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

Brian Yaun: Microbiology byaun@vt.edu           Phone: (540) 231-8697

Updates at Virginia Tech

FST Graduate To Be Inducted Into VT Ag Hall of Fame

On Saturday, October 19, Marcella Arline will be inducted into Virginia Tech’s College of Agriculture and Life Sciences Hall of Fame. 

In 1974, Marcella was the first student to receive a bachelor’s degree from Virginia Tech’s newly formed Department of Food Science and Technology.  She worked for several food processing companies in Virginia before joining Hershey Foods Corp. in 1981.  She resides in Hershey, PA and is currently vice president for quality and regulatory compliance at Hershey Foods. 

She is a professional member of the Institute of Food Technologists, and she serves on several scientific and technical committees for the Grocery Manufacturers Association and the National Food Processor’s Association.

Marcella also organized an internship program for food science students at Hershey and she has mentored Virginia Tech students.  She co-sponsors a scholarship that is awarded to a food science student annually.  In addition, she has served on the college’s leadership council, has been active in the university’s alumni association, and she was instrumental in the establishment of an alumni organization for graduates of the college.   

The FST Department will host a reception for Marcella the day before her induction.   The induction ceremony is part of the college’s homecoming activities.

HOT TOPICS AND DAIRY ISSUES

New Study Validates Light Blocking Efforts

 One way to have better tasting milk is to protect it from light.  Both natural and artificial light can induce quality defects that consumers notice – and don’t like.  Light exposure causes chemical reactions in milk that can modify the proteins and fats that are present to produce many negative flavors, ranging from burnt feathers to cardboard or metallic.  These off-flavors are dependent on various factors such as exposure time, intensity and wavelength of light, and composition of the milk. 

In a recent study that spanned 2 years, Milk Quality Improvement Program (MQIP) scientists at Cornell University measured the amount of time it took to get noticeable flavor changes. Reduced fat (2%) milk in high-density polyethylene (HDPE) containers was exposed to lighting similar to the retail dairy case (2000 lux), where average light exposure is 8 hours.  Half of the teen and adult consumers could detect an off-flavor with less than 2 hours of light exposure.  When asked how much they liked the milk, teens replied that they thought the light-oxidized milk was objectionable.  The longer the milk was exposed to light, the less they liked it. 

Light not only degrades flavor, but also vitamins.  Since vitamins are essential nutrients, their loss by photodegradation decreases the nutritional value of food.  Vitamins A, C, and B₂ are of particular concern with milk.  MQIP found that measurable vitamin A losses occurred increasingly at 2, 4 and 16 hours for nonfat, reduced fat, and whole milk, respectively.  Moderate light oxidized flavors were detected after 4 hours of light exposure in the whole and reduced fat milk and after 8 hours in nonfat milk.  The presence of increased levels of milk fat adversely affects the flavor quality of the products following exposure to light.  On the other hand, higher fat levels do appear to provide some protection against Vitamin A degradation.

To avoid photdegradation, milk should not be exposed at all to direct sunlight.  Since sunlight is even more damaging than artificial light, a few minutes exposure while on a loading dock or during consumer transport has profound results.  In storage areas, milk crates should not be stacked in close proximity to lights.  In dairy plants and stores, milk handling areas, storage coolers and display cases should be designed with minimum lighting and to facilitate product rotation.  When selecting lighting, “cool white” fluorescent lights with wavelengths ranging from 420 to 520 nm should not be used.  If lighting is necessary, “warm white” lights are preferred in the dairy display case. 

Three ways that plastics can be modified to protect products from light oxidized off-flavors and vitamin degradation are:  1. adding opaque pigment that blocks harmful wavelengths, 2. adding ultraviolet (UV) light blocking agents to clear plastic or, 3. modifying the white pigment (titanium dioxide), so that it is translucent, but still blocks the UV light.  HDPE dominates the jug business because of its low cost, durability and light weight.  However, it is a translucent container and offers little protection against UV light.  Adding colored pigments (usually yellow or white) will block light and protect against harmful UV rays.  Some consumers object to this solution because they can’t see how much milk is in the container.  Possibly, a “see-through” strip” could be incorporated into the opaque jug, giving the milk some light protection.  Adding UV light-blocking agents to clear plastic allows visible light through so the consumer can see the milk in the jug.  Eastman Chemical Company makes single serve and quart PET bottles with UV blockers by attaching an absorbing unit to the main chain of the polymers.  Amber PET and PET with UV light-blocking agents are competitive alternatives to pigmented HDPE. 

Labels, such as full-body stretch sleeves or shrink sleeves, are not only attractive, but help block light.  Dean Foods’ Milk Chug^TM  and Land O Lakes Grip-N-Go^TM , single serve HDPE containers both use shrink sleeves.

Dairy industry leader Dean Foods Co., has several processors that use protective packaging.  Mayfield Dairy in Athens, TN. is well known in its marketing areas for its distinctive yellow pigmented Flavor Tight^TM jugs.  Morningstar Foods bottles Hershey’s milk in Mt. Crawford, VA., in HDPE single-serve bottles.  The bottles have three layers including a carbon black layer that helps prevent light damage.  H.P. Hood, Chelsea, MA., developed the Light Block Bottle^TM in 1997 to protect its milk from the harmful effects of light.  Lynne Bohan, director of public relations said, “Sales have definitely increased.  Since the launch of the Light Block Bottle, Hood’s market share has more than doubled, because of consumer confidence in the product.  Consumers have been happy.”

Crowley Foods, Binghamton, NY., rolled out a Flavor Savor^TM bottle for its PenSupreme brand in the fall of 2001.  Sales of the brand have been up 40% since its introduction and further growth is expected. 

Many dairy processors are investing in packaging to make sure that their product is protected from the harmful effects of light.  Despite the increased packaging cost, sales have increased and so have profits.  Dairy processors should not be intimidated by the additional cost of light blocking bottles.  It is a financial risk that is worth taking.  In fact, most dairies that have made these packaging changes don’t view it as risk, but as a step in the right direction.