Progress 09/01/12 to 08/31/13
Outputs
Target Audience: The target audience at this meeting were food scientists, food technologists, food product developers and professionals from the food industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Two postdoctoral researchers (at 0.37 and 0.29 FTE) and one graduate student (0.041 FTE) received training in the state-of-the microfabrication techniques and fluidics. How have the results been disseminated to communities of interest? The results of the project were disseminated to the community via two peer-reviewed journal publications, listed below. 1. Kim, J. and Vanapalli, S. A. Microfluidic production of spherical and non-spherical fat particles by thermal quenching of crystallizable oils. Langmuir. Accepted, 2013. 2. Sun, M. and Vanapalli, S. A. Generation of chemical concentration gradients in mobile droplet arrays via fragmentation of long immiscible diluting plugs. Analytical Chemistry, 85, 2044-2048, 2013. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Food products such as ice cream and butter use crystallizable food oils, and capabilities to generate fat particles of finely controlled size, shape and compositon from such materials provides new avenues to control the microstructure and rheology of foods. In this project period, we focused on microfluidic production of spherical and non-spherical fat particles from crystallizable food oils (palm fat). The method is based on microfluidic production of oil droplets at a cross-junction followed by thermal solidification downstream in a microcapillary. We varied the drop production conditions and the device temperature and demonstrate that spherical or non-spherical, and liquid or solidified fat droplets can be fabricated. By measuring thermal gradients in the microcapillary, we observed that crystalline fat particles are best produced when the device temperature is below the onset temperature of bulk fat crystallization. For the production of monodisperse non-spherical fat particles, we also found that the carrier fluid flow rate needs to be high enough to provide strong hydrodynamic forces to transport the confined rod-like particles. We identified the scaling relationship between geometric confinement and particle elasticity necessary to maintain the non-spherical shape. Thus, our study provided guidelines for the production of spherical and non-spherical fat particles that can be potentially used for controlling microstructure, rheology and drug encapsulation in foods and pharmaceutical creams that employ crystallizable oils. Our project results revealed that the throughput of production of microfluidic fat particles is low, and is unsuitable for conventional bulk food production. However, the well-controlled environment offered by microfluidics enabled us to establish design rules for the production of spherical and non-spherical fat particles, which could have been difficult to glean from conventional emulsification techniques. Given the establishment of design rules, opportunities now exist to incorporate them into conventional emulsification methods. For example, oil-in-water emulsions made from conventional methods could be forced through thermally cooled membranes that contain cylindrical pores (similar to membrane emulsification), which will allow not only bulk-scale production of anisotropic fat particles but also of sizes much smaller than demonstrated in our project. Thus, our findings are likely to improve bulk food processing methods. A secondary outcome that resulted in this project period (which was not part of the original objectives) was development of a new microfluidic technique that allows fine control in tuning the chemical composition of dispersed phase in droplets (Meng & Vanapalli, Anal Chem., 2013) This technique could be useful for food emulsions to finely control the lipid composition in fat droplets. However, as is typical with microfluidic techniques, the throughput is limited, so other avenues need to be investigated to apply this new method to bulk-scale food emulsion production - which is beyond the scope of the current project.
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2013
Citation:
Kim, J. and Vanapalli, S. A. Microfluidic production of spherical and non-spherical fat particles by thermal quenching of crystallizable oils, Langmuir, 2013, Accepted, 2013
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Sun, M. and Vanapalli, S. A., Generation of chemical concentration gradients in mobile droplet arrays via fragmentation of long immiscible diluting plugs. Analytical Chemistry, 85, 2044-2048, 2013.
