Location: Dairy and Functional Foods Research
2020 Annual Report
Objectives
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 U.S. 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.
4. Investigate techniques for separating components of dairy waste to determine their potential as ingredients. [C1,PS1A]
5. Investigate technologies for large-scale production of the ingredients identified in Objective 4, with products targeted to food applications. [C1, PS1A].
Approach
Research will be conducted to extend the use of the Fluid Milk Process Model (FMPM) to simulate different types of U.S. 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 Report
This is the final report for Project 8072-41000-096-00D which ended 4/12/2020. A bridge project has been established (see 8072-41000-107-00D).
Simulation of yogurt processes. The dairy industry conducted one of the first Lifecycle Assessments (LCA) for Fluid Milk Production from the farm to the consumer. We collaborated with them to develop a process simulator for a fluid milk plant that would calculate GHG emissions, energy and process water use, and costs and again to develop a simulator for the set, stirred or strained methods of yogurt, using some of their data. Because the processors were not able to provide as much data as the fluid milk processors, the simulated models will be used to fill in data gaps for the LCA. This is a new approach for conducting LCA and will change the way LCA for any process is conducted in the future.
Digestion of processed milk. Some Americans avoid milk because of trouble digesting it. ARS researchers, Wyndmoor, Pennsylvania, used a digestion model that simulated gastric and intestinal conditions to monitor the digestibility of protein and fat from pasteurized and raw milk that had undergone homogenization and pasteurization. Protein digestibility improved by homogenization and by skimming. Ultra-high temperature (UHT) pasteurization destroyed the protein structure and reduced fat digestibility. Protein and fat digestibility were affected by skimming, homogenization, and heat processing, which has implications with people who have difficulties in digesting milk. In collaboration with -097, the protocols to characterize casein phosphopeptides (CPP) have been adapted and are being used to monitor CPP levels in store-bought homogenized HTST and UHT milk samples, and in milk samples from a local farm that underwent a variety of homogenization and pasteurization processing protocols followed by in vitro digestibility studies.
Characterizing caseinate-based films. Even though calcium and sodium caseinates (CaCAS and NaCAS) are obtained through neutralization of acid casein, with either CA or Na hydroxides, the functional properties of the edible films prepared from them differ. The differences in the two ions are shown in the electrostatic and ionic interactions between the proteins and other ingredients in the film-forming suspensions, which in turn affect the film-casting process and the structure and properties of the dried films. Extensive characterization of NaCAS films under normal and extreme environmental conditions was performed to leverage the functional differences with CaCAS films and enable a broader variety of food preservation and packaging applications. Concentrated CaCAS and NaCAS suspensions were shown to possess differing surface tension and adhesion to various substrates and widely dissimilar rheological behaviors and microscopic structures. Dynamic mechanical rheology and optical microscopy demonstrated critical structural changes in the assembly of the caseins into particles and/or a static gel configuration that is highly sensitive to the type of caseinate, as indicated by shifts of the elastic modulus values, but also to time, concentration, temperature, pH and other ingredients in the suspension. The Ca ions in CaCAS created additional electrostatic bonds between and within CAS that rendered suspensions and films structures more complex than that of NaCAS and more sensitive to formulation changes. CaCAS films are stronger but dissolve poorly, while NaCAS films are slightly more flexible and dissolve quickly in a variety of hot or cold beverages and liquid foods. A variety of single-serve food pouches (instant coffee, soup, cheese) were prepared to measure the moisture-transfer kinetics and film solubility. CAS-based films will be an excellent 1st-layer packaging or coating directly on the food, or as part of a moisture-proof multi-layer packaging with synthetic films that is also air-tight. This work was featured in a Press Release and short video documentary by the American Chemical Society. This was the first research conducted on concentrated casein suspensions at elevated pH levels and will have implications on the manufacture of dairy protein-based films and other dairy proteins research.
