Lactic acid bacteria (LAB) fermentation (F) plays a major part in traditional food processing technology all over the world. LAB produce lactic acid, a gentle tasting acid which can lower the pH of a food making it uninhabitable to other types of microorganisms. LAB F contributes to preservation, flavour and texture of foods. LAB is used to describe species from many genera, most commonly Lactobaccillus, Lactococcus, Leuconostoc and Streptococcus thermophillus. (de Vos, 2005). Certain taxa of LAB are also responsible for the production of bacteriocins, chemicals that inhibit the growth of other bacteria, the example of this par excellence being nisin. Nisin and other LAB produced bacteriocins have been shown to be effective in the prevention of many pathogenic species (Ross 2002).
LAB is the type of F occurring in sauerkraut, yogurt or kefir, cured meats, and idli. It is also responsible for the gentle acidity of the Belgian lambic beers as well as the malolactic wines where harsh malic acids from the grape are converted into softer and more palatable lactic acid.
Importantly LAB are found naturally in dairy products and many species are able to continue life in the presence of salt meaning that salt can be used as a MO selection mechanism as it is in sauerkraut. Many high quality LAB fermentations typically found in a kitchen are made by ‘master artisans’ who work with these cultures on a daily basis. This is particularly clear with cheese and other products of the dairy industry. Scandinavia has long been a homeland for dairying. Although in early times being split into tribal groups, some of whom did, and some of whom did not milk their animals (especially reindeer), it appears that those communities which practiced milking of animals have been more successful, possibly due to their use of this very important food source. Frederik J. Simoons (1973), when tracing lactose tolerance (tolerance resulting from the production of the lactose hydrolyzing enzyme lactase) in populations found significant biological patterns which led the researcher to hypothesise that nomadic tribes in Eurasia and north Africa were among the first to practice dairying. Gary Nabhan (2004) suggests that around 10,000 BP a mutation occurred in the DNA of an isolated tribe of Northern Europeans which allowed them to take advantage of this rich source of nutrition, Nabhan goes on to suggest that within as little as 15 generations, the prevalence of this specific gene mutation could have become wide.
The success of those peoples in the Nordic countries may also be in relation to the increase in Vitamin D, which normally is produced by the human body in the presence of sunlight, but can also be gained from milk. In the Nordic winters, sunlight is very short, and so, any extra Vitamin D can be key in maintaining health. Nordic cultures were much more inclined to drink their milk soured as in the old times it not considered healthy to drink fresh milk.
“I know that in the old times they milked the cow in a jar and then they put the milk in bigger container for fermentation but used a sieve made by hay or fresh grass to get rid of insects and stuff. The grass, I think, would impart LAB into the milk, and of course, also from the cows teat and the human skin”
(Patrik Johansson, personal email exchange, 2012)
It is said that when the Romans arrived in Northern Europe they were taught to make butter by the Celts, Pliny the Elder commenting that butter was “the most delicate of foods among barbarous nations, and one which distinguishes the wealthy from the multitude at large.” (McGee, 2004) Sweden was the worlds largest butter producer from the middle-ages until 1898, when Demark took over (Johansson) and Denmark has been in the lead ever since. Below Johansson a Swedish master artisan creator of ‘virgin butter’, describes the specific qualities that make the butter key to the dining experience at Noma describes how he learned to make butter and developed the technique into the ‘unwashed’ product, ‘virgin butter’.
“My grandmother had small dairy during the 50s and 60s where she made only butter on a very small scale. She taught me how to make butter. Her method involved the traditional way of washing the butter, that is, removing as much of the buttermilk as possible by washing it with cold clean water. Washed butter has a higher fat content and keeps longer but we discovered that by washing the butter you take away flavour and also the really nice acidity present in the buttermilk (pH 4,5). So rather than focus on the property of keeping longer we focused on the property of taste and how to maximize it. We maximize the butter aroma during the fermentation time, which usually lasts for 48 hours, but also during the churn by churning at a higher temp than what is usually considered normal in the butter industry. During the fermentation period we use a temp curve (the details are secret). The resulting butter has a more buttery taste but also a nice acidity due to more buttermilk present…
… Late one night I churned by hand and added salt before churning and decided to stop just when the first little butter grains formed. Normally I churn until the butter grains are as big as chickpeas and then I remove most of the butter-milk. When the first little butter grains form the separation between the fat and the water (butter milk) is just taking place and the process requires constant monitoring to the second. Virgin butter has a fat content of 40% as opposed to the regular butters fat content of 80 %. In virgin butter all the acidic buttermilk is present and retained I think thanks to the capillary effect. The result is a butter that is spreadable directly from the fridge with a pleasant acidic and buttery taste. It also has a unique grainy texture.”
