Progress 10/01/10 to 09/30/15
Outputs
Target Audience:Researchers, scientists, teachers, engineers, trade associations, and commercial handlers and shippers of food. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Research projects involved graduate students and post-doctoral scholars. They received training in conducting experiments, analyzing data, preparing oral presentations, and writing technical papers for journals. The pedagogical content in food engineering was used in teaching students enrolled in undergraduate programs. The students were able to work with computational models to enhance their learning of food processing operations. How have the results been disseminated to communities of interest?The results of this project were disseminated using oral presentations at national and international conferences, written papers published in peer reviewed journals, and online content made available on the Internet. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Research on developing new data on engineering properties of foods included studies on hydrogels subjected to freeze/thaw cycles, water adsorption by almonds and pistachios during storage, and sustained release of nutrients in food processing. The water distribution in hydrogels was studied using hydrogels prepared from xanthan, curdlan and a mixture of curdlan and xanthan. Magnetic Resonance Imaging (MRI) was used to assess the water distribution and changes in NMR relaxation times. It was found that xanthan­curdlan hydrogel complex (XCHC) is capable of retaining moisture up to 5 freeze thaw cycles. The effect of water distribution and interaction was studied with 2.0% aqueous solutions of xanthan, curdlan, and XCHC consisting of equal amounts of both polysaccharides. A gel structure with an indication of syneresis was clearly seen in the MR image of curdlan alone, whereas the distribution of protons throughout xanthan and XCHC samples remained homogeneous and showed no detectable syneresis. The three-dimensional network, indicated by frequency sweeps, of curdlan was responsible for curdlan's gel structure. The combination of texture measurements and discrete noninvasive techniques was found capable of providing insightful understanding of water distribution in a gel system. To improve our knowledge of the water adsorption by almonds during storage, the effect of water activity (aw) on mechanical properties of raw and blanched California grown "Carmel" variety almonds at different temperatures was investigated. The equilibrium moisture contents of raw and blanched almonds were determined by using static gravimetric method at 25, 35 and 45 degree Celsius over a range of water activities from 0.11 to 0.97. GAB model was found to adequately describe the sorption characteristics of raw and blanched almonds. The increase in water activity caused a progressively higher stiffness at low aw (less than 0.33). For both raw and blanched almonds, at low aw (0.11-0.32), the mechanical properties were relatively similar without significant difference. At aw above 0.75, raw almonds began to lose their brittleness, as moisture adsorption showed significant plasticization effect on raw almonds. The textural properties of blanched almonds showed dramatic change at aw above 0.65. Water plasticization effect was more significant with an increase in temperature. Follow up studies included water uptake kinetics for three almond varieties (Nonpareil, Monterey and Carmel) over a range of aw (0.11-0.97) and temperatures (7 to 50 degree Celsius). The effective diffusion coefficient (Deff) of water in an almond kernel was calculated using Fick's second law of diffusion. It was found that the Deff increased with temperature at a constant aw. At a constant temperature, Deff decreased with an increase in aw. The activation energy was obtained in the range of 16.2-75.5 kJ/mol and 37.8-46.7 kJ/mol for pasteurized and blanched almonds, respectively. These data are useful in predicting moisture adsorption behavior of California grown almond varieties. When pistachios, representing another major California crop, are stored in humid environments, they lose the consumer-favored crunchy texture and develop mold. Therefore, knowledge of moisture uptake and textural changes in pistachios at various conditions is invaluable to handlers and shippers. Adsorption isotherms and moisture kinetics of raw Kerman variety of pistachios were obtained using the gravimetric method while texture was quantified using a TA.XT2 texture analyzer with a 1-mm penetration probe. Adsorption isotherms were obtained experimentally at 5 temperatures, from 7 to 50 degrees C, and 7 relative humidity levels ranging from 11 to 82 percent. Effective diffusion coefficients of water in raw pistachios were estimated by fitting Fick's 2nd law to the moisture kinetics data