Posts Tagged: post harvest
Research aims to get people to eat right
A team of UC and University of Florida scientists have received a nearly $6 million grant from the USDA for a project designed to improve the flavor and texture of fruits and vegetables found in American grocery stores, according to reports of a variety of media outlets."The purpose of our project is to improve the flavor quality of fruits and vegetables that are available to consumers. With the ultimate goal of getting people to eat more," co-project leader Beth Mitcham told an ABC-affiliated reporter. Mitcham is a UC Davis Cooperative Extension post harvest pomologist.
The TV story was broadcast in Sacramento, Fresno and on the CNN website. Articles also appeared on the Sacramento Bee blog 'Appetizers' and in the Central Valley Business Times. The Sacramento Fox affiliate - KTXL Channel 40 - placed a story on its website and interviewed Mitcham in the studio during its morning program.
The story was originally written up by Diane Nelson of the UC Davis Plant Sciences Department for the UC Food Blog.
The Specialty Crops Research Initiative (SCRI) work began about a year ago. The researchers are studying the challenges growers, packers and shippers face in getting crops from the field to the market in a condition shoppers will buy. Slowing down the ripening process, changing handling procedures and determining how produce flavor is affected by harvest are are issues to be examined.
The ABC news story showed a researcher slicing samples of pears in a lab.
"What we want to do with these pears is we want to understand a bit more about their ripening biology," he said. "How they change from green to this lovely yellow, ripe, flavorful product."
Beth Mitcham at a farmers market.
Systemic Downy Mildew Occurring in Lettuce
Downy mildew of lettuce, caused by Bremia lactucae, is the very common foliar disease that results in the familiar yellow to brown leaf lesions and accompanying white sporulation on the lesions. However, the systemic phase of lettuce downy mildew may be less familiar to growers and pest control advisors. In the spring of 2009, systemic downy mildew was very common in coastal California. Currently in 2010, systemic downy mildew is not as serious but is still being observed in some coastal plantings.
Symptoms of systemic downy mildew may be seen on both lettuce leaves and the central, internal core of the lettuce plant. For leaf symptoms, examine the plant for large, elongated regions of the leaf that are discolored and turning dark green to brown. Such regions often develop along the midrib of the leaf and extend into the flat, outer leaf panels (photos 1, 2). White sporulation is often not present on these infected areas until late in disease development. Note that for many systemically infected lettuce plants, these leaf symptoms are absent and the only evident symptoms are in the internal core.
To check for systemic infections in the plant core, cut open and examine the central part of the plant; these tissues will show a dark brown to black streaking and discoloration (photos 3, 4). In some cases, systemically infected plants may be slightly stunted or late in maturing. Exercise caution, however, before concluding that internal core discoloration is due only to systemic downy mildew. Other important lettuce problems (Verticillium wilt, Fusarium wilt, ammonium toxicity) can cause similar internal discolorations.
Confirmation of systemic downy mildew requires laboratory testing. Affected tissues can treated with biological stains and then examined using a microscope. Such procedures can show the presence of the characteristically thick mycelium that lacks cell cross walls (photo 5). In addition, incubating pieces of affected lettuce tissue can result in sporulation of the pathogen (photo 6, showing systemic downy mildew of cauliflower), again enabling confirmation of systemic downy mildew.
Systemic downy mildew of lettuce has not been studied extensively, so researchers do not know exactly what triggers this less common phase of the disease. Some suggest that early infection of young plants may allow the pathogen to infect the inner foliage of lettuce, resulting in pathogen access to the plant growing point. Field personnel also report that some lettuce cultivars are more severely affected than others.
