What is in this article?:
- Key to delicious tree fruit
- Killing zone
- The key to great-tasting fruit with a pleasing texture, according to a UC scientist based at the Kearney Research and Extension Center near Parlier, is in the way it is handled after harvest.
- If fruit is held at 68 degrees for about two days following harvest, until it reaches a specific level of ripening measured by fruit firmness, and then cooled down, shelf life can be extended seven to 15 days.
The fond memories of delicious peaches just plucked from a backyard tree or purchased at a roadside stand can now be relived with fruit picked up at the neighborhood grocery store. The key to great-tasting fruit with a pleasing texture, according to a UC scientist based at the Kearney Research and Extension Center near Parlier, is in the way it is handled after harvest.
As long as anyone can remember, peach, plum and nectarine producers have tried to cool their fruit down as quickly as possible after picking, and keep it cool until it was placed in a grocery store display. But UC postharvest physiologist Carlos Crisosto discovered that the practice was subjecting fruit to what he calls the “killing temperature zone.”
Years of work in the state-of-the-art Gordon F. Mitchell Postharvest Laboratory, established in 1992 at Kearney, has resulted in a completely new protocol for peaches, plums and nectarines as they journey from the farm, to packing sheds, in the backs of trucks to distribution centers and finally to the supermarket produce aisle.
“This has rocked our world,” said Mike Thurlow, the sales manager for Mountain View Fruit in Reedley, whose company used to pick, pack and ship as quickly as possible. “For us to pick our fruit and delay the cooling, fiddle around with humidity, pressure and brix, then ship it two, three or four days later, ready to eat – that is totally opposite to what we had been doing.” (Brix is a measurement used by the food industry to estimate the amount of sugar in fruit.)
Even though it was hard to accept at first, the packing houses have learned that the new protocol – for which Crisosto has coined the term “preconditioned” – results in better tasting fruit, and subsequently, better sales of this Central California summertime staple.
“Preconditioned fruit is like the fruit you remember eating as a kid when you went into your backyard and picked a peach off a tree,” Thurlow said. “We are now able to commercially ship fruit that in years past you could’ve only bought at a farmers’ market.”
Fresh peaches, plums and nectarines represent an important part of the California agricultural industry, with crop production valued at $250 million in 2004. The state supplies fresh fruit to every state in the nation and several countries overseas. California produces more than 90 percent of the nectarines and plums in the United States and provides about 60 percent of the peaches. The earliest California tree fruit are harvested in mid- to late-May, but the bulk comes off trees in June, July and August. A few California fruit are still being picked as late as October.
Peach, plum and nectarine consumption has remained static in the United States the past 20 years, despite repeated recommendations from the federal government and the medical industry to eat more fruit for better health. Surveys by researchers and the tree fruit industry have pinned the lack of sales growth to negative experiences with fresh fruit, such as lack of flavor, off flavor, flesh mealiness, dry fruit and flesh browning.
“After biting into a mealy or off-flavor peach, consumers won’t likely buy any more,” Crisosto said. “We can improve the eating experience by carefully managing the peach’s journey from the farm to the consumer’s palate. That expands and strengthens the market for fresh fruit.”
In the past, UC researchers recommended fruit be cooled immediately after harvest and kept at 32 degrees during transportation and handling.
“The problem with that,” Crisosto said, “is that most of the facilities for transportation, distribution and retail sales cannot hold fruit that low. It just doesn’t work in the real world.”