at high relative humidity levels above 42 percent. The diffusion coefficients increased with increasing temperature. With texture, the yield force, hardness, and stiffness of raw kernels decreased with increasing moisture content. The adsorption isotherms, diffusion coefficients, and texture analysis were combined into a mathematical model to allow for the prediction of moisture content and texture of raw pistachio kernels during different storage conditions. The inputs of this model included temperature, relative humidity, storage time, and the initial moisture content of raw pistachio kernels. The outputs included the moisture content, texture, and water activity of the kernels. The model is useful for the optimization of packaging design and determining suitable storage conditions for pistachios. To improve our understanding of physical processes that govern gastric digestion of foods, a comprehensive study was aimed at modelling the fluid-mechanical forces in a human stomach. Computational fluid dynamics (CFD) techniques were used to develop a 3-D model of the geometry and motility of the stomach during digestion, and used to characterize the fluid dynamics of gastric contents with different rheological properties. A geometrical model of an averaged-sized human stomach was created. The gastric motility was characterized by a series of antral contraction waves (ACWs) that originate every 20s at the mid corpus and propagate towards the pylorus at 2.5mm/s (where they lead to a relative occlusion of 80%). The transient, laminar and incompressible flow within the stomach was numerically predicted for two Newtonian fluids (1cP and 1000cP, respectively) and a pseudoplastic solution (10% oat bran). The gastric flow strongly depended on the viscosity of gastric contents. For the water-like fluid, the increasing speed and occlusion of the ACWs developed a strong retropulsive jet and a series of low velocity eddies that mix and grind gastric contents. However, by increasing the viscosity of the fluid or changing its Newtonian characteristics, the jet-like motion was lost, a steeper tail in the distribution of the velocity field was observed, and a pressure field, two orders of magnitude bigger, developed. These results illustrated the capability of CFD to provide a unique insight into the fluid-dynamics of the gastric contents, and to develop a fundamental understanding and modeling of the mechanisms involved in the digestion process. With the goal of developing pedagogical methodologies for improved learning of food engineering principles, use of video games, simulated virtual laboratories and video lectures were developed. A computer video game (Beerlsland) was developed to teach College level students various aspects of brewing. For this project, Autodesk Maya was used to create various game objects, and Unity3D Pro was used to create the video game. In the game, a student discovers the principles of food science/engineering as applied in a real-world setting of a brewery. For each processing step, pedagogical elements were incorporated with different levels of challenge. Engaging questions from various fields of study representing a typical undergraduate curriculum in food science were included. The video game was used in a laboratory course taught to Senior level students at UC Davis and made available on the Internet for wider use for teaching at other stations. A set of 25 virtual experiments were developed based on process simulations written in Javascript for use on the Internet with any operating system including mobile devices such as tablet and smartphones. A set of 150 video tutorials of lectures on food engineering topics, for use in flipped classroom method of teaching, were developed on selected topics such as heat transfer, refrigeration, and freezing. These virtual laboratories and tutorials were made available at www.rpaulsingh.com. The feedback received from collaborating stations was helpful in developing new educational contents.
Publications
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: The target audience of this research is peer scientists working on topics related to gastric digestion of foods. Results of this work was presented at the annual meeting of the Institute of Food Technologists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? A postdoctoral scholar (Jerry Xue) was trained to implement computational code for predicting mixing in gastric environment. How have the results been disseminated to communities of interest? Talks presented at the Annual meeting of the Institute of Food Technologists What do you plan to do during the next reporting period to accomplish the goals? Continue development of advanced computational models of mixing and food disintegration during gastric digestion.
Impacts
What was accomplished under these goals?
