Potato bruising can have a large financial impact on many growers and processors. There are many factors that contribute to bruising including weather, temperature, equipment, poor storage handling issues and damage through processing.
While it can be difficult to measure the losses from bruising, some studies have shown that potato growers in North America could lose 20 percent directly contributed to the harvest, which equates to more than $300 million in the U.S. alone. In the United Kingdom, specialists estimate that bruising costs farmers in excess of $50 million a year. While the causes of bruising are well documented, the type of potato and its damage level are key to knowing if bruising will occur.
Bruise resistance is a key factor in knowing what to look for in the harvesting and processing of potatoes. There are a number of ways to determine at what level potatoes will damage. Two of the main methods are the traditional dye test and new, more advanced electronic devices designed to measure impact levels. These include data loggers and real-time display-based systems. The key is having a proactive damage plan and an understanding of how to interpret the data—what numbers send a warning, what level causes bruising, and what external factors could influence that number.
For the purposes of this article, let’s look at the numbers for a mechanical detection system. On a typical mechanical detection system, a grower could expect to see impact between 75G and 220G to cause damage. This ranges from scuffing all the way to severe bruising. The wide range of figures is not only attributed to the type of damage; it is also influenced by the flesh temperature at the time of harvesting, the cause of the impact (mechanical or other), and most importantly the type of potato being harvested. Through testing, it is very clear that the variety of potato is the first key to knowing the right number.
The second influence to look for is temperature. Through testing, 65 degrees was used as the base temperature. As this temperature gets lowered, so do the numbers that we see causing bruising and damage. According to research, the ideal temperature for harvesting potatoes is between 50 and 60 degrees. With advances in technology, it is now possible to account for fluctuations in temperature. Through testing at different temperatures, the bruise levels can be charted and inputted into the system to give a clear threshold number to the grower.
Proactive bruise prevention is also the key to good storage results. A number of bruise issues happen in transit to the storage sheds and on the transfer of potatoes from the truck to the shed. While proactive bruise control in the field will help with bruising, growers must also continue this monitoring all the way through to the shed. Chris Hiles, a representative for BASF, says that one of his customers “was having major bruising in storage, ran (the mechanical) device through the process, and discovered that it was caused by a machine the potatoes were going through just before storage. They stopped using that machine until it could be fixed. They have seen a large decrease in damage.”
Like growers, potato processors are also impacted by bruising. Product quality and processing efficiencies can be impacted by damage to potatoes. Even in the development of bruise-resistant varieties, knowing the level at which damage occurs is important. By having a proactive plan for bruise management, processors can target planned shutdowns for areas they know damage will occur; make data-driven decisions on equipment purchases, capital investments and line speeds; and even pinpoint areas of potential damage before they occur.
Bruising costs the potato industry in many ways, including increased disease level and reduced shelf life, losses in storage due to disease and shrinkage, raw product costs, labor costs, and the influence to turn off customers and wholesalers to fresh potatoes. In addition to these results, growers can also experience reduced payment on contracts and therefore lower profits. Proactive damage control can lead growers and processors to greater yields, better quality and higher profits.