2011 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.
A growing number of Americans believe that milk produced on organic and pasture-fed farms is inherently better in quality and nutritional value than milk from conventional farms, but research is lacking or contradictory about the bioactive compounds found in these milks. A systematic investigation into lipids, proteins, organic compounds, minerals and vitamins that are associated with human health benefits has begun (Objective 1 and 2). Multiple organic, grass-fed, and conventional dairies are currently being recruited into this project to supply milk samples at regular intervals over the next two years. Samples will undergo extensive state-of-the-art analyses to create a database from which seasonal and farm system operation effects can be compared, thus improving our understanding of the quantity and source of variation of bioactive compounds found in milk and giving insight into ways to enhance or stabilize them in dairy products.
Milk and dairy products are known to exhibit biological activities, which may be beneficial for human health. Assays to measure antioxidative (protects against harmful molecules known as free radicals in the body) and antihypertensive (lowers blood pressure) activities are being adapted for use with milk and dairy products and to identify the exact compounds that are responsible for the biological activities (Objective 1). The results of this study will provide a quantitative measure of these biological activities in milk from different farming systems and will give insight into ways to increase the concentrations of these compounds in dairy foods to benefit the dietary and health needs of American consumers.
Impact of high pressure processing on the quality of Queso Fresco cheese. Queso Fresco (QF), a popular Hispanic-style cheese, can become contaminated with bacteria responsible for food borne illnesses. Application of high pressure to cheese has been shown to reduce or eliminate the harmful bacteria on cheese, but this process is not useful to cheese manufacturers if it adversely affects the quality of the cheese. In this study, ARS researchers at Wyndmoor, PA, treated packaged QF with the high pressure process (HPP). At pressures that were effective against harmful bacteria, minimal changes in cheese quality were noted if the processing was done at room temperature and the length of exposure to pressure was kept to a minimum. This research offers guidance on minimizing the changes in the quality of QF to cheese producers who want to use HPP to improve the food safety and shelf life of their cheese.
Guo, L., Van Hekken, D.L., Tomasula, P.M., Shieh, J.J., Tunick, M.H. 2011. Effect of salt on the chemical, functional, and rheological properties of Queso Fresco during storage. International Dairy Journal. 21:352-357.
Renye Jr, J.A., Somkuti, G.A., Van Hekken, D.L., Guerrero, P.V. 2011. Characterization of microflora in Mexican Chihuahua cheese. Journal of Dairy Science. 94:3311-3315.
Tunick, M.H. 2010. Activation energy measurements in rheological analysis of cheese. International Dairy Journal. 20:680:685.
Tunick, M.H. 2010. Milk lipids. In: Sikorski, Z.E. and Kolakowska, A., Editors. Chemical, Biological, and Functional Aspects of Food Lipids. 2nd edition. Boca Raton, FL: CRC Press. p. 313-325.
Tunick, M.H., Van Hekken, D.L. 2010. Rheology and texture of Queso Fresco cheeses made from raw and pasteurized milk. Journal of Food Quality. 33:204-215.
Tunick, M.H. 2010. Food texture analysis in the 21st century. Journal of Agricultural and Food Chemistry. DOI: 10/1021/jf/02/994.
Tunick, M.H. 2010. Dynamic rheology of food protein networks. Journal of Agricultural and Food Chemistry. DOI: 10.10.21/jf10/6237.
Paul, M., Van Hekken, D.L. 2011. Assessing antihypertensive activity in native and model queso fresco cheese. Journal of Dairy Science. 94(5):2280-2284.