The mechanical disintegration of food during gastric digestion is central to nutrient bioavailability. Little is currently known regarding the role of material properties on the breakdown behavior of food during digestion. This study investigated the effect of gastric juice on the material properties and subsequent disintegration of a particulate food system when exposed to different bulk loading conditions. Steamed potato cubes (5mm) were soaked in simulated gastric juice (pH 1.8) up to 4 hours, and exposed to four different bulk compressions (20%-80%). Changes in the strength, elasticity, toughness, and surface hardness of the particles were monitored (TA-XTPlus texture analyzer). Compressed particles were dyed with an iodine solution for image capture (Nikon 1, 40mm lens) and size distributions were determined using Matlab. Exposure to gastric juice significantly affected the potato material properties; just 1h of soaking decreased the potato strength, toughness, and elasticity by over 60% and the surface hardness by over 20%. Particle area distributions exhibited a bimodal distribution, with one component always associated with particles similar in size to the original. Regardless of soaking time and compression level, particle breakdown mainly occurred due to surface damage. Fragmented particles accounted for no more than 15% of the total area, with this contribution decreasing as the structure weakened by soaking. The area of fines <1.6mm2 significantly increased by compression level and soak time (p<0.002), ranging from 10%-60% after one hour of soaking to 20%-73% after four hours. The particle area accounting for the first 10% of the cumulative area (A10) decreased with the same factors (p<0.001), with four hours of soaking always leading to A10 values smaller than 0.05 mm2. Results illustrate the role material property changes during digestion play on the breakdown behavior of solid foods and provide the data needed to further investigate and model this relationship.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Minekus, M., Alminger, M., Alvito P., Ballance S., Bohn T., Bourlieu C., Carri`ere F., Boutrou R., Corredig M., Dupont D., Dufour C., Egger L., Golding M., Karakaya S., Kirkhus B., Le Feunteun S., Lesmes U., Macierzanka A., Mackie A., Marze S., McClements D. J., M�enard O., Recio I., Santos C. N., Singh R. P., Vegarud. G.E., Wickham M. S. J., Weitschies W. and A. Brodkorb 2014. A standardized static in vitro digestion method suitable for food - an international consensus. Food and Function. 5:1113-24.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
rechsler, K., Ferrua, M.J. Singh, R.P. 2014. Role of Gastric Juice on the Material Properties and Mechanical Disintegration of Solid Food. 2014 IFT Annual Meeting, Institute of Food Technologists, New Orleans, LA. Abstract No. 024-18
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Bornhorst G.M., R.P. Singh. 2014. Gastric digestion in vivo and in vitro: How the structural aspects of food influence the digestion process. Annual Review of Food Science and Technology. 5:111-132.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Bornhorst G.M., H. Hivert, R.P.Singh. 2014. Rice bolus texture changes due to alpha amylase. LWT-Food Science and Technology. 55(1):27-33.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Target audience of this research involves peers and industry practitioners who are working in the area of food digestion and nut processing and the use of nuts as ingredients in food formulations. Results from this research were reported at the annual conference of the Institute of Food Technologists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Two post-doctoral scholars (Jerry Xu, Gail Bornhorst), one graduate student (David Phinney) and two undergraduate interns (Yamile Mennah and Krista Dreschler) were trained in the area of food digestion and in conducting in vivo and in vitro studies. How have the results been disseminated to communities of interest? Posters and talks were presented at the 2013 annual meeting of the Institute of Food Technologists. What do you plan to do during the next reporting period to accomplish the goals? Research is continuing on computational modeling of food breakdown and mixing in the human stomach during digestion.
Impacts
What was accomplished under these goals?
