Progress 09/01/24 to 08/31/25

Outputs
Target Audience:The target audiences for this project are listed below. We outline progress for each of these groups during this reporting period: Industry: Although pulses and ancient grains are becoming of ever greater interest in the food industry, there is little knowledge on how to predict their swelling and rupture behavior during pasting. This information is important to determine the texture of the foods, as well as determine particle size distribution in starch manufacturing operations. In the last reporting period, scientific work was disseminated through workshops and meetings at the Whistler Center for Carbohydrate Research, a research center at Purdue that has 27 participating industrial members (including companies like General Mills, Ingredion, ADM National Starch Food Innovation, etc.). We have also been in contact with Archer Daniels Midland (ADM) for this project, and they have provided us samples of non-traditional starches (buckwheat, pea, etc.) to characterize their swelling and rheology. We have hired an undergraduate student to write a computer program, in graphical user interface form, that can used by companies to predict swelling of starches based on physical property data. Progress is underway on this front. Scientists: The physics-based knowledge of granule swelling and rupture will be communicated via academic publications. and conferences. Currently, one paper has been published in a special issue of Soft Matter (topic "Food in Soft Matter"), for which the authors were invited and the article was featured on the back page. Several other manuscripts are under preparation, which we anticipate will be finished in the second working period. Work was also presented at conferences such as ACS Colloids and AIChE Annual Meeting. Scientific details of the work are stated in section "Accomplishments". PhD students and undergraduates: Two PhD students at Purdue are being trained on topics in colloidal and interfacial science related to starch swelling theories and rheology. Two undergraduates at Purdue were hired forthe next reporting period (Sept 2025 and Jan 2026).One postdoc at NC A&T is being partially supported by this grant to work on starch characterization, an undergraduate summer intern was trained on extraction and characterization of starch, and a PhD student is expected to be hired during the next period. At UBC, this work partially supported one PhD student doing ParCS microscopy to characterize swelling of non-traditional starches until the end of summer. One undergraduate is working on this project as well as part of their undergraduate thesis in Food Science at UBC. Also, a new research-based Master's student started at UBC (for next reporting period) and has begun developing an advanced version of the ParCS instrument to enable visualization of starch rupture/dissolution. K-3 students: In the last reporting period, PI Vivek Narsimhan was the faculty advisor for Purdue's chemical engineering honor's society (Omega Chi Epsilon). Students in this group performed science demonstrations to ~150 local students and their parents in an annual event called ChemE Kids Day. The activities (a) introduced science to young children (many of whom are from underprivileged backgrounds) while exposing them to college students as role models; (b) taught parents and children what is chemical engineering and how it is applied in everyday life; and (c) demonstrated simple science principles used in everyday objects. Some of the demonstrations related to colloidal and interfacial science (e.g., making butter, visualizing soap films, etc.) and showcased how these principles can be applied to food science. Lastly, Prof. Vivek Narsimhan is the Board Secretary for Imagination Station, a local science center in Lafayette, IN that runs science exhibits for young children (K-3 grade). This center has thousands of annual visitors, and the board meets to ensure that exhibits are running smoothly and that the center maintains collaborations with Purdue University and local businesses (e.g., Subaru, Caterpillar, etc.). Changes/Problems:During this past reporting period, PhD students were not able to be hired at North Carolina A&T and University of British Columbia. Thus, the rate of expenditure for the last period was smaller than expected, and this caused a delay in gathering data for granule dissolution and rupture. However, we refocused efforts in the last grant period on understanding swelling and rheology in more detail. We anticipate that we will be able to hire new students at UBC and NC A&T for the upcomingreporting period, and will make progress towards understanding dissolution and rupture. What opportunities for training and professional development has the project provided?This project has trained multiple PhD students, undergraduates, and postdocs at Purdue, North Carolina A&T, and University of British Columbia. Training at each institution is listed below: Purdue: This grant supports two PhD students. One PhD student is developing theories and experiments describing the swelling of starches in different ingredients (e.g., xanthan gum). The other PhD student is investigating the rheology of starch dispersions during swelling and understanding the effects of crowding and granule softening. One undergraduate has been hired in Sept 2025 (next reporting period) to writea computer program, in graphical user interface form, that can used by companies to predict swelling of starches based on physical property data. Another undergrad is expected to be hired in Jan 2026 to aid with rheology experiments. NC A&T: This grant is partially supporting a postdoc who is performing characterization of non-traditional starches. This involves differential scanning calorimetry, particle size