Nutrition, Family and Consumer Sciences
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Nutrition, Family and Consumer Sciences

UC Food Blog

Climate-change research provides tools for farmers to adapt

This is one of a series of stories featuring a sampling of UC ANR academics whose work exemplifies the public value UC ANR brings to California.

Tapan Pathak, left, and Mahesh Maskey adjust sensors in a strawberry field in 2018. Working with Surendra Dara, they have developed a model to forecast weekly crop yields based on weather data.

Farmers are already seeing the effects of warmer winter nights and hotter summer days on their crops. Climate change is gradual, but increasing overall temperatures affect many aspects of farming, including where and how crops are grown. Tapan Pathak, University of California Cooperative Extension specialist based at UC Merced, is doing applied research that farmers and ranchers can use to adapt to new conditions created by a variable and changing climate. 

“You don't have to shift your practice tomorrow, but if you are thinking of making a 30-year investment, it's important to know what risks there are for planting different crops,” said Pathak, who is based in the Sierra Nevada Research Institute at UC Merced.

Pathak co-chairs the UC Cooperative Extension Climate Change Program Team, whose mission is to increase the capacity among UCCE academics to address climate change concerns with science-based information. Pathak also collaborates with extension professionals from across the western U.S. to do extension events related to climate change adaptation. He works closely with state and federal agencies statewide and growers to identify changes occurring as a result of climate change that affect agriculture. Pathak's research will inform growers' decisions, such as crop variety, planting and harvest dates, extreme heat and frost protection and pest management.

“We are seeing impacts of climate change, that's evident. We have some solutions that are available, but we also need to do more locally relevant crop specific research to make agriculture resilient to climate risks,” Pathak said.

The UCCE scientist was the lead author on an important paper that synthesized the impacts of climate change on California agriculture and offers directions for future research and implementation. The authors concluded that almost all of California's crops, collectively valued at more than $50 billion a year, will be endangered to some degree by rising temperatures and variable weather patterns. The study “Climate Change Trends and Impacts on California Agriculture” was published in Agronomy in 2018.

“I think there's a lot of solutions available and there is also a clear need for adaptation research that include growers' perspectives,” said Pathak, who received a Climate Leadership Award for research from the California Climate & Agriculture Network.

Pathak is also collaborating very closely with UC Davis-based UCCE specialist Daniele Zaccaria, who is leading an international project on evaluating bioclimatic indices and developing the index that is more relevant to irrigated agriculture, which includes scientists from the U.S., Italy, Brazil and Chile.

“A bioclimatic index specific to irrigated agriculture can provide more accurate and valuable agricultural drought information that could be helpful for water resources planning and management decisions,” Pathak said. 

Pathak presents research results to Santa Maria growers in 2018. With input from growers, Pathak is developing a web-based decision support system called Cal AgroClimate, which incorporates historical climate data and future projections. .

Cal AgroClimate

Pathak is developing a web-based decision support system called Cal AgroClimate to help growers make decisions, in partnership with the USDA California Climate Hub director Steven Ostoja. It is being built on the same platform as AgroClimate, which is popular with growers in the Southeast.

Cal AgroClimate translates historical climate data and future projections into a useful decision support system for growers. For example, growers can get extreme heat and frost advisories for the next 10 to 14 days in their region and relevant resources to mitigate risks for their selected crop. It is in the early phase of development and will include a suite of tools based on the needs and priorities identified by UCCE colleagues, growers and the agricultural community in general.

In addition to his work on Cal AgroClimate, Pathak has been conducting research on specific crops.


In a study looking at processing tomato production in the Central Valley, Pathak and UCCE advisor Scott Stoddard found that changing temperatures will likely change the tomato growing season. The scientists looked at processing tomato data starting from 1950 and projections for 2030-2040 to see how the time to maturity is changing.

“In general, the time from emergence to maturity, the timeframe for processing tomatoes in that region is going to shrink by two to three weeks,” said Pathak. “A lot of processors have their timeline for when they need the tomatoes for processing and so when you have this shift in the phenology, that alters the timeframe for when they mature and are ready for the processors. So, there's a whole shift in the management that growers might have to think about in the future.” 


Kripa Jagannathan presented her findings on almond growers climate information needs for long-term decision-making in 2016.

To identify the climate information almond growers need to take adaptation action, UC Berkeley postdoctoral researcher Kripa Jagannathan, former UCCE advisor David Doll and Pathak interviewed almond growers in the Central Valley. During their conversations with farmers, the researchers clarified that long-term climate projections are not seasonal forecasts or weather forecasts for the next 20 to 30 years. The projections provide information on trends or potential of shifts from historical conditions for making long-term planning decisions.

