IssuesFall 2015Improving Potato Storage

Improving Potato Storage

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All growers know that significant loss can occur when potatoes suffer from storage shrink due to pathogens or water loss. The best way to avoid shrinkage is by storing the healthiest crop possible, but there are often times when farmers have no choice but to move potatoes into the bin under less-than-ideal circumstances.

When this happens, the cost of managing storages rises. Just as importantly, if a storage facility has inherent efficiencies that adversely affect the crop, this will dampen the grower’s bottom line. Spud Smart talked to storage experts across the country to get their views on best practices for improving potato storages to achieve greater cost efficiency.

The Right Environment

Stored tubers are living organisms. They produce heat through respiration and lose moisture, which causes shrinking through respiration and evaporation. The ideal storage environment will vary throughout a crop’s time in storage, and will depend on what storage phase it is in, whether that is curing, cooling, long-term storage or marketing.

In order to meet the crop’s requirements during each phase, the storage unit needs to maintain desired temperature and humidity. It should also be able to provide oxygen for tuber respiration and remove carbon dioxide to preserve tuber quality. Finally, it should be capable of dealing with adverse conditions, such as rot, excessive moisture and fluctuating temperatures.

“It’s just a matter of making sure that it’s all perfectly designed for what you want to do,” says Marlon Kuhl of Southern Potato in Winkler, Man. “You have to consider what you want to store, what your field sizes are, how long you want to store the crop, and how quickly you can fill it and empty it.”

When choosing a new storage design, he says, there are a number of factors to consider: ventilation, humidification, insulation and the style of structure, as well as additional options such as refrigeration or heating. If a potato storage is designed improperly, this can result in significant economic consequences resulting from potato loss, says Kuhl, who suggests producers spend a little more upfront to reduce costs later on.

Kuhl lists building materials and food safety as other important considerations. For instance, you need to ensure potatoes can’t come into contact with treated lumber. When using metal in construction, Kuhl recommends choosing a high-quality product that won’t rust over time.

Proper insulation is also important. Poorly insulated storage units won’t adequately protect the crop from outside elements, says Kuhl. Plus, maintaining environmental control of poorly insulated units can be a costly endeavour.

Ventilation systems are used to control rot losses due to high pathogen load in storage. According to Ray Keenan, chair of United Potato Growers of Canada, today’s ventilation systems have a much higher air capacity than older systems. For this reason, he says, it is especially important to make sure there are no air leaks where pressure and humidity can be lost. Keenan recommends using duct tape to seal culverts connecting to the plenum.

“You don’t want to use the potato as a seal,” he says. “It can start bacteria and rot growing in your potato pile. The only discharge for air and moisture should be through the vents itself, not through the air flowing around the pipes.”

Ashley Gorman, vice-president of sales at P.E.I.-based Gorman Controls, agrees. “The most efficient fans will not help if there is air leaking out of the building,” he says.

Gorman says that demand ventilation is an important aspect of efficiency. This means finding the right amount of ventilation and not over-ventilating the pile. “The most efficient fans in the world stop being efficient if they are running when they don’t have to or if they’re delivering too much air when it is not required,” he says. “This is a very poor idea, and poor policy for any grower to operate on.”

Keenan suggests that growers could monitor the timing of fans so that they’re running during times when there’s a lower demand on electricity. This can lower output costs.

Another beneficial practice is monitoring the crop throughout storage. Todd Forbush, an engineer at Techmark Inc. in Lansing, Mich., says once quality is determined, it’s up to the storage manager to utilize the ventilation control system to efficiently manage equipment and maximize profits in storage.

When pathogen loads are low, fan time and ventilation airflow rate can be reduced to save electricity. “However, fan operation decisions need to be made based on quality measurement and ventilation performance, not opinions, history or feelings,” Forbush is careful to note. “A loss in potato quality that results in a missed processing bonus or a rejected load of packed potatoes will not be recovered through savings in the power bill.

“Once the storage is stable and the quality is in good shape, continuous quality monitoring will help the storage manager set the proper course for successful storage results,” he says.

Humidity Management

Alan Christison, the Manitoba sales representative for Gowan Canada who’s based in Carberry, Man., says good humidity management is key. “Growers are selling a lot of water to the pack houses and the processors, so you want to keep the humidity up and reduce shrinkage as much as you can so you can sell as much product as possible. It’s also going to reduce pressure bruising, which is a big problem for the french fry processors late in the year,” he says.

Keenan notes training staff on how to properly handle potatoes as they’re going into the bin is an important practice that will also reduce bruising. “Mechanical bruises can act as an entry point for bacteria and rot in the pile. The storages themselves are only one more tool; there are so many things you can manage before you get to storage that have a great impact on the result you’re going to get in storage,” he says.

“We spend a lot of time schooling our help and our people who operate the machines on bruise control,” Keenan adds. “There’s no substitute for bruise control.”

Christison says temperature management when producers are first filling the bin is very important. “If the tubers are going in warm, you want to get temperature down to 55 F [13 C] and get the pile evened out as quickly as possible,” he says.

“Assess what you have going in the bin as you’re filling it. If you see trouble going into the shed, you might need to adjust humidity and temperature management,” Christison adds.

“It’s about being flexible. Every farmer starts with a plan at the beginning of harvest, but you need to be flexible because weather, field conditions and tuber quality may change. Growers need to make sure they’re putting healthy potatoes with similar maturity in the same bin, or putting trouble potatoes at the front of a pile where they’re accessible.”

Many agree that the crop that goes into storage is the single most important factor that affects overall storage costs. Money is lost through loss of quality, which can result from storing potatoes of improper maturity, poor ventilation management or pathogen activity in the tubers themselves.

“The first step to reduce potato loss in storage is to quantify the risk of these losses in storage,” says Forbush. “What is the maturity of the crop at harvest? What is the pathogen level in the tubers when the storage is loaded? These answers will determine the proper cooling rate and storage temperature, fan operation (both time and volume of airflow), humidity and CO2 management when the storage is filled and taken through the most critical first month of storage.”

Sanitation Key

Forbush maintains sanitation is important consideration for mitigating storage losses to disease. “The cost of cleaning the storage also has to be considered,” he says. “Each potato storage manager has labour-saving practices that they have adopted for their potato storage facilities.”

He also encourages storage managers to log hours put in by duct installation cleaning crews to establish a clear cost for storage, bin-by-bin. “This will target specific changes that will assist managers as they investigate storage modification or future construction,” Forbush says.

According to Keenan, good sanitation practices are especially important for keeping disease like silver scurf at bay. “We spend a lot of money on dirt elimination equipment to make sure potatoes are going in clean,” he says.

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New Technologies

Several experts refer to new wireless technologies, such as smartphone applications and other remote management tools that provide growers with increased control of storage ventilation systems from afar and can save valuable time.

“It has developed into a valuable tool for storage management,” says Ashley Gorman, vice-president of sales at Gorman Controls. “For instance, if I’m wondering what my temperatures are in a certain building that may be 30 kilometres away, the ability to look at them on my phone versus driving there can be a huge time saver.”

Many growers will tell you, though, that there’s no replacement for the eyes-and-nose method. “Having accessible platforms and catwalks to be able to look out over the pile are very valuable,” says Gorman.

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