measurments, and pasting. An undergraduate summer intern was hired to extract starches during the summer of 2025. A graduate student will be hired in the next reporting period. University of British Columbia: This grant has partially supported one PhD student who was involved in gathering microscopy data on starch granule swelling for the Soft Matter article published this year. An undergradraduate is also gathering data on starch swelling, and one new research-based Master's student has been hired this year to image granule rupture. How have the results been disseminated to communities of interest?Scientific dissemination: The physics-based knowledge of granule swelling and rupture has been communicated via academic publications and conferences. Currently, one paper has been published in a special issue of Soft Matter (topic "Food in Soft Matter"), for which the authors were invited and the article was featured on the back page. Several other manuscripts are under preparation, which we anticipate will be finished in the second working period. Work was presented at conferences such as ACS Colloids and AIChE Annual Meeting. Industrial dissemination:In the last reporting period, knowledge from our work was disseminated through workshops and meetings at the Whistler Center for Carbohydrate Research, a research center at Purdue that has 27 participating industrial members (including companies like General Mills, Ingredion, ADM National Starch Food Innovation, etc.). The results from this work were shared with industrial participants at the Whistler Center for Carbohydrate Research 2025 Annual Conference that was held at Purdue University. We have also been in contact with Archer Daniels Midland for this project, and they have provided us samples of non-traditional starches (buckwheat, pea, etc.) to characterize their swelling and rheology. We have hired an undergraduate student to write a computer program, in graphical user interface form, that can used by companies to predict swelling of starches based on physical property data. Progress is underway on this front. Teaching: Prof. Ganesan Narsimhan teaches a graduate level course on colloidal and interfacial science. Findings from this research has been incorporated the course. Prof. Frostad teaches a graduate level seminar course, where this research has been presented to a broad audience of Food Science researchers. K-3 students: In the last reporting period, PI Vivek Narsimhan was the faculty advisor for Purdue's chemical engineering honor's society (Omega Chi Epsilon). Students in this group performed science demonstrations to ~150 local students and their parents in an annual event called ChemE Kids Day. The activities (a) introduced science to young children (many of whom are from underprivileged backgrounds) while exposing them to college students as role models; (b) taught parents and children what is chemical engineering and how it is applied in everyday life; and (c) demonstrated simple science principles used in everyday objects. Some of the demonstrations related to colloidal and interfacial science (e.g., making butter, visualizing soap films, etc.) and showcased how these principles can be applied to food science. Lastly, Prof. Vivek Narsimhan is the Board Secretary for Imagination Station, a local science center in Lafayette, IN that runs science exhibits for young children (K-3 grade). This center has thousands of annual visitors, and the board meets to ensure that exhibits are running smoothly and that the center maintains collaborations with Purdue University and local businesses (e.g., Subaru, Caterpillar, etc.). What do you plan to do during the next reporting period to accomplish the goals?Predict flow behavior of non-traditional starch dispersions during swelling. Rheology of starch pastes: As stated earlier, the rheology of a starch paste is affected by swelling in two ways. At early times, the storage modulus of the suspension during granule swelling due to the crowding of the granules. As time progresses however, the storage modulus eventually starts decreasing with time, even though the size distribution shows no appreciable evidence of granule breakage. This second regime, attributed to softening of the granules, is still not understood quantitatively and is being investigated by our group. We have gathered experimental data that shows the extent of softening and the onset of softening behavior depends not only on the volume fraction occupied by the granule, but also on the initial weight percentage of the starch. The next reporting period will develop theories that link the observations to what is occurring at the microscale. We anticipate a publication will arise from this work. Work in the next period will also be extended to non-traditional starches. We are also investigating if the rheology ideas for the crowding effect can be extended to non-traditional starches.Data has been gathered for buckwheat starch (supplied from ADM), and preliminary results seem to indicate that the ideas developed previously can be applied to these starches.We are in the process of using swelling theories to forecast the rheology of this paste during when granule crowding is the dominant effect.We anticipate a paper will be written on this topic in the next reporting period. Creation of porous starch granules and the influence of porosity on the swelling kinetics: At UBC we have hypothesized that the internal structure and composition of the starch granules has an important influence on the kinetics of swelling. To test this hypothesis, we have pulled in another collaborator from the University of Life Sciences in Lublin, Poland who is an expert in porous starches. In the next research period we plan to create starch granules with varying degrees of porosity under