Yoghurt is great, but milk kefir is supreme!
Yoghurt is ubiquitous, the supermarkets have almost a whole aisle dedicated to it yet milk kefir is hard to find. Most supermarkets don’t seem to stock it but it can be found in Turkish and east European delicatessen and grocery stores.
Of course milk kefir is easy and quick to make and doesn’t require a heating stage as most yoghurt does so it can be easily produced at home with nothing more than a jar and of course the kefir grains.
It isn’t the ease of production that appeals to me though it is the flavour, texture and even the aroma. When I wrote that “yoghurt is to be eaten or drunk, but kefir is sipped like a fine ale” (Ferment, Pickle, Dry) I was merely stating my preference but I wasn’t fully aware of the connections that really exist between the milk-based drink and beer. Now a study* by the Microbiology Department of the University of Cork and others has looked more closely at the flavour production of different microbes in kefir.
Milk kefir is produced by adding kefir grains, which are polysaccharide grains containing both bacteria and yeast to milk. There are a large number of bacteria and yeast which ferment the milk but some are more dominant than others. The University of Cork found that Lactobacillus kefiranofaciens dominate during the early stage of fermentation while Leuconostoc mesenteroides dominate during the latter stages. Whilst Lactobacillus kefiranofaciens declined this also made way for Acetobacter pasteurianus, Lactobacillus helveticus, Leuconostoc citreum, Leuconostoc gelidum and Leuctonostoc kimchii. This leads to a change in the flavour profile.
These strains of bacteria might not be household names but at the same time there is our old friend, saccharomyces cerevisiae, often called brewer’s yeast which is mainly responsible for the fermentation of beer, wine and bread. Whilst the lactic bacteria create sour flavours the yeast creates a minimal amount of alcohol which can combine with acids to create esters, which are flavour compounds also found in beer. Amongst the range of esters found in milk kefir is Ethyl acetate which we would expect to find in a wheat beer and gives a flowery, pineapple or even solvent-like character. Another one Ethyl hexanoate gives apple and fruity notes.
These are just a few of the flavour compounds in milk kefir. Altogether in this study they found “nine ketones, seven aldehydes, six esters, eight alcohols, five carboxylic acids and two sulphur compounds”. They each produce quite different flavour compounds, for example:
Acetic acid (carboxylic acid) – vinegar, peppers, green, fruity, floral, sour
3-Methyl-butanol (alcohol) – fresh cheese, breathtaking, alcoholic, fruity, grainy, solvent-like, floral, malty
2-Methyl-butanal (aldehyde) – malty, dark chocolate, almond, cocoa, coffee
Ethyl octanoate (ester) – fruity, apple, green, fatty, orange, winey, pineapple, apricot
2,3-Hexanedione (ketone) – sweet, creamy, caramellic, buttery
Dimethyl sulfone (sulphur compound) – sulphurous, hot milk, burned
Most of these flavour compounds are at low levels so not individually perceptible but together they change each batch of kefir dramatically. In the study one batch was described as likeable and buttery and another as less likeable but fruity. Different grains in different areas fermented under different conditions will then produce different results. So when you are supping your next glass give a moment to seek out the aroma and flavours unique to your kefir, as long of course that it is home-made.
If you would like to learn more about milk kefir we are running a dairy ferments workshop on Sunday 29th January (2017). We will be making milk kefir using milk kefir grains, use milk kefir to make flavoured kefir, cultured butter, lebneh and yoghurt. We will also look at different varieties of yoghurt, clabbered milk, whey, cottage cheese and paneer. At the end of the course you will have milk kefir grains to take home as well as recipes and the knowledge to further experiment in the world of dairy ferments. We will also be discussing raw milk and its benefits. To book a place email: firstname.lastname@example.org
* Microbial Succession and Flavor Production in the Fermented Dairy Beverage Kefir
Aaron M. Walsh, Fiona Crispie, Kieran Kilcawley, Orla O’Sullivan, Maurice G. O’Sullivan, Marcus J. Claesson, Paul D. Cotter
Rachel J. Dutton, Editor
Teagasc Food Research Centre, Co. Cork, Ireland
APC Microbiome Institute, University College Cork, Co. Cork, Ireland
Microbiology Department, University College Cork, Co. Cork, Ireland
School of Food and Nutritional Sciences, University College Cork, Co. Cork, Ireland
Ester formation in Brewery Fermentations, Journal of the Institute of Brewing