In general, produce is sorted according to established standards. Standards for many types of produce are established by the U.S. Department of Agriculture (USDA) and can be obtained at http://www.ams.usda.gov/standards. Standards can vary for produce from different areas. Oranges produced in Florida have somewhat different standards than oranges produced in California. Differences in grade standards are related to different growing conditions and climate which influences characteristics such as sugar and acid levels. The highest grades are generally represented by produce that is free of blemishes, cuts and bruises, and any decay.
Numerous environmental and mechanical factors can influence product grade. Growing conditions and weather can dramatically affect produce quality. The consequences of environmental and mechanical factors for apples were examined by Baugher et al. . Economic losses due to various defects resulting from both environmental and mechanical factors were measured for apples at nine packinghouses. Severe drought and high temperatures caused a significant increase in losses due to undersized fruit, cork spot, and spray injury. Some types of defects, particularly bacterial soft rot of fresh fruits and vegetables, have been associated with an increased incidence of pathogen contamination. Wells and Butterfield found higher salmonella contamination (59%) in wash water from fruit and vegetables that were affected by bacterial soft rot . Wash water used for healthy produce had a lower incidence of salmonella contamination (33%). Other defects, such as undersized fruit, would appear to be primarily cosmetic and therefore of less importance in relation to spoilage or food safety. However, research suggests that lower quality produce, regardless of defect type, is more prone to spoilage. In a study on the effect of tomato grade on subsequent spoilage, it was determined that lower grade tomatoes inoculated with Erwinia carotovora subsp. carotova had higher levels of spoilage and infection after 14 days in storage than higher grade tomatoes . Although the tomatoes were inoculated with E. carotovora, 82.4% of the infection was due to Alternaria alternate, and only 17.6% was due to the bacterium. The bacterium did, however, increase decay in lower grade tomatoes to a greater extent than higher grade. This study suggested surface blemishes of any type promoted postharvest decay.
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