Effect of solid-state fermentation on select antinutrients and protein
digestibility of cold-pressed and hexane-extracted canola meals
Abstract
In this study, the effects of solid-state fermentation (SSF), including
strain (Aspergillus niger NRRL 334 and A. oryzae NRRL
5590) and fermentation time (24, 48, and 72 h) on the nutritional value
of cold-pressed (CP) and hexane-extracted (HE) canola meals were
examined. SSF increased the protein content of both types of meals (from
~36 to ~40%) while reducing the oil
content of CP meals (from ~12 to 9%). There was a
significant reduction (~80%) in the phytic acid content
of both types of meals after fermentation using either fungi. Overall,
fermented samples showed a decrease in the total phenolic content from
2.7-3.1 to ~1.0 mg gallic acid equivalents (GAE)/g DM (a
~65% reduction), of which specifically the HE meal
fermented with A. niger sample had the greatest decrease from 3.1
to 0.6 mg GAE/g DM (~81% reduction). Seventy-two hours
of fermentation decreased the in vitro protein digestibility
(IVPD) of the meals. In contrast, a shorter fermentation time (24 h)
increased the IVPD as compared to the controls (from
~73% to 77-81%), with the exception of the CP meal
fermented with A. niger which had decreased IVPD at all
fermentation times. Overall, the changes indicate that SSF using
A. niger or A. oryzae can be useful to positively modify
the composition of different canola meals and improve their nutritional
value by significantly increasing the protein content, decreasing the
levels of antinutrients, while only slightly reducing IVPD.