Effect of ultrasound pretreatment on the functional and antioxidant properties of fermented and germinated Lupin protein isolates grafted with glucose

J Sci Food Agric. 2021 Jun 19. doi: 10.1002/jsfa.11383. Online ahead of print.

Abstract

Background: This study examined the functional and antioxidant properties of Maillard reaction (MR) products of lupin protein isolate (LPI), fermented (FLPI), and germinated (GLPI) with glucose (G), treated with ultrasound (US) at different power levels (20-40-60-80%) for 15 min. The MR was conducted in a water bath for 180 min at 90 °C.

Results: The Trolox-equivalent antioxidant capacity (TEAC) values were found to be 46.79%, 56.43%, and 35.56% for the control (C), 58.99%, 80.17%, and 69.73% for conjugates of LPI-G, FLPI-G, and GLPI-G treated at 80% US, respectively. The maximum 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of LPI-G, FLPI-G, and GLPI-G was found to be 39.68%, 59.54%, and 48.41%, respectively after 80% US. The FLPI-G sample showed the highest antioxidant activity compared with the samples treated at the same power level for DPPH and TEAC. The Fe-chelating activity of GLPI-G showed significant differences when compared with FLPI-G. The solubility of LPI-G, FLPI-G, and GLPI-G increased with increasing US power. The highest solubility was 74.29% for 80% US-treated GLPI-G. The emulsifying activity index (EAI) increased at 20% US and decreased with further increase in the US power. The EAI and emulsifying stability index (ESI) were negatively affected by the MR and US processes.

Conclusion: The findings of current study proved that conjugation of LPI with G with the MR and with US pretreatment is an effective method for improving the bio- and techno-functional properties of LPI. It is therefore likely that the properties of plant proteins modified by biochemical and physical treatments may widen their applications in the food industry. © 2021 Society of Chemical Industry.

Keywords: Maillard reaction; bioactivity; fermentation; germination; ultrasound.