Progress 07/01/17 to 06/30/22
Outputs
Target Audience:The problem of stickiness of sugar-based products crosses a wide range of food product applications. Although the original focus here was on stickiness problems in reduced sugar cereal coatings, we have expanded that work into sugar-based confections like caramel, gummies and marshmallow. Thus, the primary audience is technical people in sugar-based products manufacturing sector. Changes/Problems:Due to the covid pandemic, work on this project was severely delayed, causing fragmentation of the results. In particular, work on Objective 2 was cut short when the post-doc had to return to his home in India. What opportunities for training and professional development has the project provided?Over the duration of this project, numerous students received training, with four undergrads, one grad student, and three post-doctoral researchers working on different aspects of the work. The undergrads are currently employed within the industry, one of the post-docs works for a chemical company and the other is an Assistant Professor at Nanking University. How have the results been disseminated to communities of interest?Our industry collaborator was involved throughout the work. Also, principles of stickiness developed through this work are now incorporated into material presented at University of Wisconsin-Madison short courses on confections and nutrition bars. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective 1: Characterize the effects of both amorphous phase and particles on macroscopic stickiness of sugar-based surfaces using model systems. Stickiness of sugar solutions causes problems in various food products and operations. In this study, the effects of glucose syrup type (dextrose equivalent) and crystalline particles on stickiness of sugar solutions with water contents from 10 to 20% were determined. To study the effects of both amorphous phase and particles on stickiness, four different corn syrups with varying dextrose equivalence (DE) were used to determine the effects of polysaccharide distribution on sugar syrup stickiness over a range of moisture contents. The effects of particles (zirconium oxide beads (Zr2O3), fondant sucrose and granular sucrose crystals) on the surface were then evaluated to gain a better understanding of their role in reducing syrup stickiness. Stickiness was measured as tack force and work of adhesion with a texture analyzer and was correlated against water content and glass transition temperature (Tg). Water content of the sugar coating had a major influence on stickiness although the relationship was complex based on competing adhesive and cohesive forces. As water content of the sugar coating decreased from 20% down to about 12%, the stickiness of the coating increased, as evidenced by both the amount of syrup left on the probe used to assess stickiness and the force required to remove the probe from the surface (tack force). However, below about 12% moisture content, the surface was sufficiently dry that none stuck to the probe even though the tack force continued to increase. At the same time, work of adhesion decreased as syrups underwent a transition from cohesive to adhesive failure. A similar bell-shaped relationship was shown for T-Tg, where below a certain value, stickiness decreased. The nature of the syrup used to make the amorphous phase also had a significant effect on stickiness. In general, lower DE in the corn syrup caused a reduction in both tack force and work of adhesion without a significant change in Tg. Clearly, the saccharide distribution also plays a role in stickiness, with longer chain saccharides reducing stickiness compared to lower molecular weight sugars. Of primary interest in this work was the effect of particles on stickiness. Particles in the bulk of the amorphous syrup had essentially no effect on stickiness even though viscosity was increased. On the other hand, particles at the surface, regardless of their size or origin, decreased stickiness. This decrease in stickiness was approximately linear with increasing surface coverage, verifying the hypothesis that a reduction in the surface area of amorphous sugar in contact with the probe causes a direct reduction in stickiness. Stickiness in these systems is governed by the area of amorphous phase in contact with the probe. Also, the nature of those crystals/particles did not affect the correlation since inert zirconium particles had exactly the same capability of reducing stickiness as the two types of sugar crystals. One can hypothesize that the effects of fat content in reducing stickiness of sugar syrups is due to the same mechanism, that there is less amorphous syrup in contact with the probe. Objective 2: Characterize the effects of growing sucrose crystals and surface coverage along with the inherent stickiness of the amorphous matrix with macroscopic stickiness of reduced-sugar matrices. This objective proved difficult to achieve since it was impossible to quantify the changes in surface coverage as sucrose crystals grew at the surface of an amorphous mass. Hence, an additional study on the inherent stickiness of the amorphous matrix was conducted. This study aimed to understand how moisture content and saccharide distribution impact the physicochemical properties of condensed saccharide solutions and their implications on stickiness. Using different types of starch hydrolysates and sugars, 6 binder formulations that differed in saccharide distribution were studied in terms of moisture, glass transition temperature (Tg), rheology, and stickiness. Results indicated that the Tg, shear moduli, and viscosity all decreased with moisture content, whereas the stickiness profile followed a bell-shaped pattern. Binders with higher average molecular weight generally exhibited elevated Tg and viscoelasticity, with the maximum stickiness and adhesive failure occurring at higher moisture range. Objective 3: Explore the effects of different types of additives on stickiness. For the final objective, the effects of various ingredients on stickiness of sugar-based