controlled conditions and then measure the swelling kinetics of the resulting porous starches. Predict how sugar and sugar substitutes alter starch swelling. Swelling in xanthan gum: We are writing a manuscript to describe the effect of xanthan gum on swelling of starches for low concentrations. We are also looking at explaining what occurs at higher starch concentrations, where the effect of xanthan on swelling is more subtle. Here, effects such as granule crowding and depletion interactions can increase or decrease swelling depending on the starch variety and amount of xanthan, and we are developing theories to explain each of these effects. This work, combined with the previous paragraph, will give a complete picture as to how large molecular weight macromolecules affect starch swelling. We imagine that the lessons learned from these studies will be generalizable to other macromolecules, and could also hold for other starch varieties (non-traditional starches). Swelling of buckwheat in different sugars:We are gathering swelling data for buckwheat starch (supplied by ADM) in different sugars and sugar substitutes and seeing if one can extend the Flory swelling theories to take into account the partitioning within the starch granules as well as reduction in water activity. In the next reporting period, PIs from Purdue will gather results from theories and compared to size distribution measurements (from NC A&T) and microscopy measurements (from UBC) of granule swelling with sugars/sugar substitutes, subject to different heating profiles. Incorporate starch granule rupture into swelling models. Prof. John Frostad has spent a sabbatical at Duke University learning advanced microscopy techniques that can be used to visualize starch granules as they swell and rupture.The goal in the next reporting period is to gather the first set of experimental data that visualizes starch granules as they rupture and/or dissolve into the surrounding medium.Students from Purdue and NC A&T will collaborate with Prof. Frostad as this data is being gathered to develop theories to explain the granule size versus time and to predict the onset of rupture/dissolution.

Impacts
What was accomplished under these goals? Predict flow behavior of non-traditional starch dispersions during swelling In order to predict the flow behavior of non-traditional starches during swelling, one needs to first understand swelling kinetics of starch granules. We have made significant progress on this front -- details are outlined below: Swelling of non-traditional starches: During the last reporting period, we published an invited paper for a special issue in Soft Matter (topic "Food in Soft Matter"). In the article, we used microscopy (ParCS) to visualize the swelling of individual starch granules from non-traditional sources (red bean, chickpea, green lentil, and yellow pea), and compared against theories previously developed by PIs (Flory theory of polymer swelling, combined with a diffusion equation for mass transfer into the granule). Based on the data, modifications were made to the theory. In order to capture experimental data at large and small swelling extents, one has to make the cross-link density of the starch granule vary with temperature. This reflects the idea that swelling is irreversible, with physical cross-links inside the starch granule decreasing during swelling. We also found that swelling for the different starch varieties versus time can be collapsed onto a universal curve with two empirical shift factors (one for radius, and one for time). We related the shift factors to the material parameters in the theory, so we have a better idea of what physical processes affect the swelling. The modified theory represents a major step forward in the fundamental understanding of starch gelatinization and the ability to use predictive models for optimization of industrial manufacturing processes. At NC A&T, we extracted starches from kidney bean, small red bean, cowpea, and emmer, conducted pasting tests in water, and analyzed digestion of the starches. Swelling kinetics in the presence of simple solutes: At UBC we have continued to employ the use of Particle Cohort Studies (ParCS) to obtain data on the kinetics of swelling for individual granules. This data is critical for future modeling efforts as it can be directly compared to swelling theories. In addition, this study employed the results of the previous study (published in Soft Matter as described above) in which the modeling effort revealed that an estimate of the diffusivity of water within starch granules can be obtained from non-dimensionalizing the data. The data revealed that the rate of diffusion into the starch granules was approximately three orders of magnitude slower that what we previously assumed. Among other mechanistic insights, we also showed that four parameters related to the material properties of the starch are needed to cause all of the kinetic swelling data to collapse onto a master curve, but the shape of the curve differs from one starch to the next. Rheology of starch pastes: At Purdue, we have hired two PhD students to investigate the role between swelling and rheology of starch pastes. When starch granules in a dispersion intake water, the granules occupy more volume and they soften. The first effect (crowding) increases the viscosity and elasticity of the dispersion, while the second effect (granule softening) has the opposite effect. Historically, most studies on starch rheology have investigated the crowding effect, where the storage modulus of the starch paste increases in time as the granules swell. In this regime, the measured storage modulus of a given starch variety depends only on the volume fraction occupied by the granules, and thus one can use granule swelling theories