Photo 1: Brown discoloration due to systemic downy mildew infection in a lettuce leaf |
Photo 2: Brown discoloration due to systemic downy mildew infection in a lettuce leaf. |
Photo 3: Internal discoloration of lettuce core due to systemic downy mildew infection |
Photo 4: Internal discoloration of lettuce core due to systemic downy mildew infection. |
Photo 5: Blue-stained mycelium of downy mildew that has systemically infected lettuce tissues. |
Photo 6: Sporulating downy mildew from a systemically infected piece of cauliflower stem. |
Disorders and Defects in Head Lettuce
The rainy and cold spring weather in 2010 is apparently having an effect on head lettuce quality in Salinas Valley fields. Symptoms appear as very small, brown flecks and spots along the margins of young leaves (photo 1). Affected leaves are usually found deep within the head. It appears that these defects are occurring in multiple iceberg cultivars in various parts of the valley. Clearly this is a physiological disorder and superficially looks similar to russet spot; however, most of the flecks do not occur on the leaf midribs (photo 2) as would be typical for russet spot. Russet spot is caused by ethylene production and can occur in mature to over mature lettuce, especially following anaerobic conditions in the field. However, in this instance, the location of the flecking along the margin of the leaf more closely indicates tipburn.
The extensive nature of the problem (from Salinas to San Ardo) and the occurrence across varieties indicates that a large-scale factor like weather could be the cause. The heavy rain on April 5 followed by cloudy, cool weather may account for the currently wide distribution of the problem. We are conducting further investigations to more closely determine the cause of this problem.
These defects are not caused by any plant pathogen. Extensive testing has shown that bacterial leaf spot, anthracnose, or other lettuce disease is not associated with these brown flecks. Bacterial leaf spot (caused by Xanthomonas campestris pv. vitians), however, is common this year and should not be confused with this physiological disorder. Bacterial leaf spot occurs on the outer leaves and results in large, black, angular lesions (photo 3).
Photo 1: Lettuce defects in 2010 |
![photo 1 photo 1](http://ucanr.org/blogs/SalinasValleyAgriculture/blogfiles/3569.jpg)
Photo 2: Typical russet spotting of lettuce |
![Photo 2 Photo 2](http://ucanr.org/blogs/SalinasValleyAgriculture/blogfiles/3564.jpg)
Photo 3: Bacterial leaf spot of lettuce |
![Photo 3 Photo 3](http://ucanr.org/blogs/SalinasValleyAgriculture/blogfiles/3570.jpg)
Burning question answered by UC experts
When Newsday's Erica Marcus had a burning question about ripening fruit, she turned to UC Davis post harvest experts. Marcus writes a weekly column for the magazine's Web site that answers "burning questions" about food.
In the past, she's helped readers who want to avoid soggy stirfry, identify whole grains, and know exactly when to cover or uncover a pot cooking on the stove. This week, she answered for readers: "Which fruits ripen after they are picked - and why?"
"For the lowdown on ripening," she wrote, "I called the postharvest information center at the University of California, Davis, and the California Tree Fruit Agreement."
The next 300 words of her column give details about a complex process involving starch, sugar, and cell walls of pineapples, cherries, grapes, citrus fruits, berries, watermelon peaches, nectarines, plums and apricots, cantaloupe and honeydew.
Sensory lab a Fresno Bee sensation
The new sensory laboratory at the UC Kearney Research and Extension Center won high visibility over the weekend in a prominent story on the front page of the Fresno Bee business section. The new lab was dedicated in April and is the subject of the ucanr.org feature story for May.
Fresno Bee reporter Dennis Pollock wrote that sensory research mixes science with people's senses -- especially taste -- to come up with fruit that shoppers are more likely to enjoy.
"Such results will benefit not only the consumer but our agricultural industries," the article quoted Mary Lu Apaia, a UC Riverside sub tropical horticulturalist based at Kearney.
The story said the new lab takes the place of a "makeshift" facility with less than optimal conditions because of distracting sounds from cooling equipment and odors from fruit stored in a freezer.
"This is a people science. People [the tasters] are my instruments," it quoted staff research associate Sue Collin. "I don't want any distractions."
The Fresno Bee story included mention of all the commodity and grower groups who contributed cash to construct the new laboratory.
The new KREC sensory lab.