Merced County Cooperative Extension
Merced County Cooperative Extension
Merced County Cooperative Extension
University of California
Merced County Cooperative Extension

Posts Tagged: food safety

Hotel refrigerators vary in temperature

Maureen Ladley
For food safety, storing leftovers at 33 F to 40 F is ideal

A few years ago, I was in Reno overnight for work and wanted to save my delicious dinner leftovers for breakfast. But when I opened the mini refrigerator in my room, my first reaction was, "That feels too warm!" I did not save the leftovers and made alternative plans for breakfast. Since then, I've wondered how common an unsafe hotel refrigerator might be.

The pandemic delayed my research as travel was out of the question for a while. This year, I had the opportunity to test my question when I traveled up the coast from California to Washington and back home again on vacation. I stayed in a variety of places, perfect for my casual research project. My trusty refrigerator thermometer came with me. The results: mixed!

Of the five hotels I stayed in:

  • One in-room refrigerator was too warm to store food safely overnight.
  • Two were too cold. One was so cold, it froze the beverage I placed inside. Not optimal, but better than food poisoning!
  • Two tested perfectly in the safe zone for food storage.

The score: One out of five refrigerators in my unscientific study was unsafe. One in five is not great odds.

The Ideal Refrigerator Temperature 

A temperature range of 33 F to 40 F is ideal. Refrigeration in this range slows the growth of microorganisms, including bacteria. Safe food-handling practices advise that food should be held for no more than two hours above 40 F. Keeping food overnight above that temperature could have serious consequences, meaning storing food in hotel refrigerators that are not 40o F or below for more than two hours can have serious consequences.

Refrigerator temperature ranges: what's safe and what's not safe?

Stay Safe When You Travel

Here are three ideas to help you avoid problems when you travel:

1)     Measure. Take a refrigerator thermometer with you if you plan to use the in-room mini refrigerator. There's nothing like data to let you know the refrigerator is at the right temperature. Refrigerator thermometers are readily available at grocery and hardware stores, and online.

2)     Avoid. Consider not storing anything that might spoil in your hotel refrigerator if you do not know the temperature setting. Cooling sealed canned beverages would be fine. At worst, your beverage will not be as cool as you hoped, but because it's sealed, nothing will spoil.

3)     Take a quality cooler. Since I was driving, I took my cooler, one that holds appropriate temperatures for days. Traveling with a ready supply of ice, beverages and confidence that my groceries were held safely below 40 F was lovely. This solution is not for every trip, and of course, you need to replenish the ice as you go.

As you plan your future travel, I wish you a safe journey and a skeptical mindset on the safety of your hotel refrigerator for food storage.

Do you have any questions about safe food storage? You can find your local UC Master Food Preserver program or submit questions at You can also sign up to be notified of upcoming online food preservation classes.

Posted on Monday, December 12, 2022 at 4:15 PM
  • UC Master Food Preserver of Solano/Yolo Counties: Maureen Ladley
Focus Area Tags: Food

Bringing out the best in wild birds on farms

California quail tend to offer more benefits to strawberry farmers than disservices, according to a UC Davis study's "multifunctionality index" of birds commonly found on the farms. Photo by Danny Karp, UC Davis

Natural habitat maximizes the benefits of birds for farmers, food safety and conservation

A supportive environment can bring out the best in an individual — even for a bird.

After an E.coli outbreak in 2006 devastated the spinach industry, farmers were pressured to remove natural habitat to keep wildlife — and the foodborne pathogens they can sometimes carry — from visiting crops. A study published today from the University of California, Davis, shows that farms with surrounding natural habitat experience the most benefits from birds, including less crop damage and lower food-safety risks.

The study, published in the Journal of Applied Ecology, was conducted at 21 strawberry fields along California's Central Coast. It found that birds were more likely to carry pathogens and eat berries without surrounding natural habitat.

The authors said a better understanding of the interplay of farming practices, the landscape, and the roles birds play in ecosystems can help growers make the most out of wild birds near their fields.

“Bird communities respond to changes in the landscape,” said lead author Elissa Olimpi, a postdoctoral scholar in the UC Davis Department of Wildlife, Fish and Conservation Biology at the time of the study. “As birds shift in response to management, so do the costs and benefits they provide.”

The single most important driver

The study looked at how different farming practices influenced the costs and benefits that wild birds provided on the strawberry farms. The scientists combined nearly 300 bird surveys and the molecular analyses of more than 1,000 fecal samples from 55 bird species to determine which birds ate pests, beneficial insects and crops, and carried foodborne pathogens.

They also ranked birds to see which were more likely to bring benefits or costs to farmlands. Barn swallows, for instance, got a “gold star” in the study, Olimpi said. Their mud nests are commonly seen clinging to the underside of barn eaves, from which they fly out to swoop over fields, foraging on insects.

But rather than resulting in a list of “good” and “bad” birds, the study found that most bird species brought both costs and benefits to farms, depending on how the landscape was managed.

The presence of natural habitat was the single most important driver differentiating a farm where wild birds brought more benefits than harm.

“Nature is messy, and birds are complex,” Olimpi said. “The best we can do is understand how to take advantage of the benefits while reducing the harms. Growers will tell you it's impossible to keep birds off your farm — you can't do that and don't want to from a conservation perspective. So how can we take advantage of the services birds provide?”

Win-wins for birds and farms

The study is one of several publications from UC Davis Professor Daniel Karp's lab highlighting the environmental, agricultural, and food safety impacts of conserving bird habitat around farms. A related study in 2020 found that farms with natural habitat attracted more insect-eating birds — and fewer strawberry-eating birds — so that farmers experience less berry damage on farms with more habitat nearby. Such habitats also bring greater numbers of bird species to the landscape.

“All together, these studies suggest that farming landscapes with natural habitat tend to be good for conservation, farmers, and public health,” said Karp.

Additional co-authors of this study include Karina Garcia and David Gonthier of University of Kentucky, Claire Kremen of UC Berkeley and the University of British Columbia, William E. Snyder of University of Georgia, and Erin Wilson-Rankin of UC Riverside.

The research was funded by the USDA and UC Davis Department of Wildlife, Fish and Conservation Biology.

Posted on Wednesday, February 23, 2022 at 9:38 AM
  • Author: Kat Kerlin, UC Davis
Tags: Birds (2), Daniel Karp (2), Elissa Olimpi (1), farming (5), farms (2), Food Safety (48), habitat (1), pathogens (2), Strawberries (22), uc davis (46)
Focus Area Tags: Agriculture, Environment, Food

Five questions with food safety expert, new AAAS Fellow Linda Harris

Linda J. Harris will be inducted as a member of the 2021 class of American Association for the Advancement of Science Fellows during the AAAS annual meeting. Photos courtesy of Linda J. Harris

Professor of Cooperative Extension shares career story, appreciation for UC Davis

After growing up in northern British Columbia, in a remote smelter town called Kitimat (“an 8-hour drive from the nearest McDonald's”), University of California Professor of Cooperative Extension Linda J. Harris embarked on an academic journey that crisscrossed North America and eventually led to her election as a Fellow of the American Association for the Advancement of Science.

AAAS, the world's largest multidisciplinary scientific society and publisher of the journal Science, recently announced the election of its 2021 class, which will be inducted during its annual meeting, Feb. 17-20.

In addition to Harris – a faculty member in UC Davis' Department of Food Science and Technology – four other UC Agriculture and Natural Resources affiliates will be inducted: Helene Dillard, dean of the UC Davis College of Agricultural and Environmental Sciences; Kathryn Uhrich, dean of the UC Riverside College of Natural and Agricultural Sciences; and UC Berkeley Professors Rodrigo Almeida and Paolo D'Odorico.

Harris, a Certified Food Scientist, recently shared her thoughts on the value of extension work, her contributions to the field, UC Davis' support for women in academia, and the arc of her career journey.

Harris was elected as an AAAS Fellow for her contributions to the field of food safety microbiology, especially related to control of Salmonella.

How did you get your start in food science and microbiology?

I was interested in science at an early age. As an undergraduate student at the University of Victoria in Victoria, B.C., I enrolled in biochemistry at the suggestion of my high school biology teacher. In my second year, I switched to the University of Alberta in Edmonton, Alberta and decided to review the course catalog – a paper version! When I got to the section on Food Science, the applied nature of the field just sounded right and I never looked back.