From Solution to Dried Films. Dynamic rheology revealed that CaCAS-glycerol suspensions exhibited shear thinning whereas NaCAS-glycerol suspensions were shear thickening. Models were proposed based on microstructural and rheological results. CaCAS particles were assumed to be relatively large, loosely packed, and easy to stir, resembling ball bearings or marbles. NaCAS particles were small, tightly packed, and difficult to stir, resembling sand or salt. Particle sizes and protein and electrostatic interactions can be investigated with oscillatory shear and shear rate measurements, and this information can be used to develop optimal formulations for producing stronger dried films.
Nanofibers from casein. Edible films were made from casein that can be used, e.g., to wrap and preserve cheese quality, create hot water-soluble pouches, or coat cereal to replace sugar. Building upon this work, electrospinning, which is used to produce nanofibers from synthetic polymers, was used to create porous mats from fibers of casein, to explore new applications for the proteins. Each casein-based fiber in the mats has a diameter as small as 160 nm, equivalent to 0.0000063 in., and a surface area about 1000 times greater than volume. Owing to the large surface area, these fibers have the potential to introduce intense colors, flavors or textures within or on foods, may 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 (Patent awarded).
Fibers vs Films. Pullulan (PUL)/CaCAS and PUL/NaCAS films were prepared with the casting method or via electrospinning (ES) at 50C to produce fibrous mats. Various properties were compared as a function of composition and preparation method to elucidate molecular interactions between PUL and NaCAS or CaCAS and the theoretical structure of the polymer network. 100% PUL films and mats were dense and stiff, owing to entangling of the long PUL molecules, resisted initial moisture-intake, had a lower OP and the highest mechanical strength. Incorporation of either protein appeared to cause exfoliation of the PUL network, increased OP slightly, accelerated moisture-sorption and decreased the mechanical strength of both. The NaCAS proteins may not uncoil very well during ES and intercalated between linear PUL molecules, disrupting the linear network. CaCAS disrupted the network and weakened the mats most, due to its partial assembly into large micelles at neutral pH, which caused disruption of the PUL network. Mats containing up to 67% NaCAS or 50% CaCAS, at neutral pH, were delicate but had sufficient integrity to be measured. DMA-RH and VSA indicated phase transitions caused by the dissolution of various bonds by water as humidity increased. Structural information identifies changes caused by the formulation and ES process parameters, in order to optimize the ES fibers while maximizing CAS content and predict behavior in food and food packaging.
CaCAS-NFDM films. Films were made from nonfat dry milk, CaCAS, with different concentrations and alkaline additives. Suspension properties were examined before casting. Edible films ranging from low solubility to instant solubility, and with a high strength and stiffness to high elasticity, were prepared to enable a range of film/ coatings applications. Evaluation of the shelf-life of films and stability in properties as they age, under controlled conditions, was under way. Inquiries from numerous U.S. and international companies were received for utilizing the films in a variety applications; efforts were focused on developing numerous formulations to produce films with mechanical and physical properties that fit the requests.
This project participates in the ARS Dairy Grand Challenge project “Develop genetic and management practices in the dairy industry for delivery of products that are nutrient dense and positively impact public health, but with a lower environmental impact.” Team members provided key input in designing the first working collaboration. In the first study, six shipments of 154 milk samples were sent to Wyndmoor, Pennsylvania, for proximate analysis on fresh samples and direct sugar, lactose and oligosaccharide analyses on frozen samples. One team member will work to link farm to process and nutrition data. The results will enhance our understanding of the relationship between the environment, farm, processing, and nutrition of dairy products in human health.
ARS scientists attended the annual Northeast Pasture Consortium (NEPC) Annual Meetings. Discussions on current milk research with NEPC board members and a few of the milk processors focused on the impact our research has on improving the marketability of milk from small farms through enhancements in the nutritional- and health-value of dairy foods, through our work in fatty acids and bioactive peptides, digestibility of unprocessed milk vs. processed milk, and to introduce new topics. The most recent research addressed NEPC priority of furthering fatty acid research in dairy products. NEPC board members asked a team member to talk about the current research status of 'a2' milk at a monthly NEPC board teleconference, and another to present at the annual 2019 meeting on the topic.
Accomplishments
