That opportunity partly explains why an upstate New York firm that specializes in specialized industrial ovens is trying to transfer a precision process for microencapsulation to the food industry. In late 2003, Lancaster, NY-based Harper International Corp. licensed technology from a German firm to produce perfectly rounded spheres with extremely tight size distribution, even at a microscopic level. Harper develops and designs advanced thermal processing systems, such as sintering furnaces for nuclear fuels. Precise control of temperature and atmosphere in compact, low-maintenance systems is a company hallmark.
Developed in the early 1990s by chemical engineers now affiliated with Brace GmbH, the microsphere/microencapsulation technology originally was devised for metals, ceramics and other materials with extremely high melting points. It produced precisely sized microspheres that also had applications in pharmaceuticals and feedstuffs. Harper International built a lab to develop formulations for volatile oils, aromatic and flavor essences and other food ingredients that can benefit from the Brace process. Its laboratory production unit can output test samples of encapsulated material and co-manufacturers are considering building pilot plants or commercial facilities. Production units with capacities of 10,000 liters an hour have been built in Europe.
Heading Harper's development work is Fenglin Yang, a research engineer and manager of the R&D lab. Yang received an undergraduate degree in chemical engineering in 1982 from Beijing (China) University of Chemical Technology and completed doctoral work in chemical engineering in 1999 at the University of Buffalo (NY). He joined Harper International that year and has headed numerous process development, design and scale-up projects, including microencapsulation processes for mint oil and garlic oil for food applications.
FE: The Brace process is suitable for producing microspheres and microcapsules. What is the distinction between the two?
Yang: With microspheres, the process begins by mixing a powder with water or another medium to make a uniform suspension. The resulting liquid runs through the machine and is subjected to drying, cooling or a chemical reaction to emerge as a solid sphere. With microencapsulation, a solid shell forms around the flavor or compound being encapsulated. In both processes, size distribution is very tight and ranges from 50 microns to 6,000 microns (6 mm). An exact payload of the active compound is delivered in a perfectly spherical dose.
Yang: Only one nozzle is used if microspheres are produced, while a patented double-nozzle system produces microcapsules. The machine is simple, and the concept is simple: pressure equal to one to two bars pushes the ingredient from a feed tank to the nozzle, where constant laminar flow occurs. A closed-loop control circuit to maintain a constant variable frequency and amplitude causes the flow to break up into uniform droplets. Surface tension of the feed materials causes the droplets to form into spheres, then solidify.
FE: How are you able to achieve uniform encapsulation?
Yang: The key is finding the right recipe to match the viscosity of the core-agent liquid and the shell material so that surface tension causes encapsulation to occur. A simple example is water and oil: oil doesn't mix with water, and the same principle applies to encapsulation. You have to choose materials that don't mix.
Solidification is accomplished by drying, cooling or chemical reaction. If alginate is used for the shell material, for example, it becomes a cross-linked polymer, and hardening occurs as a chemical reaction. If gelatin is used, it is heated to 70