Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
Food Science & Technology
Non Technical Summary
The long-term goal of this project is to improve the current understanding of the spray drying process of liquid foods using computer modeling and experimentation to produce high-quality products cost-effectively with small physical and energy footprints. This will facilitate the development of effective solutions to critical challenges facing the global spray drying industry. The knowledge and technologies produced in this project will allow the production of high-quality food powders and increase the performance of spray drying operations. The need for this project is encouraged by 1) the growing demand for high-quality spray dried food powders, 2) the development of new applications using mixed-flow spray drying configurations, 3) the availability of modern computing simulation tools that can be used to optimize food processing operations, 4) the insufficient scientific information about the relationship between particle surface area and the quality of spray dried food powders, and 5) the current interest to minimize quality changes of spray dried powders during storage. To help address these challenges, we are proposing to develop computational fluid dynamics (CFD) simulation models to optimize spray drying operations of foods. The specific objectives of this project are: 1) to develop steady-state CFD simulation models of concurrent and mixed-flow spray drying of liquid foods, 2) to experimentally validate the results obtained by 3D-CFD simulation models of the spray drying of liquid foods, 3) To produce spray dried particles with different particle sizes and Brunauer-Emmett-Teller (BET) surface areas, 4) to evaluate the effect of BET surface area and particle size on the shelf stability of food-grade powder particles, and 5) to develop educational tools based on the knowledge and technology developed in this project and to facilitate its adoption among food processors, regulators, educators and extension specialists through workshops and training activities. The holistic approach of this project may increase the current profits of global food industry and ultimately benefit consumers at large.
Animal Health Component
50%
Research Effort Categories
Basic
30%
Applied
50%
Developmental
20%
Goals / Objectives
The long-term goal of this project is to improve the current understanding of the spray drying process of liquid foods using computer modeling and experimentation to produce high-quality products cost-effectively with small physical and energy footprints. The proposed study will exploit the advances in computing modeling as well as state-of-the-art analytical tools to optimize the spray drying operations of liquid foods and to evaluate the effect of particle surface area and particle size on the shelf stability of spray dried powders. Moreover, the holistic approach of the proposed project will a) improve the efficiencies of spray drying operations of liquid foods, b) support the development of cost-effective spray drying operations for the production of high-quality food powders; c) accelerate the research and development of novel spray dried food materials and d) increase the current profits of the U.S. food industry. We propose to generate the resources, missing knowledge and technology needed for developing high-quality and safe spray dried food ingredients. Thus, improving the competitiveness and profitability of the global spray dried food industry. The specific objectives of the proposed project are:To develop steady-state CFD simulation models of concurrent and mixed-flow spray drying of liquid foods.To experimentally validate the results obtained by 3D-CFD simulation models of the spray drying of liquid foods.To produce spray dried particles with different particle sizes and BET surface areas.To evaluate the effect of BET surface area and particle size on the shelf stability of food-grade powder particles.To develop educational tools based on the knowledge and technology developed in this project and to facilitate its adoption among food processors, regulators, educators and Extension specialists through workshops and training activities.
Project Methods
Development of Computer simulations:The spray drying of several liquid samples will be studied using computational fluid dynamics (CFD) simulations. The CFD code ANSYS FLUENT 19.2 will be used to develop three-dimensional (3D) simulations. To carried out CFD simulations of the spray drying of liquid foods under concurrent and mixed-flow conditions. Drying air will be introduced into the drying chamber at different inlet temperatures (between 140 - 200 °C) at steady state conditions. Then, a liquid feed with different solid content (g/100 mL) (between 5 - 40) will be atomized inside the drying chamber under concurrent and mixed-flow conditions. The flow pattern, temperature, velocity of the drying air and the particles histories including: RT, particle temperature and velocity, moisture content and particle size distribution at the outlet of the spray dryer chamber will be modeled using CFD. Unstructured mesh will be created and will have less than 512,000 elements and nodes. The boundary conditions for the CFD simulations will be described. Initial droplet size distribution will be given by a fit of the Rosin-Rammler distribution which will be discretized into 10 particle size classes ranging from 35 to 75 µm. Also, the finite volume approach will be utilized to resolve the set of partial differential equations of a two-way coupled Eulerian-Lagrangian method for the continuous and discrete phases. The governing equation for the continuous and dispersed phases is detailed in (Huang, Kumar, & Mujumdar, 2006). The discrete phase will be defined as multicomponent evaporating droplets available in ANSYS Fluent 19.2. Feed with two components (solids and water) will be included in the model, being water the evaporative element. The standardk-?turbulent model will be used to describe the