Pest control is one area where growers will need to make changes. Research by UCCE advisor Jhalendra Rijal and Pathak shows the almond pest navel orangeworm is already extending its life to a fifth generation during a season. 


For strawberries, Pathak, UCCE entomology and biologicals advisor Surendra Dara and postdoctoral researcher Mahesh Maskey have developed a model to forecast weekly crop yields based on weather data. “The model was pretty accurate for the Santa Maria region,” Pathak said. “A crop-specific model can be used for labor management not just crop management.” 

Because California produces more than 400 agricultural products, adapting to climate change will be more complex than in other states.


Posted on Monday, June 29, 2020 at 9:56 AM
Focus Area Tags: Agriculture

Study finds 82 percent of avocado oil rancid or mixed with other oils

Avocados hang on a tree at UC South Coast Research & Extension Center. “Consumers seeking the health benefits of avocado oil deserve to get what they think they are buying,” says Selina Wang.

Consumer demand is rising for all things avocado, including oil made from the fruit. Avocado oil is a great source of vitamins, minerals and the type of fats associated with reducing the risk of heart disease, stroke and diabetes. But according to new research from food science experts at the University of California, Davis, the vast majority of avocado oil sold in the U.S. is of poor quality, mislabeled or adulterated with other oils.

In the country's first extensive study of commercial avocado oil quality and purity, UC Davis researchers report that at least 82% of test samples were either stale before expiration date or mixed with other oils. In three cases, bottles labeled as “pure” or “extra virgin” avocado oil contained near 100 percent soybean oil, an oil commonly used in processed foods that's much less expensive to produce.

“I was surprised some of the samples didn’t contain any avocado oil,” said Wang.
“I was surprised some of the samples didn't contain any avocado oil,” said Selina Wang, UC Cooperative Extension specialist in the UC Davis Department of Food Science and Technology, who led the study recently published in the journal Food Control.“Most people who buy avocado oil are interested in the health benefits, as well as the mild, fresh flavor, and are willing to pay more for the product. But because there are no standards to determine if an avocado oil is of the quality and purity advertised, no one is regulating false or misleading labels. These findings highlight the urgent need for standards to protect consumers and establish a level playing field to support the continuing growth of the avocado oil industry.”

Testing domestic and imported brands  

Wang and Hilary Green, a Ph.D. candidate in Wang's lab, analyzed various chemical parameters of 22 domestic and imported avocado oil samples, which included all the brands they could find in local stores and online. Wang and Green received a $25,000 grant from Dipasa USA, part of the Dipasa Group, a sesame-seed and avocado-oil processor and supplier based in Mexico.

“In addition to testing commercial brands, we also bought avocados and extracted our own oil in the lab, so we would know, chemically, what pure avocado oil looks like,” Wang said.

Test samples included oils of various prices, some labeled extra virgin or refined. Virgin oil is supposed to be extracted from fresh fruit using only mechanical means, and refined oil is processed with heat or chemicals to remove any flaws.

Fifteen of the samples were oxidized before the expiration date. Oil loses its flavor and health benefits when it oxidizes, which happens over time and when exposed to too much light, heat or air. Six samples were mixed with large amounts of other oils, including sunflower, safflower and soybean oil.

Only two brands produced samples that were pure and non-oxidized. Those were Chosen Foods and Marianne's Avocado Oil, both refined avocado oils made in Mexico. Among the virgin grades, CalPure produced in California was pure and fresher than the other samples in the same grade.

A push for standards

Ensuring quality is important for consumers, retailers, producers and people throughout the avocado oil industry. Retailers want to sell quality products, shoppers want to get their money's worth and honest producers want to keep fraudulent and low-quality oil out of the marketplace.

But since avocado oil is relatively new on the scene, the Food and Drug Administration (FDA) has not yet adopted “standards of identity,” which are basic food standards designed to protect consumers from being cheated by inferior products or confused by misleading labels. Over the last 80 years, the FDA has issued standards of identity for hundreds of products, like whiskey, chocolate, juices and mayonnaise. Without standards, the FDA has no means to regulate avocado oil quality and authenticity.

Avocado oil isn't the only product without enforceable standards. Honey, spices and ground coffee are other common examples. Foods that fetch a higher price are especially ripe for manipulating, especially when adulterations can be too subtle to detect outside a lab.

Wang is working to develop faster, better and cheaper chemical methods to detect adulteration so bulk buyers can test avocado oil before selling it. She is also evaluating more samples, performing shelf-life studies to see how time and storage affects quality, and encouraging FDA officials to establish reasonable standards for avocado oil.

