Increasing Shelf Life

Rapidly Cooling Eggs Can Double Shelf Life and Decrease Risk of Illness
Taking just a few seconds to cool freshly laid eggs would add weeks to their shelf life, according to a new Purdue University study. The rapid-cooling process, developed by Kevin Keener, a professor of food science, uses liquid carbon dioxide to stabilize the proteins in egg whites so much that they could be rated AA for 12 weeks. Eggs cooled under current methods lose the AA grade in about six weeks, Keener said. In addition, the technology could significantly reduce occurrences of Salmonella illnesses.

“There is no statistical difference in quality between eggs as measured by Haugh units (which measure an egg white’s protein quality) just after laying and rapidly cooled eggs at 12 weeks,” he said. “This rapid-cooling process can provide a significant extension in the shelf life of eggs compared to traditional processing.”

Keener’s results, published in the journal Poultry Science, also show that membranes surrounding the eggs’ yolks were maintained for 12 weeks when eggs were rapidly cooled. “The structural integrity of the yolk membrane stays strong longer, which may provide a food safety benefit,” he said. “The membrane being stronger would be another defense against bacterial invasion, such as Salmonella.”

The rapid-cooling technology takes liquid carbon dioxide and turns it into a “snow” to rapidly lower the eggs’ temperature. Eggs are placed in a cooling chamber and carbon dioxide gas at about -110°F is generated. The cold gas is circulated around the eggs and forms a thin layer of ice inside the eggshell. After treatment, the ice layer melts and quickly lowers an egg’s internal temperature to below 45°F, the temperature at which Salmonella can no longer grow.

Traditionally, eggs are at more than 100°F degrees when placed into a carton, and the eggs in the middle of a pallet can take nearly six days to cool to 45°F, Keener said. A 2005 U.S. government report showed that if eggs were cooled and stored at 45°F within 12 hours of laying, there would be about 100,000 fewer Salmonella illnesses from eggs in the nation each year, Kenner said. Rapid cooling could also increase the ability to export eggs to places where this isn’t possible today.

New Technique Helps Edible Flowers Last Longer
Many fine dining restaurants and catering establishments garnish dishes with flowers or use them as ingredients in salads, soups, entrees, desserts, and drinks. A new study in the May issue of the Journal of Food Science published by the Institute of Food Technologists reported that the use of a new storage technique could enable edible flowers to maintain a higher quality for longer.

Flowers have a large surface area to volume ratio and many delicately attached parts, making them susceptible to petal loosening, discoloration, and wilting. Edible flowers are even more vulnerable to post-harvest quality loss than other cut flowers, because their stems are cut very short, and they are stored without additional water supply.

Currently, edible flowers are often packed in clamshell containers and must be used within two to five days of harvest, which generally requires air transportation. The study compared a new controlled-release technology along with modified atmosphere packaging to the packing technique that is currently being used. The freshly harvested carnations and snapdragons that were packaged in trays with a 1-MCP strip (a synthetic plant growth regulator), sealed with a gas permeable film, and stored at 41°F had significantly reduced dehydration and maintained higher overall quality compared to flowers commercially packaged in plastic clamshell containers.