NOVEL CELLULOSE-BASED ICE RECRYSTALLIZATION INHIBITORS FOR FROZEN FOODS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1022162
• Grant No.: 2020-67017-31271
• Cumulative Award Amt.: $469,000.00
• Proposal No.: 2019-06761
• Project Start Date: Jun 1, 2020
• Project End Date: Feb 28, 2025
• Grant Year: 2020
• Program Code: [A1364]- Novel Foods and Innovative Manufacturing Technologies

Recipient Organization
UNIVERSITY OF TENNESSEE
2621 MORGAN CIR
KNOXVILLE,TN 37996-4540

Performing Department
Food Science Research

Non Technical Summary
The global frozen food industry is predicted to have a market value of $150 billion in 2019. Frozen food products such as ready-to-eat meals, fish/seafood, meat products, pizza, potato products, bakery products, fruits and vegetables, and ice cream and frozen desserts are the major segments of the global frozen food market. Despite frozen foods are as nutritious as and safer than conventional foods, consumers commonly perceive that the texture, taste and flavor quality of foods have been negatively affected by the frozen storage. Additionally, certain frozen products are associated with the problems of moisture separation from the food matrix and drip loss at thawing, which may lead to potential microbial safety concern. The loss of quality in frozen foods is linked to the formation, growth and recrystallization of ice crystals. Many efforts, such as rapid freezing technologies and use of antifreeze proteins have been explored to reduce the size of ice crystals and improve the quality and safety of frozen foods. Biopolymers, such as polysaccharides and proteins are important ingredients providing thickening, gelling, emulsion and foam stabilization functionalities in frozen foods. Additionally, biopolymers are used to control the ice recrystallization. A current consensus in food science about the ice recrystallization inhibition (IRI) mechanism of biopolymers is based on their thickening and cryogelation effects. However, recent studies propose a new theory about the IRI mechanism based on an absorption-inhibition mechanism. In this project, we will prepare cellulose-based ice recrystallization inhibitors (IRIs) and use these materials to understand how food ingredients influence the ice recrystallization. Meanwhile, the structure and activity relationship of these materials will be studied. Additionally, the effects of processing conditions and food composition on the IRI activity of these materials and the efficacy of these materials in ice creams, frozen meat and surimi will be studied. Completion of this project will fill the knowledge gaps in understanding of how food ingredients influence ice recrystallization. Meanwhile, novel cellulose-based ice recrystallization inhibitors can be developed to improve the quality of frozen foods, and to increase the competitiveness of U.S. manufacturers in global frozen food industry. Additionally, exploring novel food ingredients of agricultural and forest origin will increase the profitability of biomass industry associated with agriculture and forestry.

Animal Health Component

30%

Research Effort Categories

Basic

70%

Applied

30%

Developmental

0%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
502	5010	2000	100%

Knowledge Area
502 - New and Improved Food Products;

Subject Of Investigation
5010 - Food;

Field Of Science
2000 - Chemistry;

