Featured Research

from universities, journals, and other organizations

Dairy researchers identify bacterial spoilers in milk

Date:
July 20, 2012
Source:
Cornell University
Summary:
Our days of crying over spoiled milk could be over, thanks to food scientists. Milk undergoes heat treatment -- pasteurization -- to kill off microbes that can cause food spoilage and disease, but certain bacterial strains can survive this heat shock as spores and cause milk to curdle in storage.

Gram stain showing Paenibacillus, a spore-forming bacteria that can cause off-flavors in a variety of foods and curdling in dairy products.
Credit: Image courtesy of Cornell University

Our days of crying over spoiled milk could be over, thanks to Cornell food scientists.

Milk undergoes heat treatment -- pasteurization -- to kill off microbes that can cause food spoilage and disease, but certain bacterial strains can survive this heat shock as spores and cause milk to curdle in storage.

Researchers in the Milk Quality Improvement Program at Cornell's College of Agriculture and Life Sciences have identified the predominant spore-forming bacteria in milk and their unique enzyme activity, knowledge that can now be used to protect the quality and shelf life of dairy products.

"Control of food spoilage is critical in a world that needs to feed 7 billion people," said Martin Wiedmann, food science professor and study co-author. "Approximately 25 percent of post-harvest food is spoiled by microbes before it is consumed."

The study, published in the March issue of Applied Environmental Microbiology by the lab of Wiedmann and Kathryn Boor, the Ronald P. Lynch Dean of the College of Agriculture and Life Sciences, identified the predominant strains of spore-forming bacteria, which can foul milk and other food products. The culprits, Paenibacillus bacteria, are ubiquitous in nature and cause off-flavors in a variety of foods and curdling in dairy products.

As spores, the bacteria can survive in dormant form for years despite the best practices in cleaning, processing and packaging.

In fact, the bacteria may be uniquely adapted to overcome the twin tactics of dairy protection: pasteurization followed by refrigeration. According to co-author and research support specialist Nicole Martin, the spores are not only resistant to heat, the small jolt of heat during pasteurization may actually stimulate them to germinate. Some can reproduce in refrigerated dairy products at temperatures that would stymy other types of bacteria.

"We studied 1,288 bacterial isolates in raw milk, pasteurized milk and the dairy farm environment; however, only a handful of strains accounted for 80 percent of the spore-formers present," said Wiedmann. "They grow well in milk -- and possibly other foods -- at temperatures as low as 43 F, and we can identify Paenibacillus because of their uniquely high galactosidase enzyme activity at 32 C."

They also investigated how pasteurization affects the presence of such bacteria.

Concerns about food safety have prompted many dairy processors to increase pasteurization temperatures above the 161 F minimum set by the government. Anecdotal reports, however, suggested this practice actually led to more spoilage once the products were refrigerated.

Tallying bacterial numbers throughout the refrigerated shelf life of milk pasteurized at two different temperatures -- 169 F and 175 F -- the Wiedmann-Boor lab found that lowering the temperature significantly reduced bacterial growth during refrigerated storage, especially by 21 days after pasteurization.

The findings are already being applied in the field. The Wiedmann-Boor Lab was enlisted by Upstate Niagara, a cooperative of more than 360 dairy farm families throughout western New York, to further improve the quality of their award-winning milk by assessing milk samples for spore-formers.

Data on samples that contained spore-forming bacteria are now being analyzed using DNA fingerprinting to identify the types of organisms present and where they might have come from.

Martin said she hopes the collaborative project will become a model for how to approach spore-forming bacteria in individual dairy processing plants.

"It's one of the strengths we have at Cornell -- we are able to do advanced research and immediately turn it around to help the industry," Martin said.


Story Source:

The above story is based on materials provided by Cornell University. Note: Materials may be edited for content and length.


Cite This Page:

Cornell University. "Dairy researchers identify bacterial spoilers in milk." ScienceDaily. ScienceDaily, 20 July 2012. <www.sciencedaily.com/releases/2012/07/120720201531.htm>.
Cornell University. (2012, July 20). Dairy researchers identify bacterial spoilers in milk. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2012/07/120720201531.htm
Cornell University. "Dairy researchers identify bacterial spoilers in milk." ScienceDaily. www.sciencedaily.com/releases/2012/07/120720201531.htm (accessed July 30, 2014).

Share This




More Plants & Animals News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Raw: Otters Enjoy Water Slides at Japan Zoo

Raw: Otters Enjoy Water Slides at Japan Zoo

AP (July 30, 2014) River otters were hitting the water slides to beat the summer heatwave on Wednesday at Ichikawa City's Zoological and Botanical Garden. (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins