UC Food Blog
Although the outbreak earlier this month of E. coli O145 in shredded Romaine lettuce hasn’t touched California consumers and local retailers, it is impacting the industry. Once again, the safety of pre-washed and cut leafy vegetables are in headlines, raising the fears of consumers and producers alike.
The Centers for Disease Control have confirmed 23 illnesses and 7 probable illnesses in New York, Michigan, Ohio and Tennessee from the contaminated lettuce. The traceback investigation is stretching west to Yuma, Ariz., where the lettuce may have been grown. So far, the source of the contamination has not been identified.
A source of confusion and alarm, however, is the contaminant’s O145 designation. For the past 30 years, the majority of the E. coli illness outbreaks in America were serotype O157:H7. UC Davis Cooperative Extension produce safety specialist Trevor Suslow said E. coli O145 doesn’t come completely out of the blue. O145 is recognized in its association with food in other countries and more often with animal products, not produce.
Suslow and his staff were well aware of E. coli O145 prior to this month’s outbreak and included it in their recent research aimed at development of a new method for detecting a broad range of the most dangerous E. coli bacteria in produce and produce production environments.
The new test was not designed to identify a particular strain of E. coli, but to determine whether a pathogenic/toxigenic strain of E. coli – such as O145 – is present. If the test comes up positive, a secondary test can be conducted to narrow down the specific type of E.coli.
Pathogenic/toxigenic E. coli are of tremendous concern for the fresh produce industry. “Generic” E. coli live in the guts of most mammals; they are typically harmless and may even be beneficial. However, pathogenic/toxigenic E. coli, when ingested by humans, can cause bloody diarrhea and, particularly in the very young and very old, may lead to kidney failure and even death.
Suslow said the new test, which goes by the working name “total pathogenic E. coli,” or TPEC, was tested in a variety of different types of samples: irrigation water, feed lot surface material, manure, compost, soil and produce.
“With all those materials, we had very good effectiveness, but especially with water and produce,” Suslow said.
The research will be presented at the UC Davis Center for Produce Safety Produce Research Symposium on June 23. The Produce Research Symposium is open to the public. A $150 registration fee includes all symposium sessions, breakfast, lunch and an evening reception in the courtyard and gardens of the Robert Mondavi Institute for Wine and Food Science.
For more information or to register for the symposium, see the Center for Produce Safety website at http://cps.ucdavis.edu.
Bagged lettuce was implicated in a recent food safety outbreak.
Farmers markets and produce stands are starting to bulge with the bounty of California's fields as strawberries, artichokes and asparagus mark the start of the spring and summer produce seasons.
But have you ever wondered what to look for when selecting fruits and vegetables? Why does your refrigerator have separate bins for fruits and vegetables? Should fresh tomatoes be stored in the refrigerator or on the counter? And how do you keep fresh basil fresh until you're ready to use it?
These and many more questions are answered in the colorful handbook: From the Farm to Your Table: A Consumer's Guide to Fresh Fruits and Vegetables available at anrcatalog.ucdavis.edu
This guide contains tips from the pros on selection, storage and handling for quality and safety. Handy tables show you which fruits and vegetables should be stored in the refrigerator, which should be stored on the counter, and what to look for when selecting popular produce items. And if you've ever wondered the steps your produce takes to get from the field to your market, the journey is explained here.
After reading this guide you'll know why there's more to fruit and vegetable quality than meets the eye.
Oh, and the answers to those questions?
Your refrigerator has separate bins so you can keep keep ethylene-producing fruits such as apples, peaches and pears away from vegetables.
Uncut tomatoes should be stored on the counter, not in the refrigerator.
And keep your basil fresh by treating it like cut flowers; place the stems in a glass of water on the counter until you're ready to use it.
Workers sort tomatoes at Russell Ranch
Part of our mission at the Agricultural Sustainability Institute at UC Davis is to ensure access to healthy food. So we’ve focused much of our work on the intersection between agriculture and human nutrition.
An interesting new field of study in this area looks at flavonoids, which are compounds in fruits and vegetables thought to have beneficial antioxidant effects and other medicinal value – they may even help reduce cancer risk.
Measuring the amount of flavonoids is one way we can figure out just how nutritious the food we’re eating really is.
At our Russell Ranch Sustainable Agriculture Facility, UC Davis Food Science professor Alyson Mitchell has looked at the relative nutrition of organic and conventional tomatoes by measuring flavonoid levels in samples from dried tomatoes over a 10-year period.
Aerial view of Russell Ranch Sustainable Agriculture Facility
She found that flavonoid content is greater in organic than conventional tomatoes, and the differences have increased with time. Over time, it also appears that an increase in flavonoid content is correlated with lower amounts of organic nitrogen application.
These results suggest that over-fertilization can result in lower flavonoid content – and a reduction in the health benefits of tomatoes. You can find out more about this research here.
Catechins are phytochemical compounds found in plant-based foods and beverages. Consumption of catechins has been associated with a variety of beneficial effects including: ability of plasma to scavenge free radicals, blood vessel expansion, fat oxidation and more.
High concentrations of these helpful compounds can be found in many foods and beverages including: red wine, broad beans, black grapes, apricots, strawberries, apples, cherries, pears, raspberries, chocolate and both black and green tea.
To learn more about the benefits and research related to catechin rich foods, please see UC ANR’s free publication, Nutrition and Health Info Sheet Catechins.
I’m lucky enough to live about a mile from a small, family-run strawberry patch in Yolo County. From some time in April until October, the Laotian family members pick berries in the mornings and sell them from their small wooden stand until they run out of fruit for the day.
Flats of 4 or 6 baskets are the most economical to buy. I carefully place the flat on the floor of the passenger seat; by the time I have walked around to the driver’s seat, the fragrance of the fresh berries has filled the car with instant summer.
Once home, I don’t wash the berries unless I plan to eat them right away. Instead I keep the berries in their baskets and cardboard flat and just cover them loosely with a paper towel. They keep their flavor and texture up to 5 days this way.
According to UC ANR Food Safety Specialist Linda Harris, washing berries in a sink filled with water can spread contaminants from one berry to another; it’s best to hold them under running water, drain them in a clean strainer and pat them dry with a paper towel. I use a clean grapefruit knife with a serrated, slightly curved tip to cut out just the green stem and white part of each berry.
On summer days I get up early and prep the berries like this before my dog and I head out for a run in the cool morning air. Then all I must do when we return—hot and thirsty—is toss the smoothie ingredients in a blender and turn it on.
You can keep your smoothie simple or pack it full of healthy ingredients, as I do below, so it essentially serves as a full breakfast. Either way, its fresh strawberry flavor is one of the culinary pleasures of an early California summer.
Serves two; exact amounts are not critical
3 – 4 ice cubes
1½ – 2 cups washed strawberries, stem and core removed
1 banana, peeled
½–3/4 cup protein drink, such as Odwalla Super Protein
½ cup pomegranate, orange or any real fruit juice
½–2/3 cup nonfat vanilla yogurt
Optional: a handful of other fruit such as a peeled, cored pear or a slice of cantaloupe
Place ice in the blender first, then add fruit, yogurt and juice. Cover and blend 1–2 minutes or until ice and fruit are pureed.
If you don’t use a full flat of strawberries, you can freeze, dry and can the extra berries. See Harris’ Strawberries: Safe Methods to Store Preserve and Enjoy http://anrcatalog.ucdavis.edu/pdf/8256.pdf for information on those methods.
Cleaned strawberries ready to be prepped