Keywords

cellulose-based ice recrystallization inhibitors

frozen foods quality

ice recrystallization

Goals / Objectives
Freezing can effectively retard biochemical reactions, inhibit the growth of spoilage and pathogenic microorganisms, and extend the shelf-life of many foods, such as ready-to-eat meals, fish/seafood, meat products, fruits and vegetables. And freezing has been an inherent processing method for many products, such as ice cream and frozen desserts. However, as a result of the formation and growth of ice crystals, frozen foods are commonly associated with a variety of problems that include moisture separation from the food matrix, drip loss on thawing, and deterioration in texture, flavor and taste, which have negative impacts on consumer acceptance of frozen foods. Mitigating these deleterious properties will have a great impact on improving food quality in the global diet. There are three processes in the formation and growth of ice crystals: nucleation is the formation of stable ice nuclei. Ice crystal growth is the incorporation of water molecules into the crystal lattice of ice when latent heat is removed. Ice recrystallization is the change in the size, number, and shape of already-formed ice crystals during freezing, storage (with or without temperature fluctuation), and thawing. The size of ice crystals in the final product is predominately affected by the recrystallization step. Inhibiting ice recrystallization is thus key to obtaining high-quality frozen foods.Biopolymers such as polysaccharides and proteins are major food constituents and important ingredients providing thickening, gelling, emulsion and foam stabilization functionalities in frozen foods. Additionally, the presence of biopolymers and their assemblies can conversely affect the recrystallization of ice and eventually affect the texture, flavor, and taste quality of frozen products. The long-term goal of this research is to understand the fundamental physicochemical mechanisms and factors necessary to develop low-cost and potent ice recrystallization inhibitors (IRIs) for frozen food industry. We plan to accomplish this goal by pursuing the following objectives:Objective 1: To understand the mechanisms of cellulose-based IRIs. A current consensus in food science about the IRI mechanisms of food polysaccharides is based on their thickening and cryogelation effect, which slow the diffusion of water molecules. We hypothesize that the absorption-inhibition is the major IRI mechanism, whereas the thickening and cryogelation have little influence. Completion of this task under this objective will fill the knowledge gaps in understanding of how food ingredients influence the ice recrystallization.Objective 2: To elucidate the factors affecting the activity of cellulose-based IRIs. The surface charge density and degree of polymerization (DP)/fiber length are the two most important structural parameters of nanocelluloses. We will elucidate how they affect the IRI activity of nanocelluloses. Similar works will be conducted on other cellulose-based IRIs. Additionally, we hypothesize that the IRI activity of cellulose-based IRIs in frozen foods will be influenced by processing conditions and food compositions. We will test the effects of processing conditions and food compositions on the IRI activity of cellulose-based IRIs. The knowledge gained here will be used to tailor the production methods of cellulose-based IRIs and optimize their application in the frozen food industry.Objective 3: To verify the efficacy of cellulose-based IRIs in frozen products. Cellulose-based IRIs will almost certainly find application in many frozen food products. We will choose ice cream and frozen meat or surimi as examples to demonstrate the activity of cellulose-based IRIs and the resulting quality improvement. We hypothesize that adding cellulose-based IRIs can inhibit the ice recrystallization in these products and thus improve their qualities. Cellulose-based IRIs will be used as ingredients in formulating the products. Ice recrystallization in products will be monitored and quality parameters will be determined by instrumental methods..

Project Methods
Method.(1) Cellulose nanocrystals (CNCs) with different surface charge densities, but fixed degree of polymerization or fiber lengths will be synthesized by a strong acid hydrolysis with sulfuric acid followed by a mild acid hydrolysis using hydrochloric acid. TEMPO oxidized cellulose nanofibrils (TEMPO-CNFs) will be synthesized by varying the amounts of oxidants followed by sonication to prepare TEMPO-CNFs with different surface charge density, but same fiber length. Electrosterically stabilized CNCs (ECNCs) and cellulose oligomers with different structural parameters will be synthesized. The determination of cellulose content, crystallinity index, sulfate/carboxylate content, ζ-potential, Z-average hydrodynamic diameter, degree of polymerization (DP), and the morphological analysis by atomic force microscopy (AFM) will use our published methods. For cellulose oligomers, additional DP characterization by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) will be conducted.(2) The ice recrystallization inhibition activity of cellulose-based ice recrystallization inhibitors will be determined by a standard splat assay. A 10 µl droplet of sample solution was dropped from a height of 1.5 m onto a glass slide surface precooled to -80oC. Next, the samples were annealed at -8oC for 30 min before the polarized microscopy images were collected. A smaller size of ice crystals indicates a stronger IRI activity. The 'splat' assay of cellulose-based ice recrystallization inhibitors will be conducted at different processing conditions and food compositions. Only the components that are expected to be present at sufficiently high concentrations or strongly interacted with cellulose-based IRIs will be studied.(3) The freezing-induced thickening or gelation of these materials will be studied by rheological testing. The diffusion of water molecules will be determined by pulsed-field gradient nuclear magnetic resonance spectroscopy (PFG-NMR). The absorption of IRIs on ice surface will be studied by thermal hysteresis/dynamic ice shaping analysis, ice affinity testing and fluorescence microscopy. The amphiphilicity will be studied by interfacial tension analysis and pyrene assay. The amphiphilicity of cellulose oligomers depend on their self-assembly, which will be studied by monitoring the change of particle size, amphiphilicity, and microstructure through dynamic light scattering (DLS), pyrene assay, and scanning electron microscopy, respectively, after freeze-thaw or lyophilization.(4) Cellulose-based IRIs will be used as an ingredient in the preparation of low-fat and standard ice cream. A commercial stabilizer with the best IRI activity will be used as a control. The ice recrystallization process, the structural/physical properties of the final product will be monitored or evaluated. We will add meat product application in the revised plan. Only cellulose oligomers will be tested in this part due to their good solubility in high ionic strength condition. They will be injected into meat before freezing. The ice recrystallization during frozen storage and the main quality attributes affected by freezing and thawing will be monitored.Efforts: Formal classroom instruction is given to undergraduate and graduate students on the research methodology described above. Undergraduate and graduate students will receive research training described in this project and prepare for their career. Seminar course, symposia, workshops and training courses are provided to deliver science-based knowledge to professionals in the biopolymers and frozen foods industries.Evaluation: The success of this project will be evaluated based on the successful completion of the activities, events, services, and products, as outlined in the previous section. A special emphasis will be placed on the submission of peer-reviewed publications, initiation of industrial collaborations, and the development of intellectual property.