What was accomplished under the major goals of this project? (more info…) Thermal processing of foods may influence food structure, causing changes in food digestion and nutrient absorption. A comprehensive study was conducted to examine the ileal digestibility of crude protein and amino acids in pigs that consumed a meal of raw or roasted diced almonds. Pigs were chosen as an appropriate model of human gastro-intestinal tract. Seventy-two male pigs (23.0 +/-0.2 kg bodyweight) were fed raw and roasted diced almonds for 1 wk. Pigs were fed a final meal of only raw or roasted almonds, labeled with indigestible markers titanium dioxide and chromium oxide. At 8 and 12 h after meal consumption, pigs were euthanized, and samples were taken from the terminal ileum. True ileal digestibility of protein and amino acids was calculated using the protein or amino acid content, titanium, and chromium marker concentrations, and previously reported values for endogenous nitrogen and amino acid content in the small intestine. At 12 h after meal consumption, true ileal digestibility of crude protein was 74.7+/-2.9% in raw almonds and 67.3 +/-6.9% in roasted almonds. Crude protein digestibility was not statistically significant between almond type or digestion time. Overall, amino acids had a higher digestibility in raw almonds compared to roasted almonds. For example, in the terminal ileum 12 h after meal consumption, threonine digestibility was 79.8 and 0% and leucine digestibility was 79.0 and 40.6% for raw and roasted almonds, respectively. Almond type was statistically significant in the digestibility of aspargine, threonine, serine, proline, glutamine, valine, leucine, and tyrosine (p < 0.05), with raw almonds having increased digestibility compared to roasted almonds. In conclusion, roasting influenced the amino acid but not the crude protein almond digestibility. This suggests that thermal processing of almonds may alter the protein structure, influencing the specific digestion of amino acids. These findings help establish a link between food processing and nutrient breakdown and absorption. Another study was conducted to understand changes in the mechanical properties of foods during gastric digestion due to their influence on the overall rate of breakdown, gastric emptying, and ultimately nutrient release. The aim of this in vitro study was to examine textural changes and moisture absorption in diced raw and roasted almonds in a simulated gastric environment. Diced almonds were soaked in simulated saliva and gastric juice for 13 time periods up to 24 h under static and bi-directional shaking conditions at 37 C. Texture changes were measured by bulk compression with a TA-94 back extrusion cell (Texture Technologies Corp., Scarsdale, N.Y.). Bulk compression results showed that a rapid decline in the peak (fracture) force and the compression work occurred during the first 5 min of soaking, with average peak force values decreasing from between 245 and 490 N (undigested almonds) to between 20 and 79 N after 5 min of digestion of raw and roasted almonds, respectively. A rapid increase in almond moisture content was similarly observed with increased soaking time during the first 5 min of soaking. Moisture content values increased from an average of 4.2 and 1.2% to 26.7 and 22.9% after 5 min of soaking, for raw and roasted almonds, respectively. The rate of change in the peak force, compression work, and moisture content decreased over the 24-h digestion period, with the greatest change occurring during the first hour of digestion. Almond type (raw or roasted), particle size (small or medium diced), and digestion time all significantly affected the peak force, compression work, and moisture content (p < 0.01). The specific changes in almond breakdown during digestion caused by almond particle size and roasting conditions need to be fully understood, as they may influence the satiation properties and nutrient release from almonds.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Citation: G.M. Bornhorst, M.J. Roman, S.M. Rutherfurd, B.J. Burri, P.J. Moughan, R.P. Singh. 2013. Gastric digestion of raw and roasted almonds in vivo. Journal of Food Science. 78(11): H1807-H1813.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
G.M. Bornhorst, M.J. Roman, K.C. Dreschler, R.P. Singh. 2013. Physical property changes in raw and roasted almonds during gastric digestion in vivo and in vitro. Food Biophysics. DOI: 10.1007/s11483-013-9315-2.
