Flavors are delicate and valuable additives used across various industries, including pharmaceutical, chemical, cosmetic, and food.
Defining Flavors and Flavorings
The International Organization of the Flavor Industry (IOFI) defines flavor as “the sum of those characteristics of any material taken in the mouth, perceived principally by the senses of taste and smell, and also the general pain and tactile receptors in the mouth, as received and interpreted by the brain. The perception of flavour is a property of flavourings.”*
The IOF addresses both chemically defined substances and natural complex substances in its Code of Practice of the International Organization of the Flavor Industry and defines flavorings as products that are added to food to impart, modify, or enhance the flavor of food (with the exception of flavor enhancers considered as food additives. “Flavourings may consist of flavouring substances, natural flavouring complexes, thermal process flavourings or smoke flavourings and mixtures of them and may contain non-flavouring food ingredients….”
Encapsulation of Flavors
Over the years, these flavors and active ingredients have been encapsulated in a polymeric matrix to provide protection against oxidation, prevent loss of flavor, mask taste, control release, and enhance product handling.
Traditionally, encapsulation of flavors involved a batch process where polymers are melted with the addition of water. The flavors or active ingredients are then added and mixed by vigorous kneading. This process is not only laborious and time-consuming, but it also lacks flexibility since the material amount is predetermined by the size of the batch mixer. The spray drying method, another traditional encapsulation technique, also comes with drawbacks such as flavor loss, shorter shelf life, high energy consumption, and the potential need for explosion protection measures due to high process temperatures.
Food Extrusion
Food extrusion is an established and highly versatile technique for the production of food, feed, nutritional additives and flavors. It enables a continuous and cost-effective means of production, and its precise control ensures a high and constant product quality.
Twin-screw extruders are extruders with two co-rotating intermeshing, self-wiping screws and are well-established tools for the mixing, compounding, and processing of materials. The twin-screw melt extrusion method offers a more efficient and controlled way of encapsulating flavors. (Read more about twin-screw applications in this application note: Relevant process parameters for twin-screw compounding.)
In twin-screw extrusion processing, the polymer matrix material is metered and conveyed into the first mixing zone where, due to heat and shearing, it is transformed into a homogenous melt. The flavor is then added to a secondary feed zone using a liquid feeding pump. In a further mixing zone, the flavor is dispersed and evenly distributed into the polymer matrix. The final compound is pressed through a die, shaped into strands, and cut into fine pellets by a rotating knife of a face-cut pelletizer, or extruded onto chill-rolls which freeze and shape the material into flakes.
Testing the Twin-Screw Extrusion Method
In a test run for encapsulating a flavor in a sugar matrix using a parallel twin-screw extruder, the sugar was metered into the cooled, first feeding zone of the extruder, with a gravimetric twin-screw feeder. The sugar was then conveyed into the first mixing zone where it was melted due to the shear and heat generated by the kneading elements. The flavor was added to the molten sugar by a peristaltic pump. The mixture was then transported into two subsequent mixing sections where the flavor was dispersed and evenly distributed in the sugar matrix. At the end of the extruder, the pressure was built up, and the final compound was pressed through the die head, into the face-cut pelletizer.
Summary
In conclusion, we found that using twin-screw extruders for flavor encapsulation offers several advantages over traditional processes. It provides milder process conditions, reduces the risk of product denaturation, and allows for the production of application-specific end products.
You can read more details about the testing, including schematics, instruments used, and pictures of the final products in the Application Note: Encapsulation of flavors and ingredients.
Additional Resources
- Application Note: Encapsulation of flavors and ingredients
- Application Note: Relevant process parameters for twin-screw compounding
- Code of Practice of the International Organization of the Flavor Industry
- Online resources for compounding and extrusion instruments and applications