Progress 06/01/23 to 05/31/24

Outputs
Target Audience:Industry professionals, researchers, and graduate students working on ice cream and other frozen foods. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project has provided training opportunities for a Ph.D. student. How have the results been disseminated to communities of interest?A journal article has been published. Additionally, research findings have been shared through a conference meeting and the PD meeting. What do you plan to do during the next reporting period to accomplish the goals?One Ph.D. student will complete her dissertation work in the summer of 2024. The remaining funds will be used to support a postdoc for six months to do more work under the long-term research goal of this project.

Impacts
What was accomplished under these goals? Objective 1: To understand the mechanisms of cellulose-based IRIs. Based on the improved understanding of the working mechanisms of cellulose-based ice recrystallization inhibitors through this project, recently we have discovered a new ice recrystallization inhibitor - chitin nanocrystals. The work was completed and published in Food Hydrocolloids (2024, 150, 109669). When the 2-hydroxy group in the monomer of cellulose is replaced with an acetyl amine group, the resulting polymer is chitin. Similar to various nanocelluloses that can be prepared from cellulose materials, various nanochitins can be prepared from chitin materials. Chitin nanocrystals is the most potent IRI active material discovered through this project. Objective 2: To elucidate the factors affecting the activity of cellulose-based IRIs. We have studied the influences of milk fat and milk protein on ice recrystallization in ice cream. Our results indicate that higher milk fat levels significantly reduce ice recrystallization, suggesting an inhibitory role of milk fat. However, the inhibition role of milk fat is not related to the state of fat (either in partially coalesced networks or as dispersed particles). At protein concentration lower than 5%, milk protein does not inhibit ice recrystallization without milk fat and does not have consistent results in the presence of milk fat. At a concentration of 10%, milk protein alone demonstrates IRI effect. In the presence of low concentrations milk fat, 10% milk protein significantly reduced ice recrystallization. In the presence of high concentrations milk fat, 10% milk protein does not contribute to the ice recrystallization. Objective 3: To verify the efficacy of cellulose-based IRIs in frozen products. We have tested the efficacy of cellulose nanocrystals in ice cream. Unfortunately, cellulose nanocrystals do not inhibit ice recrystallization in ice cream. One explanation is the presence of salt in ice cream mix leads to the aggregation of cellulose nanocrystals, resulting in a decreased ice recrystallization inhibition activity. We also tested the efficacy of chitin nanocrystals in ice cream. Chitin nanocrystals are IRI active, which may be caused by their potent IRI activities.

Publications

• Type: Journal Articles Status: Published Year Published: 2024 Citation: Correa-Gonz�lez, X. Y.; Sena, C. T.; Wu, T*. Chitin nanocrystals  a new material with ice shaping and ice recrystallization inhibition activities. Food Hydrocolloids. 2024, 150, 109669.
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Wu, T. Factors that influence the ice recrystallization inhibition activity of stabilizers in ice cream. University of Wisconsin, Madison. October 2023. Invited talk.

