Pregermination in Grain

In January 2004 representatives of the MAGB and Banks Cargill Agriculture met at a workshop to see if a truly definitive method could be agreed for the detection of pregermination in malting barley.

All involved were experts at evaluating the different testing systems used, and they were able test a range of barleys using both the ‘official method’ and the Tetrazolium staining method. Moreover, some funding from the AHDB GSAP project enabled a photographer to be on site to take directly comparative images. Those  photographs were most useful in selecting malting barley from the 2004 crop that had some signs of pregermination.

View below Tetazolium staining images with descriptors that can also be found on the Laboratory Analysis page (link).

This is a potential problem, that only occurs infrequently in crop years, and one which is linked to growing conditions for the grain. Because it does not occur often it has tended to be tested for using a variety of methods. At the time the recognised ‘official’ test method used Fluroescien Dibutyrate, which has never been considered suitable for testing grain at intake to a store or maltings and the chemical needed became very difficult to obtain.

There are other methods that involve staining the grain, to help view the embryo and see if a physical change has taken place.The most common staining agent used is 2,3,5-triphenyl tetrazolium chloride, more commonly referred to simply as the ‘Tetrazolium Staining Test’. Because pregermination only happens occasionally, and the Tetrazolium Staining Test needs a certain amount of knowledge for accurate interpretation, it was always seen by the industry as a potential source of discord between the seller and  buyer of the barley.

Dr David Griggs told the MAGB secretariat that the poster had been well received, eliciting much discussion with representatives of non-UK malting companies. At the time maltsters were aware of tetrazolium staining for the determination of germinative capacity, with a few using the technique for the assessment of pregermination. This provided another example where UK maltsters were actively managing their raw material quality ensuring only barley of the correct standard was accepted at intake. At this time the Analytica-EBC method for germinative capacity by tetrazolium staining was revised to include the assessment for pregermination.

Click on the grain below to view a handout from the EBC Prague Conference, giving details of the pregermination testing procedure available.