Rheological measurements
The rheological properties of fermented soy milk were
measured using a controlled-viscometer (Brookfield DV-II þ Pro
Viscometer). The temperature was kept constant at 4 C by using a
circulating bath and pump (Masterflex L/S model 77250-62,
ColeeParmer, USA). By using small device adapter, the fluid flow in
a dead zone and/or the formation of unstable flow was minimized.
Rheological measurement was performed as a shear rate sweep by
increasing the shear rate from 0 to 200 rpm. During measurements,
shear rate, shear stress, apparent viscosity and tork (%) values were
recorded. Experimental shear stress-shear rate measurements
were fitted to selected rheological models to assess the flow
behavior of the fermented soy milk. Three different rheological
models were applied; Power Law Model (Eq. (1)), Herschel Bulkley
model (Eq. (2)), and Vocadlo model (Eq. (3));
t ¼ K gn (1)
t ¼ t0 þ K gn (2)
t ¼
t
1=n
0
þ K g
n
(3)
where t is shear stress (Pa) and t0 is yield stress (Pa) while n is flow
behavior index, K is consistency coefficient (Pa sn) and g_ is the shear
rate (1/s).