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

Current research at virginia tech    

Light-Induced Flavor of Milk Fortified with a-Tocopherol and Ascorbic Acid

    The effectiveness of added antioxidants against oxidation off-flavor development in light-exposed milk was evaluated using sensory and chemical analysis.  Sensory testing for similarity showed no perceivable difference between control milk and milk with added (i) a-tocopherol (0.05%) and (ii) a-tocopherol (0.025%) and ascorbic acid (0.025%), but did demonstrate a perceivable difference when adding ascorbic acid alone (0.05 %) (n = 30, b = 0.05, a = 0.30).  Subsequently, sensory testing for difference showed a significant change in oxidation off-flavor between light-exposed control milk and light-exposed milk with added a-tocopherol (0.025%) and ascorbic acid (0.025%), while addition of a-tocopherol (0.05%) alone showed no significant difference (n = 24, b = 0.40, a = 0.05). 

    Gas chromatography-olfactometry showed that more aroma-active flavor compounds were observed in light-exposed milk treated with 0.05% a-tocopherol, and a combination of 0.025% a-tocopherol and 0.025% ascorbic acid than light-exposed milk with no added antioxidants.  The thiobarbituric acid (TBARS) test verified chemically the extent of oxidation in control and antioxidant-treated milk samples.  Milk that was exposed to light for 10 hours showed a significantly higher TBARS value (0.92 ± 0.093 mg/kg) than milk that was protected from light (0.59 ± 0.184 mg/kg), or milk that was treated with a combination of 0.025% a-tocopherol and 0.025% ascorbic acid (0.26 ± 0.092 mg/kg).

 HOT TOPICS AND DAIRY ISSUES

Scientists to Probe Milk’s Genes to Understand Its Health Benefits

    Scientists are addressing a new nutrition question:  How can healthy foods be changed to be even better for you?  They want foods that go beyond preventing nutrient deficiencies by boosting immune function, reducing chronic disease risk, or protecting against stressors and toxins.  So, they’ve begun to study nature’s original “health food”, milk.

    “The things milk does are pretty impressive,” says Bruce German, a UC Davis food science professor.  “For example, the ability to cure bacterial disease with antibiotics is one of the greatest boons to the human condition in history.  Milk inhibits the growth of bad bacteria but also encourages the growth of beneficial bacteria.  Milk thus works in innovative ways that scientists have not traditionally considered, but we still don’t know how.”

    Milk can also improve immune function, lower blood pressure and speed the uptake of hard-to-absorb nutrients, like iron.  It may even be helpful in weight control.

    Once scientists learn how milk works, German thinks they’ll be able to transfer its benefits to other foods, making them healthier.  He is organizing an international research consortium to study the “milk genome”, the genes that encode instructions for making milk.

    “Milk evolved to be nourishing,” German said. “And the footprints of evolution are in the genes, so the [milk] genome is a real obvious place to look for ways to improve foods.”

    The new research consortium will be supported by funding from Australia, Canada, the Netherlands, New Zealand and Switzerland.  Its work will compare genes telling how to make milk in many species, with an emphasis on human genes.  And when the benefits of milk are understood, they will theoretically be transferable to any type of food.  For example, lactoferrin, a milk protein that improves iron absorption, is already added to non-dairy foods in Japan.  “Just because a specific benefit originates in milk, that doesn’t mean that milk is the only way you could get it,” German says.

 Cheese that Helps Lower Cholesterol

    Lifeline Food Co. has reformulated their Lifetime^® Low Fat Cheese to include phytosterol esters.  Phytosterols are natural compounds derived from plants.  Based on data from research studies, a daily intake of at least 1.3 grams of phytosterols (accompanied by a low saturated fat and low cholesterol diet) helps lower blood cholesterol, thereby reducing the risk of heart disease. 

    In order to make the ‘reducing cholesterol’ claim, there can be no more than 1 gram of saturated fat in the cheese.  Lifetime^® Low Fat Cheese satisfied this requirement.  A single 1ounce serving of the cheese contains 0.65 grams of phytosterols.  A serving at two meals provides the recommended amount to benefit from the cholesterol-lowering qualities of phytosterols.  The cheese comes in Cheddar, extra sharp Cheddar, jalapeno Jack and mozzarella.  Phytosterol esters have properties that mimic fat. These characteristics give cheese containing phytosterols a creamier taste than the regular low-fat product. 

    The Lifetime cheeses are made with CoroWise^TM phytosterols, with front labels boldly displaying the CoroWise logo.  Phytosterols help lower blood cholesterol because they are structurally similar to cholesterol, and consequently, compete with ingested cholesterol for absorption through the small intestine.  The more phytosterols present in the gastrointestinal tract following a meal, the less likely cholesterol absorption is to occur.  Interestingly, phytosterols are not absorbed to any appreciable extent.  They simply block cholesterol absorption and get flushed through the intestines.

    The new Lifetime Low Fat Cheeses with Phytosterols are part of the trend in making traditional foods healthier through the addition of value-added ingredients.

 Winter Milk Contains More Calcium

    A study carried out in the Czech republic has revealed that central European dairy cows produce milk with higher levels of calcium in the winter months of the year than they do in the summer months. The study was carried out by Professor Jindra Lukasova and a colleague at the University of Veterinary and Pharmaceutical Science in Brno.

    The results build on research that was carried out in 1973 that found a connection between the winter fodder feed to cows, and the increase in calcium content of cows’ milk.

    Researchers concluded that a number of factors can affect the calcium mineral and vitamin levels in a cow's milk production. These include the animal's physical condition, genetic characteristics, food, health and the way the cow is cared for.

    Two hundred dairy cows were tested in the study and the tests were carried out before and after pasteurization. The study found that calcium content for cows in the lowlands of the Czech Republic was 1.11 grams of calcium per liter of milk in the summer and 1.22 grams of calcium per liter in the winter. Cows that grazed in the mountains, and at higher altitudes overall had elevated calcium levels in their milk. In the summer these cows had an average of 1.28 grams of calcium in the summer and 1.37 in the winter.  Dairy foods are the primary source of calcium for Europeans.