A thawed pure yeast culture was added to sterile YM broth at 1% v/v
and sub-cultured twice under the aforementioned conditions to obtain
a cell count of about 6 log CFU/mL. It was then centrifuged (8000 g,
15 min, 4 °C) and the supernatant discarded. The pellet was washed
twice with 10% v/v phosphate saline buffer (pH 7.4), and the washed
cells were resuspended in the same buffer to obtain the yeast preculture.
Frozen okara was thawed, and 600 g of okara were placed in a glass
container and autoclaved at 121 °C for 15 min. Yeast pre-culture was
added to the sterilised okara at 2% v/w to and mixed evenly with a
sterilised metal spoon, obtaining an initial cell count of about 4 log
CFU/g okara. The airtight containers were incubated at 30 °C for
5 days. Aerobic condition within the container was maintained by
ensuring sufficient headspace (bed height: 3–3.5 cm; headspace: 3.5–
4 cm) and bymixing the substrate bed daily to introduce oxygen during
sampling under aseptic conditions. Uninoculated, autoclaved okara
incubated under the same conditions served as the control, while
fresh, unheated okara served as the blank. All treatmentswere prepared
in triplicate. Samplingwas conducted daily over 5 days for the determination
of viable yeast cell count, sugars, organic acids, amino acids and
volatiles. Samples collected on days 0 and 5 were also subjected to
proximate composition and antioxidant capacity analyses. Samples
collected were stored at −20 °C before the analyses.