systems were studied. This included a caramel system where we could study different attributes. Formulated with varied moisture contents (10-12%), dextrose equivalence (DE) of corn syrups (28, 42, 63 DE), and the concentrations of mono-and diglycerides (MDG, 0-2%), 9 caramel samples were compared in terms of rheology, surface energies, hardness, and stickiness. Results indicated that moisture and DE significantly altered the rheology of the caramel matrix, whereas MDG reduced the surface energies. Results from a peel test showed that the adhesive forces between caramel and a packaging material followed a bell-shaped trend with G' and G" of the caramels and decreased with the surface energies of both the caramels and the materials. On the other hand, the caramel structure was sensitive to pressure. Increased penetration strain resulted in structural collapse, which reduced cohesion while facilitating adhesion. At 50% strain, the pressure-induced adhesive forces decreased with moisture content, DE of corn syrup, and MDG concentration. MDG (>1%) in caramel was an effective anti-sticking agent, which reduced both peel and pressure-induced adhesion. This could potentially open doors for reducing stickiness of other sugar-based foods. Another study evaluated several reduced-sugar formulations for their stickiness as well as studying the effect of vegetable oil. Maltodextrin significantly raised the sticky point of the binder system, while allulose exerted a strong plasticizing effect that drastically shifted the stickiness profile. The addition of vegetable oil significantly reduced cohesiveness and facilitated adhesive failure. These studies could potentially open doors for reducing stickiness of other sugar-based foods, particularly in sugar-reduced formulations.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Burke, J., RW Hartel, Stickiness of sugar syrups with and without particles, J. Food Eng (2021) doi.org/10.1016/j.jfoodeng.2020.110222
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Wang, R., RW Hartel, Caramel stickiness: Effects of composition, rheology, and surface energy, J. Food Eng., 289 (2021). https://doi.org/10.1016/j.jfoodeng.2020.110246
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Wang, R., RW Hartel, Understanding stickiness in the sugar-rich food systems: A review of mechanisms, analyses, and solutions of adhesion, Comp. Rev. Food Sci. Food Safety, 20, 5901-5937 (2021).
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Wang, R., RW Hartel, Stickiness of gelatin systems, Food Hydrocolloids, 124, 107132 (2022).
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Progress 07/01/20 to 06/30/21
Outputs
Target Audience:The problem of stickiness of sugar-based products crosses a wide range of food product applications. Although the original focus here was on stickiness problems in reduced sugar cereal coatings, we have expanded that work into sugar-based confections like caramel, gummies and marshmallow. Thus, the primary audience is technical people in sugar-based products manufacturing sector. Changes/Problems:The complications of the pandemic led to two no-cost extensions. What opportunities for training and professional development has the project provided?Over the course of this project, two post-doctoral researchers conducted research and published manuscripts, two graduate students conducted research, with one generating a publication, and several undergrads provided assistance at different points in the project. How have the results been disseminated to communities of interest?In addition to the several publications, various aspects of this work are being incorporated into our confectionery science short course offerings. What do you plan to do during the next reporting period to accomplish the goals?We will continue to work on objective 3.
Impacts
What was accomplished under these goals?
Objective 1 and Objective 2: completed. We found-Water content of the sugar coating also was found to influence stickiness although the relationship was complex based on competing adhesive and cohesive forces. Objective 3: The caramel study was completed and published. We moved to the effects of gelatin on stickiness using gummy candy as the model system. Different gelatin concentrations and corn syrup types were studied. This study focused on the impacts of sucrose and glucose syrups, which make up ~ 70-80% of the total solids, on the sol properties , gelling, and melting behaviors of gelatin (4-6%) gels. Gelling and melting properties of gelatin solutions with and without sweeteners (sucrose and glucose syrup) were characterized with rheology and differential scanning calorimetry, while the final gel texture and surface properties were analyzed with texture analyzer and tensiometer. In contrast to plain systems, which gelled at around 22 C and melted at 35 C, high-sweetener systems exhibited coil-to-helix transition at a higher temperature level, and the subsequent sol-gel transition depended greatly on the bulk viscosity. Below the sucrose-syrup level of 75.9%, the transition was observed at 34-43 C; higher levels of saccharides postponed or inhibited the transition. The internal interactions of high sugar gels were considerably weaker than the gels without sweeteners, suggesting smaller and more dispersed junction zones. The quantities of melting enthalpy and internal interactions increased with gelatin concentration but decreased with sucrose syrup level, due to high viscosity. Gel surfaces were generally hydrophobic (non-polar) except for the 4% gelatin gels, whose surface polarity increased with sugar level. Gel hardness and tackiness increased with gelatin concentration but did not change significantly with moisture/sugar content at 5-6% gelatin. An additional study on starch jelly candies was initiated, but will probably not lead to significant results on stickiness. However, a major review article on stickiness of sugar-based systems was recently completed, based on the summary of knowledge gained from this project. It is currently under review at Comprehensive Reviews in Food Science and Food Safety.
