- Author: Diane Nelson
One notion — the so-called “fridge-test” theory — says you can determine the purity of your extra virgin olive oil (EVOO) by putting it in your refrigerator. If it solidifies, you can trust your EVOO is pure — or so the theory goes.
Is that scientifically accurate?
No, according to new research from the UC Davis Olive Center. Testing seven samples under cold conditions over eight days, researchers discovered the fridge test is unreliable in detecting either the purity or quality of olive oil.
“None of our samples showed any signs of congealing after 60 hours in a laboratory refrigerator set to 40.5 degrees Fahrenheit,” said Dan Flynn, executive director of the UC Davis Olive Center. “Even after 180 hours, the samples never fully solidified.”
“Wouldn’t it be nice to have such a simple test that could indicate an olive oil’s market grade, but it is much more complicated than that,” said Paul Vossen, UC Cooperative Extension advisor in Sonoma and Marin counties.
“All olive oils contain a small amount of saturated fatty acids that solidify at refrigerator temperatures,” said Vossen, an olive oil expert. “The amount of solidification is equal to the amount of saturated fatty acids in the oil, which depends mostly on the varieties of olives used to make the oil and to a lesser extent where the olives were grown. Solidification does not indicate freshness, purity, flavor, extra virgin grade, or any other quality parameter.”
The fridge-test theory surfaced on a recent episode of The Dr. Oz Show which aired Feb. 11, 2013, to more than 3 million viewers. While cautioning his method isn’t fool-proof, Dr. Oz. encouraged viewers to test the purity of EVOO by seeing if it solidifies in the fridge.
“After the show aired, we were swamped with calls from people who were concerned they were being ripped off,” Flynn said.
So the Olive Center conducted a study. They refrigerated seven samples, including two EVOOs, an olive oil, a canola oil, a safflower oil, and two blends. Some samples showed minor congealing at the bottom of the bottles, but none solidified completely.
“It’s true that waxes and long-chain fatty acids in extra virgin olive oil can lead to the oil solidifying in the cold, although relative amounts of these compounds vary from oil to oil,” the study said.
Olive oils are graded based on how the oil is extracted from olives and on chemical and sensory standards. True extra virgin olive oil is extracted from olives without heat or chemicals and must have no defective flavors such as rancidity. Extra virgin olive oil is more expensive than other oils and is therefore an attractive product for fraud.
Using sensory and chemistry testing, the UC Davis Olive Center is working on dependable methods for detecting when an extra virgin olive oil is fraudulently labeled. In the meantime, the center advises consumers to choose an oil within 15 months of the harvest day (not the best-before date), look for a certification seal indicating that the oil passed chemical and sensory tests, and seek (and store) oils protected from light.
- Author: Janet L. White
- Author: Aubrey White
As California legislators focus on nitrogen use in agriculture and its ability to contaminate groundwater, potential regulation on fertilizer use will require solid information on the amount of fertilizer used by California farmers, and the extent to which that usage contributes to environmental pollution. A new study published in California Agriculture evaluates trends in fertilizer use by California's major crops. It also shows that major deficiencies in data collection need to be addressed in order to develop effective policies regarding fertilizer use.
The publication is one of the first peer-reviewed articles to emanate from the California Nitrogen Assessment (an ongoing project at UC Davis). Assessment research documents that while there are many pathways through which nitrogen can enter the environment, inorganic fertilizer use is responsible for the largest fraction of new nitrogen introduced into California annually. Currently, over 600,000 tons of nitrogen fertilizer are sold in the state each year.
Information on fertilizer sales, however, is not an accurate indicator of fertilizer application, and authors found that fertilizer use data is not easy to come by — either because it is not tracked at relevant scales or because data sources are inconsistent.
"We found ourselves with very limited information to understand an issue with sweeping implications for California agriculture,” says Todd Rosenstock, the article's lead author. "We dug deep to create an accurate picture of fertilizer use in the state, but the remaining gaps will require attention.”
To estimate the amount of nitrogen applied to different crops around the state, authors aggregated data from different sources, including grower surveys and University of California studies, and show application rates for 33 of California's major crops.