(Patrik Johansson, personal email exchange, 2012)
Interestingly, a very old relative of Patrik recounted to him that washed butter was for the weekends as it had to look pretty, but the unwashed butter was for the weekdays and that he always preferred the unwashed one.
It is important to note that some LAB preparations can be easily made in the restaurant kitchen, giving the chef some ability to manipulate the organoleptic properties by changing variables within the process. For example LAB are also extremely important in bread making, especially when the natural levitation process of using a sourdough are involved. Bread made with natural leavening is much tastier, and this is in part, is due to the high levels of LAB in the mother dough – this will be covered in a later post.
One useful way to inoculate a ferment with LAB (e.g. fish sauce (see previous post titles ‘Umami from Salt rich Fermentation’) or cured meat (future post) is with the addition of whey, thus hastening the process of acidification due to both the presence of lactose and of LAB in the whey. Whey can be collected after making cheese, or by straining yogurt. At NFL adding a little whey proved very useful in a number of experiments. Lactic fermentation of thinly sliced root vegetables (carrot and beetroot) proved useful in making deep fried ‘crisps’, due to the LAB processing of sugars, there was considerably less caramelisation during the high temperature frying to try this, mix thinly sliced carrots with 2% Salt and a bit of whey, leave them weighted and submerged in their own juices until the sweetness has turned to a gentle lactic acidity, then dry ‘em and fry ‘em - yum.
In other dairy products, yogurt and yogurt whey are used a great deal in adding certain flavours and textures to foods. Marinating meat with yogurt has long been practiced by various societies, the recipes for yogurt and a yogurt-marinated leg of lamb is given below.
Better gel is obtained with skimmed milk
Heat to 90 °C and keep there for 10 minutes – again to help with gel formation
Cool to 42 °C and add around 5 % by weight of live natural yogurt
Keep at 42 °C for 6 hours
Cool to 5 °C
Use and use a little bit of this to inoculate the next batch
Yogurt Marinated Leg of Lamb with Juniper
Remove skin and fat from leg
Rub with 2% Sea Salt and 0.5% juniper powder
Leave uncovered, hung at 5°C for 6 Days
Put leg into a vacuum bag with 300ml yogurt and leave at 5°C for 2.5 Days
Cook sous vide with 60 g butter at 58 °C / 36 hours
Remove from sous vide bag, drain and pad dry
Separate the leg into its individual muscles
Rub each of these with neutral frying oil
Roast above very hot coals until golden
Rest for 15 minutes in a warm, humid place
Slice and serve with walnut sauce and bitter greens
De Vos, W.M. (2005) Diversity of lactic acid bacteria, in Nout, M.J.R., De Vos, W.M., Zwietering, M.H. (eds) Food Fermentation pp. 21-28, Wageningen Academic Publishers, The Netherlands.
Ross, R.P. et al (2002) Preservation and fermentation: past, present and future, International Journal of Food Microbiology 79 : 3.
Nabhan, G.P. (2004) Why some like it hot: food genes and cultural diversity Island Press, USA.
McGee, H. (2004) On food and cooking: an encyclopedia of kitchen science, history and culture, Hodder and Stoughton, UK.
Simoons, F.J. (1973) The determinants of dairying and milk use in the old world: ecological, physiological, and cultural, Ecology of Food and Nutrition 2 : 83.
About the author
My Name is Ben Reade, I’m a chef from Edinburgh, Scotland, and for the past 3.5 years I have been studying at The University of Gastronomic Sciences in Pollenzo, Italy. For my final thesis, I came to Nordic Food Lab to research many subjects where my varied interests inerlaced with those of the Lab. The research arose out of time spent at the Nordic Food Lab between 29 September and 22 December 2011. The aim is to describe NFL’s current research to both chefs and non-specialized readers, explaining and coding the creative and scientific methodologies employed during the research at NFL, exploring their application in food experimentation and innovation. Over the next month or so I will be breaking down this thesis into manageable blog-style chunks, this is chunk 13ish of around 25 I hope you find it interesting. If you want to ask me any questions directly, I’m contactable on Twitter @benreade.