However, I didn't do particularly well in microbiology as an undergraduate student – too much memorization for me. At the end of my B.S. I was ready for a job in the food industry and took the very first job I was offered – ironically enough as a dairy microbiologist in a quality control lab. Thankfully, that job opened my eyes to the possibilities in microbiology. What was memorization turned into something I learned through doing and I was hooked.

Two years later, I was ready to go back to school and contacted a professor of food safety microbiology at the University of Alberta who fortunately had funding for me. During my M.S. degree in food microbiology, he encouraged me to pursue the Ph.D. – which was not something I had ever considered – and that led me to leave Canada and head to North Carolina State University and a Ph.D. in microbiology in the Food Science Department, where I worked on a project related to the fermentation of sauerkraut.

I did have one publication related to food safety during my time at NC State, and when I took my first faculty position back in Canada [University of Guelph in Ontario] I continued to work in food safety, mostly with meat and meat products.

I am so glad that I saw the advertisement for my current position and that I followed my instincts to apply for the job. The opportunities to grow professionally and to work in the food safety area at UC Davis, within the Cooperative Extension network in California, and with collaborators across the U.S., and around the world, have been enormous, and I am extremely grateful for the path that led me here.

Growing up in Kitimat, British Columbia, Harris developed a love for science at a young age.

February 11 is the United Nations-designated “International Day of Women and Girls in Science.” How has UC Davis supported women in your scientific field?

My career in STEM [science, technology, engineering and math] has been very rewarding and many of the gender barriers I faced early on have been addressed. I feel very fortunate to have landed at UC Davis and I am thankful that there is a long history of addressing these barriers at this institution.

When I was hired in 1996, the Department of Food Science and Technology was about 25% women and both the department chair and dean of the college were women. I had never been in a department or college with so many women faculty, including in positions of leadership. It was a very important consideration in my move. Today our department is 50% women and I proudly served for five years as the second woman department chair, from 2016 to 2021.

As a first-generation university graduate raised by a single mother, you have a unique perspective in encouraging young people on their path toward a STEM career. What advice do you have for them?

To those contemplating a career in STEM, I would say: be open to new opportunities and adventures – you never know where they may lead you. Get involved in leadership in any capacity you can from student organizations or around other things that interest you. Skills that you learn with these types of activities will be invaluable to your career.

I am very much an introvert and had to work hard to overcome my fear of public speaking. In addition to leadership roles in student clubs, I joined Toast Masters while working on my Ph.D. These activities had a huge impact on building my confidence and helped influence my career choices.

Through her work as a Cooperative Extension specialist, Harris has been able to understand firsthand the food-safety needs across California.

In the AAAS Fellows announcement, it says you were elected for “contributions to the field of food safety microbiology, especially related to control of Salmonella and other pathogens in low-moisture foods and fresh produce.” Is that your proudest achievement in the field?

I am most proud of the work described by that short statement especially as it applies to California-grown commodities. I would say that my laboratory is best known for work with the tree nut industry – almonds, pistachios and walnuts, as well as a range of types of fresh produce grown in this state.

My laboratory has worked to understand behavior, movement, prevalence, and especially control of foodborne pathogens like Salmonella during production in the field through harvest and postharvest handling all the way through to consumer practices.

I have been fortunate to have many terrific state, national and international collaborators and an outstanding group of people working in my laboratory as we set the foundation for some of the food safety research in tree nuts and produce. It has been most gratifying to watch the significant growth in these fields of investigation, especially with a new generation of scientists that span the country and beyond.

Another “hat” you wear is UC Cooperative Extension specialist. How have you contributed to food safety knowledge and practices in our communities?

I think you will see that my “hats” are not that different. The research from my laboratory has provided the foundation for several commodity-based, food-safety risk assessments – for almonds, pistachios, and walnuts. And these, in turn, have been used in support of regulations or helped guide implementation of safer food industry practices. Our research has also informed several publications aimed at consumer handling of fresh fruits and vegetables and has been cited in regulations pertaining to fresh produce safety. It is gratifying to see our research being used.

My research and extension work are very integrated. One feeds the other. Because I have been able to interact with stakeholders (especially integral to my position as a Cooperative Extension specialist), I have been able to understand firsthand some of the pressing food-safety issues and challenges in California. These stakeholder interactions have largely formed the basis for most of my research and extension grant proposals over the years. The collaborations that have resulted from extension activities have opened doors and access to many unique opportunities for sample collection and research exploration.

