The use of solid-state fermentation to improve the protein quality, functionality and flavour of pulse protein isolates
Date
2022-05-17
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
The aim of this research was to investigate the effect of solid-state fermentation (SSF) by Aspergillus oryzae NRRL 5590 on pea (PPI) and navy bean protein isolate (NBPI) to improve the functional properties, protein quality and flavour profiles. In study 1, proximate composition, physicochemical, functionality properties, and protein quality were evaluated. It was found that degree of hydrolysis of fermented PPI after 48 h was 9.3 and for fermented NBPI after 72 h was 3.6. Regarding to proximate composition, protein content of PPI increased from 82.0 to 83.9% and protein content of NBPI (82.7%) was similar in all fermentation times. Based on surface properties results, the surface charge increased for PPI ranged from -34.1 to -38.8 mV over fermentation time. Surface hydrophobicity increased from 19.3 to 33.2 a.u. (arbitrary units) for PPI and from 11.6 to 17.7 a.u for NBPI. According to functional properties, the nitrogen solubility was found to significantly increase with fermentation time from 8.7 to 34.2 % for PPI (p≤0.05). The emulsion stability (ES) of PPI was found to decline over fermentation time (0-48 h) from 81.1 to 61.35. Whereas foaming capacity and stability increased from 155 to 175% and 33 to 69%, respectively. The solubility, ES, foaming properties were found to remain relatively constant over fermentation time (0-72 h) for NBPI. In vitro protein digestibility (IVPD) showed a reduction during fermentation of PPI from 88.2 to 75.2%. The methionine and cysteine were limiting amino acids for both PPI and NBPI. In summary, fermentation may be used to improve the solubility and foaming properties of PPI and WHC of NBPI for potential use as a food ingredient. In study 2, the effect of fermentation on the presence of volatile compounds in PPI and NBPI were evaluated. Gas chromatography-mass spectrometry (GC) results showed that the flavor compounds in NBPI did not change significantly with fermentation time. However, SSF enhanced new desirable flavour compounds in PPI. These findings suggest that SSF of PPI could potentially improve flavour through the masking undesirable flavour compounds. Together, SSF is an efficient method for improving the solubility, foaming properties, and flavour in PPI.
Description
Keywords
solid- state, fermentation, pulse, protein, Aspergillus oryzae
Citation
Degree
Master of Science (M.Sc.)
Department
Food and Bioproduct Sciences
Program
Food Science