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Progress 09/01/09 to 08/31/13
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Overall the PI and his group appreciates this NIFA/AFRI grant, which he received as a junior faculty and jump-started his academic career. For the PI, the project provided significant exposure to the needs of the food industry by attending national and project directors meetings. The project also allowed him to better assess the significance and limitations of microfluidic technology for adding value to food production and processing. Overall the project supported two postdocs and two graduate students, and provided significant training opportunities in the cutting-edge field of microfluidics and practically important area of food processing. How have the results been disseminated to communities of interest? The results of the project were disseminated to the community via two peer-reviewed journal publications, listed below. 1. Kim, J. and Vanapalli, S. A. Microfluidic production of spherical and non-spherical fat particles by thermal quenching of crystallizable oils. Langmuir. Accepted, 2013. 2. Sun, M. and Vanapalli, S. A. Generation of chemical concentration gradients in mobile droplet arrays via fragmentation of long immiscible diluting plugs. Analytical Chemistry, 85, 2044-2048, 2013. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Food products such as ice cream and butter use crystallizable food oils, and capabilities to generate fat particles of finely controlled size, shape and compositon from such materials provides new avenues to control the microstructure and rheology of foods. In this project period, we focused on microfluidic production of spherical and non-spherical fat particles from crystallizable food oils (palm fat). The method is based on microfluidic production of oil droplets at a cross-junction followed by thermal solidification downstream in a microcapillary. We varied the drop production conditions and the device temperature and demonstrate that spherical or non-spherical, and liquid or solidified fat droplets can be fabricated. By measuring thermal gradients in the microcapillary, we observed that crystalline fat particles are best produced when the device temperature is below the onset temperature of bulk fat crystallization. For the production of monodisperse non-spherical fat particles, we also found that the carrier fluid flow rate needs to be high enough to provide strong hydrodynamic forces to transport the confined rod-like particles. We identified the scaling relationship between geometric confinement and particle elasticity necessary to maintain the non-spherical shape. Thus, our study provided guidelines for the production of spherical and non-spherical fat particles that can be potentially used for controlling microstructure, rheology and drug encapsulation in foods and pharmaceutical creams that employ crystallizable oils. Because of the low throughput (i.e. lack of sufficient sample), we could not accomplish the final objective of measuring the rheological properties of non-spherical fat particles. However, we measured the rheology of bulk fats (palm oil) and showed that elastic properties of fats play a crucial role in controlling the non-spherical fat particles (Kim and Vanapalli, Langmuir, 2013). Our project results revealed that the throughput of production of microfluidic fat particles is low, and is unsuitable for conventional bulk food production. However, the well-controlled environment offered by microfluidics enabled us to establish design rules for the production of spherical and non-spherical fat particles, which could have been difficult to glean from conventional emulsification techniques. Given the establishment of design rules, opportunities now exist to incorporate them into conventional emulsification methods. For example, oil-in-water emulsions made from conventional methods could be forced through thermally cooled membranes that contain cylindrical pores (similar to membrane emulsification), which will allow not only bulk-scale production of anisotropic fat particles but also of sizes much smaller than demonstrated in our project. Thus, our findings are likely to improve bulk food processing methods. A secondary outcome that resulted in this project period (which was not part of the original objectives) was development of a new microfluidic technique that allows fine control in tuning the chemical composition of dispersed phase in droplets (Meng & Vanapalli, Anal Chem., 2013) This technique could be useful for food emulsions to finely control the lipid composition in fat droplets. However, as is typical with microfluidic techniques, the throughput is limited, so other avenues need to be investigated to apply this new method to bulk-scale food emulsion production - which is beyond the scope of the current project.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Sun, M. and Vanapalli, S. A., Generation of chemical concentration gradients in mobile droplet arrays via fragmentation of long immiscible diluting plugs. Analytical Chemistry, 85, 2044-2048, 2013
- Type:
Journal Articles
Status:
Submitted
Year Published:
2013
Citation:
Kim, J. and Vanapalli, S. A., Microfluidic production of spherical and non-spherical fat particles by thermal quenching of crystallizable oils. Langmuir, Submitted, 2013
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Progress 09/01/11 to 08/31/12
Outputs
Target Audience: The PI's group presented the progress on the grant made in this project period (Sept, 2011 to Aug 2012) at the Annual Meeting of the Institute of Food Technologists as well as the USDA NIFA/AFRI Project Directors Meeting, held in Las Vegas. The target audience at this meeting were food scientists, food technologists, food product developers and professionals from the food industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The project provided education and training for one postdoctoral researcher (1 FTE) and one graduate student (0.0083 FTE). The graduate student attended a national conference (IFT) that led to networking and professional development. How have the results been disseminated to communities of interest? The results were disseminated to the communities of interest via two conference presentations. 1. Microfluidic production of food emulsions containing anisotropic-shaped fat particles, IFT June, 2012, Las Vegas 2. Microfluidic production of food emulsions containing anisotropic-shaped fat particles, USDA NIFA/AFRI Project Directors Meeting, 2012, Las Vegas What do you plan to do during the next reporting period to accomplish the goals? We have received a no-cost extension on the project to accomplish the remaining goals of the project. During the next project period we will focus on (1) Understanding what controls the non-spherical fat particle shape, in terms of droplet size and solid fat content (2) We will attempt to increase the throughput of production, in order to conduct rheological measurements on suspensions of non-spherical fat particles. (3) We will also submit manuscripts detailing our work to peer-reviewed journals
Impacts
What was accomplished under these goals?
Shape of particles such as ice crystals and fat particles contribute significantly to the rheology of food suspensions. For example, at the same volume fraction, a suspension of ellipsoids can generate larger shear viscosity that a suspension of spherical particles. Thus, designing particles of non-spherical shape and using them as food additives offers a promising route to control the rheology of food suspensions. However, methods to produce anisotropic food particles are scarce. In this project period, we developed microfluidic techniques to generate ellipsoidal fat particles. We assembled cross-flow microfluidic devices, using commercially available parts and fittings. We use palm oil (Sans Trans 35) as the dispersed phase and 2% Tween 20 as the continuous phase. We preheat both the continuous and dispersed phases and inject them using syringe pumps into the cross-flow device. Oil droplets produced at the cross-junction are carried downstream. We control the temperature of the downstream section to induce crystallization in the flowing droplets. Droplet generation is viewed using optical microscopy and image analysis is conducted to quantify droplet sizes. We find that confinement of the droplets in the microchannel together with partial-solidification of the droplets enables optimal production of ellipsoidal fat particles. The control parameters including local temperature, residence time, and flow rates of the incoming fluids sensitively affected the ability to continuously produce fat particles. The drop speed required for the production of ellipsoidal particles was lower than that for spherical fat particles. In addition, higher aspect ratio fat particles were obtained at lower temperature. We also observed that ellipsoidal particles of large aspect ratio were difficult to produce because these particles blocked the microcapillaries disrupting the fluid flow.
