Issue link: http://read.dmtmag.com/i/64944
through the orchard to spot the offenders and spend some time training them. An inexperienced crew can cause compression injury by grabbing the cherries instead of picking them by the stems. Compression injuries cause bruising and soften- ing of the tissue that ultimately leads to rotting. Cherries with high soluble solids levels are less susceptible to com- pression injury because they also contain more water, and that increases the turgor of the cherries, making it harder to compress them. For Sweetheart cherries, a level of 20° Brix should ensure minimal susceptibility to compression injury, Toivonen said. Compression bruising tends to be worse when the fruit is warm and can be caused by jostling fruit when it is transported from the orchard. Cherries can also suffer compression damage at the warehouse if they are stacked above the water level when they're emptied into the flumes. "Feed the packing line at the same rate as the fruit is moving out," Toivonen advised. Cool Small changes in the orchard can make big differences in the ultimate quality of the cherries, Toivonen said. For example, growers should avoid leaving bins of cherries in the sun in the orchard, which can make the stems turn brown and shriveled. The cherries should be cooled with potable water, and a shade cloth (with the silver side down and the white side up) should be placed over the bin to prevent the temper- ature of the cherries from rising and to maintain high humidity. This also prevents shrinkage of the cherries through shrivel. The cherries should be carefully transported to the warehouse, avoiding injury, and packed as soon as possible. Toivonen has done experiments to find out the impact of various postharvest temperatures on fruit quality. Titratable acidity, which is important for good flavor, is best maintained when the temperature is about 0.5°C (33°F), he has found. Low temperatures lead to less bruis- ing and fewer symptoms of pebbling (because of less evaporation of water from the fruit). A low temperature can also help maintain the stem pull force, which might be important if the grower is worried about the stems falling off or becoming loose. Firmness is also better at lower temperatures. Fruit in warm temperatures will become softer and softer. Hydrocooling removes heat from the fruit, but Toivo- nen said producers cannot rely just on hydrocooling to bring the temperature down as low as it needs to be. Even with a well-designed system, it will be difficult to get the fruit cooler than 3° to 5°C (37° to 41°F). Once the fruit is palletized, no more heat will be removed from the boxes that are in the middle of the pal- let. In fact, the cherries continue to respire, generating heat, and the fruit warm up. Refrigerated shipping con- tainers, trucks, and trailers are designed to remove heat from around the pallets but not to remove heat from the fruit, so the interior boxes will continue to warm up during shipping. It's best to bring the temperature of the fruit down to 0°C ( 32°F) before they are palletized, either through post- pack cooling, or forced-air cooling in storage, Toivonen said. Cherries that are at 0°C when shipped should still be below 5°C (41°F) after 28 days, and he believes that's prob- ably the best that producers can do in terms of preserving quality. If the temperature of the fruit starts out at 5°C, it can rise to almost 15°C (59°F) after 28 days. "You have to get the heat down as far as possible before it goes on the truck or container," he stressed. • 14 MAY 15, 2012 GOOD FRUIT GROWER www.goodfruit.com