Heat-induced aggregation of thylakoid membranes affect their interfacial properties

Many of our most popular lipid containing foods are in emulsion form. These foods are often highly palatable with high caloric density, that subsequently increases the risk of overconsumption and possibly lead to obesity. Regulating the lipid bioavailability of high-fat foods is one approach to prevent overconsumption. Thylakoids, the chloroplast membrane, creates a barrier around lipid droplets, which prolong lipolysis and increase satiety as demonstrated both in animal and human studies. However, a reduced lipase inhibiting capacity has been reported after heat treatment but the mechanism has not yet been fully established. The aim of this study was to investigate thylakoids' emulsifying properties post heat-treatment and possible links to alterations in lipase inhibiting capacity and chlorophyll degradation. Heat-treatment of thylakoids at either 60 °C, 75 °C or 90 °C for time interval ranging from 15 s to 4 min reduced ability to stabilise emulsions, having increased lipid droplets sizes, reduced emulsification capacity, and elevated surface load as consequence. Emulsifying properties were also found to display a linear relationship to both chlorophyll and lipase inhibiting capacity. The correlations support the hypothesis that heat-treatment induce chlorophyll degradation which promote aggregation within proteins inside the thylakoid membrane known to play a decisive role in interfacial processes. Therefore, heat-treatment of thylakoids affects both chlorophyll content, lipase inhibiting capacity and ability to stabilise the oil-water interface. Since the thylakoid's appetite reducing properties are a surface-related phenomenon, the results are useful to optimize the effect of thylakoids as an appetite reducing agent.