A problem that had plagued California's tree fruit industry during harvests a decade ago has resurfaced — this time in the packinghouses of the nation's leading peach and nectarine region in the Central San Joaquin Valley.

Fortunately, this time around solutions to the challenge appear to have been found by Carlos Crisosto and colleagues at the Kearney Agricultural Center in Parlier, Calif.

Just as the term indicates, inking is the presence of brown or black spots on the fruit skin. It's as if a leaking pen might have been passed over the fruit. A problem in production areas worldwide, it results in blemished, unmarketable fruit.

“Inking has been around for awhile,” said Crisosto, postharvest physiologist with the University of California Department of Plant Sciences based at Kearney. “Packinghouse inking is a little different.

“We have been getting calls on this problem from packers who say they are losing as much as 70 percent of their fruit to this problem in peaches and nectarines. They can lose their reputation and sales if it reaches the retailer.”

It was that degree of concern that brought dozens of growers and packers to Crisosto's postharvest facilities at Kearney for a talk on inking that followed a variety display at which visitors tasted offerings of new fruit from nurseries.

Crisosto talked of work he and other researchers have done on inking and white flesh skin burning disorder that appear to be triggered by the combination of physical damage during harvesting and hauling and what he termed “postharvest stresses.”

Researchers looked at a dozen approaches to packing fruit and their findings indicate that stresses that can lead to the cosmetic damage include exposure to high air velocity during forced air cooling, dehydration and high water pH during washing.

And it appears that certain varieties are more susceptible to the marking.

Crisosto conceded that using room cooling rather than forced air is not necessarily a simple solution. “Room cooling takes longer, and packers want to sell the fruit right away,” he said. “It takes longer to cool the fruit, and retailers want it delivered cool.”

He said as much as 70 percent of peach packing lines have a water pH level of around 8. His recommendation is for levels between 6.5 and 7.5.

At the Kearney field day, he showed pictures of damage to fruit packed at high pH levels.

A decade ago, results of a study on inking by Crisosto and colleagues that included Kevin Day, UC farm advisor in Tulare County, were published in California Agriculture magazine. The study found that physical injury combined with contamination can cause the skin discoloration. Among the serious contaminants were heavy-metal materials that included iron, copper and aluminum.

Among recommendations released at that time were to handle fruit gently, avoid hauling distances and keeping harvest containers free of dirt. It was also recommended that water quality be checked for heavy-metal contamination and that foliar nutrient sprays containing heavy metals should not be used 22 days before harvest unless there was a deficiency.

“This is a serious problem, the variables keep changing all the time,” said Gary Van Sickle, director of research and regulatory compliance for the California Tree Fruit Agreement in Reedley. “One time, it's out in the field and you do things there. Then it's in the packinghouse. One house is doing things the same way as the other and not having the problem. It's a difficult problem.”

The Reedley-based industry group this year spent $89,000 to fund the research by Crisosto and others. It's the first of three years of funding on research into the problem, and Van Sickles calls it “one of the most extensive projects we've ever embarked on.”

Inking is among the harshest examples of ways in which purely cosmetic problems can cripple an industry. And Van Sickle said there is no doubt that shoppers — and not merely buyers for retail groups — are very selective in their purchases.

“Go to where the peaches are, on the shelf,” he said. “Watch the people pick them out and see how critical they are. They're the best graders in the world.”

The Kearney event, which featured tasting of new varieties, gave a good look at the tough sell the industry can sometimes face because of a fruit's appearance.

“We love these as farmers,” said Eugene Enns, a principal in Enns Packing in Dinuba. He was referring to two delicious pluots on display from Dave Wilson Nursery. “But who's going to buy these? They look funny.”

Gary Kozuki, a Parlier grower, said people can often be won over by taste. “Sometimes weird is good,” he said.

It's not uncommon for growers to bemoan the fact that oddly shaped fruit or fruit that is curiously colored may not be readily accepted by the consumer. The taste could win them over, but that's not an easy sell either.

“Tastings at the retail level are expensive to do,” Van Sickle said.

The tastings during the variety display at Kearney are one way to reach growers large and small, said Dale McHaley, with Bright's Nursery in Dinuba.

“They get a chance to peek at their neighbors and see what they're doing,” McHaley said.

And such events are particularly important in a year like this, which has been marked by the closure of several high profile packinghouses.

“Our sales are off 70 percent,” said McHaley. “Growers don't have money to plant, they're trying to heal.”

Though it's not uncommon for growers to push out varieties that have lost favor with shoppers, the industry also seeks to look at ways to keep trees in the ground. Van Sickle explained that is among the reasons for the research into inking: Is there a way to handle fruit differently from vulnerable varieties and still keep it marketable, thereby avoiding the cost of ripping out and replanting an orchard?

Not all the fruit that was available for tasting left participants with a smile. Some was purposely flawed.

Gayle Crisosto, associate specialist in plant science with UC Davis, stood at a table where visitors could sample fruit that had some degree of chilling injury.

“We wanted to show people physically what the symptoms of chilling injury are,” said Crisosto, who is the wife of Carlos Crisosto. “They get to see and taste mealy fruit, fruit that lacks flavor or is off flavor or has internal browning.”

Crisosto said those qualities are often the subjects of consumer complaints “fruit that looks great in the store, but …” When the fruit ripens, she said, the symptoms “are expressed.”

“That's a poor experience, and the person will think twice about going back and buying a peach again,” she said.

The industry has made considerable strides toward remedying the chilling problems with “pre-conditioning” protocols that seek to avoid internal breakdown of the fruit.

Just as with inking, some varieties may be more vulnerable to chilling injury, Crisosto said. She said the injury is most likely to happen during shipping, but it could also occur at a distribution center. “It's not as likely in the packinghouse,” she said.

Unlike cosmetic damage, chilling injury is a death sentence.

“It's serious, it affects the whole fruit,” Crisosto said.

Also discussed at the Kearney event was research on the use of SmartFresh, a chemical being applied to some fruits to increase shelf life. It will be registered for use on tree fruit in October, said Carlos Crisosto.

He will present findings on how effective SmartFresh is Feb. 25-26, at Kearney during the 16th annual Fruit Ripening and Ethylene Management Workshop.