Publications
- Type:
Journal Articles
Status:
Under Review
Year Published:
2021
Citation:
Wang, R., RW Hartel. Stickiness of gelatin systems, Food Hydrocolloids
- Type:
Journal Articles
Status:
Under Review
Year Published:
2021
Citation:
Wang, R., RW Hartel. Understanding stickiness in the sugar-rich food systems: A review of mechanisms, analyses, and solutions of adhesion, Comp. Rev. Food Sci. Food Safety
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Progress 07/01/19 to 06/30/20
Outputs
Target Audience:The problem of stickiness of sugar-based products crosses a wide range of food product applications. Although the original focus here was on stickiness problems in reduced sugar cereal coatings, we have expanded that work into sugar-based confections like caramel, gummies and marshmallow. Thus, the primary audience is technical people in sugar-based products manufacturing sector. Changes/Problems:We had already requested an extension (to June 30, 2021) based on the problems of finding a suitable post-doc. Even despite the pandemic interruptions this year, we should be able to complete all work by June 30, 2021. What opportunities for training and professional development has the project provided?The project trained: 2 Post-doctoral researchers: Bulaji Subbiah; and Ruican Wang (supported off other resources) 1 MS student: Jen Burke 1 undergrad researchers: Jiehua Lin How have the results been disseminated to communities of interest?Not as yet, but these results will be incorporated into the appropriate sugar segments of outreach courses on Nutrition Bars, and Enhanced Gummies & Jellies, taught at University of Wisconsin-Madison, coming up within the next year. What do you plan to do during the next reporting period to accomplish the goals?We will continue to work on different additives and sugar-based products. One aspect is evaluating the effects of proteins on stickiness of sugar syrups. Also, a study on the effects of gelatin and aeration on stickiness of sugar syrups (gummy candies and marshmallows) is also currently underway.
Impacts
What was accomplished under these goals?
Objective 1 and 2 are completed. We found-Water content of the sugar coating also was found to influence stickiness although the relationship was complex based on competing adhesive and cohesive forces. As water content of the sugar coating decreased from 20% down to about 12%, the stickiness of the coating increased, as evidenced by both the amount of syrup left on the probe used to assess stickiness and the force required to remove the probe from the surface (tack force). However, below about 12% moisture content, the surface was sufficiently dry that none stuck to the probe even though the tack force continued to increase. Objective 3: In the past year, we have expanded our focus to study the effects of various ingredients on stickiness of sugar-based systems. This included a caramel system where we could study different attributes. Formulated with varied moisture contents (10-12%), dextrose equivalence (DE) of corn syrups (28, 42, 63 DE), and the concentrations of mono-and diglycerides (MDG, 0-2%), 9 caramel samples were compared in terms of rheology, surface energies, hardness, and stickiness. Results indicated that moisture and DE significantly altered the rheology of the caramel matrix, whereas MDG reduced the surface energies. Results from a peel test showed that the adhesive forces between caramel and a packaging material followed a bell-shaped trend with G' and G" of the caramels and decreased with the surface energies of both the caramels and the materials. On the other hand, the caramel structure was sensitive to pressure. Increased penetration strain resulted in structural collapse, which reduced cohesion while facilitating adhesion. At 50% strain, the pressure-induced adhesive forces decreased with moisture content, DE of corn syrup, and MDG concentration. MDG (>1%) in caramel was an effective anti-sticking agent, which reduced both peel and pressure-induced adhesion.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2021
Citation:
Burke, J., RW Hartel, Stickiness of sugar syrups with and without particles, J. Food Eng (2021) doi.org/10.1016/j.jfoodeng.2020.110222�
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2021
Citation:
Wang, R., RW Hartel, Caramel stickiness: Effects of composition, rheology, and surface energy, J. Food Eng., 289 (2021). https://doi.org/10.1016/j.jfoodeng.2020.110246
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Progress 07/01/18 to 06/30/19
Outputs
Target Audience:The problem of stickiness of sugar-based products crosses a wide range of food product applications, although the focus here is on stickiness problems in reduced sugar cereal coatings. Thus, the primary audience is technical people in this manufacturing sector. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project trained: 2 Post-doctoral researchers: First half of year, Katie Payne; second half, Bulaji Subbiah 1 MS student: Jen Burke 2 undergrad researchers: Lindsay Friedman, Heidi Gust 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?In the next reportiong period, work will continue on Objectives 2 and 3, trying to find alternative solutions to resolved stickiness problems in reduced-sugar films by better controlling adhesive versus cohesive forces.