Publications
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Progress 09/01/10 to 08/31/11
Outputs
Target Audience: The PI and his group presented the progress on the grant made in this project period (Sept, 2010 to Aug 2011) at the Annual Meeting of the Institute of Food Technologists as well as the USDA NIFA/AFRI Project Directors Meeting, held in New Orleans. The target audience at this meeting were food scientists, food technologists, food product developers and professionals from the food industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The project provided education and training for one postdoctoral researcher and one graduate student. The training involved mastering microfabrication techniques, controlling fluid flows in miniaturized devices and integrating temperature control units. The PI attended a national conference that led to networking and professional development. How have the results been disseminated to communities of interest? The results were disseminated to the communities of interest via two conference presentations. 1. Microfluidic production of monodisperse crystalline fat droplets, IFT July, 2011, New Orleans 2. Microfluidic production of monodisperse crystalline fat droplets, USDA NIFA/AFRI Project Directors Meeting, New Orleans What do you plan to do during the next reporting period to accomplish the goals? In the next project period we will focus on producing non-spherical fat particles using the set up developed (in this project period). This will require confining the produced droplets in microcapillaries followed by thermal solidification. Our technical goal is to identify the flow and thermal conditions that will allow production of non-spherical fat particles.
Impacts
What was accomplished under these goals?
The goal during this project period was to integrate temperature control units in microfluidic devices so as to locally heat and cool aqueous and oil phases that will allow production of crystalline fat droplets. To facilitate the production of crystalline fat droplets, we integrated peltier units to locally control the temperature at different regions in the device. We used hexadecane and palm oil as dispersed phases with Tween 20 as the emulsifier. We find that the ability to produce spherical fat droplets consistently requires that the droplets are unconfined in the microchannel. Moreover, we observed that to induce crystallization in the droplets, the local temperature in the device needs to be close to the bulk melting point of the fat. The droplet sizes that could be achieved were dictated largely by the microcapillary diameter.Overall, we find that our strategy to integrate peltier units on chip is effective for producing uniformly sized fat droplets that are spherical in shape.
Publications
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Progress 09/01/09 to 08/31/10
Outputs
Target Audience: The PI and his group presented the progress on the grant made in this project period (Sept, 2009 to Aug 2010) at the Annual Meeting of the Institute of Food Technologists as well as the USDA NIFA/AFRI Project Directors Meeting, held in Chicago. The target audience at this meeting were food scientists, food technologists, food product developers and professionals from the food industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The project provided education and training for one graduate student and one technician (both females). The training involved learning how to fabricate microfluidic devices and generate droplets. During this project period, the PI received professional development by attending a national conference (Institute of Food Technologists). How have the results been disseminated to communities of interest? The results were disseminated to the communities of interest via two conference presentations. 1. Engineering microfluidic devices for generating oil-in-water food emulsions, IFT July, 2010, Chicago 2.Engineering microfluidic devices for generating oil-in-water food emulsions, USDA NIFA/AFRI Project Directors Meeting, Chicago What do you plan to do during the next reporting period to accomplish the goals? The next project period will focus on integrating thermal control units into microfluidic devices to induce fat crystallization. This will allow us to test whether crystalline spherical fat particles of controlled size and composition can be generated using microfluidics.
Impacts
What was accomplished under these goals?
In this project period, we focused on the first objective in the project; which involved developing microfabricated devices for robust production of oil-in-water emulsions. We fabricated "flow-focusing" microfluidic devices using soft lithography. To facilitate the production of oil-in-water emulsions we modified the surface properties of the microchannels by exposure to plasma. We used hexadecane and palm oil as dispersed phases. The continuous phase is deionized water premixed with Tween 20 as the emulsifier. The flow rate ratio of the dispersed and continuous phase is varied from 0.05 -2. Droplet generation is viewed using optical microscopy and image analysis is conducted to quantify droplet sizes. We find that surface wettability modification of channel walls by plasma exposure, enables consistent production of monodisperse oil-in-water emulsions for < 3 days. Beyond this period, the devices lose wettability and droplet generation is uncontrolled yielding non-uniform droplet sizes. The droplet size is not strongly dependent in the explored flow rate ratio regime. These results should pave the way for further optimization of process parameters to control droplet size and throughput for production of food emulsions, using microfluidic devices.
Publications
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