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: The results from this project were presented at the Annual meeting of Institute of Food Technologists. A model developed in this study was also made available to the pistachio industry via the internet. PARTICIPANTS: R. Paul Singh, Principal Investigator, directed the research, data analysis and publication of results. Annie Dai, Graduate Research Assistant, conducted research, data analysis and prepared results for publication. TARGET AUDIENCES: Target audience of this research involves industry practitioners and peers working in the area of nut processing and strorage. Results from this research were reported at the annual conference of Institute of Food Technologists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
During the storage and shipping of raw pistachios, their quality deteriorates as they absorb moisture from their surroundings. At high moisture contents, they lose the consumer-favored crunchy texture and develop mold. However, maintaining them at low moisture contents may be more costly. Therefore, information regarding the moisture content and texture of pistachios at various conditions is valuable in maximizing quality of pistachios and minimizing costs during storage and shipping. For this research, adsorption isotherms and moisture kinetics of raw Kerman pistachios were obtained using the gravimetric method while texture was quantified using a TA.XT2 texture analyzer and a 1-mm penetration probe. Adsorption isotherms were obtained experimentally at 5 temperatures-7 C, 25 C, 35 C, 45 C, and 50 C-and 7 relative humidity levels ranging from 11 to 82 percent. Effective diffusion coefficients of water through raw pistachios were estimated by fitting Fick's 2nd law to the moisture kinetics data at high relative humidity levels above 42 percent. The diffusion coefficients increased with increasing temperature and decreasing relative humidity. At 35 C, these coefficients ranged from 0.10 to 0.20 square mm per hr while at 45 C, they ranged from 0.15 to 0.54 square mm per hr. With texture, the yield force, hardness, and stiffness of raw kernels decreased with increasing moisture content. Finally, the adsorption isotherms, diffusion coefficients, and texture analysis were combined into a mathematical model via MatLab to allow for the prediction of moisture content and texture of raw pistachio kernels during different storage conditions. The inputs of this model are temperature, relative humidity, storage time, and the initial moisture content of raw pistachio kernels. The outputs include the moisture content, texture, and water activity of these kernels. The computational program may be accessed by pistachio processors to aid in the optimization of packaging design and storage conditions for pistachios. This model has been made available to the pistachio industry.
Publications
- Dai, A., and R. P. Singh. 2012. Predicting the Moisture Content and Texture of Raw Kerman Pistachio Kernels During Storage Poster (#077-88) presented at the meeting of 2012 Institute of Food Technologists(IFT) Annual Meeting & Food Expo. Las Vegas, Nevada, U.S.A.
- Dai, A. 2012. Predicting the Moisture Content and Texture of Raw Pistachio Kernels During Storage, MS Thesis. Department of Biological and Agricultural Engineering, University of California, Davis.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: The results from this project were presented at the Annual meeting of Institute of Food Technologists PARTICIPANTS: R. Paul Singh, Principal Investigator, directed the research, data analysis and publication of results. Li Taitano, Post-doctoral scholar, conducted research, data analysis and prepared results for publication. TARGET AUDIENCES: Target audience of this research involves peers working in this field. Results from this research were reported at the annual conference of Institute of Food Technologists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Data on the kinetics of water adsorption in almonds is necessary in designing storage and distribution systems to maintain quality. Quantitative information on moisture movement inside an almond kernel is used to develop computational models to predict shelf life of almonds. The main objective of this study was to obtain the kinetics of water adsorption in unpasteurized, pasteurized and blanched almonds during storage at different water activities and temperatures. Water uptake for three almond varieties (Nonpareil, Monterey and Carmel) was studied over a range of water activities (0.11-0.97) and temperatures (7 to 50 C). The weights of almonds were measured until samples reached a constant weight. The diffusion coefficient of water in an almond kernel was calculated based on Fick's second law of diffusion. In addition, a simple empirical model was used to describe the kinetics of water adsorption in almonds. It was found that the diffusion coefficient increased with temperature at a constant water activity. At a constant temperature, effective diffusion coefficient decreased with an increase in water activity. The diffusion coefficient for pasteurized and blanched almonds of Carmel variety ranged from 1.20x10^(-8) to 5.69x10^(-8)m^2/h and 2.33x10^(-8) to 37.35x10^(-8) m2/h at temperature ranging from 25 to 45 C, respectively. The activation energy was obtained in the range of 16.24 to 75.52 kJ/mol and 37.87 to 46.74 kJ/mol for pasteurized and blanched almonds, respectively. Kinetic compensation relationship was valid between the Arrhenius activation energy and pre-exponential coefficient for pasteurized and blanched almonds. The rate constants obtained using empirical model were temperature dependent which could also be described by the Arrhenius equation. The findings of this study provide reliable data for developing predictive models to describe water uptake during the storage of almonds. Water uptake remains the most critical factor in determining the textural quality of the almonds during storage.
