2012 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.
In a collaboration with Rodale Institute, ARS DFF scientists are analyzing weekly milk samples from two dairy farms in the Kutztown, PA area to determine levels and seasonal variation of biological 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 over this 20-month study. The last set of milk samples are scheduled to be collected 10/2012. Of the samples tested to date, general composition is similar between the farms at the same time points while differences between farms and seasons are noted in the profiles of fatty acids, volatile (flavor) compounds, and protein breakdown products.
Multiple organic, grass-fed, and conventional dairies are currently being recruited for a study in which the dairies would 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 biologically active compounds (BAC) found in milk (Objective 1b) and giving insight into ways to enhance or stabilize the BAC when processing the milk into dairy products.
Compounds exhibiting antihypertensive (lowers blood pressure) and antioxidative activities (protects against harmful molecules known as free radicals in the body) are currently being evaluated in milk and cottage cheese obtained from both conventional and organic farming systems. Assays to quantify antioxidative activities of protein mixtures have been successfully adapted for use with milk and dairy products. Assays measuring antihypertensive activities are currently being studied to find the best method to use with dairy products. Initial experiments showed that, for both milk and cottage cheese, protein mixtures display antioxidative activities at similar levels, regardless of farming system used. Work is continuing to identify the exact compounds that are responsible for the biological activities in these dairy products. 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.
Although high pressure processing of high moisture cheese, such as Queso Fresco, may have the potential to improve the safety of the cheese, the effect of the process on the quality traits of the cheese must be evaluated to determine if they are altered. ARS scientists completed evaluating the effect of high pressure processing on the protein breakdown in cheese over time and how it relates to texture-function as well as health-related properties. Information from this study will help develop cheese manufacturing protocols for safe cheese that meets the expectations of the consumer as well as help establish the health value of dairy products.
Streamlining the manufacture of fresh Hispanic-style cheese. Queso Fresco (QF) is the most popular of the Hispanic-style cheeses made in the U.S. last year, yet it has a high incidence of food safety recalls. One potential point of post-pasteurization bacterial contamination is the time-consuming milling step that is traditionally included to ensure that the QF crumbles easily. ARS researchers at Wyndmoor, Pennsylvania completed a study of their modified cheesemaking protocol for QF and showed that the milling step could be omitted from the manufacture of QF with minimal impact on the quality traits. Cheesemakers and consumers will benefit by omitting this time-consuming milling step as it removes a potential point of contamination and reduces the cost of QF manufacture.
Guo, L., Van Hekken, D.L., Tomasula, P.M., Tunick, M.H., Huo, G. 2012. Effect of salt on microbiology and proteolysis of Queso Fresco cheese during storage. Milchwissenschaft. 67(1):74-77.
Olson, D.W., Van Hekken, D.L., Tunick, M.H., Tomasula, P.M., Molina-Corral, F., Gardea, A. 2011. Mexican Queso Chihuahua: functional properties of aging cheese. Journal of Dairy Science. 94(9):4292-4299.
Paul, M., Nunez, A., Van Hekken, D.L. 2012. The effect of milling on proteins in model Queso Fresco cheeses. Advances in Bioscience and Biotechnology. 3:1-6.
Tunick, M.H. 2011. Choosing techniques for analysis of food components and additives. In: Otles, S., editor. Methods of Analysis of Food Components and Additives. Second Edition. Boca Raton, FL: CRC Press-Taylor & Francis Group. p. 1-14.
Tunick, M.H., Van Hekken, D.L., Iandola, S.K., Tomasula, P.M. 2012. Characterization of Queso Fresco during storage at 4 and 10 deg C. Journal of Food Research. 1:308-391.
Van Hekken, D.L. 2012. Quality aspects of raw milk cheeses. Food Technology. 66:67-78.
Tunick, M.H. 2011. Cheese flavors: chemical origin and detection. In: Foster, R.D., editor. Cheese: Types, Nutrition and Consumption. Hauppage, NY: Nova Publishers. p. 207-220.