Microbubbles to extend shelf-life on food foams

Tag: Bee Product A collaboration between Harvard University and Unilever researchers found a way to create gas-liquid systems with tinybubbles that remain stable for up to a year. This may help to significantly extend the life of foam-based foodproducts, such as whipped cream, ice cream , sorbets, and mousses, according to Howard Stone from the Schoolof Engineering and Applied Science at Harvard. The team was able to produce the stable bubbles by using a sucrosesurfactant which forms a coating around the air bubbles. In addition, they noted that each bubble had tiny hexagonalpatterns on its surface which, they explained, is caused by theamphiphilic nature of the surfactant used. Amphiphilic means themolecules have both hydrophilic (water-loving) and hydrophobic(water-hating) properties. The hydrophilic heads of the sucrose molecules in the surfactantsit on the outside of the bubble in contact with the water, whereasthe hydrophobic chains of the molecule lie on the inside of thebubble. As the heads occupy more surface area than the tails thiscauses the surface of the bubble to bulge, resulting in thehexagonal patterns that can be observed. Dr. Rodney Bee, a retired Unilever physical chemist, initiallyproduced the unusual bubble formation in the course of his researchinto finding ways to extend the life of foams and other gas-infusedmixtures like ice cream. "We were interested in two things: Firstly, understanding how thesize of the gas cells can influence the organoleptic and visualproperties, and secondly, how to maintain their stability overtime," Dr. Bee told FoodNavigator.com. Dr. Bee confirmed that Unilever maintain an interest in applyingthe technology but couldn't predict when a commercial product wouldhit the shelves. "We've established we can put this into the products that we wantto put them in," he added. The paper reports the use of a sucrose surfactant which forms acoating around the air bubbles, but Bee added that others are beinginvestigated. "The surfactant has to be able to form a crystalline layer thatadsorbs to the surface," he said. "The interface between air and liquid is covered with surfactantmolecules, both mono- and diesters, which are irreversibly pinnedbecause of their low solubility in glucose syrup," wrote the researchers in Science . "The hydrophobic headgroups of the sucrose stearate sit in theaqueous phase, whereas the hydrophobic carbonyl chains lie insidethe microbubbles. The observed bulging domains suggest that thesurfactant molecules pack on the interface, with headgroupsoccupying substantially more surface area than the hydrophobicchains," they added.