Posted on Thursday, February 10, 2022 at 8:46 AM
Tags: AAAS (1), almonds (3), Fellow (1), Food Safety (48), Food science and technology (2), Linda J. Harris (1), pistachios (4), Q&A (1), Salmonella (6), tree nuts (3), UC Davis (46), walnuts (6)
Focus Area Tags: Agriculture, Food, Health

Researchers pinpoint which bird species pose food safety risk to crops

Species that form big flocks and are associated with livestock, like this invasive European starling, carry greater risks of foodborne pathogens. Getty photo

E. coli and Salmonella are rare in wild birds, Campylobacter more common

Concerns over foodborne risk from birds may not be as severe as once thought by produce farmers, according to research from the University of California, Davis, that found low instances of E. coli and Salmonella prevalence.

While the research found that the risk is often low, it varies depending on species. Birds like starlings that flock in large numbers and forage on the ground near cattle are more likely to spread pathogenic bacteria to crops like lettuce, spinach and broccoli, according to a study of food safety risk and bird pathogens from the University of California Davis. In contrast,  insect-eating species were less likely to carry pathogens.

The findings, published in the journal Ecological Applications, suggest that current practice of removing bird habitats around produce growers' farms over concerns the animals could bring foodborne pathogens into their fields may not solve the problem.

In this study, researchers compiled more than 11,000 bacteria tests of wild bird feces and pathogenic E. Coli and Salmonella were only found in very rare cases. Photo by Daniel Karp, UC Davis

“Farmers are increasingly concerned that birds may be spreading foodborne diseases to their crops,” said Daniel Karp, the senior author on the study and an assistant professor in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Yet not all bird species are equally risky.”

Only one foodborne disease outbreak in produce has been conclusively traced to birds: a Campylobacter outbreak in peas from Alaska. While the bacteria can cause diarrhea and other foodborne illness in humans, it's less of a concern to growers than E. coli and Salmonella, which have been responsible for multiple outbreaks across the nation. 

In this study, researchers compiled more than 11,000 bacteria tests of wild bird feces and found that Campylobacter was detected in 8 percent of samples. But pathogenic E. Coli and Salmonella were only found in very rare cases (less than 0.5%).

In addition to the bacteria tests, researchers conducted roughly 1,500 bird surveys across 350 fresh produce fields in Western states and collected more than 1,200 fecal samples from fields. They then modeled the prevalence of pathogens in feces, interactions with crops, and the likelihood of different bird species to defecate on crops to determine risk.

Insect-eating birds pose lower risk

Based on the data, insect-eating birds, such as swallows, present a lower risk, while birds that flock near livestock, such as blackbirds and starlings, are more likely to transmit pathogens.

The data can help the agricultural industry determine risk and take action, such as separating produce crops from cattle lands. They also don't need to treat all birds the same.

“Maybe farmers don't need to be quite as concerned about all types of birds,” Karp said. “Our data suggest that some of the pest-eating birds that can really benefit crop production may not be so risky from a food-safety perspective.”

Farmers may be able to promote insect-eating species like this tree swallow by installing nest boxes without increasing food safety risks. Photo by Daniel Karp, UC Davis

Removing habitat can backfire

This study and the authors' prior work indicate that removing habitat around farms may actually benefit the species that pose more risk and harm the beneficial, pest-eating ones that are less risky to food safety. This is because many prolific insect-eaters may visit crop fields to eat pests but need nearby natural habitats to survive. In contrast, many of the bird species that most commonly carry foodborne pathogens readily thrive on both cattle farms and produce farms without natural habitat nearby.

Other findings

Insect-eating birds that forage in the tree canopy pose minimal threat because they are less likely to carry foodborne pathogens and come into direct contact with produce. They can also be valuable parts of the ecosystem, particularly if they eat pests that can harm crops. Installing bird boxes could attract the pest-eaters, as well as help with conservation efforts.

“We basically didn't know which birds were problematic,” said lead author Olivia Smith, a postdoctoral researcher at Michigan State University who was at University of Georgia when the paper was written. “I think this is a good step forward for the field.”

Additional co-authoring institutions include James Cook University, UC Berkeley, UC Riverside, University of Kentucky, University of Texas, Virginia Polytechnic Institute and State University, Washington State University, BioEpAr, The Nature Conservancy and Van Andel Institute.