Publications
- Thompson, J.F., Mejia, D. and R.P. Singh 2011. Energy use of commercial forced-air coolers for fruit. Applied Engineering in Agriculture. 26(5): 919-924
- Singh, R.P. and S. Debnath. 2011. Heat and Mass Transfer in Foods during Deep-Fat Frying. In Chapter 11 in Frozen and Refrigerated Doughs and Batters, Edited by K. Kulp, K. Lorenz, and J. Brummer, 2nd edition. American Association of Cereal Chemists, Inc.
- Singh, R.P. and S.E. Zorrilla. 2011. Process and Plant Design. In Encyclopedia of Dairy Sciences. Ed. Fuquay, J.H., Fox, P.F. and P. L.H. McSweeney. 2nd Ed. Volume 4. p 124-133. Academic Press, London, UK.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: The results of this work were presented at the Annual meetings of the Institute of Food Technologists. PARTICIPANTS: R. Paul Singh, Principal Investigator. Directed the research, data analysis and publication of results. Jessica Widjaja, MS student and Fanbin Kong, Postdoctoral Scholar conducted research, data analysis and prepared results for publication TARGET AUDIENCES: Target audience of this research involves peers working in this field. Results from this research were reported at the annual conference of Institute of Food Technologists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Knowledge about gastric juice migration into food during digestion is limited. During the food digestion process, as gastric juice penetrates into food, it creates a moving boundary, which differentiates the softer texture due to the action of the gastric juice from the initial texture of the food. The goal of this work was to study the kinetics of gastric juice diffusion and evaluate the location of the moving boundary by measuring texture and using image analysis. Potato samples, cut in cylindrical shape, were submerged in simulated gastric juice for 4 hr and the texture change in the samples was measured every 1 hr using a 2 mm flat-ended probe in a Texturometer (TA-XT2). Methylene blue dye was added into gastric juice to visualize its diffusion into the sample. A blue visible region, showing the gastric juice penetration profile, was observed by taking images using a digital camera and the profile was analyzed for its intensity distribution using Image J software. Analytical solution of the Ficks diffusion equation was applied to determine the effective diffusivity of gastric juice into the food matrix. The viscosity of gastric juice was modified by adding guar gum (0.75% and 1.5% w/v) and the pH of gastric juice was varied from 1.8 to 3.0 and 5.3. It was found that gastric juice diffusion into solid foods depends on the pH of gastric juice, but not necessarily on the viscosity of gastric juice. Of the 3 treatments, only pH 1.8 gastric juice destroyed the potato cell structures, reduced the potato firmness, and consequently increased the gastric juice diffusion into potato. The formation of a tender layer due to the enzymatic hydrolysis action of gastric juice in softening the potato structures was only observed when the pH of the gastric juice was adjusted from 3.0 or 5.3 to 1.8, suggesting that there was an upper limit in pH required to alter the potatos cellular structures and allow the gastric juice to penetrate deeper into potato tissue. The effect of increasing guar gum concentration (to 1.5% w/v) on slowing down the gastric juice diffusion into potato and decreasing the tender layer thickness was observed only in pH 1.8 gastric juice but not at pH 3.0 or 5.3. Once the potato cell structures were destroyed due to the action of acid in the gastric juice, guar gum could penetrate and delay the diffusion of gastric juice into the potato. Therefore, it was determined that the internal resistance of the potato cellular structure remains the major rate limiting step of gastric juice diffusion into potato. The results of this study provide new evidence of the role of microstructure of food and its material properties in controlling food digestion in simulated gastric environment.
