Over the centuries, hops have been crafted to provide many different varieties with different levels of bitterness, flavor and aroma. The benefits that hops provide to the beer have historically contributed to the creation of many beer styles. In addition to flavor and aroma, hops antibiotic characteristic plays a important role in the early days of fermentation as well as the long term storage of beer. For hops lovers like me, some of the most important beer styles in which the preservative nature of hops has plays a role is in the creation of the Indian Pale Ale and the Imperial Stout. Both are well-known hoppy beer styles. These two styles rely primarily on the antibiotic characteristic of the hops to extend the shelf life of British Ales and Stouts to India and Russia. A happy, or hoppy, coincidence, really.
The wort is a smorgasbord of sugars and nutrients for microbes to indulge in. Some of these microbes are benign or even welcome in the fermentation process. Others are not and can ruin what may have been the best batch of beer ever made. Contamination is always on a brewer’s mind, even more so in the early days of brewing when modern microbiology had not yet developed and the necessity of sanitation was not a top priority. In the early part of the fermentation process, there are a lot of sugars flowing around in the beer and a lot of opportunities for unwelcome microbes to establish themselves. Even though that all the little microbe beasties that can contaminate a beer are killed in the brewing process, sanitation can only go so far in preventing contamination of the wort in the time between brewing and the point where the fermentation process creates enough alcohol to significantly impede bacterial growth. Hops are what help bridge the gap in the war against the unwanted bacteria squatting in your wort. The antibiotic characteristic of the hops flower slows bacterial growth, allowing the yeast head-of-the-line privileges with the sugars and nutrients in the wort.
For the big beer geeks, hops possess two types of acids: alpha acids and beta acids. The alpha acids provide the beer its bitterness and the antibiotic characteristic, while the beta acids provide an distinct hops aroma to the beer. When boiled, the lupulin glands within the hop flower go through a process called isomerization, which gradually converts the alpha acids into soluble iso-alpha acids. The isomerization process doesn’t happen right away; it takes a little time. It can take between sixty and ninety minutes of boiling hops in order to convert all the alpha acids and maximize the hops bittering potential. The ultimate result is the more bitter the beer, the more the antibiotic characteristic of the hops contribute to the shelf life. Usually. If you are, for whatever reason, relying on the preservative abilities of hops, you are better off with hops varieties that are more bitter than aromatic.
The preservative quality of the hops flower was probably discovered well before its glorious contribution to the bitterness and aroma of beer. Most likely, they were added to a “hop-less” malty alcoholic beverage specifically for the purposes of extending the shelf life of an alcoholic beverage which showed some great potential, probably sometime post-Pharoah. It reminds me of the “you chocolate bar fell into my peanut butter” ads of the late 70’s. I think it also somewhat miraculous that the antibiotic characteristics of hops do not impact the growth of fermenting yeasts. Perhaps this is proof of intelligent design. Who knows. Whether hops were first added to beer to increase its bitterness only to discover that it allowed the beer to taste great for longer periods of time or visa versa, it happened and the result is glorious.