Virginia Polytechnic Institute and State University

Susan Duncan, Dairy and Sensory Evaluation

Bill Eigel,                Food Biochemistry

Joe Marcy:               Food Processing

Merle Pierson: Food Microbiology

 Sean O’Keefe: Food Chemistry

Susan Sumner:   Food Safety

Walter Hartman:    Dairy Plant Manager whartman@vt.edu

Kim Waterman:  Dairy Chemistry    Kwater@vt.edu

updates at virginia tech

Dairy Practices Council’s Guideline #10

The second revision of Guideline #10, sponsored by the Dairy Practices Council, was completed in March and should be available in May.  Dr. Susan Duncan of Virginia Tech’s Dept. of Food Science and Technology Dept. and Dr. Steven Murphy of Cornell University’s Dept. of Food Science co-authored the publication, entitled Guidelines for Maintaining and Testing Fluid Milk Shelf Life.  This guideline provides recommendations for optimizing pasteurized product shelf life and summarizes the factors that should be considered when performing shelf life assessment procedures.  Laboratory methods that have shown promise in determining quality and shelf life potential of fluid milk are also outlined. 

The Dairy Practices Council is a nonprofit organization composed of education, industry and regulatory personnel.  The Council disseminates educational guidelines relating to aspects of milk quality, sanitation, and regulatory issues.  For more information visit http://www.dairypc.org.

 NSF Grant Funds Interdisciplinary Program on Oxidation

A team of researchers from three different colleges at VA Tech has been awarded a five-year, $3.2 million National Science Foundation Integrative Graduate Education and Research Traineeship (IGERT) award for the Macromolecular Interfaces with Life Sciences (MILES) program.   Principal investigators are Craig Thatcher, Head, Department of Large Animal Clinical Sciences, VMRCVM; Susan Duncan, professor of food science and technology in the College of Agriculture and Life Sciences; and Tim Long, professor of chemistry in the College of Science.

Oxidation is a process that involves free radicals, which cause food to spoil or taste bad, and damage cellular processes in living systems. Oxidation also can be used as a tool for creating thin films. Oxidation processes occur within both synthetic macromolecules and biological systems. Oxygen-centered radicals are intermediates in key chemical and biological processes, such as lipid oxidation, aging, and product deterioration. Oxidative stress is implicated in many chronic diseases, including cancer, diabetes, and obesity.

A chemistry-biology collaboration offers the potential for development of antioxidant (molecules that scavenge free radicals) delivery systems, including antioxidant enriched foods, novel biocompatible synthetic polymer delivery systems, or new natural and synthetic macromolecular antioxidants. Duncan, Long, Thatcher and their students have actually been collaborating for several years to determine the biochemical pathways of the oxidation process and how they can be used to protect food and health and create new technologies. Food science graduate student Heather Clarkson is determining which light waves cause oxidation in such packaged foods as milk, and student Janet Webster is evaluating polymer systems that will block those light waves.

Duncan and Long are exploring controlled release of antioxidants by polymeric films. Thatcher and his colleagues in veterinary medicine are interested in nutrition and in the roles of free radicals in disease, and will help the MILES researchers understand the biomedical implications and evaluate the success of their discoveries with animal models.  Janet Rankin and Mike Houston, professors of human nutrition, foods, and exercise, and Korinn Saker, assistant professor, Large Animal Clinical Sciences, are interested in how oxidative stress is related to obesity and Type II diabetes in animals and humans. Nutritional strategies will be developed to modify oxidative stress.

The MILES researchers will also collaborate with the Science Museum of Western Virginia to develop educational modules for K-12 students.

 HOT TOPICS AND DAIRY ISSUES

More Accurate Antibiotic Residue Test for Milk

Dairy cows are given antibiotics as part of their health maintenance program to protect them from illnesses.  Traces of these antibiotics can sometimes be found in the milk, resulting in expensive product recalls and the risk of serious health problems for humans.  As a result, antibiotic residue levels in milk are tightly regulated. The EU, for example, has set a Maximum Residue level Limit (MRL) for antibiotics in milk, with processors being responsible for ensuring that these limits are not breached.

A measurement system designed to help processors test for antibiotic residues was developed years ago. DSM’s Delvoscan product uses this standard system, but the company claims that the findings can be more accurately and rapidly assessed.

The product is part of the Delvotest system, widely regarded as the definitive testing system for antibiotic residue. It measures acidity levels using a pH indicator which indicates the level of antibiotics in the milk.  Delvoscan uses a numeric system to identify the level of acidity from the pH test, a procedure which DSM claims is more efficient than older versions of the test.

“Delvoscan testing is carried out in the same way as previously but color reflection is measured numerically rather than evaluated by sight. Results are automatically printed out and can also be saved to file for later reference,” DSM explained.  The device can be installed on a PC with Delvoscan software, allowing large numbers of samples to be stored on the hard disk.

“Delvoscan ensures accurate readings from cost-effective and simple-to-use antibiotic detection solution. Equipment is fully calibrated prior to delivery and complies with the Association of Analytical Communities (AOAC) testing standards,” the company concluded.

Test Detects Brucella in Goat’s Milk

A test for detecting the bacteria Brucella melitensis in bulk goat milk has been developed by the Agricultural Research Service's National Animal Disease Center in conjunction with the Animal and Plant Health Inspection Service's National Veterinary Services Laboratories. The test relies on an adaptation of an enzyme-linked immunoassay (ELISA) developed in 1984 for testing cattle for B. abortus.  The assay correctly detected B. melitensis antibodies in a study containing with 13 positive and 134 negative bulk milk samples.

B. melitensis, one of six known species of Brucella bacteria that induce abortions in animals, mainly infects sheep and goats. In humans, B. melitensis infection causes Malta fever.  Few cases of this infection in goats have occurred in the United States since 1972. But it is essential that vigilance be maintained to prevent introductions of the bacteria into the country. Dairy goat milk is slowly gaining popularity in the U.S. due to its high protein and low cholesterol levels, as well as its compatibility for people with intolerance to cow's milk. About 1 million goats are raised for milk and cheese production in the United States.