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United States Department of Agriculture

Agricultural Research Service


Location: Dairy and Functional Foods Research

2013 Annual Report

1a. Objectives (from AD-416):
1: Characterize biologically active compounds (BACs) in milk from organic, grass-fed, and conventional herds. 1.a: Identify and quantify the protein-based, lipid-based, and other BACs in milk from organic, grass-fed, and conventional bovine dairy herds, select the BACs that will be tracked for the rest of the study and establish assay methodologies. 1.b: Establish the seasonal variations in the concentrations of the selected protein-based, lipid-based, and other BACs in milk from organic, grass-fed, and conventional bovine dairy herds. 2: Develop technologies to modify the level and stability of selected biological active compounds (BACs) in milk and cheese. 2.a: Determine effects of common milk processing procedures and storage conditions on the concentration and stability of the selected BACs in milk. 2.b: Determine the effects of cheese manufacturing techniques and aging on the concentration and stability of selected BACs in cheese and correlate to changes in quality traits. 2.c: Develop low-salt high-moisture model cheese to determine effects of low-salt environment on the concentration and stability of BACs during aging and correlate to changes in quality traits.

1b. Approach (from AD-416):
This research will focus on measuring the quantity and quality of biologically active components, or BACs, in milk and cheese, and identifying processing factors that affect their stabilities in dairy foods. The BACs of interest contribute to the nutritional, functional, and sensorial quality traits of the products, and may have potential health benefits. A variety of state-of-the-art techniques will be used to measure the BACs (protein/peptides, lipids, minerals, vitamins, and flavor compounds), as well as the physical and microbiological properties of the milk and the functional and textural properties of the cheese. One phase of the project will characterize the naturally occurring BACs in milk and identify sources of milk with high levels of BACs; in particular, milk from multiple organic and conventional farms in mid and eastern Pennsylvania will be evaluated for BACs to determine quality and seasonal variations. Another phase will develop technologies to modify the levels and stability of selected BACs in milk and cheese. Milk will be obtained from organic and conventional farms and processed at the DFFRU milk processing pilot plant with portions being used to manufacture high-moisture cheese (Queso Blanco). The effects of common dairy industry milk processing procedures and storage conditions on the concentration and stability of selected BACs will be evaluated. In another phase of the project, low-sodium high-moisture cheese model will be created to evaluate the effect of the low-sodium environment on the stability of the BACs and the quality traits of the cheese.

3. Progress Report:
In collaboration with Rodale Institute, ARS scientists are analyzing milk samples from the third consecutive grazing season from two dairy farms in the Kutztown, PA area to determine levels and seasonal variation of biologically active compounds (BAC) in milk. The conventional farm does not graze their milking herd while the other farm obtains a minimum of 30% of energy in the cows’ diet through grazing; this herd transitioned to organic during the first year of this study. Levels of conjugated linoleic acid, which has been identified as an anti-carcinogen, have been found to be higher in milk from the organic herd during the grazing season, and levels of linolenic acid, which may improve cardiovascular health, are higher in the organic milk throughout the year. These differences could indicate that milk from grazing cows has extra benefits. Examination of proteins present in fresh milk from the two farms has confirmed that the overall identity and composition of milk proteins remained the same between samples, with little variation over time. Although the overall health-value of these two types of milk may be different, the variation is not due to overall protein content. Therefore, emphasis has shifted to identifying the peptides that are responsible for different biological activities and how processing may affect the release of these peptides. Studies to evaluate the effect of milk processing on the BACs in milk have begun by comparing raw and heat treated (pasteurized or sterilized) whole and skim milk. Initial experiments are comparing concentrations of BACs in the milk following each treatment to identify process-sensitive BACS. A visiting scientist from China is evaluating the impact of milk processing on the digestibility of milk proteins and fats when exposed to conditions that mimic the human stomach and intestines.

4. Accomplishments

Review Publications
Van Hekken, D.L., Tunick, M.H., Leggett, L.N., Tomasula, P.M. 2012. Impact of curd milling on the quality traits of starter-free pasteurized Queso Fresco. Journal of Dairy Science. 95(10):5527-5535.

Tunick, M.H., Van Hekken, D.L., Guo, L., Tomasula, P.M. 2012. Chemistry of Queso Fresco. In: Tunick, M., Gonzalez de Mejia, E., editors. Hispanic Foods: Chemistry and Bioactive Compounds; American Chemical Society Symposium Series, Washington, DC: American Chemical Society Publication. 1109:11-23. DOI: 10.1021/bk-2012-1109.ch002.

Paul, M., Van Hekken, D.L., Brewster, J.D., Tomasula, P.M. 2012. Measuring the antioxidative activities of Queso Fresco after post-packaging high-pressure processing. Advances in Bioscience and Biotechnology. 3:297-303.

Gunther, N.W., Paul, M., Nunez, A., Liu, Y. 2012. pH fractionation and identification of proteins: comparing column isoelectric focusing vs liquid based focusing techniques. Journal of Separation Science. 35(12):1399-1406.

Van Hekken, D.L., Park, Y.W., Tunick, M.H. 2013. Effects of reducing fat content on the proteolytic and rheological properties of Cheddar-like caprine milk cheese. Small Ruminant Research. 110(1):46-51.

Paul, M., Van Hekken, D.L., Brewster, J.D. 2013. Detection and quantitation of Escherichia coli O157:H7 in raw milk by direct qPCR. International Dairy Journal. 32:53-60. Available:

Tunick, M.H., Van Hekken, D.L. 2012. The power law and dynamic rheology in cheese analysis. Book Chapter. Thth, S. and Mussinan, C(eds.) Recent Advances in Analysis of food and flavors, Washington, DC: ACS Books. pp 191-199.

Last Modified: 10/17/2017
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