Optimization of Drying Parameters for “Moisture Reduced Teff Injera Making” Using Response Surface Methodology
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Date
2019-06
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Publisher
Addis Ababa University
Abstract
Teff Injera is the staple Ethiopian fermented bread processed from fermented tef [Eragrostis tef
(Zucc.) Trotter] grain flour.” Dirkosh” is the Amharic name given to the dried /moisture reduced
injera. The current potential need of the super food, Teff and its products like injera and its dried
form, Dirkosh needs a scientific research that will increase its quality, healthy and market demand.
Therefore, the objective of the study was to prepare and optimize the drying parameters of Dirkosh
using computer controlled tray dryer. The selected drying parameters were (drying air
temperature, air velocity and sample loading density) in response of the most quality parameters
of the final dried injera/Dirkosh. The response variables were the final moisture content, drying
time, color, texture, overall acceptability, water activity and drying rate. The optimization process
done by using Box-Behnken Design, response surface methodology (RSM). Drying process factors
( (drying air temperature(55-65
C), air velocity(0.5-1.5m/s) and sample loading density(12kg/m
o
2
)) were considered and made 15 experimental runs of Dirkosh drying including 3 replicates
using RSM. The investigated responses were final moisture content(5.43), color(6.02),
texture(6.23), overall acceptability(6.05), water activity(0.274) but drying time and drying rate
were not significant model terms but it was possible to estimate the drying kinetics using the better
drying process parameters. RSM with Box-Behnken Design was used to develop and optimize
drying process factors in response of the dried injera. Moreover, both numerical and graphical
optimizations were carried out to determine the optimum values of Dirkosh in terms significant
model terms. The optimum process factors of drying process parameters were drying air
temperature of 55
with a
desirability of 0.65. The study showed that all the drying process factors were important
parameters influencing the physicochemical and sensory qualities of Dirkosh.
Description
Keywords
Box-Behnken Design, Moisture-reduced injera, Optimization, Response Surface Methodology, Water Activity