Progress 06/01/22 to 05/31/23

Outputs
Target Audience:Ice cream and other frozen foods industry professionals, researchers and graduate students in related fields. Changes/Problems:Under objective 3: to verify the efficacy of cellulose-based IRIs in frozen products, we were planning to choose ice cream and frozen meat or surimi as examples to demonstrate the activity of cellulose-based IRIs and the resulting quality improvement. Our lab has conducted a lot of work in ice cream and is planning to work on surimi as well. However, a recent follow-up work reported the efficacy of nanocelluloses as a cryoprotective substance for surimi (Food Chemistry: X, 2022, 100506). The work has cited our publication and is overlapping with what we were planning to do. Therefore, we will not repeat the work in surimi. Our remaining work will focus on ice cream. What opportunities for training and professional development has the project provided?This project has provided training opportunities for one M.S. student and two Ph.D. students. How have the results been disseminated to communities of interest?Besides the publications, our research findings have been presented in the ACS 2023 Spring and Fall annual meeting. One oral and three poster presentations have been given in the 2023 ACS meeting. What do you plan to do during the next reporting period to accomplish the goals?One Ph.D. student will continue to work under these project goals.

Impacts
What was accomplished under these goals? Objective 1: To understand the mechanisms of cellulose-based IRIs. Based on the improved understanding of the working mechanisms of cellulose-based ice recrystallization inhibitors through this project, we have discovered two new ice recrystallization inhibitors - corn cob hemicelluloses and bile salts. The work has been published in Carbohydrate Polymers, 2023, 318, 121127, and Journal of Colloid and Interface Science, 2023, 629, 728-738, respectively. These works added hemicelluloses and bile salts to the existing material list of ice recrystallization inhibitors for potential applications. Additionally, we have discovered a potent ice recrystallization inhibitor from chitin materials and the work will be published soon. Objective 2: To elucidate the factors affecting the activity of cellulose-based IRIs. We have studied the ice recrystallization inhibition (IRI) effect of cellulose nanocrystals in the presence of neutral and anionic polymers. The work has been published in Food Hydrocolloids, 2023, 145, 109127. This work advances our understanding of the IRI effect for mixed stabilizers and is critical to ice cream formulation. We also studied the IRI effect of cellulose nanocrystals at constant and cycling temperatures. The work has been published in the International Journal of Biological Macromolecules, 247,125108. The research findings in this work offer a reasonable explanation for the opposing results found in the literature and indicate the importance of using long storage times to evaluate the IRI effects of ice cream stabilizers at different temperatures. Additionally, we have studied the effect of stabilizer concentrations on IRI effect. The work has been published in Food Hydrocolloids, 2023, 139, 108576. In ice cream, food hydrocolloids are commonly used as stabilizers for controlling ice recrystallization. Recent studies suggest that some stabilizers might bind to ice crystal surfaces and inhibit recrystallization. However, this ice-binding mechanism is challenged by the fact that stabilizers at high concentrations sometimes have reduced activity or even accelerate ice recrystallization. A new explanation based on the depletion-interaction-induced accretion of ice crystals was proposed. Our findings might resolve the contradiction between the ice-binding mechanism and the stabilizer concentration effect and add more support to the interfacial mechanism of ice recrystallization inhibition. They also pointed out the importance of selecting suitable stabilizer concentrations for screening IRI active materials and manufacturing frozen desserts. Objective 3: To verify the efficacy of cellulose-based IRIs in frozen products. We have evaluated corn cob hemicelluloses as a stabilizer for ice recrystallization inhibition in ice cream. The work has been published in Carbohydrate Polymers, 2023, 318, 121127. In ice cream mixes, the hemicelluloses demonstrated better ice recrystallization inhibition effect than current commercial stabilizers - guar gum and locust bean gum. The addition of 0.2-0.5 % hemicelluloses did not negatively affect the physicochemical properties of ICMs and ice cream, such as viscosity, particle size, overrun, meltdown, shape retention, and hardness.

