Virginia Polytechnic Institute and State University

UPDATES AT VIRGINIA TECH

  83 rd Collegiate Dairy Products Evaluation Contest

The 2005 Virginia Tech Dairy Products Evaluation Team participated in the national contest held in Chicago , IL October 27 – 29 th . The contest was held in conjunction with the Worldwide Food Exposition. Sixteen schools from the United States and Canada participated.

Virginia Tech's Jae Hee Hong (PhD candidate) placed well in the graduate students' division, with a 3 rd place in yogurt and 6 th in milk. Mark Kline (MS candidate) also did well, placing 4 th in butter and 7 th in cheddar cheese. Jae Hee placed 8 th overall in the contest and Mark was 11 th .

Our undergraduate team made a respectable showing, with Bethany Osborne, Vanessa Brown, and Amanda Boswell as the team members. The undergraduate team placed 13 th overall and 6 th in milk. Bethany Osborne placed 6 th in milk and was our high scoring individual. Contest products were very diverse, ranging from unsaleable to extremely high quality. While we didn't bring home any trophies, the team represented Virginia Tech very well.

The Virginia Dairy Tech Society provided scholarships for the students who competed in the Collegiate Contest. Training for and participating in the contest is a valuable experience because it teaches students to recognize sensory characteristics of high quality dairy products. Students that develop these skills can recognize a quality problem before it reaches the consumer, and they can pinpoint whether it is a problem with the raw milk, processing, or sanitation practices. Several companies were there to hire students that have these skills.

South Dakota State won the “All Products” undergraduate contest, and Thitiwan Imyim of Cal Poly won the graduate student competition.

HOT TOPICS AND DAIRY ISSUES

  Cultured Dairy Product Shelf Life

Shelf life is the length of time a product remains acceptable for consumer consumption. Shelf life of some products is regulated by the state; however, in most cases, shelf life is determined by the manufacturer and is indicated as the “best if used by” date.

Shelf life of dairy products can be altered microbiologically and/or chemically. Factors bringing about these changes can be internal (chemical composition, water activity, pH, oxidative state) or external (temperature, humidity, oxygen level). Additionally, and very important, is the possibility of post-pasteurization contamination with spoilage organisms during manufacture, transport and filling.

Chemical changes that occur during refrigerated storage of dairy products can negatively impact flavor. Fats may become metal oxidized (in the presence of copper or iron), light oxidized (due to exposure to light), or rancid (though enzyme activity). Enzymes present in the milk or starter culture can cause a bitter flavor. Product texture can change due to improper formulation, improper heat treatment or by continued production of lactic acid by the starter culture. Microbiological problems in cultured products come about because of the starter culture or from spoilage microorganisms. Post-fermentation acidification is the term used when the metabolic activity of the starter culture continues after completion of fermentation. The end result is higher than desirable lactic acid levels (lower pH than needed), and changes in flavor and syneresis of the product. Post-pasteurization contaminants can lead to formation of slime, color changes, gas production, surface mold growth, and unclean or yeasty flavors. Some microorganisms produce an enzyme that can convert diacetyl (responsible for buttery flavor in dairy products) to a flavorless compound.

To maximize shelf life, begin with high quality raw milk. You can't improve the initial quality once milk arrives at the plant. Minimize the time between receiving the milk and pasteurization. This will limit the growth of psychrotrophic bacteria which produce proteases and lipases that deteriorate quality even after they are destroyed by pasteurization. Don't allow milk or product contact with sources of copper or iron (bad welds or inadequate repairs). Light induced oxidation flavor can be avoided by packaging in light-blocking materials and minimizing exposure to light during storage. Carefully select starter culture systems and cool properly after processing to avoid microbiological issues.

With the exception of cottage cheese, all cultured dairy products have a low pH, which discourages growth of some spoilage bacteria but promotes growth of yeasts and molds that are more acid tolerant. Yeasts and molds are the main factors that limit shelf life in most cultured products. If possible, addition of preservatives such as potassium sorbate or natamycin can help limit growth of these organisms. Modifying the packaging atmosphere by flushing with carbon dioxide or nitrogen can discourage spoilage organism growth.

An effective environmental sanitation program is an excellent means to avoid contamination of product following fermentation. Spraying floors while the vat is emptying or near the filler when it is operating can produce aerosols, leading to spoilage organism contamination.

In summary, many factors influence shelf life of cultured dairy products. Details related to starter culture selection, formulation, processing and fermentation should be closely monitored. Attention to the quality of the incoming milk and other ingredients is very important. Adopt an excellent sanitation program for the plant and maintain appropriate refrigerated temperatures.

  N ew Dairy Research/Innovation Centers

Fonterra, the New Zealand dairy co-operative, is set to build a new multi-million dollar research and development center in Melbourne, Australia . The new facility will open in April 2007. Dairy firms are making these investments to meet the constant demand for dairy innovation and to get ahead in an increasingly competitive market. The new facility will employ 150 people and will focus specifically on product development to meet consumers' demand for health and nutrition as well as convenience and indulgence. Fonterra already has a good reputation for research into cheese flavor technologies, specialist milk powders and nutritional ingredients.

Danone, the French group, opened its first research and development center for fresh dairy products this month in Shanghai. China's domestic dairy production currently stands at just over 24 million metric tons of liquid milk per year and is growing by 20 – 25% per year. Yet it still requires significant imports to meet rapidly rising demand driven by increasing disposable income and the growing awareness of the nutritional benefits of dairy products. Both production and sales of yogurt and fermented milk drinks have been growing by over 40% per year over the last 2 years.