The research was funded by the United States Department of Agriculture and the National Science Foundation.

Posted on Wednesday, January 5, 2022 at 9:30 AM
  • Author: Emily C. Dooley, UC Davis
Tags: Bacteria (6), campylobacter (1), crops (6), daniel karp (2), e.coli (1), food safety (48), pathogen (1), salmonella (6), uc davis (46)
Focus Area Tags: Agriculture, Food

Using vegetation barriers to reduce transmission of foodborne pathogens from livestock operations to fresh produce fields

Approximately 48 million people are sickened by foodborne illnesses leading to 128,000 hospitalizations and 3,000 deaths every year, according to the CDC estimates. A foodborne disease outbreak occurs when two or more people get the same illness from the same contaminated food or drink. Since most foodborne disease outbreaks can be traced back to contaminated fruits and vegetables, especially leafy greens, the disease burden has been a topic of concern for the agricultural industry and the public. Bacterial pathogens like Escherichia coli (E. coli), salmonella and campylobacter are among the common causes of the reported foodborne disease outbreaks.

How can we prevent foodborne pathogens from contaminating fruits and vegetables?

Before we can explore answers to the question of preventative measures, we must step back and ask a similarly important question: How do these foodborne pathogens contaminate the fresh produce to begin with? Understanding the different ways in which contamination occurs is imperative in exploring effective prevention measures and solutions.

So, how do foodborne pathogens like salmonella and E. coli get into our fruits and vegetables and why is there an increase in the observed foodborne disease outbreaks? Well, we can loosely attribute the general public's rejuvenated interest in consumption of fresh produce grown with sustainable or organic methods as a plausible explanation for the observed increase in foodborne disease outbreaks.  

Integration of livestock and crop production as a sustainable farming practice has been speculated to be a significant contributor to the increasing numbers of outbreaks, with some research studies affirming the speculation. One such research study, conducted by North Carolina State University, showed that there was indeed significant transmission from animal operations to the fresh produce on sustainable farms. In general, contamination of fresh produce by foodborne pathogens can occur through multiple pathways including the following:

  • Environmental sources such as contaminated runoff surface water
  • Insect transmission and air transmission due to proximity of farm animals to fresh produce
  • Contaminated manure and water irrigation systems
  • Improper food handling

Some of these foodborne pathogens are resistant to antibiotics, which means that even a small case of food poisoning could become fatal, hence the need to find mitigation strategies against foodborne disease outbreaks. One solution that has been proposed is using vegetation barriers to reduce transmission of foodborne pathogens like E. coli and Salmonella on sustainable farms.

Use of vegetation barriers to mitigate transmission of foodborne pathogens on sustainable farms

Vegetative barriers are narrow and parallel strips of stiff and dense vegetation planted on or close to the contour of slopes or across concentrated flow areas. Vegetative barriers slow down runoff water and even filter it out to some extent. They also loosen and improve the soil, which allows for more water retention in the ground. Since foodborne pathogens like E. coli and salmonella can contaminate fresh produce through wind transmission and through runoff surface water from animal farms, planting vegetation barriers can effectively reduce flow of runoff water and act as a wind barrier that traps spray droplets from animal operations, intercepting foodborne pathogens and preventing them from reaching fresh produce farms.

A recent study from North Carolina State University showed evidence of decreased rates of contamination of fresh produce by foodborne pathogens, specifically E. coli and salmonella, from animal operations when vegetation barriers were employed. For this study, a five-layer vegetative barrier (31x49 m) was constructed between a dairy farm, a poultry farm, and a nearby fresh produce farm. Fresh produce, animal fecal excrement and environment samples were collected during the next 15 months and tested for the level of salmonella and E. coli contamination.

The NC State results showed that only 18% of the total E. coli and salmonella samples isolated were present in the fresh produce after installation of the vegetative barriers. Their results confirmed the effectiveness of using vegetative barriers to reduce foodborne pathogen transmission.

It is important to note, however, that while vegetative barriers might be a good measure for lowering transmission by wind and runoff surface water, other transmission pathways like using contaminated manure and improper food handling can still lead to contamination regardless of whether vegetative barriers are present or not. In such scenarios, other mitigation measures are vital. 



Posted on Wednesday, June 30, 2021 at 2:40 AM
Tags: food safety (48)
Focus Area Tags: Agriculture, Food, Health

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