Location: Dairy and Functional Foods Research2017 Annual Report
1: Integrate new processes into the Fluid Milk Process Model (FMPM) to determine the effects of reductions in energy use, water use or waste on commercial dairy plant economics and greenhouse gas emissions. 1a: Develop benchmark simulations for configurations of stirred, set and strained curd yogurt processing plants in the US that quantify energy use, economics, and greenhouse gas emissions, validated using data from industry. 1b: Use process simulation for evaluation of possible alternatives of whey utilization for the strained curd method of yogurt manufacture. 2: Integrate properties of edible films and coatings from dairy and food processing wastes with formulation strategies to better target commercial food and nonfood applications. 2a: Investigate thermal and mechanical properties of dairy protein-based edible films and coatings in real-life storage and utilization conditions. 2b: Apply new property findings to the investigation of useful and/or sustainable applications utilizing edible milk protein films. 3: Investigate the effects of different film-making technologies to manipulate the physical and functional properties of films and coatings made from agricultural materials. 3a: Investigate the effect of protein conformation on the ability to electrospin caseinates in aqueous solution and in the presence of a polysaccharide. 3b: Investigate the use of fluid milk, nonfat dry milk and milk protein concentrates as a source for production of electrospun fibers. 3c: Investigate the effects of edible and non-edible additives to the electrospun polysaccharide-caseinate fibers in aqueous solution.
Research will be conducted to extend the use of the Fluid Milk Process Model (FMPM) to simulate different types of US dairy production plants to identify the main sources of energy use and greenhouse gas emissions, propose ways to reduce water usage, and utilize waste streams more efficiently, either by water recovery or recovery of valuable constituents. Simulation results will be validated with data from industry, university and other partners. New edible packaging films and coatings from dairy proteins that can improve food quality and functionality, protect foods from spoilage and extend shelf - life, increase nutrition, reduce landfill waste, and utilize protein-rich surpluses and by-products of the dairy industry to boost their value such as nonfat-dry milk, or its derivatives casein and whey, will be designed with an emphasis on formulation and film-processing technique, for performance under commonly encountered storage and ambient conditions. Finally, those same protein-rich surpluses and by-products will be blended with other edible polymers then structurally modified using the novel electrospinning technology, to create micro- and nanofibers that can form new highly-value-added food and non-food products. This research is expected to help the US dairy and other food industries improve their sustainability, productivity, and profitability while providing new and better products to US consumers.
Progress was made on all objectives, all of which fall under National Program 306 Quality and Utilization of Agricultural Products, Component 1 Food: Problem Statement 1.B., New Bioactive Ingredients and Functional Foods, and Problem Statement 1.C, New and Improved Food Processing Technologies. The work to develop the yogurt models and simulator is essentially complete and a manuscript is being prepared with a collaborator. An additional study is being conducted on the acid whey stream to create complex process models with cost studies. This will be pursued with a collaborator who collected data for some of the processing options under consideration (Objective 1A). In addition, a literature search of whey processing options has been completed to consider additional utilization options for the acid waste stream (Objective 1B). Milk proteins are an excellent raw material to manufacture strong and edible packaging films. In the prior fiscal year (FY), we demonstrated the use of dynamic liquid rheology, dynamic mechanical analysis (DMA) and microscopy to study the relationship between the structures of the film-making suspensions and the physical properties of the dried films, under varied environmental conditions, and the differences between films made with calcium (CaCas) or sodium (NaCas) caseinates. In this FY (Objective 2A), we systematically applied these methodologies, as well as humidity-controlled texture-analysis (TA), oxygen permeation (OP), and solubility testing, to films prepared with various commercial milk protein powders, including fine and aggregated CaCas, fine NaCas, and mixtures of non-fat dry milk powder (NFDM) with CaCas. In addition, citric pectin (CP), and other additives were added to the blends. Up to 50% of the CaCas in films may be replaced by NFDM but there is a subtle shift in the TA properties over time, which is still under investigation. The rheological properties of suspensions of NaCas and CaCas were also investigated to help support the values and trends observed in the data obtained above. Citric pectin (CP) may be added to NaCas and CaCas suspensions to form a network, which occurs above a critical concentration depending on presence of calcium. Increasing the pH unfolds both CP and protein, forming a continuous network sooner than at lower pH. Caseinate suspensions exhibit decreasing viscosity with increasing nonfat dry milk (NFDM) level as the lactose in the NFDM prevents extensive networks from forming. A custom environmental chamber was designed to perform TA measurements of the dried films in tension under precise humidity conditions, from 20 to 80% RH at 23 degrees C, to evaluate the strength and elasticity of the different protein/glycerol/pectin networks and their moisture-resistance. Isohume DMA temperature ramps identified the phase transitions of each of the different protein networks - from glassy to rubbery, then plastic, then molten – as well as the shifts of transition-temperatures and moduli between films prepared from different protein powders and formulations. In most cases, a weakening of the network and degradation of the mechanical properties and of the moisture-resistance were observed after addition of a low CP content to the formulation (typically < 1 wt.%), whereas the addition of a critical minimum CP content (greater than or equal to 1 to 3 wt.%) strengthened certain film preparations. The type of protein, the particle size, calcium and lactose contents and other parameters, considerably changed the apparent interactions between the proteins, and between proteins and CP, as well as the critical CP percent necessary to form a continuous network. Optical microscopy imaging revealed widely varied configurations of the protein matrices themselves, depending on the formulation and other additions. Moreover, CP clearly segregated into droplets or gel pockets and caused disruption of the protein matrix, or on the contrary, unfolded and dispersed itself within the protein matrix, forming long strands or a fishnet-like network, depending on the formulation. The elucidation of intricate structure-properties relationships of milk-based suspensions and films is useful to design optimal formulations targeted to match desired coatings and films properties for a multitude of food and non-food applications. Electrospinning studies of CaCAS and NaCAS with other polysaccharides were conducted over a wide range of concentration ratios of the proteins and the polysaccharides. Three additional polysaccharides and compounds were found that were consistent with electrospinning of CaCAS and NaCAS. (Objective 3A).
1. Nanofibers from milk proteins. Casein is the major protein found in milk and cheese. Recently, ARS researchers at Wyndmoor, Pennsylvania, developed edible films made from casein that can be used, for example, to wrap cheese to preserve quality, create hot water soluble soup and coffee pouches, or coat cereal to replace sugar. Building upon this work, the technique of electrospinning, which is used to produce nanofibers from synthetic polymers, was used to create very fine porous mats of casein fibers with small diameters and increased surface area. Owing to the large surface area, these fibers have the potential to introduce intense colors, flavors or textures within or on foods, and can be used to deliver controlled amounts of nutrients such as vitamins and minerals, or therapeutics, from foods. This is the first example of an edible nanofiber from a milk protein.
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