Preparation of oil-in-water emulsions stabilized by faba bean protein-grape leaf polyphenol conjugates: pH-, salt-, heat-, and freeze-thaw-stability.

BACKGROUND: Plant proteins are being increasingly utilized as functional ingredients in foods because of their potential health, sustainability, and environmental benefits. However, their functionality is often worse than the synthetic or animal-derived ingredients they are meant to replace. The functional performance of plant proteins can be improved by conjugating them with polyphenols. In this study, the formation and stability of oil-in-water emulsions prepared using faba bean protein-grape leaf polyphenol (FP-GLP) conjugates as emulsifiers. Initially, FP-GLP conjugates were formed using an ultrasound-assisted alkali treatment. Then, corn oil-in-water emulsions were prepared using high-intensity sonication (60% amplitude, 10 min) and the impacts of conjugate concentration, pH, ionic strength, freezing-thawing, and heating on their physicochemical properties and stability were determined. RESULTS: Microscopy and light scattering analysis showed that oil-in-water emulsions containing small oil droplets could be formed at conjugate concentrations of 2% and higher. The addition of salt reduced the electrostatic repulsion between the droplets, which increased their susceptibility to aggregation. Indeed, appreciable droplet aggregation was observed at ≥ 50 mmol/L sodium chloride. The freeze-thaw stability of emulsions prepared with protein-polyphenol conjugates was better than those prepared using the proteins alone. In addition, the emulsions stabilized by the conjugates had a higher viscosity than those prepared by proteins alone. CONCLUSION: This study showed that FP-GLP conjugates are effective plant-based emulsifiers for forming and stabilizing oil-in-water emulsions. Indeed, emulsions formed using these conjugates showed improved resistance to pH changes, heating, freezing, and salt addition. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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

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.