All about Refermentation

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Ever wondered why a bottle of St. Stefanus Blonde tastes different at 3 months than it does at 18 months? This is all down to the process of refermentation. But what exactly is it? The technical process Refermentation is the process that allows our beer to mature over time in the bottle. Sometimes know as bottle fermentation, or secondary fermentation, it is a brewing technique whereby a secondary batch of yeast is added to the beer in the bottle, or just before bottling. This additional yeast compels the beer to undertake a secondary fermentation process. Adding a secondary batch (or batches) allows the yeast to react with the sugars in the beer, producing alcohol and carbon dioxide. Why is it used? Refermentation not only produces a stronger beer and a beer with a higher carbonation, but importantly, as St. Stefanus Master Brewer Jef notes, it “defines the flavour of the beer”. Beer can undergo one, two or even three rounds of fermentation, depending on the desired result, whether this is a stronger beer, a stronger flavour of yeast, or increased carbonation. Typically, refermentation is associated with Belgian beer styles. It is certainly a distinctive technique in beer brewing, and is used by a number of speciality beer brewers to harness the potential of the beer. Refermentation allows your beer to offer a rich taste experience that has the ability to change and develop over time, as our Blonde does. St. Stefanus Blonde St. Stefanus Blonde matures over time, allowing the flavours to change from being fruity and lively at 3 months, to complex and aromatic at 18 months. Indeed, sampling our Blonde at 3, 9 or 18 months will offer a very diverse taste experience. During the brewing process, after the initial batch of yeast is added to our Blonde, we add two additional yeasts. One of these is our Jerumanus yeast, a wild yeast strain, which gives the distinctive flavour and character to our beer. This wild yeast strain is the original strain used by the Augustinian monks at the monastery where our beer was first brewed. Leave us a comment if you’d like to find know more about refermentation…


Do you use the same yeast to referment as you do for the initial fermentation? Do you not recommend aging longer than 18 months?
Thanks for your comment! With our Blonde, we use three different yeasts in total: one for the initial fermentation, and two for the secondary fermentation in the bottle, including our wild 'Jerumanus' yeast strain. Regarding bottle maturation, we recommend enjoying our Blonde between ages 3-18 months as this is when the refermentation takes place and the beer is at its best. After 18 months, the beer stops maturing and the taste stops changing - for this reason, we have a 'Best Before' date on each bottle. Our Grand Cru can be aged for up to 36 months in the bottle, but our Master Brewer loves his aged to 9 months! Do you prefer your beer young and fruity, or richer and more complex?

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