Residence Time Distribution (RTD) in a Single Screw Extrusion of African Breadfruit Mixtures

Abstract

Mixtures of African breadfruit (Treculia africanaDecne), corn, and defatted soybean were extruded in a singlescrew Brabender laboratory extruder at process variables derived from a second-order central composite design. The variables consisted of feed composition (0-100% breadfruit, 0-55% soybean, and 0 or 5% corn); fed moisture (15-27%), and screw speed (100-180 rpm). Effects of these variables on residence time distribution were investigated using Congo red as tracer. The extrudate spent longer time in the extruder as feed moisture or screw speed was decreased from 27% to 15% or 180 to 100 rpm, respectively, thereby increasing the residence time distribution characteristics. At 70% feed composition and screw speed of 140 rpm, mean residence time ( t ) increased from 40 to 50 s, whereas extrudate total collection time (t c ) increased from 65 to 70 s. At screw speed of 100-180 rpm, mean residence time ( t ) decreased from 55 to 35 s, whereas extrudate total collection time (t c ) decreased from 75 to 65 s. At 100% African breadfruit composition, these time values decreased to 35 and 70 s, respectively, at the same screw speed, indicating the significant influence of feed composition and soybean addition to the mixture on residence time distribution. Residence time distribution curves indicated an early breakthrough time of 20 s at maximum screw speed (180 rpm), minimum tail of 65 s, and a plug flow pattern of the extrudates.tracer concentration appearing at the outlet at time, t T time (s) t mean residence time (s) t c total collection time (tail) (s) θ normalized time, a dimensionless parameter (t/t) E(t) exit age distribution. E(t) curves represent the variation of the dye tracer concentration at the exit F(θ) F(t)=∫E(t). F(θ) curves represent the accumulated quantity of tracer at the exit at a given time. These two curves {E(t) and F(θ)} are generally used to quantify the residence time distribution (RTD) t m minimum residence time (s) T extrudate temperature (°C) Y dependent process variables (T, RTD, t m, tand t c ) k number of independent process variables (three in this case) X 0 estimated regression coefficient β 0 intercept (constants and regression coefficients of the model) ɛ random error term β 1 X 1 -β 3 X 3 linear (first)-order effect b 1 X 2 1 À b 3 X 2 3 quadratic order effect β 12 X 1 X 2 -β 23 X 2 X 3 cross product (interactive) effect

Residence Time Distribution of Soy Protein Isolate and Corn Flour Feed Mix in a Twin-Screw Extruder

“…These results differ from our study, which may be due to the use of different moisture contents, raw materials, starch to protein ratio or simply different design of the extruder system. However, our findings matched the ones reported by Nwabueze and Iwe () who found that the residence time in the extruder increased when the feed moisture decreased. Higher moisture content in the sample could have contributed to a higher steam pressure within the system, which accelerates the forward push of the product in consistency with the screw speed.…”

“…; Ramaswamy et al . ,b; Chen ; Nwabueze and Iwe ). Both frequency (E‐curve) and cumulative (F‐curve) distribution can be obtained through the introduction of tracer particles at the entrance of a continuous flow system and then collecting them at the exit, by introducing the particles as a pulse or stepwise fashion.…”

Effects of fermentation time on the functional and pasting properties of defatted Moringa oleifera seed flour

“…The method described by Nwabueze and Iwe () was adopted. Each flour sample was placed in a food grade hexane at 1:3 (flour: n‐hexane) ratio for 3 h at room temperature and centrifuged at 3000 rpm for 10 min.…”

Effect of Starch Sources and Protein Content on Extruded Aquaculture Feed Containing DDGS

“…Various reactions that take place during extrusion cooking include thermal treatment, gelatinization, protein denaturation, shearing, mixing, grinding, hydration, shaping, expanding, texture alteration, partial dehydration, and destruction of microorganisms and other toxic compounds. Not only does composition play a key role, but the residence time in the extruder is also important to final product quality (Nwabueze and Iwe 2008). More importantly, the gelatinization that takes place during extrusion cooking improves the durability of the feed rations and digestibility of the nutrients (Chang and Wang 1998).…”