This is the raw milk at blood temperature. pic.twitter.com/sjJ6XWKZEZ— Wendy Shillam (@Rooftopvegplot) May 18, 2016
Above testing for blood temperature
I’ve started buying fresh, raw milk from the Calf at Foot Dairy in Suffolk. And the first thing I’ve been doing with the milk, apart from drinking it neat straight from a very cold refrigerator*, is to make yogurt. This required a bit of experimentation. The Internet seemed remarkably silent on the topic of making yogurt from raw milk. Most of the websites I looked at told me it couldn't be done and others – mainly US sites – warned that famine and plague would come of eating raw milk.** Undaunted, I transferred my gaze from cookery sites to scientific sites. Then having understood the science I started experimenting. And having devised a few good recipes, now is the time to share.
First the science
What is raw milk?
Raw milk, direct from the dairy, is untreated and comes from grass fed cows. It is neither pasteurised, nor homogenised in the way that mass market milk is. In addition grass fed cows naturally develop a whole range of good bacteria that grain fed cows do not. See Fiona Provan’s Calf at Foot Raw Milk Facts for more information.
The reason why supermarket milk is habitually treated is that the industrial process of dairy, to supermarket shelf, to kitchen, is fraught with delay and potential for contamination or putrefaction. It is necessary to sterilise the milk, denuding it of its friendly bacteria, in case some unfriendly bacteria has got in somewhere. The process also changes the structure of the milk making it white, uniform and boring. Real raw milk is creamy and delicious. It’s alive with health giving bacteria, so every batch of yogurt that I make will turn out slightly differently.
What happens when milk turns into yogurt?
When I add a yogurt starter bacteria to milk it gets to work on the sugars in the milk, turning the lactose into lactase. This increases the acidity of the milk and causes the mixture to coagulate. Adding rennet to milk – an acid – achieves the same effect, making junket or cheese curds. Movement has a similar effect whipping cream and eventually forming butter. This is called denaturisation. The casein protein, in the cream of the milk naturally denatures, i.e. unfurls itself and binds together in the presence of the appropriate bacteria. However the protein solids in the whey do not naturally change so readily unless the milk has been heat treated.
That is why pasteurised milk makes a thicker yogurt.
If we heat raw milk we get thick yoghurt, if we don't heat it we get to preserve the rich bacteria that we bought it for in the first place. But the result of a low heat yogurt process will be runny and sometimes grainy. The recipes below show how I balance these two contradictory functions to produce delicious, thick and creamy yogurt full of healthy live bacteria.
Life is too short to use cooking thermometers. In this article I'll teach you how to recognise the key set points. There is room for error.
I use two wide topped vacuum flasks, made by Thermos and available here. They hold 0.7 litres each. They are not as efficient as a coffee flask, so to conserve the heat for a long time, to mature the yogurt, I pre-heat the pots with hot water and then plunge them as soon as they are filled into a home-made haybox. Mine is an ordinary cardboard box padded with Woolcool, the sustainable packaging my milk delivery comes in.
Faisselle containers can be purchased from Fromage Maison or the pots and container can be saved from an imported faisselle cheese. I buy faiselles from La Ferme de Treillebois in Normandy from our wonderful local cheese shop Fromagerie. (but they don't do postal sales.)
How to make the yogurt
Any yogurt is best made in a warm but spotless kitchen. This is a slow process. It is not difficult, but it is one of those processes that seems to work best if not rushed.
Low heat raw milk yogurt
If I have a rich and creamy milk, I can make a small quantity of yogurt by heating 1.4l milk to blood heat. Test with a finger as you would for a baby's bottle or bath. I call this the Alice in Wonderland Test; neither too hot, nor too cold.
Add 3 heaped desert spoonfuls of a live organic yogurt (either purchased or saved from the last homemade batch.) Stir the yogurt in well before decanting the still warm liquid into two wide topped Thermos pots, secure the lids tightly and tuck them directly into a haybox, or a warm airing cupboard for 12/24 hours. The bacteria will continue to develop, if the yogurt stays at about blood heat. (37•C, 98•F)
However, it is unlikely that the yogurt will be fully set because you have not denatured the whey proteins with enough heat. The resulting yogurt will be creamy on top, and a little watery below, more like a yogurt drink than a foodstuff.
