By Hartwick College Center for Craft Food and Beverage

Gibberellic acid (also known as GA or ‘Gibb’) is a naturally occurring hormone produced in plants. GA is synthesized in germinating grain and stimulates the production of enzymes. It can also be purchased in its pure form and used as a processing aid in malting. GA was most notably discussed in a Journal of the Institute of Brewing article authored by our old friend, Briggs entitled, “Effects of Gibberellic Acid on Barley Germination and its Use in Malting: A Review.”

GA is frequently used in malting to increase the rate of enzyme synthesis in low-vigor barley varieties. This is especially useful with winter barley varieties that exhibit high levels of dormancy. It is important to note that dormancy in barley is not broken by GA during malting. It facilitates the production of desired levels of alpha-amylase without the need to unduly prolong germination. However, this is generally not required when malting North American spring barley varieties with higher vigor.  

The response of the grain to GA application is both dose and variety dependent. The ideal method of application is to apply to the germinating grain after casting, in the form of a spray, applied directly to the grain. It is critical that the solution be applied uniformly to all the grain across the breadth and depth of the grain bed, otherwise, there will be vastly different growth rates among kernels and a very heterogenous malt will result. This can best be achieved with spray nozzles mounted on the turning machine. This allows the application to be made at the instant of turning when the bed is most open and the chance of penetration to the lower grain is at an optimum. GA can also be applied during steeping, but this is less efficient due to the large volume of steep water and because the grains are at a less mature stage of germination.

The typical dose for GA application is 0.5 ppm – 1 ppm by weight of barley (or approximately 1g per tonne of grain).  A quick dissolving form can be purchased from for ~$1.50 per gram. Some experimentation may be necessary to determine dosing for your variety during the current crop year. 

There are no legislative restrictions on the use of GA in North America or Europe, although abuse of the product has led to a bad reputation among some brewers. It is important to never use GA as a crutch or as a substitute for purchasing high-quality barley. GA cannot induce proper modification in dead or dormant kernels. Barley must always have >95% germination energy to be successfully malted.  

Some noteworthy side effects of GA use include increased heat output of the grain during germination, potential increases in acrospire and rootlet growth/malting losses, and increases in S/T (soluble/total protein) and color. Use of GA must be compensated by reducing green malt moisture and germination time, which can be detrimental to overall endosperm modification.  

Always remember that there is no shortcut to achieving a high-quality malt. There are no tools or techniques for making a good malt out of poor-quality barley. Barley must be alive and sound from the start in order to yield acceptable quality in the malthouse. It must also meet strict quality criteria set forth by organizations such as the American Malting Barley Association or Brewing and Malting Barley Research Institute. As we are faced with more climate and supply chain challenges, we must take the achievement of quality very seriously, weighing every consideration about our barley before we make decisions. GA is another tool that you may choose to use wisely – and remember – there are resources (the Craft Maltsters Guild, Hartwick CCFB, the Montana State University Barley, Malt & Brewing Quality Lab, and other maltsters) to guide you through your trials and decision-making when it comes to both Decoding Malting Barley Quality and using GA.