Jack Yang1, Leonie C Waardenburg2, Claire C Berton-Carabin3, Constantinos V Nikiforidis4, Erik van der Linden5, Leonard M C Sagis6. 1. TiFN, Nieuwe Kanaal 9A, 6709 PA Wageningen, the Netherlands; Laboratory of Physics and Physical Chemistry of Foods, Wageningen University, Bornse Weilanden 9, 6708WG Wageningen, the Netherlands; Laboratory of Biobased Chemistry and Technology, Wageningen University, Bornse Weilanden 9, 6708WG Wageningen, the Netherlands. 2. Laboratory of Physics and Physical Chemistry of Foods, Wageningen University, Bornse Weilanden 9, 6708WG Wageningen, the Netherlands. 3. Laboratory of Food Process Engineering, Wageningen University, Bornse Weilanden 9, 6708WG Wageningen, the Netherlands; INRAE, UR BIA, F-44316 Nantes, France. 4. Laboratory of Biobased Chemistry and Technology, Wageningen University, Bornse Weilanden 9, 6708WG Wageningen, the Netherlands. 5. TiFN, Nieuwe Kanaal 9A, 6709 PA Wageningen, the Netherlands; Laboratory of Physics and Physical Chemistry of Foods, Wageningen University, Bornse Weilanden 9, 6708WG Wageningen, the Netherlands. 6. Laboratory of Physics and Physical Chemistry of Foods, Wageningen University, Bornse Weilanden 9, 6708WG Wageningen, the Netherlands. Electronic address: leonard.sagis@wur.nl.
Abstract
HYPOTHESIS: Plant seeds store lipids in oleosomes, which are storage organelles with a triacylglycerol (TAG) core surrounded by a phospholipid monolayer and proteins. Due to their membrane components, oleosomes have an affinity for the air/oil-water interface. Therefore, it is expected that oleosomes can stabilise interfaces, and also compete with proteins for the air-water interface. EXPERIMENTS: We mixed rapeseed oleosomes with whey protein isolate (WPI), and evaluated their air-water interfacial properties by interfacial rheology and microstructure imaging. To understand the contribution of the oleosome components to the interfacial properties, oleosome membrane components (phospholipids and membrane proteins) or rapeseed lecithin (phospholipids) were also mixed with WPI. FINDINGS: Oleosomes were found to disrupt after adsorption, and formed TAG/phospholipid-rich regions with membrane fragments at the interface, forming a weak and mobile interfacial layer. Mixing oleosomes with WPI resulted in an interface with TAG/phospholipid-rich regions surrounded by whey protein clusters. Membrane components or lecithin mixed with proteins also resulted in an interface where WPI molecules aggregated into small WPI domains, surrounded by a continuous phase of membrane components or phospholipids. We also observed an increase in stiffness of the interfacial layer, due to the presence of oleosome membrane proteins at the interface.
HYPOTHESIS: Plant seeds store lipids in oleosomes, which are storage organelles with a triacylglycerol (TAG) core surrounded by a phospholipid monolayer and proteins. Due to their membrane components, oleosomes have an affinity for the air/oil-water interface. Therefore, it is expected that oleosomes can stabilise interfaces, and also compete with proteins for the air-water interface. EXPERIMENTS: We mixed rapeseed oleosomes with whey protein isolate (WPI), and evaluated their air-water interfacial properties by interfacial rheology and microstructure imaging. To understand the contribution of the oleosome components to the interfacial properties, oleosome membrane components (phospholipids and membrane proteins) or rapeseed lecithin (phospholipids) were also mixed with WPI. FINDINGS: Oleosomes were found to disrupt after adsorption, and formed TAG/phospholipid-rich regions with membrane fragments at the interface, forming a weak and mobile interfacial layer. Mixing oleosomes with WPI resulted in an interface with TAG/phospholipid-rich regions surrounded by whey protein clusters. Membrane components or lecithin mixed with proteins also resulted in an interface where WPI molecules aggregated into small WPI domains, surrounded by a continuous phase of membrane components or phospholipids. We also observed an increase in stiffness of the interfacial layer, due to the presence of oleosome membrane proteins at the interface.