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UC Food Safety

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Winegrapes ripen, unless berry shrivel strikes

August visitors to California wine country can see winegrapes ripening – green changing to gold, red and purple. This is the critical final stage of development, and its success drives one of the state's economic engines, with wine sales generating $18 billion in revenue in 2009. Wine country is also a tourist magnet and a job generator; the industry has a $61.5 billion economic impact statewide each year.

If this is a typical year, California will produce 90 percent of the nation’s wine. In normal vines, the ripening period means sugars and pH increase, while acids (primarily malic) decrease. Other compounds such as tannins develop, and all these factors contribute to the flavors and aromas in the wine that eventually results. (See healthy Cabernet Sauvignon, at right.)

However, in recent years growers have become increasingly concerned about a malady that appears during this phase. Known as “berry shrivel,” this disorder leads to shriveling of berries on a cluster.

There are several kinds of berry shrivel. Of greatest concern to growers and winemakers are sugar accumulation disorder (SAD), in which grapes turn flabby and lack sugar, and bunchstem necrosis, (BSN) in which grapes turn raisin-like on the vine, losing juice and often developing undesirably high sugar content. (See California Agriculture) Either of these  disorders makes the fruit less desirable for winemaking, with yield and production losses.

Berry shrivel afflicts both red and white varieties. Cabernet Sauvignon and Merlot are the major red varieties to be affected so far. Among the white varieties, Sauvignon Blanc, Chardonnay, Semillon and Riesling have shown symptoms.

The malady usually becomes apparent when winemakers or sugar samplers are in the vineyard tasting fruit. Once detected, vintners will often make a pass through the vineyard just ahead of the harvest crew to drop this fruit due to its low sugar content and off-flavored juice.

"Berry shrivel usually affects a small proportion of a vineyard's fruit – perhaps 5 percent -- but in particular vineyards and years, shriveling can affect more than half of the crop," says Mark Krasnow, who was a postdoctoral student at UC Davis and is now at the Eastern Institute of Technology in Hawke’s Bay, New Zealand. "In some years and some sites, wineries will decide not to harvest a vineyard due to the amount of shrivel. Fortunately this is rare."

The origins of SAD and BSN are a mystery, in spite of research investigations. Krasnow and his colleagues at UC ran a battery of high-tech tests to determine the factors involved, but found little consistency in results and to date, all tests for pathogenic organisms have been negative.

Whether due to SAD or BSN — berry shrivel occurs in vineyards all over the world, managed under different climates, making it a globally significant problem in winemaking.

"The irregularity of when and where (or if) SAD and BSN occur makes them very difficult to study," Krasner notes. Tests conducted by UC Davis Foundation Plant Services were negative for phytoplasmas, closteroviruses (leafroll), fanleaf viruses, nepoviruses and fleck complex viruses.

“It is possible that SAD has multiple causes, and that one of those causes might be a pathogen,”  Krasnow says. “In some cases, all the fruit on a vine is affected, even clusters that appear outwardly normal. In other cases, it is only the symptomatic fruit that develops abnormally.”

Preliminary studies suggest that SAD can be propagated by chip budding, but vine-to-vine spread has not been seen, according to Krasnow.  Future studies will focus on tests for a causal organism and a more careful examination of the metabolism of fruit affected by this disorder.

Bunchstem necrosis also varies in symptoms and whether effects occur on clusters or whole vines, and can occur at bloom or at ripening (veraison). Future studies will examine varietal differences in susceptibility having to do with xylem structure, the importance of concentrations of mineral nutrients, and other cultural factors.

Posted on Friday, August 13, 2010 at 8:28 AM
  • Author: Janet L. White

Looking for a farm or ranch experience?

This weekend, you're in luck. You can bring your favorite children to Kids Day on the Farm in San Luis Obispo County to churn butter, plant sunflowers, press cider, make a cornhusk doll and lots more. You can learn draft horse driving, go on a calf feeding tour, and enjoy bluegrass music at the Heartland Festival in Merced County, take a bus tour from Berkeley to pick peaches at Frog Hollow Farm in Brentwood, shop for apple butter at the Gravenstein Apple Fair in Sebastopol, or hike to the top of the hill to see great views of San Francisco Bay on a Petaluma organic farm.

All of these events, and lots more, are listed on www.calagtour.org, the searchable online directory of California's agricultural tourism operations, hosted by the UC Small Farm Program for use by visitors looking for a farm or ranch to visit. Visitors will find farm stands with fresh-picked produce, pick-your-own berry patches, corn mazes, pumpkin patches, guest ranches, farms offering tours, classes, workshops, camps, farm stays, festivals, wedding venues, and much more. You can search the directory by county or by activity,
or you can use the calendar to find special events. The website is getting more popular every week since we worked with the ANR communications team to add the calendar and the UC Food Blog to keep it looking fresh for visitors searching for adventure and education.