Wang has experience collaborating with industry and the FDA. Ten years ago, she analyzed the quality and purity of extra virgin olive oil and discovered that most of what was being sold in the U.S. was actually a much lower grade. Her research sparked a cascade of responses that led California to establish one of the world's most stringent standards for different grades of olive oil. The FDA is working with importers and domestic producers to develop standards of identity for olive oil.

“Consumers seeking the health benefits of avocado oil deserve to get what they think they are buying,” Wang said. “Working together with the industry, we can establish standards and make sure customers are getting high-quality, authentic avocado oil and the companies are competing on a level playing field.”

Tips for consumers

  • The flavor of virgin avocado oil can differ by varieties and region. In general, authentic, fresh, virgin avocado oil tastes grassy, buttery and a little bit like mushrooms.
  • Virgin avocado oil should be green in color, whereas refined avocado oil is light yellow and almost clear due to pigments removed during refining.
  • Even good oil becomes rancid with time. It's important to purchase a reasonable size that can be finished before the oil oxidizes. Store the oil away from light and heat. A cool, dark cabinet is a good choice, rather than next to the stove.  
  • How do you know if the oil is rancid? It starts to smell stale, sort of like play dough.
  • When possible, choose an oil that's closest to the harvest/production time to ensure maximum freshness. The “best before date” is not always a reliable indicator of quality.
Posted on Monday, June 15, 2020 at 5:38 PM
Tags: Avocado (2), food safety (42), nutrition (126), Selina Wang (1)
Focus Area Tags: Food

UC conducts survey of COVID-19 prevention on farms

Agricultural employers are asked to share successful strategies as well as challenges for protecting workers from COVID-19. Photo by Hector Amezcua

All California growers, ranchers, farm labor contractors and ag supervisors are invited to complete a short survey about their experiences addressing COVID-19​ in the workplace. The survey is being conducted by the UC Davis Western Center for Agricultural Health and Safety. 

The survey ​is anonymous, should take less than 10 minutes ​to complete​, and is available in English and Spanish at

“At the UC Davis Western Center for Agricultural Health and Safety, we are working to respond to the COVID-19 crisis with practical resources for growers, ag employers, and farmworkers,” said Heather E Riden, agricultural health and safety program director. “The goal of this survey is to understand what practices farms are implementing to prevent COVID-19, where they have seen success, and where there may be challenges. We will take this information to assess whether there are new resources, trainings, or information that we can provide.” 

Respondents are given the opportunity to share their contact information at the end of the survey.

“We plan to share any findings as well as new materials with anyone who expresses interest,” Riden said. “We will also summarize the results and post them on the WCAHS website.”

For more information about the survey, contact ​

Visit for COVID-19 training resources and employer guidance. The center's COVID-19 website offers farmers many resources, including an employer checklist and tailgate training discussion guide.

Posted on Friday, June 12, 2020 at 9:05 AM
Focus Area Tags: Agriculture

California heroes continue to provide nutritious food to students

Now more than ever, California is full of heroes:  front-line workers in our hospitals, farm fields and essential businesses. And even though schools are closed, they are full of heroes, too: teachers implementing distance learning and kitchen workers who have stepped up to the heroic task of providing meals for children in their communities, despite the challenges that have come with the COVID-19 pandemic.

School nutrition professionals continue to provide nutritious food that meets dietary standards, the kitchens provide employment, and the hungry students provide a multi-million dollar market for California's agricultural products.

North Monterey County Unified School District weekly meal kit distribution has allowed them to safely provide nutritious meals to their students and the youth in their community during the school closures.

Researchers at UC Agriculture and Natural Resources's Nutrition Policy Institute received an email earlier this spring with a subject line that simply said, “HELP!!!” Local community groups had learned that some Central Valley school districts would not be providing meals over spring break. Even though that might not be cause for alarm some years, this year it would hurt. In the eight-week period between March 14 and May 14, 2020, the California Employment Development Department processed 4.7 million unemployment benefit claims – nearly seven times more claims than over a two-month period at the height of the 2008 recession. EDD estimates that California unemployment reached nearly 25% by mid-May. 

That is why school meals are more important than ever. 

On receiving the request for HELP!!!, the Nutrition Policy Institute teamed with a Stanford pediatrician to distill critical information from USDA and the California Department of Education. Connecting with child nutrition professionals throughout the state, they gleaned tips and best practices, and added COVID-19-specific resources from the Community of Practice convened by LunchAssist and the Center for Ecoliteracy. The team produced informational flyers targeted to California school district officials and food service directors:

The resources provide explanations and resources for operating school meal programs during non-instructional periods through either the Seamless Summer Option (SSO) or the Summer Food Service Program (SFSP).