Publications
- Kong, F. and Singh, R.P. 2010. Solid loss of carrots during simulated gastric digestion. Food Biophysics. Volume 6, Issue 1, pp 84-93
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: The results of this work were presented at the Annual meetings of the Institute of Food Technologists. One paper was published in Food Biophysics. PARTICIPANTS: R. Paul Singh, Principal Investigator. Directed the research, data analysis and publication of results. Fanbin Kong, Postdoctoral Scholar. Conducted research, data analysis and prepared results for publication. TARGET AUDIENCES: Target audience of this research involves peers working in this field. Results from this research were reported at the annual conference of Institute of Food Technologists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
In understanding the food disintegration kinetics during digestion, our studies focused on the digestion of almonds. We investigated the role of food processing in changing the physical properties of foods and how gastric digestion of processed food is then modified. Knowledge of disintegration rate of almonds in human stomach, as affected by roasting, is critical to establishing processing conditions at the manufacturing stage to achieve desirable release of nutrients in the gastrointestinal tract. The objective of this study was to investigate how roasting affected almond disintegration properties in simulated gastric environment. California grown Nonpareil almonds (whole kernel seeds) were roasted at 145C for 9 min, 185C for 6 min and 185C for 9 min, respectively. Raw and roasted almonds were cut into cube shape (6 6 4 mm) and tested in a model stomach system to determine their disintegration rates. Almonds were soaked in simulated juice for 16 hrs to compare water absorption, volume change and mass loss of raw and roasted almonds during digestion. Both compression and penetration tests were used to investigate the textural changes of almonds. Light Microscopy and Transmission Electronic Microscopy were used to study the change in the microstructure of almonds after simulated digestion. Roasting significantly improved the disintegration rate of almonds, with half time decreasing from 10 hrs for the raw almonds to 7 hrs for the almonds roasted at 185C for 9 min. Compared with raw almonds, roasted almonds had less water absorption and swelling, and higher mass loss during static soaking. Penetration test is more capable than compression test in differentiating the texture of almonds before and after soaking in the simulated gastric juice. Microstructure examination of partially digested almonds showed breakage and breach of cell walls due to acid hydrolysis, and intercellular and intracellular channels created during roasting that facilitated fast penetration of gastric juice.
Publications
- Kong, F. and R.P. Singh. 2009. Modes of Disintegration of Solid Foods in Simulated Gastric Environment. Food Biophysics. 4:180-190
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The results of this work were presented at the annual meeting of the Institute of Food Technologists and the International Conference on Engineering and Food. Two papers were published in the Journal of Food Science. Two more manuscripts are currently under review. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Mechanistic understanding and kinetics of food disintegration in the human stomach is essential in developing structured foods targeted for health purposes. This information is also necessary to develop a strategy for controlled release of food nutrients at desired sites in the gastrointestinal tract. The objective of this study was to investigate the influence of different food processing steps on disintegration of solid foods (peanuts) in simulated gastric environment. Raw and processed peanuts were used as representative foods for this research. For processed samples, the peanuts were either fried in soybean oil or roasted in an oven at 170 degrees Celsius for 6 min. The peanuts were cut into 2 to 3 mm cubes. The dynamic disintegration test was conducted in an in vitro stomach system, which consisted of a turn-table and a chamber containing simulated gastric juice (37 degrees Celsius). The disintegration performance of each sample was evaluated by measuring the sample weight at 30 min intervals. Samples were soaked in the simulated gastric juice for 4 hrs to determine changes in the texture and moisture of peanuts under static conditions. The moisture content and hardness of soaked samples were determined. The disintegration rate of tested peanuts was in an order of roasted, greater than, fried, greater than, raw, with a mass retention ratio (wet basis) of 65 percent, 75 percent and 95 percent, respectively, after 4 hrs trial. This order showed a good correlation with the moisture content of the soaked samples (roasted, greater than, fried, greater than, raw) and the same order observed for the sample hardness after soaking. The results indicated that frying and roasting enabled a higher water absorption capacity in the processed peanuts, resulting in a lower strength of the food matrix during digestion and consequently a faster disintegration in the stomach. The results provided quantitative evidence of increased peanut disintegration due to processing, and provided useful information for selecting processing methods to obtain optimum disintegration of foods in stomach. The in vitro stomach system developed in this project provided a reliable means to study food disintegration. Knowledge of the kinetics of food breakdown in the human stomach will enable improvements in food processing methods for optimal nutrient delivery.