If you are a working farmer or rancher operating an agritourism business or organizing agritourism events, we invite you to complete the directory application or the event listing application online so we can include your business and events in the directory. The listings and event postings are always free. You can also include a picture with your event posting.

With more than eighty-five percent of Californians living in cities of at least one million people, most of us don't know the people who grow and raise our food, and most of us don't get many chances to visit farms or ranches. A growing number of farmers and ranchers are opening their land to visitors by starting enterprises that offer urban and suburban people a chance to experience agricultural life.

These agritourism operations serve the triple purposes of bringing additional revenue to the growers, building connections between urban and rural communities, and giving the producers the chance to sell farm products directly to the public right at the farm. An apple pie bought straight from the apple ranch pie shop will just taste better than one bought in town!

Agritourism is a growing business in California. Farmers and ranchers who would like more information about starting agritourism enterprises may be interested in the agritourism section of the Small Farm Program website, and may want to subscribe to the AgTour Connections newsletter.

Have a great weekend out of town!



Posted on Wednesday, August 11, 2010 at 7:09 AM

Summon us to service

For more than a hundred years, gardening has been linked to service in American communities.  Reformers used school and community gardens to improve aspects of urban life, to educate children, to feed the hungry, to provide training to those facing economic challenges. Today, the University of California models service through gardening via its Master Gardener Program, which fields thousands of highly trained gardens who provide support for school, home and community gardens across the state.

Our nation has many needs right now. Families are economically insecure.  (This is an understatement). Communities are food-insecure. Obesity is epidemic; the figures on childhood obesity are particularly disturbing. We have a tenuous connection with the land and a poor understanding of our food system. Environmental concerns - and declining oil supplies - dictate a need to recreate more sustainable and local food systems. Despite the bad news, Americans have proven that they are hungry for change, eager to re-engage with their neighbors, their communities and their nation.

A revival of the successful national gardening programs (Victory Gardens) of the past is clearly occurring. Gardening and the local food movement are hot topics. And consider the USDA’s Peoples Garden Initiative (PGI), which was launched in 2009, on the biennial of Abraham Lincoln's birthday. (This was fitting: President Lincoln created the USDA and felt strongly that Americans needed to know how to cultivate land - even small parcels - to keep freedom secure).  

The PGI is making good progress across the nation: there are now Peoples Gardens in every state. If encouraged and supported by us, the PGI could help in myriad ways. The infrastructure for the program is already in place. The educational materials that support school, home and community gardens are available through existing government agencies and private organizations. And, as I suggested to Agricultural Secretary Tom Vilsack via the Huffington Post, thousands of highly-trained volunteer Master Gardeners (who serve under the USDA’s umbrella, through land grant institutions) can be called upon to share their expertise with school, home and community gardeners.

I’ve said it before, and I’ll say it again: all President Obama needs to do is ask. Help us once again engage Americans in service to nation through gardening. Summon us to service. Come out to your garden, admit to us that that we’re experiencing rough times, but tell us that we can make a difference by acting locally - through the simple act of gardening. Encourage those who can to plant a garden to do it. Summon us to service: Ask us to plant for our families and our communities, to grow a row for the hungry, to share any extra produce with food banks.

Mr. President, we’re hungry for change (and a shameful number of Americans are just plain hungry).  Sometimes to move forward, we must look back for inspiration. Certainly, the Victory Gardens of the past provide a wonderful example of what ordinary citizens can accomplish on the home front to respond to challenges in the larger world. The revival of a national Victory Garden campaign can provide the kind of change we can dig into, some good news we can all use right now.

I can’t miraculously create millions of jobs, or clean up the oil currently in the Gulf, but I can facilitate the small miracle of growing and providing fresh produce to my family, and perhaps sharing it with those who are experiencing hunger in my community. Please, Mr. President: Summon us to service.

Posted on Monday, August 9, 2010 at 9:58 AM

Where has all the flavor gone?

Do you remember when store-bought produce was succulent every time you took a bite? Then you’re old – well, at least you’re not a kid. Today’s youth in America have a different experience with store-bought fruits and vegetables – sometimes they’re yummy and juicy, sometimes they taste like chalk.

What’s a mother to do?



"It’s a problem, because often you have only one window of opportunity to introduce a new fruit or vegetable to your child,” says Beth Mitcham, UC Cooperative Extension (CE) specialist with the UC Davis Department of Plant Sciences, director of the UC Davis Postharvest Technology Center and concerned mother. “And if the food doesn’t taste good, they aren’t going to like it.”