flow of the drying air inside the drying chamber.Production of spray dried powders. Carbohydrate-based and protein-based spray dried powders will be obtained by spray drying fruit juices and liquid dairy foods respectively. Microencapsulated powders will be prepared by spray drying bioactive containing emulsions. Experimental data on velocity of the drying air and the particle size distribution of the spray dried powders will be used to validate the CFD simulations. Fruit juices will be obtained from pomegranate, peach, blueberry, and satsuma fruits and will be homogenized with maltodextrin (MD) as a drying agent. MD will be added at a ratio 1:1 (°Brix in juice: g of MD/100 mL juice). Liquid dairy beverages will be prepared by homogenizing whey protein concentrate, whey protein isolate and/or whey protein hydrolysate powders in distilled water at a concentration of 45 g/100 mL using an ultra-shearing mixer. Liquid emulsion containing cannonball jellyfish (LCJ) gelatin, and other encapsulating agents including, starches and alginates will be prepared. Oil in water emulsions (O/W) and water-in-oil emulsions will (W/O) will be prepared by homogenizing distilled water, vegetable oils, encapsulating agents, and bioactives using an ultra-shearing homogenizer. Liquid foods will be characterized for droplet size distribution and zeta potential using a Zetasizer Nano ZS device (Malvern, Southbough, MA). Flow behavior and viscoelastic properties liquid foods will be determined by following a method described by (Mis Solval, Bankston, Bechtel, & Sathivel, 2016) using an advance rheometer (AR 1000, Texas Instrument, New Castle, DE) fitted with a 40 mm parallel plate geometry placed at 200 µm with the lower platform. Brix values of liquid foods will be determined using digital refractometer, the pH of the liquid foods will be determined by using an electronic pH meter, and titratable acidity will be determined by following the method described in AOAC (2019). Liquid samples will be spray dried under concurrent and mixed-flow conditions using a pilot-scale spray dryer (Anhydro, PSD 52, Denmark), the feed flow rate will be set between 2 - 5 L/h and the inlet air temperatures will be set from 140 to 200°C. The spray dried powders (SDP) will be stored in a dried environment at room temperature until needed for further analysis. Air temperature and velocity will be recorded using a wireless thermo-anemometer (Series AP2, Dwyer Instruments, Inc. USA).Production of spray dried powders with different mean particle sizes and BET surface areas. Our team has hypothesized that spray dried particles with different sizes will have different BET surfaces areas. Hence, five mean particle sizes are targeted (very small < 5 µm, small (20 - 30 µm), medium (50 - 75 µm), large (75-125 µm), and agglomerated (>125 µm) particles). According to Elversson and Millqvist-Fureby (2005), powders with larger particle sizes are produced by spray drying liquid feeds with higher solid concentrations. Therefore, liquid foods, including fruit juices, dairy foods and liquid nutraceutical foods, with solid content (g/100 mL) from 1 to 50 will be prepared, and spray dried as previously described. Liquid foods will be spray dried at feed rates from 1 to 5 L/h (this is given by the capabilities of our spray dryer). According to Huang and Mujumdar (2008), atomization conditions affect the particle size of spray dried powders. Rotary atomizers operated at higher rotational speeds apply higher shear rates and reduces the viscosity of the atomized liquids which results in smaller droplets and powder particles. For concurrent spray drying experiments, the rotational speed of the atomizer will be set between 6,000 to 9,000 rpm. It is expected that lower rotational speeds of the rotary atomizer will produce bigger powder particles. Agglomerated particles (>125 µm) will be produced by mixed-flow spray drying. The pressures of the two-fluid nozzle are controlled by pressures of the compressed air which are between 150 and 400 kPa. It is believed that higher pressures will apply higher shear rates to the atomized liquids and produce spray dried powders with smaller particle sizes. Pressures between 150 - 300 kPa will be used to produce agglomerated powders.Shelf life study of spray dried powders: Spray dried powders with different particle sizes and BET surface areas produced in objective 3 of this proposal will be stored in controlled conditions and their physico-chemical and microbial properties will be monitored for 180 days. Controlled storage conditions: Powder samples will be stored at two temperatures (room ~25°C, and 40°C) and 3 levels of relative humidity (RH): (low (20-25%), medium (50-55%) and high (>75%). Desiccators /chambers with specific a relative humidity will be prepared by following the method described in Lipasek, Taylor, and Mauer (2011) using saturated solutions of potassium acetate (20-25 % RH), potassium carbonate (40-45 % RH) and sodium chloride (>75% RH). The RH of each chamber will be monitored weekly using a digital hydrometer. Plastic centrifuge tubes containing 50 g of spray dried powders will be placed inside the conditioned desiccators which will be stored at room temperature conditions and in a lab incubator at 40°C. Physico-chemical and microbial analysis of powders will be conducted at days 0, 30, 60, 90, 120, 150 and 180 days and will include moisture content, water activity, particle size distribution, BET surface area, microstructure, and color as previously described. Microbial quality of spray dried powders will include total aerobic counts, total coliforms, yeast and molds in spray dried powders will also be determined.Statistical analysis: Statistical significance of observed differences among means of experimental results will be determined by repeated measures Analysis of Variance (ANOVA) using SAS statistical software version 9.2 (SAS Institute Inc., Cary, NC) and followed by post-hoc Tukey's studentized range tests. All the experiments will be conducted in triplicate.