Issue link: http://read.uberflip.com/i/12477
diggin’ in BRUISE MANAGEMENT A S GROWERS PREPARE FOR HARVEST, ONE CONCERN THAT IS ON THE MIND OF UNIVERSITY SCIENTISTS—AND SHOULD BE FOR GROWERS—IS THAT OF BRUISING, PARTICULARLY BLACKSPOT BRUISING. WE’VE ASKED THREE DIFFERENT UNIVERSITY OF IDAHO SCIENTISTS FOR THEIR INPUT ON BLACKSPOT BRUISING: DR. NORA OLSEN, ASSOCIATE PROFESSOR AND EXTENSION POTATO SPECIALIST, MIKE THORNTON, SUPERINTENDANT, SW ID R&E CENTERS AND DR. BILL BOHL, BINGHAM COUNTY EXTENSION EDUCATOR. THE FOLLOWING ARE THEIR PERSPECTIVES. Harvest Goal: Maximizing bruise-free potatoes by Nora Olsen, UI extension educator | by Mike Thornton, superintendent, SW ID R&E Centers HARVESTING A QUALITY CROP IS AN important topic on everybody’s mind for the upcoming season. One major quality requirement in all marketing channels is to minimize the incidence of blackspot bruise. There are two components involved in blackspot bruise formation: a physical impact, followed by a chemical reaction that causes the discoloration. A blackspot bruise will not occur without a physical impact. Physical impacts and mechanical injury are inevitable during the harvest and handling process, but a lot of things can be done to minimize the severity of these impacts. A survey by Kleinschmidt and Thornton in 1991 showed that about 70 percent of all mechanical injury occurred as tubers moved through the harvester. The remaining injuries occurred during loading of the truck (14 percent), transfer onto the bin piler (14 percent) and with rollback on the pile (2 percent). This information emphasizes the need to reduce drop heights and add cushioning on all equipment that handles potatoes. Calibrating harvester chain and conveyor speeds so that they are always loaded with tubers is also extremely important. UI has worksheets available to help with calibration and timing of your harvesters. (See the article by Bill Bohl on the next page.) The potential for blackspot bruise formation for fresh potatoes does not stop at storage—it continues into packing. Research in the Netherlands showed 79 percent of all impacts occurred during packaging and only 11 percent at harvest and 10 percent during transport. In addition, tubers stored for several months www.potatogrower.com 23 may be more dehydrated than freshly harvested potatoes. Therefore potatoes may be more likely to bruise when removed from storage. What is interesting about blackspot bruise formation is that the skin is not physically broken. Instead, the cell membranes within the impacted tissue of the tuber are damaged or broken. The damaged membranes cause chemicals to come in contact with each other that STEM BUD are normally compartmentalized away from one another. Polyphenol oxidase (an enzyme) comes in contact with phenols,