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United States Department of Agriculture

Agricultural Research Service

Research Project: PROTEIN PROCESSING USING HIGH-PRESSURE GASES AND SUPERCRITICAL FLUIDS
2009 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
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%). Work is continuing to design a large-scale reactor that uses supercritical CO2 to fractionate WPI to produce kilogram quantities of the enriched fractions. Pilot-scale studies to produce the fractions demonstrated that the quantity and quality of the alpha-LA aggregates and soluble beta-LG produced, as well as their production rates, are significantly improved by increasing the CO2 pressure and carefully adjusting the temperature during the fractionation reaction. Increased product yields and increased purities of the two enriched protein fractions are commercially desirable and economically advantageous.

To investigate the molecular details involved in the precipitation of casein proteins from milk by CO2, systematic analytical and microscopic studies have been conducted. Significant progress was made in understanding the effect of CO2 processing on the quality and properties of the casein molecules relative to that obtained by other methods such as acid precipitation. Results showed that interactions among casein molecules are also important in the precipitation process in addition to the acidification effect of CO2.

In the last report, genipin was used as a crosslinking agent to improve the water resistance and lower the solubility in water of edible films made from calcium caseinate. The films are completely soluble in water if not crosslinked. The solubility of the films was reduced to 40% with crosslinking. The studies were expanded to explore the impact of pH and temperature adjustment, with or without genipin, on film solubility. Preliminary results show that solubility of the crosslinked films was lowered further at the highest pH and temperature studied.

A computer process simulation of the fluid milk process was expanded to examine energy and water use in representative small, medium and large processing plants. Data obtained from a life cycle analysis of the process helped refine the model. Early results seem to indicate that the estimated greenhouse gas emissions/gal of milk processed of the largest plant is about the same as that of the smaller plants.


4.Accomplishments
1. Microfilter process developed to remove spores from liquid egg white. Pasteurization, a food processing operation which is used to reduce or eliminate the natural microflora in foods such as fluid milk or liquid egg whites (LEW), is ineffective against threat agents such as spores of Bacillus anthracis (BA) if intentionally added to these foods through a terroristic act. In this study, a cross-flow microfiltration (CFMF) membrane process was designed as an intervention strategy to filter spores of BA from LEW. Since LEW is a viscous material, new techniques were developed to alter the viscosity of the LEW and the properties of the proteins so that only the LEW would pass through the membrane. The optimum operating conditions that preserved the delicate functional properties of LEW, such as foaming, and ensured that the constituent egg white proteins permeated through the membrane were also determined. Greater than 99.9999% of BA spores were intercepted when a 30-gal capacity pilot scale microfiltration unit was used to filter LEW inoculated with the surrogate strain of BA (Sterne) spores. These studies demonstrate that the addition of a microfiltration step followed by pasteurization will ensure the safety of LEW while preserving its nutrients and quality.


5.Significant Activities that Support Special Target Populations
Collaboration with members of the Northeast Pasture Consortium representing rural farm producers in the Northeast. Research needs for small-farm dairy producers. Presentation to the Northeast Pasture Consortium, Van-Hekken and Tomasula, West Virginia. Collaboration with Delaware State University, an HCBU, has trained minority students for careers in Food Science and Food Safety. 4 students earned Masters’ degrees in 2009.


6.Technology Transfer

Number of Web Sites Managed1
Number of Other Technology Transfer1

Review Publications
Farrell, H.M., Malin, E.L., Brown, E.M., Guitierrez, 2009. M. REVIEW OF THE CHEMISTRY OF ALPHA S-2 CASEIN AND THE GENERATION OF A HOMOLOGOUS MOLECULAR MODEL TO EXPLAIN ITS PROPERTIES. Journal of Dairy Science. 92:1338-1353

Tomasula, P.M., Qi, P., Dangaran, K.L. 2009. Structure and Function of Protein-Based Edible Films and Coatings. In: Embuscado, M.E., Huber, K.C., Editors. Edible Films and Coatings for Food Applications. New York, NY:Springer Science Media. Chapter 2: p.25-56.

Last Modified: 4/16/2014
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