Publications
- Kong, F. and Singh, R.P. 2008. A model stomach system to investigate disintegration kinetics of solid foods during gastric digestion. Journal of Food Science 73(5): E202 E210.
- Kong, F. and Singh, R.P. 2008. Disintegration of solid foods in human stomach (Review). Journal of Food Science 73(5): R67 R80.
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Progress 01/01/07 to 12/31/07
Outputs
Upon ingestion, food particulates are conveyed in a bolus to the stomach where further size reduction takes place by chemical and physical forces. Stomach wall contracts to form a wave shaped deformation in the antral region of the stomach. An antral contraction wave starts from the middle of the stomach wall and moves towards the pylorus. Propagation of contraction waves along the stomach wall results in a complex peristaltic flow of gastric juice inside the stomach. The churning effect causes the disintegration of food particulates (<2mm). The goal of our research is to develop rigorous computer models of the flow field inside the stomach to understand the process of food breakdown and digestion. We developed a 3-dimensional computational model of the human stomach. The model can simulate the unsteady flow field generated due to the movement of contraction waves of the stomach wall. The size, shape and movement of the contraction waves were obtained from the reported
measurements of human stomach using MRI. The low velocity and highly viscous flow inside the human stomach is in the laminar regime according to recent studies. The model uses the Navier-stokes equations for fluid flow with deforming boundary walls. Fluent, a computational fluid dynamics (CFD) solver was used to solve the flow equations. The flow profile obtained by the CFD model shows the basic features reported in the literature (flow recirculation and retrograde jet). The predicted strain rate was higher near the occlusion created by the contraction waves in the antral stomach region. Food particulates are expected to undergo maximum erosion in this region. Flow was minimal in the fundus region. Using this flow information one can predict the breakdown and release of nutrients from a given food particulate for designing novel foods for sustained health.
Impacts
The CFD model of the flow field in a human stomach is useful to predict the role of food structure and properties in nutrient release during digestion.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
Increasing evidence in the scientific literature indicates that optimum efficacy of many healthy nutrients in a food is realized only when those nutrients are released in a desired region of the human gastrointestinal tract (GIT). Notable examples in the marketplace are probiotics in yoghurt and omega-3 oils in snack bars to promote a healthy colon. When these nutrients are introduced into a food, using technologies such as microencapsulation, they must be protected from the detrimental physico-chemical environment of the stomach and released later in the colon. Thus for the purposes of targeted-delivery (TD) of nutrients, the food processing chain must encompass the GIT. There is an identified need in the food industry to develop predictive capabilities to determine appropriate processing conditions during food manufacturing that ensure reliable delivery of nutrients at targeted sites. For this purpose, we are developing a computational fluid dynamics (CFD) model of
the human stomach and duodenum. We hypothesize that learning and predicting the breakdown kinetics of food particulates in the GI tract will provide new information useful in formulating next generation of foods with TD nutrients and associated processing technologies. From an engineering standpoint, stomach is a grinder, mixer, storage reservoir, and a pump that moves its contents with peristaltic waves generated in the walls. Many of the stomach's functions have been well documented in the medical literature. Considerable research has been done in the pharmaceutical field on targeted delivery of drugs. Recently published data obtained with MRI studies of stomach provide quantitative information on gastric wall motility and anatomical details that are necessary for CFD modeling. However, there is a notable lack of information regarding mechanical stresses and kinetics of the breakdown of ingested food particulates in the stomach. Using standard Navier-Stoke's equations, we are using
a CFD solver to model the flow field to compute mechanical stresses and predict kinetics of breakdown of a food matrix under known physiological conditions of the stomach. Future work will involve refining the model and seek validation with published results.
Impacts
The proposed predictive model of flow field in a human stomach will assist food manufacturers to select food formulations and processing conditions that ensure targeted delivery of desired nutrients to promote optimum health.
Publications
- No publications reported this period
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