Options abound for controlled delivery of ingredients
compounds and flavours, is far behind the pharmaceutical world, but
the balance is slowly being redressed.
The controlled release of ingredients can improve the efficacy of bioactive compounds allowing much smaller quantities of the bioactive to be used, so their value to the food industry, particularly as the more and more manufacturers explore the realm of functional foods. Few examples, if any, of food-related commercial applications of controlled release exist, Dérick Rousseau, PhD, from Ryerson University in Canada told attendees at the IFT International Food Nanoscience Conference in New Orleans. But while the science is coming along, the understanding of controlled release of ingredients for food is still full of holes. "When it comes to foods and the concept and application of controlled release, what we do know is dwarfed by what we don't," said Dr Rousseau. There are options available to food scientists however, and Dr Rousseau has his finger in a lot of research pies, being active in the study of many different types of controlled release. These include microemulsions containing nano-scale particles, self-assembled dairy proteins, and phase-separated hydrogels. Which has the most potential for food? "It really depends on the application," Dr Rousseau told FoodNavigator.com. Microemulsions Work at Ryerson University has examined the potential of these clear, transparent liquids with a dispersed phase in the nanometre scale to carry bioactive ingredients. The micro emulsions are thermodynamically stable, meaning they are formed almost instantly on mixing, and they also do not separate over time. "These offer the easiest application," said Dr Rousseau. "Due to a judicial combination of ingredients, our microemulsions are produced by an elegant and simple technique." But it's not all plain-sailing, and innovation is handicapped by the limited choice of food grade surfactants. The use of surfactants like triglycerides is not possible since the triglycerides are typically relatively large and inflexible. Dr Rousseau's research group has developed a combination of ingredients, including water and propylene glycol, triceprylin (a relatively short triglyceride), and Tween 80 as the surfactant. Ingredients such as plant sterols and resveratrol are being added to these microemulsions. Self-assembling dairy proteins "The idea of being able to self-assemble protein structures is intriguing," said Dr Rousseau. "But they do have inherent difficulties from an industrial point of view." A project funded by the advanced food and materials network (AFMNet), a Canadian research network, uses short sequences from beta-lacto globulin. These shorter peptides become multifunctional ingredients since, by themselves, they are able to reduce a person's blood pressure (anti-hypertensive). By loading the self-assembled protein with another bioactive compound, say a plant sterol, and you have quite the heart-healthy combination. Hydrogels A hydrogel is formed when gelatine and maltodextrin are mixed together at a set concentration and at a high temperature to obtain a homogeneous mixture. If the temperature is then dropped a water-in-water emulsion is formed. "How you drop the temperature dictates the characteristics of the hydrogel," explained Dr Rousseau. By decreasing the temperature to just above the temperature at which gelatine solidifies and a temperature-induced phase separation occurs: "You obtain a maltodextrin-enriched droplets in a gelatine-rich continuous phase," he said. Drop the temperature again and a subsequent phase separation occurs. "Through modulation of the phase pattern you can impact on the release of the bioactives in the hydrogel," he explained. Keeping it simple Dr Rousseau's research is guided by the desire to keep things simple - the matrices should be simple, as should the technology involved. "You need to keep it simple at first, especially if you want to scale it up," he said.