Effect of Galacto-oligosaccharides with Different Degrees of Polymerization on the Storage Stability of Freeze-Dried Lecithin Liposomes

Galacto-oligosaccharides (GOS) are widely recognized as prebiotic ingredients, whereas their technological role in stabilizing lipid-based systems remains poorly understood. In this study, GOS were synthesized by enzymatic transgalactosylation of lactose and enriched by ethanol precipitation. Carbohydrate composition, glass transition temperature (Tg), and their influence on the formation of primary lipid oxidation were evaluated using freeze-dried lecithin liposomes as a model membrane system. Ethanol precipitation increased the GOS content from 22.8% to 50.7% (w/w) while reducing the proportion of monosaccharides from 40.0% to 15.5% (w/w). Tg was strongly influenced by carbohydrate composition and relative humidity (RH), with GOS-enriched preparations exhibiting higher Tg values than the crude reaction mixture. The formation of primary lipid oxidation products, assessed by UV spectroscopy through conjugated diene formation at 234 nm, was significantly lower in liposomes freeze-dried with GOS-rich preparations or sucrose than in phosphate-buffered saline (PBS) controls, particularly under storage conditions in which the carbohydrate matrices remained in the glassy state. At higher RH, transition to the rubbery state was associated with increased conjugated diene formation. These findings suggest that the protective effect of GOS-rich formulations is associated with the physicochemical properties of the carbohydrate matrix and is consistent with the proposed role of the glassy state in limiting molecular mobility, rather than direct antioxidant activity. Beyond their established prebiotic properties, GOS-rich preparations may also contribute to the stability of dehydrated lipid-containing systems, supporting their use as multifunctional food ingredients.