4MMP Thiol Spotlight
4-Mercapto-4-Methylpentan-2-One
What is 4MMP?
4MMP is a sulfur bound aroma compound that has become highly sought after by brewers due to its high impact on aroma. Humans have an extremely low sensory threshold for thiols, but 4MMP is particularly potent and is present in beer at about 200 parts per trillion. Trillion with a T.
Julia Jennings, Research Scientist at John I. Haas, described how incredibly low of a threshold humans have for thiols in an interview with Hop Culture. "When talking about how much thiols are in beer, it is analogous to a drop of water in twenty Olympic-sized swimming pools," says Jennings.
4MMP is important because it hold the key to some highly sought after flavors and aromas like tropical and sweet fruits. On its own, 4MMP is most commonly described as having an aroma of black currants, as well as gooseberries and passion fruit, but it also is a flavor and aroma booster that helps elevate other contributors like linalool and geraniol.
How to Maximize 4MMP Content in Beer
With regards to thiols, more isn't always better, but it would be very difficult to overdo thiols in beer with traditional brewing methods. Since thiols have a very low sensory threshold, large quantities can actually be perceived as unpleasant. Humans are so sensitive to thiols, because they are present in human sweat and body odor, and in large quantities that is exactly how they are perceived. But with the very low amounts that are present in beer, thiols are fruity, pleasant, and delicious.
As an example, 3MHA smells like citrus and passion fruit in low quantities, but above a certain threshold it is distinctly like a sweaty armpit. And to complicate the matter, everyone's thiol threshold is different, so perception and preference can be very subjective. But again, with traditional brewing methods thiols are present in beer in such very, very, very, very, very small amounts that there isn't a practical risk of overdoing it.
So if you are looking to maximize the 4MMP content in your beer, then it is important to add it to the cold size as it is very volatile. 90°C is an important temperature threshold where 4MMP content starts to decrease. That is why whirlpooling at cooler temperatures and dry-hopping late in the fermentation are the two best ways to maximize 4MMP in beer. 4MMP is quickly extracted during dry hopping and full utilization is reached in just two days, with very little to be gained after that.
4MMP Flavor Synergies
4MMP also synergizes well with popular monoterpene alcohols like linalool, geraniol, and citronellol. 4MMP amplifies the perceived magnitude of tropical and sweet fruit flavors, even when present in small amounts that are below the typical sensory threshold. That is why Citra is such a popular hop when brewers are trying to target 4MMP. Not only does Citra offer good amounts of 4MMP, but it also has linalool and geraniol. So that makes Citra super synergistic when it is used both in the whirlpool and during dry hopping.
4MMP Fun Facts
Main Descriptors: Box tree, black currant, gooseberries
Sensory Thresholds: 1.5 ng/L
Top Hops with 4MMP: Citra, Cascade, Chinook, Topaz, Sabro, Galaxy
3 Tips to Maximize 4MMP:
1. Add to the cold side because temperatures above 90°C reduce 4MMP content.
2. 4MMP synergizes with monoterpene alcohols like linalool, geraniol, and citronellol to enhance tropical and sweet fruit flavors.
3. During dry hopping, full 4MMP extraction can be achieved in two days.
BONUS FACT: 4MMP is a "free thiol" as opposed to a "bound thiol" that requires various enzymes to release.
4MMP Sources and Citations:
1. A Case for Short And Cool Dry Hopping by Scott Janish
2. Development of Thiols and Thiol Precursors in different Hop varieties during Hop Harvest and their impact on beer flavor by Dr. Christina Schönberger and Laurent Dagan [link to PDF]
3. Dry Hop Best Practices: Using Science as a Guide for Process and Recipe Development by Scott Janish for MBAA [link to PDF]