And if they don’t like it, they’re not going to eat it. That’s how it is for all of us, but new research by Mitcham and a broad group of experts may remedy the situation. Mitcham and her team recently received a nearly $6 million grant from the USDA for a project designed to improve the flavor quality of fruits and vegetables available to U.S. consumers and thereby increase their consumption.

A collaboration between UC Davis and the University of Florida, the project is co-directed by Mitcham and Jeff Brecht from the UF along with nearly 30 faculty members between the two institutions including CE Specialists Marita Cantwell, Trevor Suslow and Carlos Crisosto and Assistant Professor Florence Negre-Zakharov from the UC Davis Department of Plant Sciences. Other UC Davis faculty represent Agriculture and Resource Economics, Biological and Agricultural Engineering, Food Science and Technology, Viticulture and Enology and Public Health Sciences. More than twenty-five stakeholders from the produce industry are also on board.

As a postharvest technology specialist, Mitcham knows full well the challenges growers, packers and shippers face in getting crops from the field to the market in a condition shoppers will buy.

“Experience shows produce buyers rarely reject produce because it’s under-ripe,” Mitcham says. “But they will reject it if there is any bruising or decay.”

Most of us understand the problem – in broad strokes, at least. Take a tomato, for example. If we have the time, space and climate to grow them ourselves, the shelf life of our homegrown tomatoes would be the time it takes to pick one from the vine, walk into the house and slice it open. (Or the time it takes to bite into it right there in the yard. Yum.) If we’re harvesting tomatoes to deliver to a friend some distance away, we might want to pick them when they’re a little less ripe so they won’t get squished along the way.

Imagine, then, the challenge growers, shippers and retailers face delivering tomatoes to customers all across the globe year-round. Since shoppers eschew bruised produce, growers have to harvest them before they’re fully ripe, before their flavor has reached its full potential.

The team is looking at how they can alter that equation so our produce is more flavorful and still safe and economically viable for the industry. Their research will examine each step in the post-harvest chain asking questions like these:

  • Can we slow the ripening process, so it can be picked later and still be fresh when it reaches the market? Is there new technology – in sorting, packing, shipping or anything else - that can help? How is flavor enhanced and inhibited during shipping and storing?

  • If produce was riper during postharvest handling, would that affect our food safety risk? Would more pathogens survive?

  • If produce was consistently flavorful, would consumers buy more?

“I think we can do a better job developing varieties with more flavor and improving postharvest performance so consumers can count on flavorful fruits an vegetables,” Mitcham says. “And I think this project will help.”

More information on this flavor project can be found in The Spring 2010 Leaflet.

Posted on Friday, August 6, 2010 at 8:27 AM

Depressed people eat more chocolate

Depressing news for those who love chocolate. A recent study published by UC Davis and UC San Diego medical scientists in the Archives of Internal Medicine found that consumption of the delicacy appears to be associated with depression.

The scientists examined the relationship between chocolate and mood among 931 women and men who were not using antidepressants. Their surprising conclusion: Participants who screened positive for possible depression ate an average of 8.4 servings of chocolate per month; those who weren't depressed ate on average 5.4 servings per month.

People who reflected major depression ate an average of 11.8 servings per month. What does that say about people like me who eat 30 or more servings of chocolate every month? It is depressing to contemplate.

The study's authors offered some possible explanations for the seeming correlation of chocolate consumption with depression:
  • Depression could stimulate chocolate cravings as 'self-treatment'
  • Depression may stimulate chocolate cravings for other reasons
  • Chocolate could contribute to depressed mood
  • Inflammation could drive both depression and chocolate cravings
"Future studies are required to elucidate the foundation of the association and to determine whether chocolate has a role in depression, as cause or cure," the authors conclude.

If you are looking for some good news associated with chocolate consumption, go to the UC ANR website Feeling Fine Online and view the 15-minute video of UC Davis nutrition professor Carl Keen explaining the health benefits chocolate.

According to Keen, a diet high in flavanols, such as those in chocolate, can reduce inflammatory conditions associated with cardio vascular disease, vasoconstriction and the risk of forming a blood clot.

A new study indicates that flavanols may increase a population of certain cells in the blood that scientists think help repair the inner walls of blood vessels, improving blood flow and potentially lowering blood pressure. This suggests that, in the future, isolated flavanols or flavanol-rich foods might be useful in preventing or possibly even treating coronary artery disease. For more information, read the UC Davis College of Agricultural and Environmental Sciences story Flavanol-rich foods may help heart disease patients, study suggests.

(Ann King Filmer contributed to this story.)

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iStockphoto

Posted on Wednesday, August 4, 2010 at 6:39 AM

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