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United States Department of Agriculture

Agricultural Research Service

Research Project: PROTEIN PROCESSING USING HIGH-PRESSURE GASES AND SUPERCRITICAL FLUIDS
2008 Annual Report


1a.Objectives (from AD-416)
The objectives of this research are to:.
1)develop new, cost effective technologies for processing protein fractions from NFDM into food and non-food products by utilizing concepts from physical chemistry, (2) develop new environmentally benign processes for dairy protein modification that utilize supercritical fluids as reaction media and solute carriers; and.
3)develop new processes for producing enriched fractions of the whey and casein proteins to utilize surplus NFDM and whey.


1b.Approach (from AD-416)
This research will focus on the means of developing new food and non-food uses for whey and casein, as well as nonfat dry milk (NFDM), through basic research and process development engineering. Specifically, new processing techniques for production of edible films from the milk proteins will be investigated to expand their utilization into new food and nonfood products. High pressure and supercritical carbon dioxide will be investigated as media for creating modified casein and whey proteins to increase the functionality of the proteins for food uses. A new environmentally benign process will be designed based on one that was developed in our laboratory for fractionation of whey proteins concentrate into two enriched fractions, alpha-lactalbumin (a-LA) and beta-lactoglobulin (B-LG). Process simulation will be incorporated into the study to guide process development for the most efficient production scheme. In addition, the possibility of producing a fully soluble form of a-LA and a form in the so-called molten-globule state will be investigated. This will ultimately expand the range of products that can be obtained from a single process thereby reducing the costs associated with whey protein concentrate. Finally, casein molecular models developed previously in our lab will be used to guide production of enriched fractions of the individual caseins.


3.Progress Report
Sweet whey is concentrated using membrane or ion-exchange processing to produce whey protein concentrates (WPC) and whey protein isolates (WPI). In past studies, scientists have demonstrated that carbon dioxide (CO2) may be used instead of acids to produce enriched fractions of the whey proteins, alpha-lactalbumin (a-LA) and beta-lactoglobulin (ß-LG), from WPC. A large-scale reactor, that uses SCO2 to fractionate WPI is being designed to produce kilogram quantities of the enriched fractions. Estimating the volume of the reactor requires information on the thermodynamic equilibrium, or end point, of the reaction as well as information on the dissolution rate of the SCO2 in WPI. Scientists completed a detailed calibration of the pH of WPI solutions as a function of CO2 pressure and solution concentration at 60ºC, and a preliminary study of thermodynamic equilibrium times versus WPI solution concentration. In experiments to determine the mechanism for the fractionation of whey protein isolate (WPI) in aqueous solutions using CO2, it appeared that the CO2 was not only behaving as an acid when it was dissolved in the WPI solutions, but also as a gas antisolvent that changed the solvent properties of water, which in turn changed the rate at which alpha-lactalbumin (a-LA) formed aggregates. Experiments were conducted to determine the effects of the individual process parameters, temperature, pressure, pH and WPI concentration on the aggregation rate of a–La and compared to HCl fractionation studies, which is an acid and not an antisolvent. Comparison of the results showed that CO2 is not an antisolvent and exhibits an acidification effect only.

The use of genipin as a crosslinking agent for improving the properties of casein-based edible films was continued. The reaction kinetics of casein – genipin blends under various temperature, pH and solvent conditions are under study. Whey proteins are also being studied in comparison. Scientists have made significant progress in uncovering the mechanism for the crosslinking reaction using ß–lactoglobulin, a major whey protein and genipin, by examining the protein structures that result after crosslinking using modern mass spectrometry and microscopic techniques.

A computer process simulation of the fluid milk process was conducted and is being used to examine energy use, water use and packaging in the processing of milk. This research will focus on development of best practices to reduce energy use and the potential of integration of edible films into milk packaging. This research addresses NP 306 Action Plan Component 2. New Processes, New Uses and Value – Added Foods, and Biobased Products. Problem Areas 2a. New Product Technology and 2c. New and Improved Processes and Feedstocks.


4.Accomplishments
1. Enriched whey protein ingredients from a sustainable processing method. Commercial whey protein isolate (WPI), a concentrated form of cheese whey, provides superb functional and nutritional properties when added to foods because it contains the whey proteins, beta-lactoglobulin (60%) and alpha-lactalbumin (30%). Separation of these proteins from WPI has the potential to enable creation of new food ingredients with even greater benefits. Existing processes to separate the two proteins tend to contaminate the products with acids or salts. In this study, engineers developed a process to separate the proteins from WPI into two protein-rich fractions using supercritical carbon dioxide (SCO2). SCO2 becomes an environmentally friendly acid during processing and vaporizes upon completion of the experiments without contaminating the enriched protein fractions. The protein-rich fractions contain approximately 85% beta-LG and 70% alpha-LA, respectively. This research will provide processors with new whey ingredients for enhancing the properties of foods using a sustainable processing method. (NP 306 Action Plan Component 2. New Processes, New Uses and Value-Added Foods.)

2. Improvement of functional properties of biodegradable films: Films made from dairy proteins would help serve the current need for sustainable alternatives to petroleum-based packaging, but most are completely soluble in water and sensitive to humidity. Crosslinking, a procedure for attaching a chemical compound to the protein, may render the films less sensitive to water by modifying the structure of the proteins. In this study, scientists explored the use of genipin to modify edible films made from calcium caseinate to lessen their solubility in water. Genipin, isolated from the fruits of Genipa Americana and Gardenia jasminoides Ellis and traditionally used in Chinese medicine, is an effective crosslinking reagent capable of reacting with proteins such as gelatin and collagen. Films made from the modified proteins exhibited a 40% reduction in water solubility. The films may be used as part of multi-layer packaging systems to replace the petroleum-based layers. NP 306 Action Plan Component 2. New Processes, New Uses and Value – Added Foods, and Biobased Products. Problem Areas 2a. New Product Technology and 2c. New and Improved Processes and Feedstocks.


5.Significant Activities that Support Special Target Populations
Collaboration with members of the Northeast Pasture Consortium representing rural farm producers in the Northeast. Invited a representative to the NP 306 research listening session. Tomasula, P. 2008. Research needs for small-farm dairy producers. Presentation to the Northeast Pasture Consortium, Binghamton, NY. Established collaboration with Delaware State University, an HCBU, to train minority students for careers in Food Science and Food Safety.


6.Technology Transfer

Number of the New MTAs (providing only)2
Number of New Patent Applications Filed1
Number of Web Sites Managed1
Number of Non-Peer Reviewed Presentations and Proceedings4
Number of Newspaper Articles and Other Presentations for Non-Science Audiences1

Review Publications
Mora-Guitierrez, A., Farrell Jr, H.M., Attaie, R., Mcwhinney, V.J., Wang, C. 2007. Influence of bovine and caprine casein phosphopeptides differing in alpha s1-casein content in determining the absorption of calcium from bovine and caprine calcium-fortified milks in rats. Journal of Dairy Research. 74(3):356-366.

Bonnaillie, L., Tomasula, P.M. 2008. Whey protein fractionation. In: Onwulata, C.I., Huth, P.J., editors. Whey Processing, Functionality and Health Benefits. Ames, IA: Blackwell Publishing and IFT Press. p. 15-37.

Qi, P.X. 2007. Casein micelle structure: the past and the present. Le Lait. 87(4-5):363-383.

Last Modified: 4/17/2014
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