Real yogurt (or yoghurt if you are British) has only 2 ingredients, milk and cultures. Yogurt making at home has become more popular as more people are enjoying the health benefits provided by live, natural yogurt with no additives.
The quality of the milk used and the strains of cultures added determine the taste, consistency & health benefits of home-made yogurt.
Most commercial yogurt cultures are laboratory isolated single strains of bacteria, selected for a narrow set of qualities – mostly ones which provide a very mild taste & creamy texture similar to commercial yogurts. But as with the fast growing popularity of heirloom vegetables that offer a diversity of flavours not found in commercial produce, heirloom yogurt cultures are finding their way into connoisseurs and chefs kitchens, providing a whole universe of yogurt tastes & textures.
The added benefit of heirloom yogurt cultures include being able to self reproduce themselves indefinitely – unlike commercial strains of bacteria that must be renewed every generation to get a consistent product. Also, many proponents consider heirloom yogurts to be healthier as they contain entire ecosystems of beneficial bacteria, rather than just a single strain or two.
Heirloom yogurts cultures have been passed down through generations in places that have a long history of yogurt making, such as Greece, Bulgaria, Armenia, Iran, India & Scandinavia. Each yogurt has a different taste ranging from sour, tangy, mild & sweet and textures such as silky, solid, creamy, runny & even slimy (which is better than it sounds!)
The 2 major families of heirloom yogurt cultures are mesophilic & thermophilic. Mesophilic cultures reproduce (& create yogurt) at ambient (room) temperatures, whereas thermophilic yogurt cultures require extended periods of constant warm temperatures to reproduce.
Thermophilic (heat loving) cultures are the most popular and commonly used for commercial & home made yogurts. Perhaps the best known of these are Greek and Bulgarian yogurts. Typically heirloom Greek yogurts are fairly mild flavoured, thick & creamy (especially when strained or made with added cream) and Bulgarian yogurts are full of flavour, more tangy and less set. However the manufacturing process can result in a wide range of flavours & textures for both strains. A typical incubation of thermophilic yogurt is 39-43 degrees centigrade for a period of 6-10 hours. Hotter temperatures can cause seperation of curds from the whey and longer durations results in a more complete digestion of lactose by the bacteria.
Experimentation is needed with heirloom cultures to find the ideal method for your tastes, both with thermophilic & mesophilic yogurts.
Mesophilic yogurts have traditionally been more popular in Scandinavia and the Caucasus (countries such as Armenia, Georgia & Azerbaijan). These are made at low temperatures, typically ranging from 19 – 26 degrees centigrade, with a much longer incubation period of 12 – 24 hours (sometimes even longer when ambient temperatures are low). Popular mesophilic cultures include Filmjolk, Viili and Matzoon (Caspian Sea) yogurts.
For someone familiar only with “traditional” yogurts, many of the mesophilic yogurts can be quite an experience – with flavours ranging from nutty, cheesy, sweet, sour and an array of textures from creamy and set to cottage cheese, fizzy and gloopy.
Making heirloom yogurts
The first step is to acquire cultures. Farmers markets can be a good source of heirloom cultures – talk to people selling yogurts to see what cultures they use. If they specify an exact strain such as X11 or HN19, then they are using commercial laboratory isolated cultures and not heirloom. The Internet is probably the easiest way to source true heirloom cultures, but do your research on sellers and read reviews of previous customers to ensure the cultures reproduce themselves reliably and that the yogurt produced is to your liking.
Once you have cultures, either in a dried sachet form or a small quantity of ready-made heirloom yogurt then the only other ingredient needed is milk. While any full-cream milk will do (reduced fat milk will also work, but avoid fat-free or skim unless you want to make drinking yogurt), our preference is to use raw unprocessed milk from farmers markets (or straight from your cows if you are lucky to have a herd). The extra cream and natural texture of unprocessed milk creates a richer, tastier yogurt with a delicious creamy layer on top.
If you are concerned about consuming raw milk, have no fear – the first step of making yogurt is heating the milk on a stovetop. Ideally you want to slowly heat the milk without burning or boiling it up to a temperature of between 86 and 90 degrees centigrade. This changes the structure of the milk, resulting in a thicker set yogurt as well as killing any bacteria or other pathogens that might cause health concerns. Yogurt can also be made from entirely raw (unheated) milk, however care should be taken to verify the safety of the milk and health of the cows from where it comes. Unheated milk will also not create nearly as thick a yogurt.
Keep the milk at a simmer for at least 15 minutes, longer periods (up to an hour) will steam off more water, creating an even thicker yogurt. Then take the milk off the heat and let cool until it is about 46 degrees centigrade for thermophilic cultures, or around 30 degrees for mesophilic ones.
A yellow-orange milk skin will form on the surface of the milk once hot. Ideally leave this undisturbed until the milk has cooled, this keeps more protein and cream in the milk rather than scraping off as it appears.
Once the milk has reached the target temperature, gently lift the skin off with a slotted spoon – which by now will probably be a spongy texture & orange cheddar cheese color. Put this aside for use in a range of other products. Ensure that all skin has been removed for the smoothest possible yogurt.
In a separate container or jar, whisk or thoroughly mix a cup of warm milk with the starter culture. If you are using ready-made yogurt, a ratio of 2 tablespoons per litre milk is about standard. Then whisk or stir in the culture-milk mix with the rest of the warm milk either in the pot or a seperate bowl. Take care not to scrape any hardened milk off the bottom of the pot so you avoid lumps in your yogurt.
Then quickly pour the innoculated milk into jars and place in your pre-warmed incubater for thermophilic yogurts or into a kitchen cupboard for mesophilic ones (or just leave the jars on a kitchen counter).
Thermophilic heirloom yogurts will be ready after about 8 hours at 40 degrees centigrate. Mesophilic yogurts will take 12-24 hours depending on the strain used and the room temperature.
Then place into a fridge of 3-5 degrees for at least 2 hours to cool before eating. The yogurt will continue to set for 2-3 days in the fridge, we find the best consistency is attained after this period.
Make sure you save a few tablespoons of yogurt to make your next batch – most heirloom yogurts should be made every 7-14 days to keep the cultures strong & healthy
Enjoy the delicious taste & health giving benefits of natural heirloom yogurts with fruit, desserts, sauces, meditteranean recipes, drinks or just on its own.