Wheat from where?

NIR spectroscopy can offer a quick and easy way to determine where wheat was grown, say Chinese scientists.

This is because the precise chemical composition of wheat, meaning the combination of lipids, proteins and minerals, depends on the environmental conditions the wheat plant was exposed to in the field, including rainfall, amount of sunshine and temperature. These environmental conditions are obviously different in different regions, and so the chemical composition of wheat grown in a hot, dry region will be slightly different to the composition of wheat grown in wetter regions.

Various analytical techniques, including gas chromatography and inductively coupled plasma mass spectrometry, have already been used to detect compositional differences in wheat from different regions. But these techniques are too expensive and time-consuming to be used on a regular basis, as is required for tracking food production.

So Yimin Wei and his team from the Chinese Academy of Agricultural Sciences' Institute of Agro-Products Science and Technology in Beijing wondered whether NIR spectroscopy might make an effective alternative. Especially as NIR spectroscopy has already shown itself able to determine the geographical origin of various other foodstuffs, including olive oil, cheese, wine and honey.

As they report in a paper in Food Chemistry, Wei and his team used NIR spectroscopy to probe 240 wheat samples harvested in 2008 and 2009 from four wheat-growing regions in China. These regions included the Hebei province, which has a temperate monsoon climate, and the Shaanxi province, which has a semi-arid climate.

Analysing the NIR spectra with linear discriminant analysis and discriminant partial least squares analysis, Wei and his team found they could accurately distinguish between wheat samples from the four different regions. This accuracy was slightly hampered by the fact that climate conditions differ between years, even in the same region, but Wei says this unavoidable variation could be allowed for by simply analysing wheat samples from a greater number of years.

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