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

Displaced Students Welcomed by Tech

Numerous VA Tech administrators, faculty and staff worked through the Labor Day weekend to help more than 30 students displaced by hurricane Katrina enroll at the university for the rest of fall semester.

Twenty-three undergraduate students and about 10 graduate students, most of them from Tulane University in New Orleans , were enrolled at VA Tech by Wednesday (9/7). The colleges of agriculture and life sciences, architecture, business, engineering, liberal arts and human sciences have all accepted displaced students. Tech will cover tuition and fees through scholarships for the undergraduate students, who range from freshmen to seniors. Many of these students left New Orleans and arrived in Blacksburg with only a backpack.

About 15 of the undergraduates are being housed in dormitories on campus, and there is a long list of volunteer families from Tech and the community that are willing to host students.

VA Tech has 57 currently enrolled undergraduates from Alabama , Louisiana and Mississippi . None of them want to return home immediately, and they are being offered counseling through VA Tech.

HOT TOPICS AND DAIRY ISSUES

Raw Milk Quality Determination

Milk obtained aseptically from the udders of healthy cows contains a very low number (<1,000/ml) of bacteria, but it is an excellent bacterial growth medium. Microorganisms introduced during milk production and handling can multiply rapidly if the milk is subjected to slow cooling and/or storage between 40°F and 45°F.

Microbial quality of Grade A raw milk depends on the rate of cooling, the temperature of storage and the sanitary conditions in which it was produced. Spoilage microorganisms, particularly psychrotrophic bacteria, grow at temperatures of 40°F and above. Psychrotrophic bacteria not only exist at cold temperatures, but can actually grow slowly; causing off-flavors and other quality defects. Standard Methods for the Examination of Dairy Products states that psychrotrophic bacteria are the most important group of organisms that effect milk quality. These bacteria, commonly found in raw milk, are Gram negative and will be destroyed by pasteurization. They may gain access to pasteurized milk through defective gaskets/systems or by spills of raw milk. As spilled milk stands on the plant floor, the organisms can become airborne and be deposited on milk-contact surfaces, eventually contaminating the pasteurized product.

Additionally, some species of psychrotrophic bacteria, particularly Pseudomonas , can produce proteolytic and lipolytic enzymes, which can cause a variety of off-flavors and physical defects that cannot be halted or reversed. Gram positive thermoduric, psychrotrophic spore formers (usually Bacillus ), are less common. These organisms can survive pasteurization and cause spoilage several days after packaging. Extended shelf life products may be even more vulnerable to spore formers.

Regulatory standards set forth by The Grade A Pasteurized Milk Ordinance (PMO) give the minimum requirements for assuring a safe product for consumption by the public. The PMO sets the current microbiological standards for raw milk. Standard plate counts (SPC) performed on samples from individual producers should contain <100,000 cfu/ml total viable bacteria, and commingled samples (from more than one producer) should contain <300,000 cfu/ml. The PMO regulatory standards have served the industry well for many years, but they are not quality standards. Raw milk microbiological quality depends on the type, number, and ability of the organisms to grow, multiply and alter the components and characteristics of milk.

The Standard Plate Count (SPC) test is required to ensure that milk meets the minimum Grade A standards. This test does not accurately determine the number of psychrotrophic bacteria present or their ability to multiply under favorable conditions. As a result, more than fifty years ago, Dr. C. K. Johns of the Canadian Department of Agriculture developed the Preliminary Incubation (PI) test. The PI test measures the true microbiological quality of raw milk.

The PI test procedures are found in the 15th edition of Standard Methods, but are not included in the latest editions. Samples are incubated at 12.8°C (55°F) for 18 hours. SPCs are performed according to Standard Methods before and after PI. Interpretation: PI counts of =100,000/ml indicate gross contamination while PI counts that are double or more than the SPC, but are <100,000/ml, indicate psychrotrophic growth. The PI test should be performed on plant silo and tanker samples. The PI test is a valuable quality improvement tool.

Cattle Diet Influences Milk Composition

New evidence indicates that dairy processors may be able to add more value to their diary products and still maintain the products' natural image with consumers. Dr. Bill Wales, a University of Melbourne researcher, found that cows fed local pasture grasses such as clover and ryegrass produced milk with higher concentrations of polyunsaturated fatty acids (PUFAs) than cows fed high grain diets. Cows produced milk containing up to 3 times the PUFA levels of milk from feed lot cattle fed total mixed grain rations. PUFAs have been linked to a range of health and disease prevention benefits, including improved mental performance in children. Wales ' findings join other international studies that claim a cow's diet can affect healthy fat levels in milk, notably conjugated linoleic acid which may possess anti-cancer properties.

Adding value to dairy staples like milk is now a major focus of the world's biggest dairy producers. And improving nutritional characteristics of milk through the diets of dairy cattle means that extra ingredients are not added to the end product. Consumers construe this practice as ‘tinkering' with the food and tend to view it as less wholesome and natural.

Orange Juice Recall

Fort Pierce , FL - Sept. 6, 2005. As a precautionary measure, Orchid Island Juice Company of Fort Pierce, Florida, is voluntarily recalling fresh squeezed (only) orange juice with an expiration code date of 9/15/05 thru 9/22/05, because it has the potential to be contaminated with Salmonella . Orchid Island Juice Company distributes fresh squeezed orange juice to states that include Maryland , New Jersey , North Carolina , Pennsylvania , South Carolina , Tennessee , Virginia , Washington , D.C. , and West Virginia . Consumers may have purchased or consumed the product through retail or foodservice establishments such as restaurants, hotels, resorts, or country clubs. Routine testing by the company revealed the potential for contamination. No illnesses have been reported associated with this recall.