While nitrogen fertilizer use on a crop-by-crop basis has risen over the last three decades, this increase has been more modest than fertilizer sales suggest. Between 1973 and 2005, fertilizer sales increased 31 percent, but nitrogen application rates increased on 25 percent across the 33 crops studied. Both data sets reflect increased nitrogen application and a shift to growing more nitrogen-intensive crops.
For many crops, nitrogen use increases have been accompanied by well-recorded yield increases — at rates that show nitrogen's benefit, and also suggest that farmers may be becoming more agronomically nitrogen-efficient, requiring less nitrogen per unit of production.
"In the absence of good information, we could do the wrong thing,” says Tom Tomich, co-author of the article and director of the Agricultural Sustainability Institute at UC Davis.
"Regulation without supporting data could fail to address the heart of the problem, or could damage agriculture,” says Tomich, who is also professor in the Department of Environmental Science and Policy at UC Davis, W.K. Kellogg Endowed Chair in Sustainable Food Systems and director of Sustainable Agriculture Research and Education Program. "Better information on nitrogen use is indispensable to collaborative development of effective solutions that can increase nitrogen use efficiency and save farmers money.”
The article makes recommendations on how data could be better compiled to improve our understanding of statewide trends in fertilizer use. To read the article, visit http://ucanr.edu/calagnassessment.
This article is part of an ongoing study, the California Nitrogen Assessment (CNA), a project of the Agricultural Sustainability Institute at UC Davis and UC Sustainable Agriculture Research and Education Program. The CNA reviews existing data on nitrogen to draw connections between nitrogen use, surplus, and established environmental and human health effects of excess nitrogen. The CNA is a stakeholder-driven assessment that seeks public input on its research and products. To learn more about the California Nitrogen Assessment, visit http://nitrogen.ucdavis.edu.
- Author: Diane Nelson, (530) 752-1969, denelson@ucdavis.edu
“HLB is not just bad for growers and for the economy,” said Slupsky. “The loss of fresh oranges and other citrus could seriously impact our health.”
HLB is a disease caused by a microbe called Candidatus Liberibacter asiaticus and spread by the Asian citrus psyllid, a tiny insect that feeds on the leaves and stems of citrus trees. There is no cure yet for HLB, so once a tree is infected, it will slowly die. The disease has decimated citrus groves in Asia, Brazil and the Dominican Republic. Florida has lost one-third of its citrus to the disease. Both HLB and the Asian citrus psyllid have recently been spotted in California.
HLB is a silent killer – an infected tree can live for years without symptoms, allowing the pathogen to spread undetected to other trees. Symptoms emerge over time, as a tree’s fruit starts to turn green and misshapen, with a bitter, metallic taste.
Is there a way to spot HLB before visual symptoms occur? The microbe that causes HLB can sometimes be found in a leaf sample, but since the pathogen isn’t evenly distributed throughout the tree, results can be misleading.
“Just because the pathogen doesn’t show up in one leaf, that doesn’t guarantee the tree isn’t infected,” said MaryLou Polek, vice president of science and technology for the California Citrus Research Board. “So when you sample a leaf, there’s a high probability of a false negative result.”
Slupsky and Andrew Breksa, research chemist with the USDA Agricultural Research Service based in Albany, Calif., tried a different tack, searching for clues in a tree’s chemical fingerprint. They used nuclear magnetic resonance spectroscopy to study the amino acid composition of juice from three types of citrus: fruit from healthy tress, symptom-free (asymptomatic) fruit from HLB-positive trees, and fruit with symptoms from HLB-positive trees.
“We found major differences in the chemical fingerprint among healthy, asymptomatic and symptomatic fruits,” Slupsky said.
With further research, the profiles may prove to be a reliable, rapid, and early indicator of the presence of the HLB pathogen. With early detection, growers and regulators can know which trees might need to be removed before the disease spreads throughout the orchard (and beyond).
“These findings are huge for citrus growers, backyard gardeners and everyone who loves fresh citrus,” Polek said.
And there’s more. While analyzing the amino acids, Slupsky and Breksa discovered what looks like a mechanism underlying the microbe’s mode of attack.
