Sigma is a 10.0% dark sour ale. It pours a murky dark brown, with a lively head that quickly disappears completely. The aroma is typical of a sour ale, strongly acidic, with a little funkiness in the background.
The flavour is somewhat like a Flanders Oud Bruin, with a strong, sharp acidity which grips the sides of the tongue early. Tartness of green apples and a prickly carbonation make for a lively mouthfeel. There is subdued dark malt, which softens the puckering somewhat. The finish is very dry, sucking the moisture from the mouth, with a lingering tartness. As for the alcohol, you’d never know it was 10%!
The Morpheus yeast: Unusually for a microbrewery, Alvinne has cultured its own unique yeast strain – Morpheus – which it uses in many beers; including the sour series. Developed by the third member of the brewery team who has a Masters in Food Science Engineering, Marc de Keukeleire is known as ‘the Yeast Whisperer’!