There is no time to lose. Click here to make sure your local school district's food services division is taking advantage of the many strategies that can support children's nutrition this summer.

Food sacks prepared for drive-by pick up by families in the North Monterey County Unified School District.
Posted on Monday, June 8, 2020 at 3:54 PM
Focus Area Tags: Food

How has coronavirus pandemic impacted California food, agriculture and environment?

New report examines the impact of the coronavirus pandemic on food system and what the future holds for California's cattle, dairy, produce, strawberry, tomato, nut and wine industries.

New report explores long-term effects of COVID-19 on state's cattle, dairy, produce, strawberry, tomato, nut and wine industries.

COVID-19 continues to affect parts of California agriculture in different ways. A new report from agricultural economists at the University of California examines the current and long-term impacts on California's leading agricultural industries.

Profiles in the report illustrate the different ways the pandemic has impacted dairy, beef and produce – industries that have scrambled to repurpose products from foodservice to retail – and tree nuts, an industry that saw a temporary spike in sales as consumers hoarded storable goods. The report includes expert assessments of what the future holds for California's cattle, dairy, produce, strawberry, tomato, tree nut and wine industries.

The studies are contained in a special coronavirus issue of ARE Update, a bimonthly magazine published by the University of California Giannini Foundation of Agricultural Economics. Contributors include several experts from the UC Davis Department of Agricultural and Resource Economics. 

Social distancing drives up strawberry harvest costs because increasing the space between workers slows picking.

In addition to industry profiles, the report includes three articles addressing the effect of the pandemic on farm labor, food security, and traffic and pollution in California. The authors conclude that farm labor supplies are likely to be reduced due to the pandemic, hastening the trend toward mechanization. Authors of the study on federal nutrition assistance programs expect participants in these programs to face unprecedented economic hardship due to the COVID-19 pandemic. They suggest specific policy responses to reduce the impact. The study on vehicle traffic (and associated pollution) in California shows that travel dropped dramatically—by 40% to 60%—in California following the stay-at-home order, but then began increasing in mid-April, long before any restrictions on the stay-at-home order were lifted.

“Although the coronavirus pandemic continues to afflict most parts of the world, states and countries are attempting to reopen their economies and assess the damage that has been wrought,” said Richard Sexton, UC Davis distinguished professor and co-editor of ARE Update. “We look at the impacts on California agricultural industries and the implications for the environment and consumers, especially the most vulnerable among us.” 

COVID-19 and farmworkers

No state relies upon agricultural labor more than California, where employment peaks seasonally in June. When stay-at-home orders were issued in March 2020 to slow the spread of COVID-19, farmworkers were deemed essential and expected to continue working.

As California's farm employment climbs toward its June peak, sick farmworkers, closed schools and uncertainties surrounding the H-2A guest worker program could reduce the supply of farmworkers, accelerating trends already underway such as mechanization.

Full article can be found at

Nutrition assistance programs

With record unemployment, CalFresh enrollments are as much as 80% higher in California than last year at this time.

Processing plant closures, consumer stockpiling of key staple foods and other supply chain disruptions have raised serious questions about food security in the U.S. Enrollments in CalFresh, for example, are up as much as 80% in California from last year at this time.

The authors address the role policymakers, food banks and food assistance programs like the National School Lunch Program and Women, Infants and Children (WIC) can play in meeting food-security challenges now and in the future.

Full article can be found at

Traffic, travel and pollution

Shelter in place orders reduced traffic, but had no effect on fine particulate concentrations, a key contributor to air pollution.

Near real-time data can give key insights into how the pandemic and economic shutdown have impacted behavior in California. Using Caltrans traffic sensor data and Apple data, economists show that travel in California dropped precipitously when the stay-at-home orders were issued—down 40% to 80%, depending on the data source—but the rate of decline varied considerably by regions within the state.

While the stay-at-home order did reduce travel, the report found that the shutdown had no effect on fine particulate concentrations, a key contributor to air pollution.

Full article can be found at

To read ARE Update's Special Issue: Implications of the Coronavirus Pandemic on California Food, Agriculture, and the Environment, visit or

Commodity profiles can be found at

Tree nuts:








Posted on Wednesday, June 3, 2020 at 2:48 PM
  • Author: Diane Nelson, UC Davis College of Agricultural and Environmental Sciences
  • Author: Tiffany Loveridge, UC Davis Department of Agricultural and Resource Economics
Tags: coronavirus (3)
Focus Area Tags: Agriculture Environment Food

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