Virginia Polytechnic Institute and State University

UPDATES AT VIRGINIA TECH

FST Holiday Luncheon

The Department of Food Science and Technology hosted its Christmas luncheon at noon on December 6 th . The annual event brought together students, faculty, staff, alumni and retirees for excellent food and good conversation. The department provided the turkey and ham, and the menu was rounded out with covered dishes provided by those attending. The event is a great opportunity to catch up with colleagues and to relax a little.

  Receive Dairy Facts by Email

Those of you who currently receive a hard copy of the Dairy Facts newsletter can switch to email if you're interested. In order to save time and paper, we encourage you to convert to the electronic version. Send your name and email address to kwater@vt.edu if you would like to be added to the electronic mailing list. Otherwise, you will continue to receive the publication by traditional mail.

  HOT TOPICS AND CURRENT ISSUES

Shelf Life and Dairy Packaging

Refrigeration and freezing are commonly used to provide protection from spoilage during the recommended shelf life of dairy products. Modified atmosphere (removal of oxygen and incorporation of nitrogen) has been used for chunk and shredded cheeses for more than twenty years. Current work being conducted at the university level includes packaging cottage cheese and sour cream with a modified atmosphere of carbon dioxide in the head space. Noticeable shelf life improvement has been observed with this technology.

In the last decade, the most notable work in shelf-life extension has been in single-serve, flavored milk in plastic bottles. Using either extended shelf life (ESL) and/or aseptic packaging, processors have increased the shelf life of these products up to six months. Aseptic packaging and shelf-life extension have also afforded the supply chain significantly more flexibility in distribution, warehousing and logistics.

ESL (Extended Shelf Life) and aseptic technology development has been a major driving force in the growth of flavored milks, but there is more to be done. Active packaging is likely to be the next opportunity to provide packaging shelf-life improvement.

From technology to communication, packaging is key to dairy product shelf life. The critical issue is to have excellent seals and proper equipment to seal through excess material, especially zipper material. Without good seals, oxygen will gain entrance into the package and, in the case of cheeses, mold will develop.

Paper versus plastic packaging for milk is an ongoing question for dairy processors. Numerous research papers have provided data on the problem of light oxidation causing off flavors and Vitamin A degradation. Some stores turn off the lights in the dairy case to minimize the problem, and consumers frequently purchase milk in paperboard cartons for enhanced protection. Some dairies provide opaque plastic containers. However, most consumers and processors just deal with the off flavor and vitamin degradation in HDPE plastic jugs.

Skim Milk…Straight from the Cow?

Scientists in New Zealand have discovered that some cows have genes that give them a natural ability to produce skim milk, and they plan to use this information to breed herds of milkers that produce only skim milk. The researchers also plan to breed commercial herds producing milk with the unique characteristics required to make a butter that is spreadable straight from the refrigerator. They have already identified a cow, Marge, with the genes required to do this and say a commercial herd is likely by 2011. The milk is very low in saturated fats and so should be high in poly- and mono-unsaturated fats.

Experts say that the discovery of these rogue milkers could completely revolutionize the dairy industry. Ed Komorowski, technical director at Dairy UK, says that this approach could be used to breed cows that still produce full fat milk, but with only the good fats. In the UK , only 25% of milk sold is full fat. According to Komorowski, “In the future, if whole milk can be made to contain unsaturated fats – which are good for you – then it might mean that people change back to whole milk products. The big thing about dairy products is taste, so this would be a way of giving the benefits of taste without the disadvantage of saturated fats.”

This may also overcome the problem of waste. “If you can genetically produce milk without fat, then that may turn out to be a very good solution to what might later be a big disposal issue,” says Komorowski. Producing skim and semi-skim milk means there is a lot of fat left over.

Komorowski noted, however, that although the lower fat milk may be healthier, it will be interesting to see how much milk the cows actually produce.

The rogue cows were discovered when biotech company ViaLactia screened the range of milk compositions across the entire herd of 4 million New Zealand cattle. New Zealand dairy firm Fonterra has already made milk products from Marge's milk and they maintain the positive taste.

Researcher Looks Genetics Behind Cheese

Ng-Kwai-Hang has spent the last 25 years studying the genetics of cows and how they affect quality and type of cheese. "There are more than 100 different breeds of cows. However, the best milk producers are Holsteins ," says Ng-Kwai-Hang. "Within a specific breed, the milk these cows produce is not the same - it differs in its fat, protein and lactose (a type of sugar found only in milk) content. Consequently, the cheese made from this milk will also differ in its composition and the taste will be affected. "By looking at the genetic profile of cows, we are able to predict which one will produce the best cheese."

Ng has identified the role of specific milk protein genes that affect cheese yield, composition and quality. He and his research team have found that small changes or mutations in the DNA of certain genes lead to changes in the protein which results in dramatic changes in the cheese. Their findings show that a mutation in the particular protein, the kappa-casein, is associated with a higher yield of cheese, and one which is better quality.

According to Ng, in addition to the two genetic variants for kappa casein, there are about 50 known milk protein gene variants and they have diverse effects on dairy product production. These findings have generated a great interest in the dairy industry. Attempts are underway in some countries to breed for specific genetic variants.

"Because the genetic variants are inherited according to simple Mendelian rules, it is possible to breed for specific variants," says Ng. "We are seeing this already where breeding programs are in place to increase the frequency of kappa-casein in cow populations in order to improve the milk quality and its cheese making characteristics."