Progress 12/01/13 to 11/30/17
Outputs
Target Audience:Manufacturers of ice cream and whipped toppings are the primary audience, particularly research scientists. One of the largest whipped toppings makers, Rich Products, has been, and remains, a supporter of this work, checking updates on an annual basis. Further, ice cream manufacturers, as well as ingredient suppliers to those manufacturers, have been targeted, particularly through an outreach effect, the Frozen Dessert Center symposium (October, 2017). Changes/Problems:One major issue faced in this project was the ability to find sufficiently small particles to coat the surface of small fat globules, as we suggested we would do for Objective 2. For this reason, we turned to looking at particulates as a complete replacement for fat globules. See Accomplishments for more details of the work on this area. What opportunities for training and professional development has the project provided?One post-doc, two PhD students (one was not funded by this project) and two undergrad students have received valuable research experience to further their careers. One of the PhD students spent a 6-month research stint at a collaborator at University of New South Wales in Australia to help broaden her perspective. How have the results been disseminated to communities of interest?Results have been presented at AOCS (American Oil Chemists' Society) meetings, at an international Food Engineering congress, in several publications, and at the Frozen Dessert Center Annual Symposium. What do you plan to do during the next reporting period to accomplish the goals?Although this is a final report, work on this project will continue (as the PhD students complete their dissertations) for part of 2018. We will continue our work on Objective 1, completing an ingredient inventory to clarify which components of food emulsions have the greatest effect on partial coalescence (and why). We also will continue our work on Objective 3, completing the characterization of the effects of partially-coalesced fat globules on foam stability.
Impacts
What was accomplished under these goals?
Impact: The formation of clusters of fat globules during processing of ice cream and whipped cream is an essential step in forming well-behaved products (e.g., whipped cream that maintains its structure and height). This cluster formation is driven by a phenomenon known as partial (or arrested) coalescence. Two oil droplets begin to coalesce based on thermodynamic principles, but then stop because of a partially crystalline network of solid fat within the droplet. These clusters help to stabilize air cells and provide desirable physical attributes in these products. For example, fat globule clusters in ice cream influence the ability of ice cream to melt and collapse, while also influencing the rheological and sensory properties. In whipped cream, the desirable stand-up properties are provided by a high level of fat globule clustering during aeration. In this work, we studied (1) the mechanisms by which fat globules partially coalesce, (2) the range of parameters that influence partial coalescence, and (3) the effects that these clusters have on the physical properties of the end product. The results (1) allow better control of the process to control product quality, (2) provide insight to manufacturers who wish to dial in a specific effect in their product, and (3) provide a target for manufacturers to optimize their product's behavior. In addition, we studied the use of edible particles to replace fat globules in various products. Although this met with limited success, there is still considerable potential for this approach. A "side" result of this line of investigation was the development of pigments based on these edible particles to replace aluminate-based lakes that are used now as food colors. A provisional patent application was submitted on this idea. Objective 1: Using micromanipulation techniques, the coalescence behavior of droplets made from natural fats (palm kernel, palm, milk fat, and coconut stearin) was investigated. For all fat systems, the larger G' led to coalescence being halted earlier and the smaller the droplet pairs the higher the degree of coalescence, or strain, achieved. The energy balance model created to predict strain between two petrolatum droplets was not successful at predicting strains for natural fat systems. The stability of oil droplets to coalescence depends on the composition of the fat phase. When methylcellulose was used as a stabilizer, two completely liquid oil droplets would not coalesce upon contacts. Even when a spear-like interfacial crystal was aimed at the liquid droplets, no coalesce was observed. The liquid droplet was deformed wherever a second liquid droplet or interfacial crystal was touched. However, when a droplet contained a small amount of solid fat internally, and the crystals of a second droplet were aimed at this patch, the droplets would easily coalesce. The coalescence event between two droplets became time dependent when the interface of oil droplets was composed of a mixture of protein, MDG, and PS80. Coalescence was initiated through a small oil neck even when large strains were ultimately observed. As the protein level was altered from 1%-5.5% no chance in strain was seen. Emulsions that contained no MDG or PS80 underwent much higher strains than emulsions that contained any ratio of MDG:PS80. No difference could be seen in emulsions that contained any ratio of MDG:PS80. Capillary micromechanics, a new method to probe the elastic characteristics of soft particles, was applied to fat globules. Here, an emulsion is run through a tapered capillary tube until one particle plugs the tip. This particle is slowly deformed by applying pressure through a water reservoir and shape measurements of the