Foaming properties of potato (Solanum tuberosum) proteins: A study by the gas sparging method

The proteins used in food industry to make foams are mostly of animal origin, thus arising ethical and health concerns. for this reasons, protein of plant origin, such as those of potato, may represent an interesting alternative. In this research, the foaming behavior of potato proteins have been studied, using a commercial sample of potato proteins enriched in patatin (Laffort), intended for use as a fining agent in wine. The potato proteins, solubilized in buffers at different pH (3-7), were subjected to foaming by sparging N2, air and CO2, in the same conditions of pressure and time. The results showed a significant foam expansion (400%) in samples in which N2 and CO2 were sparged. However, some differences were observed in foam stability. In particular, foam was very stable when produced with N2 (40%), less stable with air (30%) and very unstable with CO2 (10%). Image analysis carried out on foams by a stereomicroscope and d32 (Sauter mean diameter) measurements showed significant differences related to the nature of the sparged gas and the pH. In particular, the foam obtained with N2 produced very small bubbles, with low polydispersity. Electrophoretic analyses of the proteins migrating into the foam revealed differences in protein patterns, especially in relation to the sparged gas, indicating that the nature of the dissolved gas affects the behavior of the different protein components. In conclusion, the patatin preparation here tested produces foams with stability and expansion which depend not only on the pH but also on the type of gas sparged in the liquid.