω > 11.56 rad/s. Meanwhile, in the present experiments the impact of  on SGSD was difficult to evaluate for T hj ≤ 70ºC, while for T hj ≥ 85ºC the increase in SGSD with the increasing ω (without changing the tendency) was observed.…”

“…CFD simulation was used in order to compare gelatinization in the studied CTF apparatus with the other two apparatuses studied by Hubacz et al (2013). The size of the latter apparatuses was defined by the radius of outer cylinder R 2 = 0.026m, the radius of rotor R 1 = 0.016 m or 0.021 m, and the length L = 0.3 m. This comparison can provide interesting information how to scale-up or intensify the process by changing the geometry of a CTF apparatus.…”

“…In addition to this, energy and species transport equations were solved (see Hubacz and Buczyńska, 2011). These equations were included into the model in order to calculate rheological properties of starch slurry, which was modelled using a power-law equation (see Hubacz et al, 2013):…”

“…Additionally, in order to ensure good heat transfer conditions and to avoid separation of the starch from the water phase, an agitation of the slurry is needed (Sakonidou et al, 2003). In such a context, Couette-Taylor flow (CTF) apparatus was proposed for wheat starch processing (Hubacz and Buczyńska, 2011;Hubacz et al, 2013;Masuda et al, 2013). This type of apparatus consists of two cylinders with the inner one (rotor) rotating, while the fluid flows in the gap between these cylinders.…”