deformation are taken. From this the elastic modulus of the droplets can be determined and compared to measurements of the bulk modulus. With petrolatum and paraffin systems, the droplet rheology and bulk rheology mimic each other more than we had expected. For duck fat, composed of a variety of triglycerides, the droplet elastic modulus varied highly within samples. This is due to internal fat network not being homogenous distributed within the droplet making orientation within the capillary tube important. There was also variation within droplets of the same emulsion where the amount of solids seen within droplets after 24 hours of storage could vary widely. The formation of large scale fat globule networks was studied. Here an emulsion droplet was pipetted onto a glass slide where fat globules then aggregated at the top of the host droplet, forming networks as the water was evaporate from the sample. Paraffin was the chosen fat and solid fractions from 0.25-0.7 were investigated. It was seen that the fractal dimension decreases from 1.82 to 1.68 for 25% and 70% solids, respectively. This is due to the lower solids droplets resulting in networks that are compact where the higher the solids level the more spread out, or fern-like the networks became. Droplets with lowers solids were also seen to have a higher coordination number, or nearest neighbors, than droplets composed of higher solids. Objective 2: The use of colloidal particles, e.g., microparticulated whey protein concentrate and biologically inactive lactic bacteria, to replace fat globules and provide structure to aerated foods was studied. Some success was found but it became clear that this idea requires much more attention to develop and study feasibility. To this end, a USDA NIFA proposal was submitted in 2017 based on this idea. However, it received only a moderate rating and was not funded. The use of these colloidal particles to mimic light properties of fat droplets was investigated. Possible application: replacing fat droplets in coffee creamer, reducing the fat content in coffee creamers. This effect was successfully shown, although the potential application is limited. This finding led to use colloidal particles as dye carrier and developing color pigment for food application. Production of colored pigments based on these particles for application in food, pharmaceutical and cosmetic industries was developed. A provisional patent application (# 62586252) is filled with United States Patent and Trademark Office (USPTO), entitled "Insoluble and Dispersible Protein and Dye-Containing Particles for Use as Colorants". This idea has received considerable interest from the food colorant industry, with substantial potential for further development. A proposal in-house (UW-Madison) has been submitted for further work to develop this concept for commercial application. Objective 3: The rheological properties of foams stabilized by partially-coalesced fat networks were measured. Several tests were conducted, including a temperature ramp from -15 to 35°C, frequency sweep, flow ramp, creep-recovery test, and stress growth. Although we are still in the midst of data analysis, our results to date confirm that systems with high levels of fat globule clusters have "stronger" rheological properties (higher G' values, etc.) than those where the fat emulsion remains as small, intact, individual fat globules. In principle, the samples with stronger rheology will induce a greater mouthcoating response in the consumer.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Thiel, AE, RW Hartel, PT Spicer, KJ Hendrickson, Coalescence behavior of pure and natural fat droplets characterized via micromanipulation, J. Amer. Oil Chem. Soc. 93, 1467-1477 (2016).
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Thiel, A.E., R.W. Hartel, P.T. Spicer, Fat crystals influence methylcellulose stabilization of lipid emulsions, J. Amer. Oil Chem. Soc. Short Comm., 94(2), 325-331 (2017).
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Dahiya, P., Caggioni, M., Atherton, T.J., deBenedictus, A., Prescott, S.W., Hartel, R.W., Spicer, P.T., Arrested coalescence of viscoelastic droplets: Triplet shape and re-structuring, Soft Matter, 13, 2686-2697 (2017).
- Type:
Book Chapters
Status:
Awaiting Publication
Year Published:
2018
Citation:
Van Wees, S.R., Hartel, R.W, Microstructure of ice cream and frozen dairy desserts, In: Microstructure of Dairy Products (M. El-Bakry, A. Sanchez, B. Mehtaor, Eds), Wiley, UK (submitted).
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Progress 12/01/14 to 11/30/15
Outputs
Target Audience:The target audiences are manufacturers of ice cream and whipped toppings and research scientists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One post-doc, one PhD student and one undergrad student are receiving valuable research experience to further their careers. How have the results been disseminated to communities of interest?To date, the only dissemination has been conference presentations, primarily at the American Oil Chemists Society (AOCS) annual meetings. A presentation at the 2016 AOCS conference is scheduled. What do you plan to do during the next reporting period to accomplish the goals?• Continue to evaluate effects of interfacial tension on status of coalescence. • Study different emulsifiers to determine the effects on status of coalescence. • Continue to work on the physical model that describes arrested coalescence. • Continue to investigate particles at oil interfaces to control arrested coalesence. • Initiate a research plan for measuring rheological properties of fluid emulsions to make whipped cream and toppings. This will be done in conjunction with our industry support to ensure these results have practical implications.
Impacts
What was accomplished under these goals?