Publications

• Type: Journal Articles Status: Published Year Published: 2023 Citation: Li, M.; Reeder, W. M.; Wu, T*. Ice recrystallization inhibition and acceleration by cellulose nanocrystals in the presence of neutral and anionic polymers. Food Hydrocolloids. 2023. 14.109127.
• Type: Journal Articles Status: Published Year Published: 2023 Citation: Reeder, W. M.; Li, M.; Li, M.; Wu, T*. Corn cob hemicelluloses as stabilizer for ice recrystallization inhibition in ice cream. Carbohydrate Polymers. 2023, 318, 121127.
• Type: Journal Articles Status: Published Year Published: 2023 Citation: Li, M.; Reeder, W. M.; Wu, T*. Ice recrystallization inhibition effect of cellulose nanocrystals at constant and cycling temperatures. International Journal of Biological Macromolecules. 2023, 242,125108.
• Type: Journal Articles Status: Published Year Published: 2023 Citation: Li, M.; Reeder, W. M.; Wu, T*. Depletion interaction may reduce ice recrystallization inhibition activity of cellulose nanocrystals at high concentrations. Food Hydrocolloids. 2023. 139.108576
• Type: Journal Articles Status: Published Year Published: 2023 Citation: Wang, Z.; Li, M.; Wu, T.* Ice recrystallization inhibition activity in bile salts. Journal of Colloid and Interface Science 2023, 629, 728-738.
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Reeder, M.; Wu, T. Inhibiting ice recrystallization by corn cob hemicelluloses. ACS national meeting, 2023 Spring.
• Type: Theses/Dissertations Status: Published Year Published: 2023 Citation: Factors influencing the ice recrystallization inhibition effects of cellulose nanocrystals in model ice cream. Ph.D. Dissertation. Min Li. UTK
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Li, M.; Wu, T. Ice recrystallization inhibition and acceleration by cellulose nanocrystals in the presence of anionic and neutral polymers. ACS national meeting, 2023 Fall.
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Li, M.; Wu, T. Depletion interaction reduced ice recrystallization inhibition (IRI) activity of cellulose nanocrystals (CNCs) at high concentrations. ACS national meeting, 2023 Spring.
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Correa-Gonz�lez, Y.; Wu, T. Ice recrystallization inhibition activity of chitin nanofibers prepared by phosphoric acid dissolution and water regeneration. ACS national meeting, 2023 Spring.
• Type: Theses/Dissertations Status: Published Year Published: 2023 Citation: Inhibiting Ice Recrystallization in Ice Cream with Corn Cob Hemicelluloses. MS. Thesis. Matthew Winston Reeder. UTK.

Progress 06/01/21 to 05/31/22

Outputs
Target Audience:Food professionals in the frozen foods, food hydrocolloids, and biomass industries, and graduate students in the relevant/related fields. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training for two Ph.D. students. How have the results been disseminated to communities of interest?Besides the publications, our research findings have been presented at the ACS 2022 Spring meeting - M. Li, T. Wu. Inhibiting ice recrystallization by cellulose nanocrystals: Influences of sucrose concentration and storage time. ACS national meeting 2022 Spring. Our research works have been highlighted by a press release by the American Chemical Society (ACS) entitled "Giving the Cold Shoulder to Crunchy Ice Cream with a Dash of Cellulose." ACS is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks, and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted, and most-read within the scientific literature. Https://www.acs.org/content/acs/en/pressroom/newsreleases/2022/march/giving-the-cold-shoulder-to-crunchy-ice-cream-with-a-dash-of-cellulose.html https://www.youtube.com/watch?v=E4uKEakhyZU The original story from the American Chemical Society has been republished by many other media: Grainy ice cream is unpleasant. Plant-based nanocrystals might help - News reported by ScienceNews. March 29, 2022 . https://www.sciencenews.org/article/ice-cream-crystals-grainy-nanocrystals-cellulose Cold war: solving ice cream's ice problem. https://cosmosmagazine.com/science/chemistry/ice-cream-hard-rocky-solution-cellulose/ Secret to keeping ice cream creamy (not crunchy) might be plant-based nanocrystals. https://arstechnica.com/science/2022/03/plant-based-nanocrystals-could-be-the-secret-to-preventing-crunchy-ice-cream/ Plant-Based Cellulose May Be the Solution to Ice Cream's Crunch Problem. https://www.techtimes.com/articles/273537/20220326/cellulose-solution-ice-creams-crunch-problem.htm Can't Keep Your Ice Cream Creamy? Newly Developed Plant-Based Nanocrystals Might Just Help Preserve Frozen Products. https://www.sciencetimes.com/articles/36815/20220327/cant-keep-ice-cream-creamy-newly-developed-plant-based-nanocrystals.htm A new ingredient saves ice cream from being ruined by ice. https://www.freethink.com/science/ice-crystals-in-ice-cream Now there's a way to stop ice crystals forming in ice cream. https://www.freemalaysiatoday.com/category/leisure/food/2022/05/11/now-theres-a-way-to-stop-ice-crystals-forming-in-ice-cream/ No More Ice Cream Crystals Thanks to Cellulose. https://darik.news/tennessee/no-more-ice-cream-crystals-thanks-to-cellulose/549184.html Cellulose may keep ice cream from getting gritty in your freezer. https://nationworldnews.com/cellulose-may-keep-ice-cream-from-getting-gritty-in-your-freezer/ Cellulose Nanocrystals Prevent Recrystallization in Ice Cream. https://www.chemistryviews.org/details/news/11345267/Cellulose_Nanocrystals_Prevent_Recrystallization_in_Ice_Cream/ Hate Those Little Ice Crystals All Over Your Ice Cream? Here's Why That Happens! https://www.indiatimes.com/trending/human-interest/why-ice-cream-has-ice-crystals-569268.html Stopping crunchy ice cream cold. https://www.makewaterfamous.com/news/fancy-less-ice-in-your-ice-cream-science-has-the-answer Cellulose gives no more Ice Cream Crystals. https://list23.com/834050-cellulose-gives-no-more-ice-cream-crystals/ Why do ice cream and yogurt bought in the refrigerator, not eaten immediately, become crispy and crunchy? https://blogtuan.info/2022/03/30/why-do-ice-cream-and-yogurt-bought-in-the-refrigerator-not-eaten-immediately-become-crispy-and-crunchy/ Scientists have found a way to stop ice crystals growing in your ice cream. https://asianewstoday.com/scientists-have-found-a-way-to-stop-ice-crystals-growing-in-your-ice-cream/ Do you hate the ice that grows on your ice cream? Scientists know how to stop them. https://achinews.com/do-you-hate-the-ice-that-grows-on-your-ice-cream-scientists-know-how-to-stop-them-achi-news/ Nanoparticle Ice Cream. https://womeninsciencepdx.org/2022/05/11/nanoparticle-ice-cream/ "Giving the cold shoulder to crunchy ice cream -- with a dash of cellulose". https://www.eurekalert.org/news-releases/945808 What do you plan to do during the next reporting period to accomplish the goals?We will continue to work under these project goals.

