As a result, fruit would be exposed to a temperature range of 36 to 50 degrees, the range he calls the “killing zone” because it halts ripening and damages the fruit. Crisosto studied previous research, worked closely with the industry and exposed fruit to a wide variety of temperatures in five temperature- and humidity-controlled fruit storage chambers. He found that, in general, if the 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 and, most importantly, the fruit would be more consistently pleasing when it reached consumers’ mouths.

“It initially blew our minds to walk out into our ripening room and smell fruit,” Thurlow said. “We’ve got a lot of money out there ripening.”

But soon packers and grocers realized that preconditioning produced a better product. Grocery companies now offer premiums of $1 to $4 per box of preconditioned fruit, compared to fruit that has been handled the old way.

“It’s made a huge difference in the quality of the fruit we provide to the consumer,” said Herb Kaprielian of Kaprielian Brothers Packing Co. in Reedley. “We are able to deliver fruit that is juicier and more consistent in quality.”

A group of fruit packers, including Kaprielian Brothers, have pooled resources and developed a brand for fruit that has been preconditioned called “Ripe ‘N Ready.” According to Steve Kenfield, the manager of Ripe ‘N Ready, some grocery chains will stock only preconditioned fruit.

“Retailers take the heat for fruit not eating well,” Kenfield said. “Retailers are looking to stop those complaints.”

More than 200 varieties of peaches, 200 varieties of plums and 175 varieties of nectarines are sold commercially from California – each with its own harvest time, flavor and color. Crisosto has found that each one also has its own specific needs in terms of postharvest storage temperature and timing.

Identifying each variety’s needs will keep the industry and its research partners at the University busy perfecting fruit handling protocols in order raise consumers’ confidence in the peaches, plums and nectarines they buy at stores.

“You can’t shame people to eat more healthy food,” Kenfield said. “They have to enjoy it. We are working to fix the eating quality of fruit.”

Tips for handling the fruit once you have it at home

After purchasing fresh peaches, plums or nectarines at the grocery store, do not eat them and do not put them in the refrigerator until they are ripe.

The fruit looks nice in a basket or bowl on the countertop or table, or it can be placed inside a paper bag. It is ripe when it smells sweet and fruity and yields slightly to the touch. The fruit can then either be eaten or placed in the refrigerator to be eaten in the next few days.

Putting fruit in the refrigerator before it is ripe exposes it to the “killing zone,” temperatures between 36 and 50 degrees, which stops the ripening process and ruins the fruit.

For more information, contact Carlos Crisosto at (559) 646-6596 or