The effects of low-molecular-weight emulsifiers in O/W-emulsions on microviscosity of non-solidified oil in fat globules and the mobility of emulsifiers at the globule surfaces.
Electron Spin Resonance spectroscopy (ESR) was used to measure the mobility of the spin probe TEMPO in O/W-emulsions. This allowed determination of temperature-dependent microviscosity of the liquid fraction in lipid globules. Six hydrogenated palm kernel oil (HPKO) based emulsions containing caseinate and different combinations of lactic acid ester of monoglyceride (LACTEM), unsaturated monoglycerides (GMU) or saturated monoglyceride (GMS) were studied. The non-solidified oil in emulsions made with LACTEM+GMU had a high microviscosity, whereas the emulsion made with GMS had a low microviscosity. Also the partitioning of TEMPO between the lipid and aqueous phases was found to be highly temperature dependent, most likely due to the change of solid fat content with temperature. This behaviour may mimic the partitioning of aroma compounds in emulsions. The spin probe 5-doxylstearic acid was used to study the mobility of the components at the lipid globule surfaces. At 5°C all emulsions had a very low surface mobility. At 25°C the mobility of the spin probe was found to be correlated to the surface protein load. Emulsions with GMU had a high protein surface coverage and low mobility of the spin probe on the droplet surfaces. Conversely, in presence of LACTEM and GMS, the protein surface loads decreased and high surface mobilities were observed. Based on these results it is argued that the high macroscopic viscosity and lipid agglomeration of emulsions containing GMU is due to a lipid globule-protein-network where the lipid globules are connected via caseinate.
Palsgaard A/S, Palsgaardvej 10, 7130 Juelsminde, Denmark.
Merete B
MB
Munk
Department of Food Science, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg C, Denmark.
Henriette R
HR
Erichsen
Department of Food Science, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg C, Denmark. Electronic address: mola@food.ku.dk.
Mogens L
ML
Andersen
D002364:Caseins / Q000737:chemistry*; D045703:Emulsifying Agents / Q000737:chemistry*; D004655:Emulsions / Q000737:chemistry; D019344:Lactic Acid / Q000737:chemistry*; D050178:Monoglycerides / Q000737:chemistry*; D000073878:Palm Oil; D010938:Plant Oils / Q000737:chemistry*; D013499:Surface Properties
D002364:Caseins; D045703:Emulsifying Agents; D004655:Emulsions; D050178:Monoglycerides; D010938:Plant Oils; D019344:Lactic Acid; D000073878:Palm Oil
Electron spin resonance; Globule surface; Low-molecular-weight emulsifiers; Microviscosity; O/W-emulsions; Partial coalescence; Protein displacement