Impacts
What was accomplished under these goals? Objective 1: A current consensus in food science about the IRI (ice recrystallization inhibition) mechanisms of food polysaccharides is based on their thickening and cryogelation effect, which slow the diffusion of water molecules. Our research works demonstrate the IRI mechanisms of food polysaccharides is not related to their thickening and cryogelation properties. These works also suggested a surface binding mechanism of IRI. Our recent publication (Biomacromolecules, 2022, 23, 2, 497-504) provided further support to this surface binding mechanism. In this paper, we have studied the effect of storage time on the IRI activity of cellulose nanocrystals, which is a novel ice recrystallization inhibitors discovered by our lab. Exploring novel materials with ice recrystallization inhibition (IRI) activity in several fields often starts with a quantitative analysis of ice crystal size change by a splat assay or sandwich assay on a short time scale from 0.5 to 1 h. This study found that this time scale was insufficient to evaluate the IRI activity of cellulose nanocrystals (CNCs) in a model ice cream system-25.0% sucrose solution. No IRI activity was observed in CNCs incubated with ice crystals on a short time scale of 0.5-2.0 h. However, over longer time scales, the growth of ice crystals was entirely inhibited by 1.0% CNCs (between 2 and 24 h) and 0.5% CNCs (between 24 and 72 h) with corresponding final crystal sizes of 25 and 40 μm, respectively. Additionally, ice shaping was observed on a long exposure time, but not on a short exposure time. The findings presented here can be explained by a time-dependent surface coverage of CNCs on ice crystals. Objective 2: We have studied the effect of storage time on the IRI activity of cellulose nanocrystals. The study described in the last paragraph can explain some opposing data in the literature. For example, locust bean gum (LBG) was IRI inactive in a study that lasted only 64 min. However, it was found to be IRI active in other studies that lasted from 20 h to 24 weeks. While the IRI effect of stabilizers is affected by other test conditions, such as the types and concentrations of sweeteners, storage temperature, stabilizer concentrations, and presence of fats and proteins, which all varied from study to study, the role of storage time should not be ignored. The aforementioned contradicted results on LBG can be explained by a time-dependent IRI effect similar to CNCs: no IRI activity would be observed at a short-time scale, but better IRI activity would be observed at a long-time scale. These works have been invited to publish in a special Issue in Biomacromolecules - Nature and Synthetic Materials that Interact with Ice. This paper was 1 out of 8 papers in this special issue. Biomacromolecules is a leading American Chemical Society (ACS) journal for disseminating cutting-edge research at the interface of polymer science and biology.