Impacts
What was accomplished under these goals?
Driven by consumer demand, many companies are pursuing means to reduce sugar content in their products. However, this often is accompanied by concomitant losses in quality. For example, sugar reduction in cereal coatings generally leads to problems of stickiness, with individual pieces sticking together or on the conveyor belts during processing. In the past year, we have shown that this increase in stickiness is caused by a decrease in the sucrose crystalline content of the cereal coating. In fact, stickiness of sugar coatings was directly proportional to the amount of crystals at the interface. Also, the nature of those crystals did not seem to affect the correlation since inert zirconium particles had exactly the same capability of reducing stickiness as sugar crystals. Water content of the sugar coating also was found to influence stickiness although the relationship was complex based on competing adhesive and cohesive forces. As water content of the sugar coating decreased from 20% down to about 12%, the stickiness of the coating increased, as evidenced by both the amount of syrup left on the probe used to assess stickiness and the force required to remove the probe from the surface (tack force). However, below about 12% moisture content, the surface was sufficiently dry that none stuck to the probe even though the tack force continued to increase.
Publications
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Progress 07/01/17 to 06/30/18
Outputs
Target Audience:The problem with stickiness of sugar-based products crosses a wide range of food product applications, although the focus here is on stickiness problems in reduced sugar cereal coatings. Thus, the primary audience is technical people in this manufacturing sector. Changes/Problems:The post-doc on this project had to be assigned to another project this past year, delaying the work on Objectives 2 and 3. What opportunities for training and professional development has the project provided?One post-doc, one MS student and one undergrad student are receiving valuable research experience to further their careers. How have the results been disseminated to communities of interest?We continue to have discussions on results with our industry collaborator. What do you plan to do during the next reporting period to accomplish the goals?• Continue to evaluate effects of crystal content (surface and bulk) on stickiness of sugar syrups • Continue to evaluate effects of varying DE content on stickiness of sugar syrups • Characterize cohesive versus adhesive forces to correlate with stickiness using syrups with varying degrees of starch hydrolysis and varying addition levels of zirconium oxide beads
Impacts
What was accomplished under these goals?
Objective 1: The sucrose bulk in reduced-sucrose syrups is often replaced with corn syrup; we hypothesize that the resulting increase in amorphous sugar phase is the primary culprit for the increased stickiness of these syrups. We have been investigating this over the past year by using the TA.TX2 Texture Analyzer with standard protocol at room temperature. The experiments involve creating a sucrose/corn syrup solution to press between the probe and the stage - a flat probe (with larger surface area than the sample) was selected to assess the stickiness of the sample surface - by using a constant depth analysis, the sample is compressed to a volume with consistent surface area (allowing for the work associated with removing the probe from the surface to be normalized across samples). Our investigations on the effects of surface sucrose crystal content are performed by sprinkling the surface of sucrose/corn syrup samples with sucrose seed crystals and assessing the work of removing the probe from the surface of the sample. We have found that increasing the amount of surface covered by seed crystals reduces the work required to remove the probe from contact with the sample - supporting our hypothesis that crystalline sugar content impacts the stickiness of reduced-sucrose syrups. In addition to surface texture, we would like to assess the influence of seed crystals on the rheological properties of the syrups and use the debonding model of cohesive forces compared against adhesive (surface) forces. For this, the sucrose seeds would be mixed into the bulk; however, the seed crystals dissolve or grow when mixed into these syrups, so we have determined zirconium oxide beads (similar size and inert) will be used as a substitute, both on the surface for comparison with the sucrose seeds and mixed into the bulk for assessment of how cohesive and adhesive properties are influenced. In addition to the seed content, we have also started to consider the degree of starch hydrolysis in the corn syrup used to replace sugar. These experiments will allow us to determine the influence that DE content has on the stickiness of the amorphous phase - can altering the DE content of the corn syrup alter the stickiness of the amorphous phase of the sugar syrup? Objective 2 and 3 are not completed as the post-doc left the project (expained in the Changes section). Work will begin again on these objectives in December.
Publications
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