Growers warned over free fatty acid levels in OSR

Oilseed rape growers are being urged to pay attention to harvest timing and post-harvest grain handling to reduce the risk of high free fatty acid levels.

Crop maturity has been variable and a late harvest is increasing grower anxiety to get the crop in the shed, so could result in green seed making it into samples.

Immature green seed considerably increases the risk of higher free fatty acid (FFA) levels in oilseed rape, which can make the oil unfit for human consumption or cause foaming in biofuels.

Last year the HGCA conducted a survey of oilseed rape samples that uncovered a problem with FFA in oilseed rape, particularly in northern areas.

Growers were questioned on practices for desiccation, harvest and storage to uncover any consistencies where hotspots for high FFA occurred.

Senior research and knowledge transfer manager Simon Oxley believes the problem could be more widespread this year, with monitoring continuing on a national scale.

“Growers must be aware of the factors that increase the risk of FFA levels breaching the 2% permissible threshold,” he explains.

Samples that contain more than 2% FFA will be subject to penalties from processors and there are a number of measures growers can take to reduce the risks.

He urges growers not to harvest crops before reaching maturity and says ventilation prior to drying is vital to ensure that hotspots or sprouting doesn’t occur in store, which can also raise levels above the 2% threshold.

High drying temperatures can also contribute, so where possible growers should avoid drying wet rapeseed too quickly with too much heat.

“We know the causes and effects, so it’s about finding a compromise when drying and maintaining adequate ventilation before and after the process,” says Dr Oxley.

“After last year, processors will be more vigorous with their testing, so growers should ensure they are doing all they can to minimise the risk.”

The HGCA’s continuing investigation will use commercial samples and samples from Recommended List trials to pick up any issues across the UK.

The study will aim to link agronomy and variety characteristics to the occurrence of high FFA levels and will issue detailed advice on how to avoid high levels to growers.

Oil samples are taken during Recommended List trials, but are usually disposed of after testing.

However, this year the HGCA will be holding back samples to pick up any issues with individual varieties and FFA levels after crushing.

“I would urge caution, though, as conditions can also influence FFA levels, but if it becomes a problem year on year we will have the information to draw some conclusions,” he says.

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