Publications

• Type: Journal Articles Status: Published Year Published: 2022 Citation: Li, M.; Luckett, R. C.; Wu, T*. Potent time-dependent ice recrystallization inhibition activity of cellulose nanocrystals in sucrose solutions. Biomacromolecules. 2022,23,2,497-504.
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: M. Li, T. Wu. Inhibiting ice recrystallization by cellulose nanocrystals: Influences of sucrose concentration and storage time. ACS national meeting 2022 Spring.
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: M. Li, T. Wu. Inhibiting ice recrystallization by cellulose nanocrystals (CNCs): Influences of CNCs concentration and storage temperature. ACS national meeting 2022 Fall.

Progress 06/01/20 to 05/31/21

Outputs
Target Audience:food professionals in the frozen foods, food hydrocolloids, and biomass industries. Graduate students in the revelant fields. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Provide one-on-one training for one Ph.D. student on ice recrystallization inhibition assay, polymer characterization, data analysis, and scientific writing. How have the results been disseminated to communities of interest?Besides the publications, our research findings have been presented in the ACS 2021 Spring annual meeting. An oral presentation has been given on inhibiting ice recrystallization by nanocelluloses: effects of surface charge density and fibril length. What do you plan to do during the next reporting period to accomplish the goals?Another Ph.D. student has been recruited and is starting to work in the Fall of 2021. We will continue to work under these project goals.

Impacts
What was accomplished under these goals? Under objective 1: A current consensus in food science about the IRI (ice recrystallization inhibition) mechanisms of food polysaccharides is based on their thickening and cryogelation effect, which slow the diffusion of water molecules. Through our recent publication (Carbohydrate Polymers, 2020, 116275), we have shown the IRI activity is not correlated with the viscosity or gelling properties of nanocellulose dispersions. Another publication from our group (Food hydrocolloids, 2021, 107011) has shown that the IRI effect of nanocellulose is correlated with the ratio between nanocellulose concentration in the unfrozen phase and total surface area of ice crystals. Another recent publication from our group (Carbohydrate Polymers, 2020, 115863) has shown that the IRI activity of nanocelluloses is favored by an increase of surface hydrophobicity. Overall, our research works demonstrate the IRI mechanisms of food polysaccharides is not related to their thickening and cryogelation properties. Under objective 2: We have studied the effect of surface charge density and fibril length on the IRI activity of nanocelluloses. When the surface charge density of nanocelluloses was progressively reduced, an initial increase of IRI activity was observed, followed by a decrease due to fibril aggregation (Carbohydrate Polymers, 2020, 115863). Another publication from our lab indicate longer nanocelluloses are more IRI active (Carbohydrate Polymers, 2020, 116275). A recent publication (Food hydrocolloids, 2021, 107011) from our group investigated the influence of sucrose concentration on the IRI effect of nanocelluloses. The IRI activities of nanocelluloses were higher at low sucrose concentrations, almost disappeared at medium sucrose concentrations, and restored slightly at high sucrose concentrations.

Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: Li, M.; Dia, V.; Wu, T*. Ice recrystallization inhibition effects of cellulose nanocrystals: influence of sucrose concentration. Food Hydrocolloids. 2021. 121. 107111
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Li, T.; Li, M.; Zhong, Q.; Wu, T*. Effect of fibril length on the ice recrystallization inhibition activity of nanocelluloses. Carbohydrate Polymers 2020, 240, 116275.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Li, T.; Zhong, Q.; Zhao, B.; Lenaghan, S.; Wang, S.; Wu, T*., Effect of surface charge density on the ice recrystallization inhibition activity of nanocelluloses. Carbohydrate Polymers 2020, 234, 115863.
• Type: Conference Papers and Presentations Status: Published Year Published: 2021 Citation: Inhibiting ice recrystallization by nanocelluloses: effects of surface charge density and fibril length. 2021. ACS Spring meeting.