to forecast the rheological behavior during heating. However, such theories do not work when a paste is heated for longer times when the storage modulus eventually starts decreasing with time, even though the size distribution shows no appreciable evidence of granule breakage. This second regime is attributed to granule softening, and it is found that the extent and onset of softening depends not only on the volume fraction occupied by the granule, but also on the initial weight percentage of the starch. We have performed experiments to characterize this softening behavior in more detail, and are developing theories that link the observations to what is occurring at the microscale. Experiments have been performed on waxy maize starch so far, but work in the next period will also be extended to non-traditional starches. Lastly, we are currently investigating if the rheology ideas for the crowding effect can be extended to non-traditional starches. Data has been gathered for buckwheat starch (supplied from ADM), and preliminary results seem to indicate that the ideas developed previously can be applied to these starches. We anticipate a paper will be written on this topic in the next reporting period. Predict how sugar and sugar substitutes alter starch swelling. Swelling in xanthan gum: Currently, there is considerable confusion in the literature as to the effect of xanthan gum on swelling of starches. Some papers report that xanthan increases swelling, while other papers report a decrease. To understand the physics behind these observations, we performed experiments where we heated three different starch dispersions (normal and waxy maize; waxy rice) in xanthan gum solutions, for two different starch concentrations (dilute (0.1% wt) and concentrated (5% wt)). We found that consistent with literature, depending on the type of starch and concentration, xanthan can increase or decrease swelling. To explain what is occurring in the dilute dispersions, we compared the molecular weight distributions of xanthan in the continuous phase of unheated and heated starch suspensions by multi angle laser light scattering (MAALS). These experiments found that waxy rice starch (WRS) starch granules are impervious to xanthan whereas normal maize starch (NMS) granules were permeable to low molecular weight xanthan fraction. We updated our Flory swelling models to take the partitioning of low molecular weight xanthan fractions within starch granules and consider the effect of osmotic pressure of xanthan in the continuous phase. The model agreed fairly well with experiments for low concentrations of both starch fractions. The work suggests why one sees increased swelling for some subset of starches in the presence of xanthan for low starch concentrations. Xanthan gum may partition into certain starch varieties, which increases swelling due to entropy and enthalpy of mixing inside the granule. When xanthan does not penetrate into the granule, other effects (e.g., osmotic pressure) alter swelling negligibly. The above work is being written as a manuscript. We are also developing theories to explain what occurs at higher starch concentrations, where the effect of xanthan on swelling is more subtle. Here, effects such as granule crowding and depletion interactions can increase or decrease swelling depending on the starch variety and amount of xanthan. This work, combined with the previous paragraph, will give a complete picture as to how large molecular weight macromolecules affect starch swelling. We imagine that the lessons learned from these studies will be generalizable to other macromolecules, and could also hold for other starch varieties (non-traditional starches). Incorporate starch granule rupture into swelling models. Prof. John Frostad has spent a sabbatical at Duke University learning advanced microscopy techniques that can be used to visualize starch granules as they swell and rupture. The goal in the next reporting period is to use these techniques to visualize starch granules as they rupture and/or dissolve into the surrounding medium. Students from Purdue and NC A&T will collaborate with Prof. Frostad as this data is being gathered to develop theories to explain the granule size versus time and to predict the onset of rupture/dissolution.

Publications

• Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: R. Nandini, V. Narsimhan and G. Narsimhan. Swelling of Starches in Presence of Xanthan Gum. Poster at Whistler Center for Carbohydrate Research Annual Conference. May 2025, Purdue University, West Lafayette, IN
• Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: J.M. Frostad, B. Li, L. Mo, V. Narsimham, G. Narsimhan. Swelling of polymer networks: starch gelatinization. Presentation at American Chemical Society Colloids and Surface Science Symposium. Edmonton, Alberta 23 June 2025.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: Botong Li, Lanxin Mo, Vivek Narsimhan, Ganesan Narsimhan, and John M. Frostad. "A refined mechanistic model for swelling kinetics of starch granules", Soft Matter, 2025, 21, 4351-4367
• Type: Other Journal Articles Status: Under Review Year Published: 2025 Citation: Santos OKeefe, L., Frostad, J.M. Quantification of starch gelatinization properties in glucose and sucrose solutions using ParCS.  in revision (2025)
• Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: R. Nandini, V. Narsimhan, and G. Narsimhan. Equilibrium swelling of starch suspensions in presence of xanthan gum upon heating, AIChE Annual Meeting presentation, Nov 2025
• Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: G.Narsimhan. Microstructure and Rheology of Starch Suspensions During Heating. Presentation at Whistler Center for Carbohydrate Research Annual Conference, May 2025, Purdue University, West Lafayette, IN