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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..

Wu, T.
University of Tennessee
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