Objective 1. Characterize the effects of operating parameters on status of coalescence (complete, arrested, or none) of fat globules that contain particles completely within the interior. Coalescence status of several lipid systems has been explored using the micro-manipulator technique. The fat systems include tristearin in triolein, anhydrous milk fat in soybean oil, palm oil in soybean oil, and palm kernel oil in soybean oil. Five droplet diameters (10 to 90µm) were studied for each lipid system. And one system was used for a study on effects of emulsifier concentration. The aim of these experiments was to evaluate state of coalescence in these systems at different solid fat content (SFC) by changing the ratio of hard to liquid fat. Arrested coalescence, as measured by the strain, or total length, of the two droplets, was then compared to our model predictions based on the competing forces of coalescence (minimizing surface energy) and rigidity of the internal fat crystal structure (measured as elastic modulus). All systems exhibited a range of coalescence status, from none to complete, depending on SFC. However, the SFC values were different for each lipid system. That is, when SFC was very low (5%), complete coalescence occurred since the internal structure was not sufficiently rigid to prevent complete coalescence. At high SFC (15%), the droplets were sufficiently rigid that no coalescence occurred under these conditions. Droplet size, from 10 to 90 µm, had a significant effect on arresting coalescence. In all cases, smaller droplets led to an enhanced level of partial coalescence. For the sake of completing experiments, carboxymethylcellulose (CMC) was chosen as the thickener despite its effect on interfacial tension. This limited the range that we could study. Within the limited scope of emulsifier concentrations (interfacial tensions), no effect on partial coalescence was observed. This is an interesting results because the model clearly has interfacial tension as an important parameter. The results of fat crystal rigidity (elastic modulus) were put into the physical model along with strain from the coalescence results, it became clear that the model does not always work very well. For the tristearin-tripalmitin fat system, the model actually predicts pretty well the experimental results. However, for the systems with real food fats, the model comes up short in all cases. We are in the process of trying to understand where the differences lie between the model and the experimental systems. Clearly, one or more of the measurements is off with these real fats, especially compared to the simple systems. Further work is needed to modify the model to predict the data. Objective 2. Characterize the effects of formulation and processing parameters on status of coalescence (complete, arrested, or none) of fat globules with particles situated at the interface. Numerous attempts have been made to find particles sufficiently small that they can coat a fat globule of sizes realistic to commercial applications. Further efforts in this direction are underway. Objective 3. Characterize the effects of arrested coalescence on rheological properties of emulsion-based fluids. We have just begun developing an experimental plan for this objective.
Publications
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Progress 12/01/13 to 11/30/14
Outputs
Target Audience:The target audiences are manufacturers of ice cream and whipped toppings and research scientists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One post-doc, one PhD student and one undergrad student are receiving valuable research experience to further their careers. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?• Continue studying coalescence status of multiple natural fats. • Investigate effects of droplet size on coalescence status. • Continue efforts to study effects of interfacial tension on coalescence status. • Apply physical model from previous to current results.
Impacts
What was accomplished under these goals?
Objective 1. Characterize the effects of operating parameters on status of coalescence (complete, arrested, or none) of fat globules that contain particles completely within the interior. Coalescence status of a model system of tristearin (SSS) in triolein (OOO) was studied. The aim of these experiments was to evaluate state of coalescence at different solid fat content (SFC) by changing the ratio of SSS to OOO. Arrested coalescence, as measured by the strain, or total length, of the two droplets put into contact, was then measured. A range of coalescence status, from none to complete, was found depending on SFC. When SFC was very low (less SSS), complete coalescence occurred since the internal structure was not sufficiently rigid to prevent complete coalescence. One single larger droplet was formed. At high SFC (higher SSS), the droplets were sufficiently rigid that no coalescence occurred under these conditions. Essentially, the two droplets "bounced" off each other without interacting. This behavior is similar to what was found with a model system made up of an alkane liquid phase and a wax solid phase. The second set of experiments focused on changing interfacial tension to evaluate its effect on partial coalescence. As expected, interfacial tension decreased as emulsifier (SDS) concentration increased, up to a point. Above the critical micelle concentration (CMC), interfacial tension reached a plateau. Unfortunately, when a thickener was used to control fat globule motion in the microscope stage, that also came with a significant decrease in interfacial tension since it seems all the thickeners tried have some surface active properties. This limits the range of interfacial tensions we can investigate in this study. Objective 2. Characterize the effects of formulation and processing parameters on status of coalescence (complete, arrested, or none) of fat globules with particles situated at the interface. No progress to date. Objective 3. Characterize the effects of arrested coalescence on rheological properties of emulsion-based fluids. No progress to date.
Publications
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