“The pathogen responsible for HLB seems to cause havoc with a tree’s ability to defend itself from infection,” Slupsky said.
Trees need amino acids for growth, development and defense. From Slupsky and Breksa’s studies, it looks like the HLB pathogen affects the trees’ ability to create, use and recycle some of those amino acids. For example, a tree can convert the amino acid phenylalanine into cinnamic acid, a precursor to compounds important to the tree’s defense systems. But juice from oranges of HLB-positive trees had significantly higher concentrations of phenylalanine. Also, juice from oranges grown on HLB-infected trees contained a lot less of the amino acid proline, which a tree usually synthesizes when it knows something is wrong.
“It could be that the pathogen is outsmarting the tree by undermining its defenses,” Slupsky said. “That’s a spectacular discovery, because when we understand the mechanisms behind the attack, we have a chance at blocking them. Maybe we can find ways to enhance a tree’s natural immunity.”
As tough as HLB has been on citrus in Florida, the stakes are even higher in California where so much of the world’s fresh citrus is produced.
“Florida’s citrus industry produces mostly orange juice, and they can use additives and filtration to adjust for the bitter taste of HLB-affected fruit,” Polek said. “It can be reduced to sugar water, essentially, and then built back up to taste like orange juice. We produce fresh citrus here in California, and chemistry is not an option.”
Losing fresh citrus is a real possibility if HLB spreads throughout California, and that prospect is the driving force behind Slupsky’s research.
“From a nutritional standpoint, it’s hard to beat the importance of fresh citrus,” Slupsky said. “Oranges provide energy, pectin, and a wide variety of nutrients, vitamins and minerals. They’re one of the most consumed fruits in the United States. I can’t imagine life without fresh citrus.”
Slupsky and Breksa collaborated with Thomas G. McCollum of the ARS Horticultural Research Laboratory in Fort Pierce, Florida, along with Anne Slisz and Darya Mishchuk of Slupsky’s lab. A peer-reviewed article on their findings was published in the Journal of Proteome Research in June 2012. You can access the article at http://pubs.acs.org/doi/abs/10.1021/pr300350x.
- Author: Janet White
Original research and literature reviews on these subjects appear in the January-March 2013 California Agriculture, UC’s peer-reviewed research journal of research in agriculture, natural and human resources (http://www.californiaagriculture.ucanr.edu).
UC Agriculture and Natural Resources (ANR) has launched a strategic initiative to help California youth. Called Healthy Families and Communities, it includes research and programs to encourage healthy lifestyles, boost science literacy, and foster positive youth development. Delaine Eastin, former State Superintendent of Public Instruction, notes, “At the end of the day, the Healthy Families and Communities Strategic Initiative is about change, scientifically measurable change, yielding concrete evidence of youth improvement due to these efforts.”
In addition, each year about 100,000 California youth who reach graduation age fail to graduate from high school, a predictor of their future social and financial difficulties as well as a missed opportunity for training skilled workers to replace those close to retirement. Finally, California’s eighth-grade science scores ranked 47th among the states in the National Assessment of Educational Progress’s 2011 report. A workforce with the knowledge and skills for scientific careers is critical to the state’s economy, and to full participation in today’s technological society.
Confronting these complex issues requires a multifaceted approach that leads to strategic change, says David Campbell, UC Cooperative Extension specialist in the Department of Human and Community Development at UC Davis and leader of ANR’s new youth-focused initiative.
“We’re bringing a lot of people together across disciplines,” he says. “If our work is going to be relevant to the real world, we need to reflect its complexity.”
As part of the initiative, UC researchers are partnering with schools and youth organizations in controlled studies to learn what works in the real world.
Summaries of projects and links to articles:
Integrating local agriculture into nutrition programs can benefit children's health (page 30). Sheri Zidenberg-Cherr, UCCE specialist in the Department of Nutrition at UC Davis, leads a K-6 nutrition education effort, called Shaping Healthy Choices. Designed to both improve child health and support local agriculture, the program incorporates serving regional fruits and vegetables, a school garden, and classroom nutrition and physical fitness lessons. In this controlled four-year study, investigators have matched schools in Northern and Central California, and will compare those that are implementing the program with those that are not.
