Performing Department
Food Science & Human Nutrition
Non Technical Summary
Microencapsulation is defined as a technology of packaging solids, liquids, or gaseous materials in miniature, sealed capsules that can release their contents at controlled rates under specific conditions. Encapsulation technology in food processing consists of coating minute particles of ingredients (e.g., acidulants, fats, and flavors), as well as whole ingredients (e.g., raisins, nuts, and confectionery products), by microencapsulation and macrocoating techniques, respectively. Microcapsules offer the food processor a mean to protect sensitive food components, ensure against nutritional loss, utilize otherwise sensitive ingredients, incorporate unusual or time release mechanisms into the formulation, mask or preserve flavors and aromas, and transform liquids into solid ingredients that are easy to handle.Food ingredients, enzymes, cells, or other materialscan be encapsulated by many different techniques including physical methods (e.g., spray drying and extrusion), chemical methods (e.g., interfacial polymerization), and physicochemical methods (e.g., coacervation). Among those techniques, spray drying is the most common and economical technique to produce microencapsulated food materials. Liquids are atomized by centrifugal atomizer or nozzle and immediately dried by hot air flowing in the chamber. The main advantage of the spray drying is the ability to handle labile materials because of the short contact time in the dryer. Various polymer systems such as alginate, carrageenan, protein, and starch have been used to encapsulate target materials using spray drying. Protein and carbohydrate are the most commonly used as wall materials in microencapsulation due to their good encapsulation properties.A conventional route to form a core-shell structure requires mixing of two immiscible phases in order to generate an emulsion, which is generally an energy intensive process. The emulsion is pumped through an inner channel and transformed into mist by a compressed gas flowing through the outer channel. In addition to the need for the step to create an emulsion, it is difficult to encapsulate two miscible materials in a core-shell structure using a two-fluid nozzle. The focus of this proposed project is to encapsulate various target materials in core-shell structures using a three-fluid nozzle.A three-fluid nozzle has three fluid channels; a center channel for liquid 1 (target material), a middle channel for liquid 2 (wall material), and a outer channel for compressed gas. One of the notable advantages of using a three-fluid nozzle is that the core-shell structure can be formed with a one-step process without requiring any pre-treatments such as pre-mixing or pre-homogenization. Also, it is possible to form a core-shell structure with two miscible materials.
Animal Health Component
30%
Research Effort Categories
Basic
30%
Applied
30%
Developmental
40%
Goals / Objectives
Our long term goal is to provide a novel technique for a microencapsulation that can be applied to a wide range of applications. We hypothesize that the adaptation of a three-fluid nozzle to spray drying will enable the formation of core-shell structures without energy intensive additional steps. For this long term goal, three specific aims were developed.The specific aims include:1. Revise the design of three-fluid nozzle to improve the formation of core-shell structuresThe working hypothesis for Aim 1 is that the design of the three fluid nozzle is a critical factor and the relative length of the center, middle and outer channels of the three-fluid nozzle will be the main factor to form and control the core-shell structure.2. Identify the additional factors to control core-shell structure of encapsulated particles.The working hypothesis for Aim 2 is that there are inter-related factors in spray drying to control the core-shell structure of microcapsules. The inter-related factors may include the viscosity, surface tension, absolute flow rate, and relative flow rate of the two liquids.3. Apply the three fluid nozzle to encapsulate various target materials.The working hypothesis for Aim 3 is that the spray drying using a three-fluid nozzle can be applied to encapsulate a wide range of target materials including solid-lipid carriers, hygroscopic materials in core-shell structures.
Project Methods
Objective 1. Revise the design of three-fluid nozzle to improve the formation of core-shell structure. The current design of the three-fluid nozzle has the same length for the center, middle and outer channels.This design is simple but provides limited coverage of the core material due to the same discharge points for both core and wall materials. The design will be revised to implement different lengths for each channel so the core material will be encapsulated by the wall material completely. The modification will be made at the Electrical & Computer Engineering machine shop at the University of Illinois, Urbana-Champaign.The material used for this aim will be whey protein isolate (WPI) as a wall material and anhydrous milk fat (AMF) as a core material. The spray dried microcapsules using the revised nozzle design will be analyzed for morphology and surface oil content. The design of the three-fluid nozzle will be revised to improve the coverage of the core material. The spray drying will be conducted with inlet temperature of 170 degrees C and outlet temperature of 90 degrees C.Objective 2. Identify the additional factors to control core-shell structure of encapsulated particles.There are many factors affecting a spray drying process. In this proposed study, viscosity, total flow rate of liquid 1 and 2, and flow rate ratio between liquid 1 and 2 will be controlled. The viscosity of liquid 1 and 2 will be adjusted by varying solid concentration and feed temperature. The materials to be used for this aim is the same as the aim 1; WPI and AMF. To assess the effect of the factors on the microcapsule formation, morphology and surface oil content will be analyzed.Objective 3. Apply the three-fluid nozzle to encapsulate various target materials.Based on the nozzle design fromaim 1 and the factors fromaim 2, the spray drying with a three-fluid nozzle will be applied for various core materials.The first type of core materials will be a solid lipid particle encapsulated using WPI and AMF. Fat soluble bioactive compounds such as oregano essential oil or tributyrin will be dispersed in AMF and encapsulated using the three-fluid nozzle. The particle morphology, encapsulation efficiency and release profile of the bioactive compounds will be analyzed. The morphology will be assessed using a Scanning Electron Microscopy (SEM). The encapsulation efficiency will be analyzed by quantification of the core materials in microcapsules using a high-performance liquid chromatography (HPLC) and a gas chromatography (GC) and comparing it with the amount initially added to the microcapsule. The encapsulation efficiency will be calculated by the following equation:Encapsulation Efficiency (%) = (Amount of core detected in microcapsule / Amount of core added) x 100The release profile of the bioactive compound will be analyzed by measuring the concentration of the target bioactive compound in a solvent (for example water) after dispersing the microcapsules in the solvent. The concentration of the bioactive compound will be measured over period of time until a concentration equilibrium is achieved.To investigate the release of bioactive compounds in digestive system, a static in-vitro digestive model will be used. The in-vitro model will be composed of three phases: oral, stomach, and small intestinal phases. The microcapsules will be placed in each phase in sequence and incubated at 37 degrees C. The release of the bioactive compound from the microcapsules will be analyzed using a HPLC and a GC.The second type of core materials will be a hygroscopic material such as oligosaccharides. Hygroscopic materials are extremely difficult to spray dry due to their low glass transition temperature (Tg). When Tg is low, the material tends to stick on various surfaces during the spray drying process and results in very low yields. Microencapsulation may be able to provide a thin layer of coating with high Tg to prevent the stickiness issue occurring during spray drying as well as storage. Oligosaccharides will be used as a hygroscopic core material and maltodextrin will be used as a wall material. The yield, encapsulation efficiency, morphology, and storage stability will be assessed. The yield is the measurement of ration between the collected spray dried material and total material fed into the spray dryer. The encapsulation efficiency will be calculated using the equation above and morphology will be assess using the same SEM as explained above. The encapsulated hygroscopic material will be sealed in airtight containers and stored at room temperature and at 40 degrees C for an extended period (at least three months). The glass transition temperature, moisture content, degree of aggregation will be measured to evaluate the storage stability.