If you hold a sample of good-quality, high-protein wheat in one hand and some that has been damaged by excessive heat from a dryer in the other, can you tell the difference? Ed Lysenko, a baking research technician at the Canadian Grain Commission (CGC), says no, that isn’t always possible. Samples sent to the CGC lab for evaluation sometimes reveal protein has been damaged by excessive dryer heat but to the naked eye, the kernels look identical to premium grades.
“You’re cooking the wheat,” says Lysenko. “The trouble with overdrying is it can’t be seen in grading.”
That can lead to some serious problems for end-users, such as bakeries that require certain characteristics from each grade. “The reputation of the CGC for quality grading would be in jeopardy (if it becomes a widespread problem),” he says. That could affect the price all farmers get for wheat.
To help farmers avoid the pitfalls of drying, the CGC has established a web page on its main site, www.grainscanada.gc.ca, with tips on what to do, and what not to do, when drying wheat. Following those guidelines will get damp grain safely dried to proper levels.
Optimal air temperature
The CGC’s first recommendation is to ensure on-farm dryers are working properly. “For safe drying of your wheat, the dryer must keep the wheat moving and mix the wheat with the hot air. If wheat is not kept moving, kernels lying next to the heat source dry first. These may be damaged if the air temperature is above 60 C.”
Generally, the CGC recommends not exceeding that level, especially when using non-recirculating dryers. But for other dryer types, do an initial batch at that temperature and have it tested by sending a sample to the CGC’s lab in Winnipeg. If the results show there is no damage, try raising the temperature to 65 and submit another sample. Some dryers will work properly at temperatures as high as 70 C.
But be sure to measure air temperature before it enters the dryer. Sampling grain layers will likely not provide an accurate reading of how hot incoming air is. But that doesn’t mean you shouldn’t take internal temperatures, in fact it means just the opposite. You need to keep a close eye on them, too. In some cases, installing extra temperature sensors may help provide a better idea of what’s going on inside, according to the CGC.
Farmers should resist the urge to fire up the dryer at the start of the season and keep it going until the entire crop has been dried. Lysenko recommends always doing an initial batch and sending samples off to the CGC lab for analysis. “It’s about a three-day process, he says. So waiting for the results won’t hold things up too much. Basing the rest of the drying on those findings will ensure quality isn’t lost. “We encourage them to hold off (with more drying until the results come back).”
Lysenko says two 500-gram samples are required for any test. Take one of the damp grain before drying and another of the dried product. Send them both to the lab via regular mail or courier (see their web page for their mailing address and telephone number).
For very damp wheat anything with a moisture content over 20 per cent, don’t try and bring the level down by more than six per cent in one pass through the dryer. Reducing the drying temperature to 50 during the last quarter of the cycle will also help prevent damage.
But what works for wheat, won’t necessarily do for canola. Canola destined for seeding purposes should be dried at less than 45 C, according to information published by the Canola Council of Canada (CCC). However, when used for oil extraction, it can be dried at up to 82 C. So knowing where each batch is going will help when making drying decisions.
“If you overheat it, you can alter the oil content, cautions Doug Moisey, senior agronomy specialist at the CCC. “Heat from the dryer will denature the oil. And that will reduce the grade, meaning less money in your pocket.
When canola is very damp or when it is to be stored for over six months, Moisey recommends lowering dryer temperatures. “Temperatures should be no higher than 71 C for a mixing (recirculating) dryer and no higher than 60 C for a non-mixing (non-recirculating) dryer when moisture exceeds 12 per cent, he says. “You can dry it very nicely with lower temperatures.”
And be careful not to overdo it. Drying canola to below six per cent can cause the seed coat to crack and make it susceptible to damage during handling. Above seven per cent, those problems are less likely to occur.
The smaller seed size will also make forcing air through canola much more difficult than through larger-seeded cereal crops. The increased static pressure means temperatures in the plenums on some dryers can easily climb too high unless the fuel rate is reduced. Monitor dryers carefully.
For more on drying canola, visit www.canolacouncil.org.