Communitywide strategies key to preventing childhood obesity (page 13). According to Pat Crawford, UCCE specialist in the Department of Nutritional Science and Toxicology at UC Berkeley, increasing consumption of fruits and vegetables is important but not enough by itself to combat obesity. Two of the strongest factors driving obesity are sweetened beverages and fast food, and decreasing their consumption is just as important as increasing the consumption of healthy foods. “You have to do both,” she says.
Her team at the Center for Weight and Health in Berkeley, with funding from ANR, is evaluating Team Up for Good Health, a community-based approach to preventing obesity in elementary school children. Investigators are studying fourth- and fifth-grade participants in school and after-school obesity prevention programs, using body mass index (BMI) reductions after two years as a measure of success.
Lessons of Fresh Start can guide schools seeking to boost student fruit consumption (page 21). In 2005, California became the first state to address the availability of fresh and local produce in the federal School Breakfast Program through state funding. This evaluation of the California Fresh Start program reveals lessons that are especially important now, as schools across the country prepare to increase the number of fruits and vegetables offered in the School Breakfast Program by July 2014 as part of the Healthy, Hunger-Free Kids Act.
Inquiry-based learning (pages 47 and 54). Another innovative aspect of these UC programs is the curriculum. Based upon inquiry-based learning, it captures the attention of students by focusing on the real world and children’s day-to-day lives. For example, in the Shaping Healthy Choices program (page 30), a lesson on food labels at school will be followed by students comparing food labels on their own, at home and in grocery stores. “Application is what makes learning stick,” says Martin Smith, UCCE specialist in the School of Veterinary Medicine who works on youth science literacy. “Inquiry-based learning takes longer, but it’s deeper — kids own the knowledge because they figured it out themselves.”
Positive youth development merits state investment (page 38). A team of UC researchers reviews studies supporting a new paradigm for youth programs, and proposes increased state investment in this area. Research over the last 30 years has shifted thinking away from the deficit model, in which researchers and practitioners considered high-risk youth behaviors to be their focus, and toward promotion of positive patterns. “Far too many California youth are not thriving,” the authors note. “Promotion of healthy pathways to college, work and community engagement is of urgent concern.” They cite findings that positive youth development is linked to improved school achievement, higher graduation rates, and fewer risk behaviors.
The entire January-March 2013 issue can be downloaded at http://californiaagriculture.ucanr.edu.
California Agriculture is the University of California’s peer-reviewed journal of research in agricultural, human and natural resources. For a free subscription, go to: http://californiaagriculture.ucanr.edu, or write to calag@ucanr.edu.
WRITERS/EDITORS: To request a hard copy of the journal, e-mail crllopez@ucanr.edu.
- Author: Pamela Kan-Rice
UC ANR scientists are working with the California Department of Food and Agriculture to develop a curriculum and certification program to protect water quality, as recommended by the State Water Resources Control Board. The classes will begin in January 2014.
Last week (Feb. 20) the State Water Resources Control Board released its recommendations to the Legislature for addressing nitrate in groundwater.
The recommendations are based on a UC Davis study commissioned by the water board and released last March titled “Addressing Nitrate in California's Drinking Water,” which focused on the Tulare Lake Basin of the San Joaquin Valley and the Salinas Valley in Monterey County.
“While we know that farmers have already begun employing techniques to reduce the amount of nitrogen fertilizer that can ultimately end up in our groundwater, we also know that there are additional actions that can be taken,” said Doug Parker, director of UC’s California Institute for Water Resources and leader for the UC Agriculture and Natural Resources water strategic initiative.
“In our training for certified crop advisers, we will apply the latest UC research to refine their methods for helping farmers manage nitrogen more effectively.” Parker said.
Plants need nitrogen to grow, but nutrients that are not used by the crop may move below the root zone. Nitrate, a byproduct of nitrogen, may infiltrate to groundwater used for drinking water.
For other examples of UC ANR research and extension projects under way to ensure that all Californians have access to safe drinking water and that the state’s farmers can grow enough food to help meet the world’s increasing demand, please visit http://ucanr.edu/News/Healthy_crops,_safe_water.
