ducted on overwraps that accumulate carbon dioxide 

 in the pack, but even this new technology is not very 

 effective without good temperature management 



A 10°F reduction in temperature reduces the respi- 

 ration rate by approximately 50%. Furthermore, at 

 77°F and 30% relative humidity, fruit will lose water 35 

 times faster than it would at 32°F and 90% relative 

 humidity. Prompt cooling, and maintenance of proper 

 temperatures and humidity, are essential. 



The cooling process should occur in two stages. 

 Simply setting harvested berries in a cold room is not 

 adequate because the field heat is not removed fast 

 enough. Rapid movement of cold, humid air through 

 the berries is essential during the first few hours after 

 harvest. Brokers contend that for every hour delay in 

 cooling, shelf life is reduced by one day. Growers can 

 take advantage of night cooling by harvesting fruit as 

 early in the morning as possible. 



Large growers may have a separate pre-cooling 

 facility specifically designed for removing the field heat, 

 but inexpensive, effective improvisations can be 

 adapted for any cold storage. If a grower only has a 

 walk-in cooler, recently picked flats of berries can be set 

 into a cardboard box which is opened at both ends. A 

 household fan is then placed at one end of the box to 

 draw air through the flats. Once the berries are cool, 

 flats are removed from the cardboard and wrapped in 

 plastic. The plastic will reduce water loss during 

 storage, and prevent condensation on the berries when 

 flats are removed from the cooler. The plastic should 

 not be removed until the temperature of the berries 

 warmsto nearthe temperature of thedisplay. Conden- 

 sation will then form only on the outside of the plastic, 

 while the berries inside will remain dry. 



The storage room itself can be maintained as low as 

 30°F. Berries will not freeze at or above this tempera- 

 ture, because the sugars in the fruit depress the freez- 

 ing point. One may want to maintain the storage at a 

 slightly warmer temperature (32°F) to allow some 

 room for error. Major shippers, however, report that 

 storage at 40°F reduces shelf life by 50% compared to 

 30°F. 



The selection of a cooling unit is very important 

 when designing a cooler. If the temperature difference 

 between the air and the cooling unit is large, then the 

 condensers will accumulate ice from moisture in the 

 air. This drying of the air would not cause a problem for 

 dry goods, but will severely dehydrate fruit. The at- 

 mosphere around the fruit should be humid to prevent 

 shrinkage, so a cooler should be selected which can 

 maintain a relative humidity of 90-95% at 32°F. These 

 types of coolers are more expensive and less common 

 than those for dry goods. Consult your agricultural 



engineering specialist for help with selecting a cooling 

 unit and building a storage facility. 



Transporting Berries to Market 



The loss of soft fruits such as raspberries and 

 strawberries from harvest to the consumers table is 

 estimated at more than 40%. A 14% loss occurs from 

 farmer to wholesaler, a 6% loss occurs from wholesaler 

 to retailer, and 22% is lost between the retailer and 

 consumer. Much of these losses are due to poor han- 

 dling of berries after harvest. 



There are many steps in the distribution chain 

 which can negatively affect fruit quality. A typical 

 handling scheme might be transporting berries from 

 the field to the pre-cooler, wrapping flats after pre- 

 cooling, loading them into a refrigerated truck, trans- 

 porting to a distribution center, unloading into the 

 warehouse, loading into a truck, transporting to retail 

 store, unloading, handling in the backroom, and set- 

 ting up the display. Mishandling at any point along this 

 route can result in unacceptable berries. 



You should work to minimize the number of han- 

 dling steps from field to display. Berries should remain 

 cold and wrapped during each phase of transportation. 

 Never allow the berries to sit on u n refrigerated loading 

 docks. When loading a truck, stack flats on a pallete 

 and away from the walls. Ensure that cold air is free to 

 circulate around the sides of the pallete and across its 

 top and bottom. When flats of fruit are allowed to touch 

 the floor or side walls, temperatures in the flats can rise 

 as much as 20°F. Do not stack flats directly over the 

 rear wheels, and use strapping or stretch film to stabi- 

 lize the load. Refrigerated trucks should be equipped 

 with air-suspension systems rather than spring sys- 

 tems to reduce transit vibrations. 



Most mechanical refrigeration equipment in cur- 

 rent use is designed to maintain temperature, but lacks 

 the air flow and refrigeration capacity for rapid cooling. 

 Temperature regulating equipment in trucks does not 

 have the accuracy to achieve temperatures below 40°F 

 without danger of freezing. Furthermore, high density 

 loads are used to minimize transportation costs, but 

 this practice inhibits cooling during transit. Thorough 

 product cooling before loading is very important. 



Allow berries to warm only when they are ready for 

 display to consumers, and before removing the plastic 

 wrap over the flats. Any condensation will then form 

 on the plastic wrap rather than on the berries inside. 



Often the transportation of berries is beyond the 

 control of the grower. To develop new and distant 

 markets, receivers must be educated in proper han- 

 dling procedures. Personal contact with the receiver 



Fruit Notes, Spring, 1990 



11 