Straining the yogurt through a cheesecloth for a couple of hours, will produce a thicker yogurt, but will obviously reduce the quantity. Straining the yogurt overnight will produce a much drier product that by then will have developed the characteristics of cream cheese. Don’t be put off by the rich, almost buttery residue that sometimes floats to the top. This is actually clarified butter and can be folded into the rest of the yoghurt.
Have turned the kitchen into a raw yogurt dairy. This is straining. pic.twitter.com/IIf4l9Owba— Wendy Shillam (@Rooftopvegplot) May 18, 2016
Above: The fresh yogurt being strained in a cheesecloth
Another solution is to purchase a faisselle box. This is a plastic container with four slotted pots within it. Spoon the yogurt into the pots. The whey will naturally drain out of the pot, into the container, but will continue to blanket the pot, keep the resulting faisselle cheese or fromage frais in excellent condition. The little mounds of fresh white cheese can be sweetened, salted or flavoured with herbs to provide a variety of treats.
High Heat Raw Milk Yogurt
One of the pitfalls of a low heat yogurt is the uncertainty of knowing what bacteria might or might not be present in the raw milk. In this more controlled method I heat the milk to scalding point. This will kill off a lot of the natural bacteria, but it doesn't damage the proteins and it will fully denature the curds and the whey, forming a set yoghurt.
Testing the temperature:
Scalded milk is brought gently to the point of boiling, but it is not allowed to boil. It is pretty easy to see when this stage is reached. A skin might start to form and crinkle. Keep stirring to discourage this skin formation. Steam will start to be rise, a few bubbles might form around the rim of the pan. If I take a sniff I can smell that sweet, hot milky aroma, reminiscent of bedtime drinks and rice puddings. It is the smell of lactose as it starts to break down into lactase.
Heating raises the acidity of the milk, the sugars break down and the curdling process can begin. As long as I am heating the milk gradually it won't matter if the milk starts to bubble. I simply turn down the heat and keep stirring.
Heat 1.4l of raw milk to just below 100•C (212•F) (as described above) I try to keep the milk at the scalding stage for two or three minutes. I want the curding process to be able to begin as soon as I put the starter yogurt into the mix.
Now I let the milk cool slowly to blood heat. Don’t rush this process, putting the yogurt in too quickly might kill it. As before once you can stick your finger into the milk and it feels just right mix 3 heaped dessertspoonful’s of starter yogurt into the milk. Place in two Thermos flasks and plunge straight into the haybox or airing cupboard for 12/24 hours. The yogurt should still be warm when you remove it from the box.
You will find that you have a lovely thick yogurt. If it is not set enough for your tastes, but has cooled down you can re-heat to blood heat and re-seal the Thermos flasks.
The rational for heating
Now the observant among you will recognise that in heating the milk to near boiling, I have effectively pasteurised it. But there is no cause for despair. The factory process involves a lot more that heat. Milk can be denuded of its cream to thin it or have dried milk added to it, which thickens it. The milk can be forced through a spray device, that breaks down the nodules of fat, making them easier to digest and thus more fattening. And milk destined for yogurt manufacture can, quite legally be adulterated with stabilizers such as alginates (carageenan), gelatins, gums (locust bean, guar), pectins, and corn starch.
My yogurt will only contain milk. By heating the milk I have created a blank canvas on which to caste my own cocktail of microbes. I can use some of the yogurt from the low heat batch, which will contain replicas of the raw milk microbiology that I've just 'killed off". The important thing to remember is that this higher level of heat has changed the state of the milk, meaning that we don't have to rely quite so much on atmospheric souring as the low heat yogurt does.
Keeping any yogurt or cheese in the fridge will stop it maturing, but will not kill the microbes. Keeping the produce in the larder will maintain the process and gradually change the flavours.
If it tastes funny, don't eat it. If it tastes and looks fine, it probably is!
Above: High heat raw milk yogurt.
* I keep most foodstuffs in a cool larder these days. So my tiny fridge is reserved for things that really need cooling. Fresh milk and yogurt are two of these perishable items, being kept in peak condition at a temperature of 2°C (36°F)
** Fortunately my canning research has taught me that some people in the USA are terrified of the real. I think that is partly because American food is generally so industrialised, adulterated, diluted and generally messed about with. For example, in America they wash their fresh eggs in something nasty, and in so doing remove the delicate shell coating that naturally protects an egg from tainting! So, American housewives can no longer keep their eggs in the larder, as we do. They have to seal and refrigerate them – ugh!