Location: Dairy and Functional Foods Research2016 Annual Report
1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
The sustainability of the Greek-style yogurt (GSY) process has been questioned because unlike the more popular stirred and set curd yogurt processes, it generates an acid whey stream, which is usually spread on farms or fed to animals, and is costly to utilize. In addition, proposed regulatory measures may limit land application. The dairy industry is in the process of developing a Lifecycle Analysis of the yogurt industry for examination of yogurt processing and has provided us with data and information from their subject matter experts so that we may construct simulation models of the various processes used to make yogurt (Objective 1a). As reported previously, we are using our models to assist the industry in filling in process data that they don’t have, to conduct a robust Lifecycle Analysis. Using our preliminary simulations, we provided them with information for stirred, set and GSY processes to estimate their energy use, greenhouse gas emissions (GHG), and acid whey production, and also developed an acid whey process in which the acid whey is fed to an anaerobic digester to produce biogas. We also devised an alternative GSY process made from fortified milk without acid whey production. In all plants, production of nonfat yogurt with blended fruit was simulated assuming a raw milk input of 27,300 L/h (113.2M L/y). Simulations of the plants were conducted and energy use and GHG emissions were similar for the stirred and set curd processes but higher values were obtained for the GSY processes because less yogurt, but more concentrated yogurt was produced with whey removal. Addition of an on-site anaerobic digester to the process increased energy use and GHG for the GSY process to operate the digester with production of unrefined biogas and additional wastewater and digestate. Simulation of biogas refining was not conducted in this study but this would eliminate the GHG associated with the trucks that haul the acid whey from the plant to farms where it is used in animal feed or as a soil amendment and help prevent water pollution. For the alternative GSY process without whey removal, GHG were the same as that for the stirred and set curd simulations since the concentration step was removed, but the impact on the functional properties of yogurt are unknown. We are currently working with the industry to refine the models for publication and use by the industry. Even though calcium and sodium caseinates (CaCas and NaCas) are both obtained through neutralization of acid casein, with either calcium or sodium hydroxides, the functional properties of the edible packaging 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 calcium ions in CaCas create additional electrostatic bonds between and within the casein particles that render the structure of CaCas suspensions and films more complex than that of NaCas and more sensitive to formulation changes. A patent is being filed on the surprising relationships between the electrostatic state of the suspensions and the resulting films’ properties. CaCas films are stronger and more environmentally-resistant but dissolve poorly, while NaCas films are slightly more flexible and can dissolve quickly and completely 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 solubility of the films, as well as the shelf-life of the food in different storage conditions. Casein-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 recently featured in a Press Release and short video documentary by the American Chemical Society. It should also be noted that this is the first research to be 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. The new methodology developed in fiscal year 2015 to study the behaviors of biopolymer films under extreme environmental conditions, was adapted for Pullulan/Cas cast films and the newly developed electrospun fiber mats (Objectives 2a and 3a). A variety of Pullulan (PUL)/CaCas and PUL/NaCas film compositions were prepared with both the solvent-casting method used with the Cas films, above, or via electrospinning (ES) at 50°C to produce randomized fiber mats of desired thickness. The films and fiber mats were measured with texture analysis (TA), vapor-sorption analysis (VSA), Oxygen permeation (OP) and humidity-controlled dynamic mechanical analysis (DMA-RH). The mechanical and functional behaviors were compared as a function of the composition and the preparation method to elucidate molecular interactions between PUL and NaCas or CaCas and theoretical structure of the polymer network. All methods demonstrated that 100% PUL films and mats were dense and stiff, owing to the theoretical compact stacking and entangling of the long and flat PUL molecules, resisted initial moisture-intake, had a lower OP and the highest mechanical strength. The incorporation of NaCas or CaCas proteins appeared to cause exfoliation of the PUL network and increased OP of the films slightly, accelerated moisture-sorption of the films and decreased the mechanical strength of both films and mats during humidity-ramps at 20°C in the DMA-RH. The globular-shaped NaCas proteins may not uncoil very well during ES and intercalated between linear PUL molecules and disrupted the linear PUL network. CaCas disrupted the PUL network and weakened the mats most, due to its partial assembly into large micelles at neutral pH, which may be hardest to flatten during ES and may cause greater disruption of the PUL network and a more chaotic structure (PUL-CaCas may be similar to spaghetti and meatballs (oft-used analogy from polymer science); while PUL-NaCas is more like spaghetti and ground-beef sauce). Fiber mats containing up to 67% NaCas and up to 50% CaCas, at neutral pH, were delicate but possessed sufficient integrity to be measured with DMA-RH. DMA-RH and VSA also indicated phase transitions caused by the dissolution of various molecular bonds by water as humidity increased, with sudden ‘melting’ and shrinking of all the mats at 80-82% humidity, as the molecules that were stretched into fibers via ES, relaxed and recoiled into a more globular shape and the mats shrunk to a tenth of their initial size. Structural information for the PUL/Cas films and mats is invaluable to identify changes caused by the formulation and ES process parameters, in order to optimize the ES fibers while maximizing their Cas content, and predict their behavior in food and food packaging.
5. Significant Activities that Support Special Target Populations:
1. The Unit collaborates with Delaware State University (DSU), an HBCU, to mentor master’s degree candidates in food science on research projects developed by ARS researchers and DSU professors. The students perform their research in the Dairy and Functional Foods Research (DFFRU) laboratories and at DSU. A NIFA grant, with a DFFRU co-PI, is supporting the students. 2. The Unit assisted Anita's Yogurt, a small specialty yogurt start-up company in New York, NY, in getting off the ground, by discussing and demonstrating the techniques for quality assurance of their raw materials and products, and providing expert advisory on their yogurt-making process. Several critical questions were answered and major roadblocks were solved by the Unit. This enabled successful commercialization of the product: the company is growing quickly and Anita's yogurt is currently found in Whole Foods and other health food stores in New York City.
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