NEPC2011 Meeting Index

Session 4, Raw Milk Update followed the afternoon poster paper break convening back at the Grand Ballroom. Angus Johnson, Executive Committee member and Chair of the Stakeholders Action Committee, moderated this session and was a speaker.

Dr. Diane Van Hekken, USDA-ARS, research chemist, Dairy & Functional Foods Research Unit at Wyndmoor, PA led off the session with a presentation entitled, Mooving forward on determining biologically active compounds in milk and their impact on health. She is a chemist who is initiating research into biologically active compounds (BACs) in milk such as proteins, peptides, fatty acids, vitamins, minerals, and less known organic compounds. These BACs play a role in cancer prevention, cardiovascular fitness, suppress hypertension, immune responses, and bone health. Dr. Michael Tunick and Dr. Moushumi Paul also spoke to the session attendees during this presentation. Both are research chemists working with Diane on milk component research.

There is a growing grass-fed and organic dairy market as consumers strive to improve their health through dietary intake choices. Currently, this niche market is worth \$20 billion in 2009 (Ruegg et al., 2009). Consumers will pay premium prices for dairy products because they believe milk from grass-fed and organic herds taste better and are healthier for them than milk from conventional herds. However, there is a critical need that the added health-value of grass-fed and organic dairy products be supported by scientific research.

Health value comes from biological active compounds (BACs) in milk. They are proteins/peptides, lipids, vitamins, minerals, organic acids and flavor compounds that have a function within the human body associated to human nutrition and health, product functionality, and flavor (consumer acceptability).

The research project will study processing methods to enhance bioactive compounds in milk and dairy products. It will characterize BACs in milk from grass-fed, organic, and conventional herds. Milk samples will be taken throughout the year to establish seasonal variations in the levels of BACs in milk from grass-fed, organic, and conventional herds. The project will also develop technologies to modify the level and stability of selected BACs in milk and cheese. It will also evaluate effect of heat processing (pasteurization) on BACs stability in milk.

Working on an USDA-NIFA, Organic Research & Extension Initiative (OREI) grant proposal with Penn State to bring dairy nutrition researchers and extension advisors on board to study impact of feed on BACs in milk. This project plans to get milk samples from 25 dairy farms in southeastern PA. These 25 farms will be representative of 5 groups, 4 of which will be organic producers that all must use pasture during the growing season to be certified organic. One organic dairy group is one that feeds a high amount of corn silage and grain in addition to forage from pasture or stored forages. Another organic dairy group feeds low amounts of corn silage and grain to supplement pasture or stored forages. Another organic diary group feeds no corn silage, but a high amount of grain to supplement pasture or stored forages. The last organic dairy group feeds no corn silage and a low amount of grain to their cows. The fifth group is made of conventional diaries that feed fermented forages primarily with grain and the cows have no access to pasture or minimal access.

Projected milk sample collection will be monthly and begin in July in 2011 and extend to August of 2013. The pasture season is from early April to late October typically in southeastern PA.

In a study on organic and conventional retail milk produced in northeastern England, researchers found organic milk had higher concentrations of beneficial fatty acids (FA) than conventional milk, including total polyunsaturated fatty acids (PUFA; 39.4 vs. 31.8 g/kg of total FA), conjugated linoleic acid cis-9,trans-11 (CLA9; 7.4 v 5.6 g/kg of FA), and α-linolenic acid (α-LN; 6.9 vs. 4.4 g/kg of FA) (Butler et al., 2011. J. Dairy Sci. 94 :24–36). Differences in fat composition between systems were greater for summer compared with winter milk since both would have to rely on stored feeds in winter.

Some health attributes of various BACs were reviewed. The first BACs presented were the saturated fatty acids. Some short-chain (C4-C10) saturated FA found in milk are thought to help prevent cancer and may have antiviral properties. Lauric acid (C12) may have potential in preventing tooth decay and plaque. The next BACs were the unsaturated fatty acids. Milk is high in oleic acid (C18:1), which may reduce plasma cholesterol and triacylglycerol levels. The polyunsaturated FA include linoleic acid (C18:2) and α-linolenic acid (C18:3), also called omega-3. Omega-3 is associated with prevention of cardiovascular disease. The BACs, conjugated linoleic acids (CLA), are responsible for reduction of body fat gain, enhancing growth and feed efficiency, and inhibiting mammary carcinogenesis. All known physiologic effects of CLAs are found in cis-9, trans-11-linoleic acid and trans-10, cis-12-linoleic acid. Fat soluble vitamins A, D, E, and K are also BACs of interest.

The milk analysis techniques were then presented. FA will be extracted with ether, converted to methyl esters, and separated by gas chromatography. A FA profile will be generated for each milk sample to understand the overall fat composition of milk. Fat-soluble vitamins (A, D, E, and K) will be separated from lipids with gel permeation chromatography and also analyzed using liquid chromatography to determine their concentration.

An area of keen interest for this project is antioxidant potential of BACs in milk. Oxidative stress occurs in humans. When oxidation occurs, it produces free radicals in the body. This causes oxidative stress and can damage healthy cells. Oxidative stress increases with aging and is associated with a variety of diseases.

Antioxidants naturally occur in many foods. They are beneficial in that they stabilize free radicals before they can damage human cells or the circulatory system that they invade. This inhibits oxidative stress. Natural antioxidants are b-carotene, lycopene, flavanols, vitamin A, and vitamin C.

Measuring antioxidant active is done by Oxygen Radical Absorbance Capacity (ORAC), which measures fluorescence. When reactive oxygen species (ROS) are present, they cause a loss of fluorescence. If antioxidants are present, they slow the fluorescence decay. This then is measured against a standard to quantify the amount of antioxidants in the food sample.

This ended their presentation and they were hopeful their grant proposal would be approved. This type of research is sorely needed to quantify the health benefits of organic milk.